The Minnesota Project’s Fruits of the City program
Fruit Tree
Maintenance Guide
The Key Elements of Fruits of the City
Participation
A Statement of Model
and Mission
Fruits of the City is a program of
The Minnesota Project that helps
Minnesota neighborhoods and
communities grow and harvest fresh
fruit for local food shelves. Our goal is
to link under-utilized food sources with
programs that provide locally produced
fresh and nutritious food and other
resources to families in need. This Tree
Maintenance Guide offer tips on how to
improve the health of your fruit tree
and therefore increase the amount of
fresh fruit available to those in need.
First, we thank you for your willingness
to participate in this important
program. Your efforts are a key part of
our goal and we hope this guide will
help provide more and better quality
fresh fruit to our local food shelves and
underserved populations.
Have more questions regarding
tree care? See page 19 for additional
resources.
Want to be more involved with
Fruits of the City? Read more about
the multiple opportunities we offer
which are mentioned with this booklet.
Thank you for your participation in the
Minnesota Project’s Fruits of the City
program. Your efforts help those in
need and support our community in a
big way.
Jared Walhowe, Bill Hughes,
and David Glenn
FruitsoftheCity.org
[email protected]
651-789-3321
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Opportunities for participation include homeowners with one or more fruit
trees who want to donate their harvest, local food shelves, Neighborhood
Coordinators and volunteers who pick the fruit, and community and
corporate leaders who commit to developing a plan to grow and “donate”
a community orchard’s produce.
Tree Owners
For most of the home fruit tree owners in urban areas, the harvest exceeds
their personal use. They may be only a suggestion or personal contact away
from interest in donating their fruit to a local food shelf. With your help,
Fruits of the City would like to be the connecting link between their supply
and the ongoing need for fresh fruit at or local food shelves.
Food Shelves and Food Banks
Fruits of the City delivers harvested fruits to local food shelves and food
banks who distribute the fruits to those in need.
Volunteers
Volunteers and Neighborhood Coordinators are the core of the harvest
endeavor. Once trained to pick and sort the fruit, volunteers are the lifeblood
connection between the donor’s supply and the needs of those who visit the
food shelves. They provide the force to harvest the fruits and get it to those
in need.
Active and Under-Utilized Orchards
A surprising number of older orchards in the 11-county metro area are
presently not the operational commercial orchards they used to be. Once
family owned and operated, they now lie unattended or under-utilized, yet
their owners would appreciate both the opportunity to donate the fruit to
local food shelves and the volunteer service of gleaning much of the fruit
that might otherwise fall and litter the ground. Help us find these orchards
as well as active orchards interested in donating fruit.
New Initiatives & Community Orchards
Fruits of the City is looking to find communities and corporations who have
spaces and campuses where small orchards could be planted. As a longrange goal, it has the potential to provide significant quantities of fruit while
fostering volunteer opportunities within these respective communities. These
plans require ready funding and a volunteer corps to plant and care for a
community orchard.
Fruit Tree Maintenance Guide
1.Fruit Quality 4
2.Fruit Ripeness 5
3.Tree Staking 6
4.Tree Wrapping 7
5.Watering and Mulching 8
6.Fruit Pests 9
7.Fruit Diseases 12
Apple Scab
Cedar-Apple Rust
Fire Blight
8.Fruit Thinning 14
9.Fruit Bagging 15
10.Tree Training 16
11.Tree Pruning 17
Pruning for Fruit Production
Fruit Pruning Tips
12.Tree Maintenance Calendar 19
This publication is a group effort of Fruits of the City team. It was initiated by David Glenn and
Heidi Coe, reviewed by Rebecca Koetter, University of Minnesota and Jeffrey Johnson, arborist
with the University of Minnesota Landscape Arboretum.
Fruits of the City is generously supported by the SUPERVALU and General Mills Foundations
and in 2013 through Seward Co-op’s SEED donation program where over 39,000 customers
generously “rounded up” for Fruits of the City.
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1. Fruit Quality
Donating Your Fruit
We greatly appreciate your donation of fresh fruit to the Fruits of the City
program that we then share with local food shelves. Because we can only
accept high quality fruit, we want to give you insights to improving the
health of individual trees that will help with yield and quality.
Poorer quality fruit, or “seconds,” are useful foods that do not go to waste;
however, they are reserved for organizations that have the capacity to cook,
process, or preserve food before they are distributed to those in need.
These apples have apple scab, which affects
the skin of the fruit. Apples with light scab
are considered “seconds” and can still be
donated.
(Photo by T. Sutton, courtesy University of
Minnesota Extension)
Fruits of the City cannot accept fruit that is in poor quality or fruit that has
even fallen on the ground. These fruits have a lower shelf life and are less
desirable to local food shelves and their participating families.
Please use the following guidelines to estimate the quality of your fruit:
1.Minimal spots or blemishes. No worms.
Is this fruit you would eat? If so, this qualifies as a “fresh eating fruit.”
2.Minor surface blemishes that do not affect the flesh of the fruit. This qualifies as “fresh eating fruit” or “second” depending on severity of surface blemishes.
3.Blemishes that affect the flesh of the fruit cause the fruit to have a mealy texture.
This fruit cannot be donated.
4.Wormy fruit?
If so, depending on severity, this fruit is either a “second” which can be utilized, or if too severe, cannot be donated.
These guidelines apply primarily to apples. However, similar guidelines can
apply to all fruits.
This apple has apple maggot which
damages the flesh of the fruit. Apples with
apple maggot cannot be donated.
(Photos by Dept. of Entomology, University of
Minnesota, courtesy University of Minnesota
Extension)
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2. Fruit Ripeness
When is my fruit ready to pick?
Apples
Knowing when fruit is ripe and ready to be picked can be a challenge.
Flavor and texture are important indicators, but are also quite subjective.
One of the better indicators of ripeness is the color of the seeds inside an
apple. As the fruit ripens, the seed will turn from a near white color to tan,
sometimes streaked brown, to full brown.
The redness of an apple is not a good indicator of its ripeness. When
assessing maturity of apples, look for a change in the background color, the
part of the skin not covered with red pigment. When the background color
begins to change from green to a greenish yellow color, the apple is starting
to ripen. Among Minnesota apple varieties, only “Northwestern Greening” is
truly green at harvest. All other apples should have a yellowish background
color when fully ripened. This happens as the starch is converted to sugar in
the fruit.
Apple seed color is a reliable indicator of
fruit ripeness. The dark brown seeds of this
apple show that it is ripe.
Pick a few apples that appear to be ripe and taste them to be sure they
are at the maturity stage you prefer. As apples ripen, starch in the flesh is
converted to sugar. An unripe apple will be starchy and leave a sticky film
on your teeth. A ripe apple may still be tart, but it should also be sweet and
have developed aromatic flavors.
Pears
Minnesota pears should not completely ripen on the tree. Fruit that ripens
on the tree ends up gritty and unpleasant. Instead, fruit is picked at a
“physiologically mature” stage and then is ripened indoors. However, fruit
should not be picked too early either.
A pear fruit is ready to harvest when:
The yellowish skin color of these pears
indicate that they may be ready for harvest.
• The skin color turns from dark green to a lighter yellowish green
• The lenticels (dots) change from white to brown (not in all varieties)
• The skin develops a smoother, waxy look and feel
(Photo courtesy Ed Bacchus, Flickr user)
Pears ripen fully when allowed to sit at room temperature for a few days.
When the fruit turns a more golden color and the flesh at the stem end
yields to thumb pressure, the fruit is ready to eat.
Unfortunately, Fruits of the City cannot
harvest cherries, plums, and other soft
fruits as we do not have access to
appropriate storage. Please consider
donating these fruits directly to your
local food shelf.
Donating Soft Fruits
To locate a nearby food shelf, visit:
www.hungersolutions.org/give-help/map/
Excerpts from University of Minnesota Extension publications “Apples and Pears in Minnesota Home
Gardens” (www1.extension.umn.edu/garden/yard-garden/fruit/apples-and-pears-in-minnesota-home-gardens/)
and “Stone Fruits for Minnesota Gardens” (www1.extension.umn.edu/garden/yard-garden/fruit/stone-fruitfor-minnesota-gardens/)
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3. Tree Staking
How to Stake a Tree
Staking is commonly only needed for trees with abnormally small root systems
or when the planting site is very windy. If necessary, tree owners may place one
to three equally spaced stakes around the tree to provide temporary support.
One stake method,
attach two-thirds up trunk
(Images provided by www.myminnesotawoods.
umn.edu)
Dwarfing rootstock apple tree with
permanent metal staking.
Two stake method,
attach one-third up trunk
Three stake method,
attach one-third up trunk
Stakes should be three-quarters the height of the tree (prior to being put in
the ground) and placed outside of the planting hole. Once all stakes are
secure, the tree may be fastened firmly but in a manner that allows some
natural stem movement from wind. Attach the tree to the stakes with a
synthetic woven strap material such as “Tree Tie Webbing.” Tree owners may
remove the stakes of fall-planted non-dwarfing trees by mid-spring if the
trees have established themselves. Stakes left in place for too long may actually
reduce the amount of root and stem diameter growth put on by the tree.
– Jeffrey Johnson, Minnesota Landscape Arboretum
We suggest permanent staking for dwarfing rootstock fruit trees because
their root systems do not typically provide adequate anchoring and support
on their own. For these trees, we recommend using a single metal stake
placed approximately one foot away from the trunk. Semi-dwarfing rootstock trees may require staking for the initial years of development, especially
if planted in exposed areas. In areas exposed to excessive wind, three to five
(or more) years of staking may be required.
Staking is not necessary for vigorous, non-dwarfing rootstock trees that are
one year old. However, if these trees are planted as two or three-year old
trees, we suggest staking for the first three years to allow the root systems to
stabilize. Please note that two and three-year old trees purchased potted,
bare-root, or balled and in burlap do not have the full root system needed to
support their size since much of it has become separated in the transplanting
process. Temporary staking may be necessary for these trees while they
redevelop their root systems.
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4. Tree Wrapping
Protect your tree from winter damage
Fruit trees are especially tasty to rabbits who gnaw bark entirely off tree
trunks or branches if the opportunity presents itself. In order to protect your
trees from rabbits and voles or other rodents, it is necessary to wrap the
entire trunk of your trees in the fall, particularly before the first snowfall.
18” to 24”
above
snowline
When putting on the wrap make sure it fits snugly to the ground so animals
cannot get below the plastic or paper materials. Wrap the entire length of
the trunk, all the way up to the first tier of branches. Make sure to consider
snowfall when wrapping. You need to wrap as high as a rabbit can reach
standing on top of the anticipated snowfall.
Anticipated
snowline
Specially designed hard plastic wraps that wind around the base of a tree or
trunk sleeves are available for purchase at garden centers and at stores such
as Menards, Lowes and Home Depot.
We also recommend installing “hardware cloth” around the base of the tree
to prevent voles from damaging the lower trunk. This cloth is made of metal
mesh and is similar to window screen material. One-quarter or three-eighths
inch hardware cloth will prevent most all types of rodents. It can be found at
most hardware stores.
Be sure to remove tree wrap in the spring. Removal of tree wrap
eliminates the likelihood of stem damage caused by binding and girdling as
the tree grows and moisture build up.
2” to 3”
below soil
Hardware cloth installation
(Illustration courtesy University of Minnesota
Extension)
Stem Girdling Roots
The root systems of potted trees that
have become overgrown in the pot may
continue to grow in an inward fashion
and girdle the stem of the tree –
causing the tree to die. These trees are
considered root bound. In this situation,
loosening up or cutting the overgrown
root system is suggested to allow roots
to grow outwards and
provide stability. Temporary staking
may be needed for these formerly root
bound potted plants.
For more information on stem girdling
roots, visit:
www.myminnesotawoods.umn.edu/
2009/01/stem-girdling-roots-booklet/
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5. Watering and Mulching
Proper moisture is essential
Adequate watering and the proper moisture content of the soil are essential
in growing fruit trees and even more essential for young trees. During
summer dry periods, most trees need to be watered at least once a week.
Trees need enough water to wet the roots that may be many inches deep. It
is especially important to water newly planted or transplanted trees regularly
for three to five years as they develop healthy root systems. Before watering,
check the moisture of the soil with your finger or by digging six inches deep
with a trowel. Water the entire root systems to about one foot deep. Be
careful not to over water if you have poorly drained soil. If you are interested
in reducing the need to water your trees or if your trees are in an area where
it isn’t feasible to water them, it is highly recommended that you use mulch
around the base of your tree.
Mulching is a proven technique for conveniently capturing water and
maintaining soil moisture. Mulch also inhibits the growth of weeds that
would otherwise take away nutrients your tree needs to bear fruit. In
addition to helping you conserve water in the summer months, mulch also
decomposes slowly and eventually becomes fertilizer.
There are many varieties of mulch. One of the most accessible and effective
types of mulch is the fallen leaves from your tree; however this is generally
not recommended particularly if you have a fungal disease on your leaves
that can over-winter on the fallen leaves. Fully decomposed compost is also
very effective. Many tree owners choose to use wood chips as mulch. Tree
bark is especially effective as mulch. Tree bark is both long-lasting and easily
broken down to help replenish the soil. The use of chipped wood as a mulch
also promotes beneficial fungal activity as it decomposes. Many types of
fungi work symbiotically with trees helping them to make use of many of
the nutrients within the soil.
When adding mulch, create a layer two to four inches (or more) thick in a
circle around the base of the tree. Make the mulched area as wide as you are
able or willing to make it. Extend the ring of mulch out to the tree’s drip line
if possible. Leave the area directly touching the base of the tree un-mulched.
For more information, see “Seasonal care for trees & shrubs: Mulching” (www.
myminnesotawoods.umn.edu/2008/04/seasonal-care-for-trees-shrubs-mulching/)
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6. Fruit Pests
Apple Maggot
The apple maggot is the most destructive pest of apples grown in home
gardens in Minnesota. Also known as the railroad worm, this insect is a type
of fly. Commercial growers are usually successful in managing apple
maggots, but the general public faces a more difficult task when attempting
to protect only one or a few trees.
Successful management depends on the number of apple maggots in your
area each year, the extent of unsprayed or unmanaged apple trees around
your yard, and the thoroughness of your management program.
Life Cycle
Adult apple maggot fly
(Photo courtesy Wiki Commons)
Apple maggots spend the winter in the ground as nonfeeding pupae. They
begin to emerge from the soil as small (about one-quarter inch long) flies
starting in July. You can identify an apple maggot fly from the characteristic
black and white banding pattern on its wings and a conspicuous white spot
on the body. These flies do not all appear at the same time, but emerge
at different times from early July until September. Peak emergence usually
occurs from late July through early August. They can be found on apple tree
foliage, fruit, or bark as well as nearby trees, shrubs, and weeds.
About seven to ten days after emergence, adult females start to lay eggs.
They possess a sharp ovipositor (egg laying apparatus) that pierces the skin
of the apple and allows eggs to be inserted into the apple flesh. One egg is
laid per site, although more than one egg is often laid in a single apple. In
about five to ten days, eggs hatch into cream colored legless maggots that
feed and tunnel in the flesh of the fruit, leaving brown ‘tracks’ or trails.
Apple maggot damage
Damage
Apple maggots cause two types of injury. The first injury is caused by
oviposition that damages the area around the site where the eggs are laid.
The flesh stops growing, resulting in a sunken, misshapen, dimpled area. The
second injury, which is the more severe of the two, occurs as the maggots
tunnel through the flesh. As a result, the pulp breaks down, discolors, and
starts to rot.
Management
Apple maggot tunnels in ripe fruit
Sanitation
Sanitation is important in reducing apple maggot numbers. Pick up and
dispose of apples properly within a few days after they have fallen to the
ground. This reduces the number of overwintering pupae on your property.
Bury the apples in the ground at least one foot deep. You can also use these
apples for cooking or cider. Cooperation among neighbors increases the
effectiveness of sanitation – management efforts will be disappointing if
there are unmanaged apple trees nearby producing a significant apple
maggot population.
Excerpts from University of Minnesota Extension Publication “Apple Maggot Management in Home Gardens”
(www1.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/maggot/)
9
Fruit Pests
Apple sticky trap with apple maggot fly
(Photo courtesy USDA)
Apples grown using two types of fruit
bagging
continued
Trapping
Although results may not be as good as insecticide sprays, you can manage
adult apple maggots by capturing them with sticky red sphere traps. These
traps are readily available from gardening stores or gardening catalogs. You
can also make your own traps. Use a plastic or wooden ball about three
inches in diameter (a little bigger than a real apple) and colored red or black.
Attach a wire to the traps (e.g., using an eye screw). Coat the traps with a
sticky substance such as Tangle Trap. You can purchase a feeding attractant
to increase the number of apples maggots that go to the traps (if you buy a
kit, many include the lure with it).
Hang one trap for approximately every 100 apples in your tree. That’s about
five traps for an average standard tree in Minnesota. Traps should be hung
by July 1. When an insect lands on the sticky sphere, it becomes trapped
and dies. Check traps periodically. Traps become ineffective when they are
covered with insects and/or debris. Clean off the spheres and reapply the
glue as needed. Removing the glue can be challenging; try vegetable oil for
the best results.
Bagging
Apple maggot flies can be prevented from laying eggs in apples by placing
a plastic bag or nylon footie over each apple. Many types of plastic bags will
work. Place the bag over the apple before the apple maggots emerge, no
later than July 1. Tie or staple the bag loosely around the stem. Cut off the
bottom corners of the bag to allow moisture to drain out.
For more information on bagging, please see Fruit Bagging, page 15.
Insecticides
When properly timed and applied, insecticide sprays help manage apple
maggots before the flies are able to lay eggs. Once eggs are laid, there is no
effective management. Sprays need to thoroughly cover all surfaces of fruit
and leaves to be effective. Generally, do not spray insecticides before July 1.
It is more difficult for home gardeners to find insecticides labeled for
treating apple maggots. Diazinon and dimethoate are no longer available.
Home gardeners can still buy carbaryl but it is available in fewer products.
Also look for products containing esfenvalerate. However be careful of
potential restrictions. In one case, the product is limited to treating just
dwarf and young apple trees.
Caution! Always read pesticide labels carefully before buying and again before
using these products. The label is the final authority on how you may legally use
any pesticide.
When using insecticide sprays, be sure to note the interval between the last
spray and when you can safely harvest the apples (the preharvest interval).
Do not pick apples any sooner than what is indicated on the label. Time is
necessary to allow insecticide residues to break down.
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There are several different schedules for applying insecticides. You can
manage apple maggots on a regular schedule (also referred to as calendar
spraying) by treating once every 10-14 days beginning July 1. This method is
the most effective, but it also uses the most insecticide.
Another method uses the above mentioned spherical sticky traps to
determine the best timing of sprays. Place one trap at eye level on the south
side of each apple tree by July 1. Spray whenever you have trapped at least
five apple maggot flies in one week. Identifying apple maggots on a sticky
trap can be challenging, as there will be a variety of other insects that will
also be trapped. Look closely for the characteristic wings and the white spot
on the body to correctly identify it.
A third alternative is to spray an insecticide two days after any rainfall,
irrigation, or sprinkling of one-half inch or more, beginning July 1. Apple
maggots are more likely to emerge when soil is damp. This method is not
as effective as monitoring with traps, although most apple maggots are
managed this way.
Fruits of the City volunteer gleaners at Oak
Lake Orchard in Watertown, MN
Volunteer with
Fruits of the City
Volunteers make the Fruits of the City
program possible. With their help, Fruits
of the City is able to harvest and deliver
thousands of pounds of fresh fruit to
those in need each year.
We can use your help!
• Volunteers to pick fruit at our gleaning events
• Homeowners to donate unwanted fruit on their trees
• Neighborhood coordinators to help organize the volunteers in designated neighborhoods
• Donors to support our work
financially
This is a great opportunity for business,
churches, student groups and others to
get involved with our work.
To learn more about volunteer
opportunities, visit:
www.fruitsofthecity.org.
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7. Fruit Diseases
Apple Scab
The most troublesome disease for apple growers in all parts of Minnesota
is apple scab. Scab is caused by a fungus that infects both leaves and fruit.
Scabby fruit are often unfit for eating, and continued infection of leaves
weakens the tree.
Identification
Scab infections on leaves start as olive green to brown spots with an irregular
or feathered edge. As leaf infections grow, they may merge together and
assume a dark brown velvety appearance. Severely infected leaves may turn
yellow and drop prematurely. Scab infections on young fruit start out as
olive green to brown spots. As the lesions enlarge, they harden, and
eventually become black, corky, inedible areas on the fruit. Severely infected
fruit may be deformed and often crack open.
Apple scab
(Photo courtesy Wiki Commons)
Important Biology
Apple scab survives Minnesota’s winters on infected leaves that have fallen
to the ground. In spring, spores are ejected from last year’s fallen leaves
and create new infections on the young leaves and tiny fruitlets. Leaf spots
quickly mature and produce new fungal spores. These spores spread to
other leaves to create new infections throughout the growing season.
Abundant rainfall in May and early June is conducive to scab infection, and
rainy summers allow the fungus to infect trees even more severely.
Many ornamental crab apple trees are susceptible to apple scab, so the
disease can be spread to your fruit trees from nearby flowering crabs.
Plant resistant varieties
The best way to deal with apple scab is to avoid it altogether by planting
disease resistant varieties. Many varieties of apple trees are resistant or
Susceptibility to apple scab of apple
completely immune to apple scab. Susceptible and very susceptible trees will
varieties grown in Minnesota
require fungicide sprays every year to
Very susceptibleSusceptibleResistantImmune
control the apple scab fungus. Resistant
Cortland
Beacon
HoneycrispTMDayton
trees will only require fungicide sprays in
very wet years, where the apple scab
Honeygold
Fireside
Freedom
fungus is nearby in other infected trees
McIntosh
Haralson
Liberty
or in infected leaf litter. Good sanitation
State Fair
Keepsake
McShay
and cultural control practices will
Zestar!TM
Paula Red
Pixie Crunch
minimize the need for even these sprays.
Immune trees do not require any
Sweet Sixteen
Pritine
fungicide sprays at any time, and will
Wealthy
Redfree
remain disease free all season long.
Chestnut Crab
William’s Pride
Excerpts from University of Minnesota Extension Publication “Apple Pest Management in Minnesota Home
Orchards” (www1.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/)
12
Sanitation
Rake all the fallen leaves from around your trees each autumn and remove
them from the area. Infected leaves can be burned, buried or composted.
Perfect sanitation in an apple planting could, in theory at least, control the
disease. If there are other apple or crab apple trees in the vicinity of your
planting, however, spores could become airborne and drift onto your
property, starting the infection cycle again.
Pruning
The apple scab fungus needs moisture on the leaves to start a new infection.
A well pruned tree with an open canopy will allow air to move through the
tree and dry the leaves quickly. This will create an environment less favorable
to the fungi and can help reduce the severity of apple scab in a tree.
See Tree Pruning, page 17, for more information. For best pruning practices, see
“Apples and Pears in Minnesota Home Gardens” (www1.extension.umn.edu/
garden/yard-garden/fruit/apples-and-pears-in-minnesota-home-gardens/)
For more on apple scab and fungicide sprays, see “Apple Scab” (www1.extension.
umn.edu/garden/yard-garden/fruit/apple-pest-management/apple-scab/)
Cedar-Apple Rust
Cedar-apple rust is a common fungal disease in Minnesota. It requires the
presence of both Red Cedar or juniper trees and apple or crab apple trees to
complete its life cycle. Cedar-apple rust affects the appearance of an apple,
yet has little effect on the taste and other qualities. Since fungal spores can
travel distances over a mile long via wind, removing nearby cedar trees will
not necessarily decrease your occurrence of cedar-apple rust. Of trees common
in Minnesota, only Beacon and Wealthy apple tree types are considered very
susceptible to cedar-apple rust. When planting trees, consider selecting
varieties that are highly resistant such as Freedom, Liberty, and McIntosh.
For more information, see “Cedar-Apple Rust” (www1.extension.umn.edu/
garden/yard-garden/fruit/apple-pest-management/cedar-apple-rust/)
Cedar-apple rust
Fire Blight
(Photo courtesy Wiki Commons)
Fire blight is a bacterial disease that spreads naturally by rain, wind, birds,
and insects from one plant to another. Fire blight is a potentially fatal
disease that can enter fresh pruning wounds during misty or rainy weather.
For this reason, it is important to prune all apples and pears in winter. A
combination of good pruning technique and low fertilization can help
control and minimize fire blight. A few apples trees that are most resistant
in Minnesota include Haralson, Liberty, and Chestnut Crab.
For more information, see “Fireblight” (www1.extension.umn.edu/garden/
yard-garden/fruit/apple-pest-management/fire-blight/). For more on best pruning
practices, see Tree Pruning, page 17.
Fire blight
(Photo courtesy Wiki Commons)
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8. Fruit Thinning
Remove Some Fruits for Better Harvest
Removing a portion of the fruit from fruit trees often results in larger yields
of better quality fruit. Thinning during an “on” year also tends to reduce
biennial bearing tendencies of some varieties.
Unthinned, about July 1
Unthinned, harvest time
Thinned, harvest time
Thinning is best accomplished by hand picking fruits after June drop, about
July 1. Where fruits are clustered, remove all but one fruit per cluster. Space
fruits from 5-8 inches apart, removing the small insect and disease injured
fruit first. Fruits may be spaced closer together on the outside and top of
the tree than in the center, because such branches receive full sunlight.
– Deborah L. Brown, Extension Horticulturist
Excerpts from University of Minnesota Extension “Yard and Garden Brief: Thinning Fruit Trees” by Deborah
L. Brown, Extension Horticulturist (1/99)
The following suggestions are intended for owners of single fruit trees or
small orchards who plan to harvest their fruit for home use or donate the
crop to local food shelves as opposed to horticulturists working to develop
and test new strains of apples at an experimental station and who typically
leave only one per cluster when thinning:
Because the fruit-set on apple tree branches varies from singles to clusters
and from a heavy crop to none on a given branch, thinning should be
tailored to each tree, each branch, and the distribution of fruit-set. Leaving
as many as three in a cluster may be considered depending on the strength
of the branch, how many other apples remain on the branch, how many
remain on the tree, and whether one is aiming for maximum fruit size or
simply healthy development. For example, thinning to a mixture of triple
clusters, pairs, and singles on the Honeycrisp and Zestar trees at a Watertown
orchard during 2011, which was relatively dry, was not a hindrance to the
harvest of very large apples.
– Bill Hughes
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9. Fruit Bagging
Effective Alternative Pest Management
Apple bagging is a technique used by homeowners and even some west
coast commercial orchards. The bags act as a barrier to protect the fruit
against attack by summer insect pests and diseases such as apple maggot.
Individual fruits are bagged in the spring (no later than July 1st) when they
reach three-quarters inch in diameter and remain bagged until three weeks
before harvest. No additional pesticide sprays are needed once the bags are
placed on the fruit. When the bags are used on disease resistant cultivars, all
but two insecticide sprays used just after bloom can be eliminated.
Preparation
All trees should be pruned normally (see Tree Pruning, page 17). For owners
applying a minimal spray program, their trees receive a thorough dormant
oil spray during the late winter or early spring. Plum curculio attacks the
apples before the fruit are large enough to bag and codling moth can lay
eggs on the fruit prior to bagging. Therefore, before bagging, gardeners
who choose to spray apply an insecticide, such as Imidan, at the petal fall
stage and again two weeks later. Petal fall is when all of the petals have
fallen off of the blossoms. Organic growers may select Rotenone to control
plum curculio. These would be the last pesticide applications of the year
when bagging. The fruit can also be thinned at the same time that the
apples are bagged.
Bagging
Bag apples when the apples reach one-half to three-quarters inch in
diameter. There are a few different ways to bag apples. One method is to
use bags from Japan that are specially designed for fruit bagging. The most
common and cheapest method uses small plastic bags (such as sandwich
bags) and twist ties or zip bags.
(Sources of Japanese fruit bags include Apple Corps, 509-886-9204; Wilson Irrigation
& Orchard Supplies, 800-232-1174, www.wilsonirr.com; and Gardens Alive!,
812-537-8650, www.gardensalive.com.)
Testing
In their research experiment, the University of Minnesota Extension Service
used two commercial orchards and five home backyards. All apples were
bagged between June 1 and June 18. Five different bag treatments were
tested: plastic bags, brown paper bags, commercial (gray) paper bags, Saran
wrap, and zipper closure plastic bags. The bags were attached with twist ties
or masking tape. In the process, some apples were knocked off the trees.
In the experiment, the most efficient method was stapling the zipper
closure plastic bags. In the experiment, the team could apply more than 30
bags per hour. They stapled the bag one-third of the way across the zipper,
Excerpts from University of Kentucky Entomology and University of Minnesota Extension “Yard and Garden
Line News” article by Larry Zilliox (www2.extension.umn.edu/projects/yardandgarden/YGLNews/YGLNFeb0102.html)
15
Fruit Bagging
continued
slipped the plastic bag over the apple, and then zipped it closed. The apple
stem, aligned with the staple on the one side, was then secured by another
staple on the other side. Results were positive: During a summer where
maggot infestation was high and some trees were so damaged that there
was not an edible apple on the tree, the bagged apples did not show any
signs of apple maggot damage.
The Minnesota Project’s Fruits of the City program has also tested a stretch
nylon bag. Hospitals commonly use these nylon socks as “footies.” Nylon
bag advantages include ease of application, aeration of fruit, and stretching
as the fruit grows. Problems include penetration of the permeable nylon by
fungal and bacterial based diseases.
In our test the nylon bags had a significant positive effect when compared
to non-bagged apples. Overall, the fruits were larger and had fewer
blemishes. The nylon bag method did not, however, demonstrate the same
level of success as the plastic zipper bag method.
In our experiment, the plastic zipper bag method had a success rate close to
100%, while only a rough majority of the nylon bagged apples were
unblemished. While the results were much better, we weren’t exactly
excited about using plastic zipper bags as they have their own “footprint”
concerns. This becomes a personal choice for the tree owner.
10. Tree Training
(Photo courtesy Jeffrey Johnson)
Fruit tree training is the physical positioning of limbs to a desirable
orientation for optimal balance of growth, exposure, and fruit production.
Training can be accomplished through various methods, including
toothpicks or spring clothing pins to establish wide branch angles, tying to
a trellis, securing branches with bonsai wire, various lengths of lath sticks
with a “V” cut in the ends, or half-inch square sticks with nails in the ends
cut off to a point. Lath and half-inch sticks with points are placed between
the branch and the trunk to brace the branch to a desired position. Other
inventive methods may be available that accomplish the objective. Weights
are not recommended.
Training should be performed in the spring to allow for new circumference
growth to form in the new position. Training hardware shall be removed
late summer with minimal ‘spring back’ of branches.
For more information on training fruit trees, visit:
www.learningstore.uwex.edu/assets/pdfs/A1959.pdf
16
11. Tree Pruning
Pruning for Fruit Production
Pruning a tree grown for fruit is somewhat different than it is for pruning
a landscape tree such as a birch. Although there is more than one way to
prune a fruit tree, home gardeners in Minnesota commonly prune and train
using a “central leader” system. With this system a single central trunk runs
the entire height of the tree and supports the fruiting branches.
The ideal central leader fruit tree has a single main trunk and a number of
well-spaced branches. The tree’s form is conical or Christmas tree-like. This
form allows light and air to penetrate the canopy, aiding in fruit ripening
and disease prevention. Prune to keep enough open space between each
level of scaffold branches that you can imagine tossing a football between
the branches or at least a foot of vertical space between branches on the
same side of the tree.
In order to develop this framework, the first pruning task is to select and
develop what we call “scaffold branches.” These four to five scaffold
branches should begin about 30 inches from the ground (40 inches if turf
will be located beneath the branches and needs to be mowed), should be
spaced as equally around the trunk as possible and should be spaced
vertically at least six inches from one another.
Begin pruning your fruit tree the spring after you plant it by removing any
suckers originating from the base of the tree, removing any branches lower
than 30 inches and removing or reducing any branches that are competing
with the leader. If possible select four or five scaffold branches from those
that remain, pruning out any “duplicate” branches that are growing just
above or just below scaffolds. The scaffold branches should have wide
angles, at least sixty degrees relative to the trunk.
Fruit trees should be pruned on an annual basis in late
winter – preferably after the coldest weather is past – before
they break bud. Prune minimally, especially with young trees,
as excessive pruning may delay or reduce fruiting and create
too much leafy growth.
Radial arrangement
of scaffold branches
45°- 60°
Once all scaffold branches have been selected, pruning
consists mostly of removing the following:
• Any vertical branch competing with the central leader
• Dead, broken, or obviously fire blight-infected branches
• Suckers coming up from the roots or low on the trunk
• Watersprouts, which are vigorous vertical branches
• Downward-growing branches
• Vigorous new growth in the middle or upper levels of the tree. Such growth can ruin the desired cone shape of the tree. The lowest branches should always be the longest.
Optimum attachment
of scaffold branches
Excerpts from University of Minnesota publication “Apples and Pears in Minnesota Home Gardens” (www1.
extension.umn.edu/garden/yard-garden/fruit/apples-and-pears-in-minnesota-home-gardens/) by Doug Foulk,
Regional Extension Educator and Emily Hoover, Professor, Department of Horticultural Science
17
Tree Pruning
continued
Fruit Pruning Tips
Cut Outside the
Branch Collar
Prune with a Purpose
Cuts should be done as follows:
• Sanitation: Remove dead, broken, and crossing branches. Allow for good air flow.
• Structural: Minimize weak branches that aim downwards or are too vertical.
• Frame: Space branches radially and vertically.
• Clearance: Make room for traffic only as necessary.
• Balance: Unify texture and density. Remove duplicators.
Things to think about when pruning:
Branch bark ridge
First cut
notch A
Second cut
along line A-B
Third cut
along line C-D
Do not cut
along C-X
Branch bark collar
The 1/3 Rule
• Thin to a branch at least one-third the diameter of the branch removing.
• Thin no more than one-third of the live wood in any year.
For example, branch “A” is no more than three times the diameter of branch
“B.”
Reduction cut
Remove this
Branch bark ridge
Keep this
Guidelines for Pruning
• Young trees: Remove less than or equal to one-third leaf area
• Immature trees: Remove less than or equal to one-quarterleaf area
• Mature trees: Remove less than or equal to one-tenth leaf area
Join us to learn many tips like these, in detail, at our regular Fruit Tree
Pruning classes. For more about classes, see the next page.
For more information about pruning, see:
www1.extension.umn.edu/garden/yard-garden/fruit/apples-and-pears-inminnesota-home-gardens/#pruning
Pruning tips provided by Jeffrey Johnson, Minnesota Landscape Arboretum arborist
18
12. Tree Maintenance Calendar
January
February
March
• Order new fruit trees
(if planting in spring)
• Prune existing trees
(see Tree Pruning, page 16)
• Prune and train existing trees (see Tree Pruning and Tree Training, pages 16-17)
April
May
June
• Clean up fallen leaves and fruit to prevent potential for disease and insects
• Thin fruitlets
• Bag apples (optional)
• Plant and stake trees
• Thin fruitlets
• Prune existing trees
(see Tree Pruning, page 16)
• Bag apples (optional)
• Spray trees for apple scab (optional)
July
August
September
• Hang Maggot Traps (optional)
• Estimate ripeness and harvest time
• Harvest (depending on variety)
• Spray for apple maggot if trees are 3 years or older (optional)
• Harvest early fruit in late
August
• Clean up fallen leaves and fruit to prevent potential for disease and insects
October
November
December
• Harvest
• Prune (see Tree Pruning,
page 16)
• Prune (see Tree Pruning,
page 16)
• Tree wrap (see Tree Wrapping, page 6)
• Clean up fallen leaves and fruit to prevent potential for disease and insects
• Clean up fallen leaves and fruit to prevent potential for disease and insects
Fruit Tree Classes
Fruits of the City, as well as many other
organizations, offer regular education classes
on topics that help our partnering fruit tree
owners work toward higher quality fruits and
improved yields. Learn more about your trees
through these classes. Better yet, consider
bringing a young person to a class. Learn
together and enjoy your trees even more.
Please refer to our website for a list of upcoming classes:
www.mnproject.org/food-FruitEducation.html
For more information on caring for fruit trees, including pear, plum,
apple and cherry, please see the following UMN extension publications:
www1.extension.umn.edu/garden/yard-garden/fruit/
www1.extension.umn.edu/garden/yard-garden/fruit/apples-and-pearsin-minnesota-home-gardens/
19
At Fruits of the City, we take seriously the participation of each
and every individual and group, whether you are with us this year
for the first time or are a seasoned veteran.
We greatly appreciate you giving your valuable time and energy
to help someone else in need. This is special work and we are
thankful you are joining with us in providing fresh food for others.