October 25, 2014

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Apples and Pears in Minnesota Home Gardens

Doug Foulk, Regional Extension Educator
Emily Hoover, Professor, Department of Horticultural Science

Copyright  ©2003  Regents of the University of Minnesota. All rights reserved.

Apple and pear trees require patience, knowledge and skill to grow well. Despite the effort required, apple trees in particular remain a popular addition to many home gardens. Pear trees are not as commonly grown by Minnesota home gardeners as are apples. Perhaps this is due to the pear tree’s reputation for becoming very large, for its history of susceptibility to fire blight disease, or the fact that varieties hardy to our region do not include the well-known and popular ‘Bartlett’ or ‘Bosc.’ Yet, high quality, hardy pears are moderately easy to grow in the southern half of Minnesota – easier in some ways than apples. And even northern Minnesota gardeners have a hardy option.

Varieties and Rootstocks

Selecting Apple and Pear Varieties

Apple flowers must receive pollen from another variety of apple to produce fruit. Therefore, plan to plant two or more varieties of apple, unless there are ornamental crabapple trees or other apple trees in your neighborhood. Two trees of the same variety cannot provide pollen to each other. Apples are insect pollinated, with bees and flies transferring pollen from flowers on one tree to those on another.

Pear trees, as a rule, also require cross-pollination by another pear variety to produce a large crop. However, evidence indicates that some pear varieties may be self-fruitful under some conditions, and you might be able to get a small amount of fruit with only one tree. At the other end of the fruitfulness spectrum, some varieties are pollen sterile, meaning they do not have the ability to pollinate another tree. If you plant a pollen-sterile variety, you may need to plant a third variety in order to get fruit on all three pear trees. Like apples, pears are insect-pollinated.

When choosing which apple varieties to grow, consider what you plan to do with the fruit. If your goal is to have a supply of fruit to eat for snacks and desserts, you probably will want to choose an early variety and a later one, so that you are not overwhelmed by too many apples all at once. If you want to dry, can, freeze and/or press cider from the fruit, you may be able to handle two trees’ worth of fruit ripening at the same time.

The varieties shown in Table 1 are recommended on the basis of their suitability for the four fruit zones shown on the map. Where higher-quality varieties are not cold-hardy enough, lower quality varieties have been listed. Note that the fruit zones on the map correspond approximately to USDA plant hardiness zones; however, they are not identical to the USDA zones.

See the publication “Apples for Minnesota and Their Culinary Uses,” and the “Apples” section of the “Commercial Fruit Production in Minnesota” web site, for more information about listed apple varieties.


Fruit Hardiness Zones
These zones are based upon, but are not identical to, USDA Plant Hardiness Zones.

 

Table 1. Apple Varieties Recommended for Minnesota Fruit Zones.
Varieties are listed in order of ripening, from mid-August through mid-October.

 

Fruit Zones

 

4b

4a

3b

3a

Early-Maturing Apples

Oriole

x

x

x

 

Mantet◊

x

x

x

t

Hazen

x

x

x

x

State Fair

x

x

x

 

Beacon◊

x

x

x

 

Zestar!™

x

x

t

 

William’s Pride**

x

x

   

Paulared

x

x

   

Chestnut Crab

x

x

x

t

Centennial Crab

x

x

x

t

Whitney Crab

x

x

x

t

Wealthy◊

x

x

   

Red Baron

x

x

x

 

Mid-Season Apples

Sweet Sixteen

x

x

x

 

McIntosh

x

x

   

Honeycrisp™

x

x

x

 

Cortland

x

x

   

Northwestern Greening

x

x

   

Prairie Spy◊

x

x

   

Liberty**

x

x

   

Redfree**

x

x

   

Late-Maturing Apples

Haralson/Haralred

x

x

x

 

Honeygold◊

x

x

   

Regent

x

x

   

Fireside/Connell Red

x

x

x

 

Keepsake

x

x

x

 

Pears

Summercrisp

x

x

   

Ure

x

x

x

t

Gourmet

x

x

   

Luscious

x

x

   

Parker

x

x

   

Patten

x

x

   

University of Minnesota Introduction

x

suitable for this zone

t

trial in this zone

higher than average susceptibility to fireblight

**

resistant to apple scab


Selecting Pear Varieties

The varieties we purchase at the grocery store – ‘Bartlett,’ ‘Bosc,’ and the pricey Asian pears – are not hardy here. The good news, however, is that the main differences between grocery store pears and those we can grow here are size and fresh fruit keeping ability. Pears for Minnesota are smaller and do not keep as well. But in terms of quality, Minnesota-grown pears should not disappoint.

Gourmet: From South Dakota State University, ‘Gourmet’ produces medium-sized fruit in mid- to late September that are juicy and sweet with a firm, crisp texture somewhat reminiscent of an Asian pear. ‘Gourmet’ is pollen-sterile, so it cannot be used to pollinate a second pear tree. It is somewhat resistant to fire blight.

Luscious: Also from South Dakota, ‘Luscious’ bears medium to medium-small fruits in mid to late September with a flavor similar to ‘Bartlett,’ but more intense. Texture is firm but melting. Like ‘Gourmet,’ ‘Luscious’ reportedly is somewhat resistant to fire blight and is pollen-sterile.

Parker: An older University of Minnesota release (1934), ‘Parker’ produces fruit similar in size, flavor and texture to ‘Bartlett.’ Somewhat less hardy than other varieties listed here, it may not grow well north of the Twin Cities. Harvest mid-September.

Patten: Originally from Iowa, ‘Patten,’ like ‘Parker,’ produces fruit comparable in character to ‘Bartlett.’ Hardiness is slightly better than ‘Parker.’ Both ‘Parker’ and ‘Patten’ are reputed to produce some fruit without a second variety for cross-pollination. Harvest mid- to late September.

Summercrisp: Released by the University of Minnesota in 1985, ‘Summercrisp’ produces medium-sized, red-blushed fruit that is mild and sweet with a crisp texture strongly reminiscent of an Asian pear. Hardy in most of Minnesota and moderately resistant to fire blight. An early variety—harvest in mid-August.

Ure: Developed in 1978 at the Morden, Manitoba Research Station, and potentially hardy through most of Minnesota, ‘Ure’ produces small, juicy ‘Bartlett’-type fruit with good flavor when perfectly ripe. In areas too cold for other pear varieties, ‘Ure’ may be grown with the inedible Siberian pear (Pyrus ussuriensis) for pollination. ‘Ure’ ripens in mid-August.
Other reputedly hardy pear varieties may be available through various mail-order sources, but have not been tested by the University of Minnesota. Grow untested varieties on a trial basis only.

One other cultivar of interest, Golden Spice, is a variety released by the University of Minnesota breeding program in 1949. It is still sometimes seen in nurseries. ‘Golden Spice’ is hardy into USDA Zone 3, making it useful as a pollinizer for ‘Ure.’ Small 1¾-inch pears ripen in September; however, confusion exists as to eating quality. Some sources report the fruit to be spicy and pleasant for fresh eating, while others report bitter, inedible fruit. Whether the reason is misnamed nursery stock or a flavor that varies widely depending upon site, weather and/or harvest timing, you may not want to choose ‘Golden Spice’ as your primary variety.

Disease-Resistant Apple Varieties

There are a few varieties of apple available that are resistant to apple scab, the most important and destructive disease of apples in Minnesota. ‘Liberty,’ ‘Redfree,’ and ‘William’s Pride’ are all scab resistant. Scab resistant varieties will not require fungicide sprays for this disease, an appealing factor for many people. The quality of the fruit from these disease-resistant trees is acceptable, although it may not measure up to that of some other varieties recommended in Table 1 for zones 4a and 4b. However, home growers who prefer not to spray fungicides may enjoy growing these varieties. Scab resistant varieties, however, are not resistant to insect damage and may still require insecticide sprays to manage insect pests.

Dwarfing and Standard Rootstocks

When purchasing an apple or pear tree, one is actually selecting a plant made up of two genetically different individuals grafted together, the scion and the rootstock (Figure 1). The scion is the aboveground part of the tree that produces the type of fruit desired (for example, ‘Keepsake’ or ‘Summercrisp’). The rootstock, on the other hand, plays a major role in determining the tree’s ultimate size and how long it will take to bear fruit. When purchasing an apple or pear tree, you should know both the scion and the rootstock you’re getting.

click to enlarge
Figure 1. A graft union, the point where the scion and rootstock have been joined together.

Seedling or standard rootstocks may cause the tree to grow 20 or more feet tall. Dwarfing rootstocks reduce tree size by up to 75%, so that a tree may be only 8, 12, or 15 feet tall when mature, depending upon its rootstock, scion variety, and growing conditions. Whether the fruiting variety is grafted onto standard or dwarfing rootstock, the fruit size and quality will be the same. Standard trees can yield up to 10 bushels of fruit per tree. Dwarf trees are likely to produce 2 to 3 bushels per tree.

Choosing an apple or pear tree on a dwarfing rootstock has many benefits. Because the trees are shorter than standard trees, pruning, pest control, thinning, and harvest are all simplified. Trees grafted to dwarfing rootstocks require only 3 to 4 years to begin bearing fruit, while standard-sized trees may require eight years or more. Because the trees are also proportionally narrower in spread, you may be able to fit two or three trees into a small space, making them a better choice for the urban landscape.

There are, of course, advantages to standard sized apple trees as well. Standard rootstocks are more tolerant of both wetter and drier soils, and are better anchored than are the dwarfing types. If these factors are of primary importance to you, and you have the space, then a standard sized tree may be your best choice.

Apple Rootstock Options

Apple rootstocks commonly available to the home gardener include:

SEEDLING: A ‘seedling’ rootstock is actually grown from the seed of an apple, often McIntosh or another common, hardy variety. Although one will not know exactly what one is getting with a seedling rootstock—every single seed is a genetically different individual—hardiness, anchorage and adaptability to different soil types are generally excellent.

MM.111: This rootstock, sometimes termed ‘semi-dwarfing,’ other times ‘semi-standard,’ produces a tree about 80 percent the height of a standard tree. In many areas of Minnesota, this can work out to roughly a 14-18 foot tree. MM.111 is a hardy, well-anchored rootstock that can withstand drier soil conditions, making it an excellent choice, especially for western parts of the state.

M.7a: (also: EMLA 7) This semi-dwarfing rootstock produces a tree 10-14 feet in height. Trees planted on M.7a generally do not require staking, except on windy sites. M.7a would seem to be a good compromise between the standard and truly dwarfing rootstocks. Although it is the least hardy of the group and may sustain damage during unusually cold, snowless winters, it has generally performed well in our climate. It has a tendency to sucker profusely.

M.26: (also: EMLA 26) This dwarfing rootstock produces a tree 8-10 feet in height. Trees planted on M.26 generally require staking for the first few years of growth or, on windy sites, for the life of the tree. M.26 is reliably hardy, does not sucker as much as M.7a, but is especially susceptible to fire blight, a disease that can shorten the life of the tree if not carefully managed. Fruit is produced very early in the tree’s life, sometimes within three years from planting.

Pear Rootstock Options

The University of Minnesota has long advised gardeners to plant pear varieties grafted only to hardy seedling pear rootstocks to ensure survival in Minnesota. The primary drawback to the seedling pear rootstock, however, is that it produces a fairly large tree, 25 or more feet tall at maturity. A tree this large is difficult to care for and can be impractical in the urban landscape. Fortunately, pear rootstock options have improved for Minnesota fruit growers.

A planting of pear trees on “Old Home X Farmingdale” (OH X F) semi-dwarfing rootstocks at the Horticultural Research Center in Chanhassen has performed quite well for the last decade. Such rootstocks may well prove to be hardy enough for our region. Some resources suggest mulching a dwarfing rootstock to a level above the graft union in winter for protection from severe cold. If you elect to follow this advice, wait until the ground freezes to apply the mulch and be sure to pull the mulch away from the trunk again in early spring.

Most dwarfing rootstocks grafted to pears in colder regions carry an OH X F designation followed by a number. For example, pear trees produced by a local wholesaler are grafted to the semi-dwarfing rootstock OH X F 333, one of the reportedly hardiest semi-dwarfing rootstocks. Although mature tree size will vary based upon site, scion variety and cultural practices, expect a tree in the 12-15 foot range on this rootstock.

Site Selection

Apple and pear trees require a site in full sun, so choose a spot where the sun shines directly for at least 8 hours each day. Because they bloom fairly early in spring, the trees should not be planted on low sites where cold air may settle.

Any good garden soil should suffice, but avoid areas where water stands for several hours after a rain. Good drainage is important to the health of fruit trees. The pH of the soil should be slightly acidic to neutral, about 6 to 7. Conduct a soil test to determine soil conditions before planting and amend the soil as suggested by the results. Pick up a soil test form at your county Extension office, or see http://soiltest.cfans.umn.edu/submitti.htm.

How much space do you need for apple or pear trees? A good rule of thumb for a home garden fruit tree is to provide at least as much horizontal space as the anticipated height of the tree. Closer planting will make training and management of the trees difficult, and the trees may shade each other so that fruit quality is harmed. For standard trees, allow 20-25 feet in all directions from buildings or other trees. Allow 12-15 feet for semi-dwarf trees and 8-10 feet for dwarf types. For best pollination, plant your apple or pear trees within 100 feet of each other.

Planting Fruit Trees

Dig a hole for each tree that is no deeper than the root ball, and about twice as wide. When you dig the soil out of the hole, pile it on a tarp or piece of plywood so it’s easier to get it back in the hole. You may mix in up to one-third by volume compost, peat moss, or other organic matter. Most of what goes back in the planting hole should be native soil. This is particularly important in heavy soils. There is no need to add fertilizer to the hole or to the backfill soil.

Apple and pear trees may be sold bare-root or in containers. If purchasing bare-root nursery stock, closely examine the root system and remove encircling roots or J-shaped roots that could eventually strangle the trunk. For containerized trees, inspect the root systems for encircling woody roots. If woody roots are wrapped around in a circle, straighten them or make several vertical cuts through the root ball prior to planting. This may seem destructive, but it actually helps the plant produce a stronger root system and prevents the formation of girdling roots that eventually weaken the tree. For more information, see “A Practitioner’s Guide to Stem Girdling Roots of Trees“.

Position each tree so that the graft union (identifiable as a swelling several inches above the root system) is 2 to 4 inches above the soil line. If the graft union is placed close to or below the soil line, the scion will take root, causing a semi-dwarf tree to grow to full size. Spread the roots of bare-root stock, making sure none are bent. Have someone help you get the tree standing up straight. Begin adding the backfill soil, removing air pockets as you go.

After the hole is filled, tamp gently and water thoroughly to remove air pockets. The soil may settle an inch or two. If this happens, add more soil. Throughout the life of the tree, you should water its root zone thoroughly during the growing season whenever there is a dry spell. Ideally, the tree should receive one inch of water from rainfall and/or irrigation every week from May through August.

Apply wood chip mulch four inches deep in a three-foot circular area around the tree. Keep the chips away from the trunk of the tree. The mulch will keep weeds and lawn grass from competing with the tree for water and nutrients, while also contributing organic matter to the soil and moderating soil temperatures in the root zone. Reapply the mulch every few years as it breaks down.

It’s a good idea to stake the tree for the first few years. Either a wooden or metal stake will work. It should be six to ten feet long, and pounded two feet into the ground. Use a wide piece non-abrasive material to fasten the tree to the stake. Narrow fastenings such as wire or cord may cut into the thin bark.

Tree Guards

Planting time is a good time to install a tree guard to protect your tree from winter injury and bark chewing by small mammals. One type of tree guard is a plastic spiral. These exclude voles (“meadow mice”) and rabbits, preventing them from feeding on the bark. The white plastic also reflects sunlight from the trunk, which helps prevent the trunk from heating up on a cold, sunny winter day. If the bark temperature gets above freezing, water in the conductive tissue under the bark becomes liquid and begins to flow through the cells. When the sun goes down or behind a cloud, the liquid water suddenly freezes, damaging the cells and sometimes killing all the conductive tissue on one side of the trunk.

Plastic tree guards are not a perfect solution, however. Because some types fit tightly to the trunk, they can cause the bark to stay moist, leading to disease. They also can constrict the trunk as it grows. If you use plastic tree guards, make sure they are pushed down into the soil to a depth of two inches. This will keep voles from burrowing under them to get at the trees. Loosen the guard periodically, if necessary, to allow the tree to expand. The best way of using a plastic tree guard is to remove it for the growing season and put it back on in fall.

Another option is to put a hardware cloth cage around the base of the tree. Like a plastic tree guard, it should be pushed into the soil to prevent entry of voles. It should extend up the trunk to just below the first branch, and should not fit tightly around the tree. Leave a few inches of room for the tree to expand. The hardware cloth cage will not protect the tree against winter injury, so if you plan to use this method, first paint the trunk of the tree with white latex paint. The paint will reflect the heat of the sun just as the white plastic tree guards do.

Once the tree has rough and flaky mature bark, neither winter sun nor chewing animals can harm it, so tree guards will not be necessary. For the first years of its life, however, it’s important to protect the trunk of your fruit tree.

Tree guards should prevent vole damage and reduce rabbit damage (Figure 2). When the snow is deep, however, rabbits can eat branch tips and strip bark on scaffold branches. Leaving pruned branches on the ground may be an effective method to reduce this kind of damage. The rabbits will chew the bark from the branches and leave the living trees alone as long as the branches remain above the snow. Rodenticides should be avoided, especially in urban areas where pets may find the poison.

click to enlarge
Figure 2. A young apple tree with a trunk guard. The guard prevents damage caused by rodents, mowers and string trimmers, and helps prevent winter damage as well.

Limiting damage caused by deer may be more difficult. Deer typically eat branch tips throughout the year, but particularly in winter. One method of control is to hang a very strongly scented bar of soap in each tree in summer. The deer do not like the smell of the soap and are discouraged from eating the tree. Since the deer may become desensitized to the soap over time, you may need to periodically change the brand of soap.

Other repellents, such as spray-on bittering agents, may discourage browsing by deer. Keeping a dog in the yard will also provide some protection. Some home fruit growers construct chicken-wire cages around their fruit trees to keep deer from eating their trees in winter. These structures may be unsightly but effective. Reducing the deer population is a temporary solution at best, and an option not available to fruit growers except those in rural areas.

Pruning and Training

Pruning for Fruit Production

Pruning a tree grown for fruit is somewhat different than it is for 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, where 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. The goal in pruning fruit trees is to develop and maintain this conical form, always keeping the central leader the tallest and most vigorously growing shoot, and allowing the lowest branches to spread the widest. Prune to keep enough open space between each level of scaffold branches that you can imagine tossing a football through: at least a foot of vertical space between branches on the same side of the tree.

For a nonbearing fruit tree, prune to develop a basic structural framework that will support future crops. In order to develop this framework, the first pruning task is to select and develop what we call “scaffold branches.” These 4 to 5 scaffold branches should begin about 30 inches from the ground (40 inches if turf will be located beneath the branches and need to be mowed), should be spaced as equally around the trunk as possible and should be spaced vertically at least 6 inches from one another.

Begin pruning your fruit tree when you plant it. Remove any suckers originating from the base of the tree. Remove any branches lower than 30 inches. Remove or cut back any branches that are competing with the leader. Now select 4 or 5 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.

If you have purchased a smaller tree with little or no branching, remove any branches, and prune the trunk to about 30 to 40 inches above the ground. Pruning the trunk back in this way will induce branching, resulting in scaffold branch options the following year. This may be a difficult cut to make, but it will be worth it!

After the initial pruning at planting, 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. Once the first set of scaffold branches has been selected, select a second set above it, with the new scaffold branches beginning about 12 inches above the top branch of the first. Always keep the conical form in mind.

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.

The need for annual pruning is a good reason to choose dwarf or semi-dwarf trees, since it’s safer and easier to prune from the ground or from a low ladder.

Fireblight, a serious and potentially fatal disease, can enter fresh pruning wounds during misty or rainy weather, so it is important to prune in winter. If you must prune during the growing season, to do it on a day when no rain is forecast and the air is dry. For more information about fireblight, see the Yard & Garden Brief “Fireblight”.

Pruning a mature apple or pear tree that has been neglected for several years can be a challenge. For information on approaching this task, see the “Renovating Old Fruit Trees” section of the Penn State publication, “Fruit Production for the Home Gardener”.

Training

As you prune your young tree to achieve a good form, you may also need to train it. Training primarily consists of bending young, flexible branches that are growing vertically into more horizontal positions, toward an optimal 60 degree angle from the main stem. Pear branches in particular have a tendency to grow in a more vertical fashion than is optimal for early fruit production, although apple branches can also grow too vertically. Some apple varieties produce strongly vertical growth and need more training; others tend to produce branches that are naturally well-angled.

Training branches at about a 60 degree angle from the main stem slows down the production of new leaves and branch growth, and encourages fruiting. The more vertical a branch, the more vigorously it grows, and the less fruit it tends to produce. Branches that have relatively wide crotch angles are also stronger and better able to support the weight of the crop. Branches that grow more vertically often break away from the tree under the weight of fruit. You don’t want to train a branch to be truly horizontal or to grow downwards; it should still be growing more or less upwards.

If a young branch is well placed, but has a narrow branch angle, the use of a device called a “spreader” may help. The spreader—as simple as a notched stick, but otherwise available in various forms at a well-stocked garden center—is wedged in between the branch and the trunk to create a wider angle. To train new branches less than six inches in length, use a wooden spring-type clothespin. Clip the clothespin onto the leader and position the flexible shoot between the other ends of the clothespin. Move the clothespin up or down the leader until you have the young shoot at the proper angle. Always go back and remove the spreaders at the end of the growing season.

Mineral Nutrition

Once established, an apple or pear tree planted on a favorable site, in properly prepared soil, should thrive with minimal fertilization. Nitrogen is normally the only mineral nutrient that needs to be added on an annual basis.

The branches of non-bearing young apple trees will normally grow 12 to 18 inches per year (15 to 20 inches for pears), while the branches of bearing apple trees will grow 8 to 12 (8 to 15 for pears) inches in a season. If growth exceeds these rates, apply no fertilizer at all, as excessive growth inhibits fruit production, and lush growth is more susceptible to fireblight infection. If growth is normal, however, apply a low-phosphorous fertilizer, such as a lawn fertilizer containing no herbicide, at the rate of 1 ounce of actual nitrogen per year of tree age, not to exceed 16 ounces per tree.

To calculate the amount of fertilizer to apply, divide the actual nitrogen needed by the percentage nitrogen (indicated by the first number in the three-number analysis listed on the bag, e.g. 28-0-5) in the fertilizer. For example, you would calculate an application of ammonium nitrate (33-0-0) for a three-year old tree this way:
3 ounces actual nitrogen ÷ 0.33 nitrogen in fertilizer = 9 ounces fertilizer.

Thinning Fruit

Both apple and pear trees will set abundant crops of fruit if conditions are good during bloom. Some of the fruitlets will drop in mid-June, but the tree may be left with more fruit than is optimal for fruit quality development. Heavy crops can also result in limb breakage, especially in younger trees. In addition, heavy crops can cause a phenomenon known as biennial bearing, in which a heavy crop is followed the next year by little or no crop. Fruit thinning can minimize biennial bearing.

Thin the crop within the first month after bloom occurs, when the fruits are still marble-sized (Figure 3). Aim for one fruit per cluster, or for truly optimal fruit quality, about eight inches between fruits on any branch. Leave more fruit on the outer portion of the tree and less in the shaded center, where it will not get good sunlight. Although it may be difficult to make yourself remove fruit, the quality of the apples or pears you will harvest in the fall will be greatly improved by thinning.

click to enlarge
Figure 3. Apple fruitlets should be thinned within the first month after bloom, when they are still marble-sized.  

Insects and Diseases

Apple Pests

Apples are hosts to many insects and diseases. Some common diseases include apple scab and fireblight. Some common insect pests on apples are apple maggot, plum curculio, and codling moth. Growing clean fruit requires a careful program of sanitation and, often, spraying chemical pesticides.

Apple scab is the most damaging disease of apple trees in Minnesota. Scab spores overwinter on fallen apple leaves, so removing all leaves from under the tree in autumn can lessen the severity this disease, although it may not prevent it. Some varieties are resistant to apple scab; see Table 1. The Yard & Garden Brief “Apple Scab” contains detailed information about identifying and controlling this disease.

The most damaging insect pest in most Minnesota home orchards is the apple maggot, a small fly whose larvae tunnel through the flesh of the apple, making it inedible. For information on managing this pest, see “Apple Maggot Management in Home Gardens”.

A new non-chemical technique for preventing apple maggot involves fastening plastic sandwich bags over the apples when they are still small and green. The apples develop normally inside the bags, and the adult flies cannot lay eggs in the flesh. Clip the lower corner off the bag so that any rainwater can drain.

Many pest insects overwinter in weedy areas near the trees. Thorough clean-up of flower beds and vegetable gardens may reduce overwintering sites for these pests.

For information on chemical control of insects and diseases, refer to the spray schedule given in FO-0675, “Home Fruit Spray Guide”.

Pear Pests

Although pear trees are generally susceptible to a number of disease and insect problems, the fact that they are relatively uncommon in the Minnesota landscape often prevents these problems from becoming severe for home gardeners. As more people add pears to their gardens, this situation may change. For now, however, sanitation (promptly removing and destroying fallen fruit and leaves), cultural practices designed to promote optimum tree health, and perhaps occasional physical or chemical intervention are all that is normally needed to obtain a satisfying crop in most years.

Fireblight easily ranks as the major pest of pears in Minnesota. This bacterial disease has the potential to spread quickly and damage—or even kill—unprotected trees. However, in a home garden situation, the observant gardener can keep this problem from getting out of hand. The best solution is to choose varieties with some resistance to the disease. If fire blight symptoms are spotted, infested branches should be promptly removed. For more information on managing fireblight, refer to the Yard & Garden Brief “Fire Blight”.

The same insects that are pests of apple – codling moth, plum curculio and apple maggot among them – may harm developing pear fruits as well. However, damage is often not serious enough to warrant chemical control.

Harvest and Storage

Apples

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 ground 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.

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. You may need to pick the fruit several times over the course of a week or two, in order to get all the fruit at the right stage of maturity.

To pick an apple, gently take the fruit in the palm of your hand, then lift and twist in a single motion. Alternatively, use one hand to hold the short, thick fruiting spur that bore the apple, and the other hand to lift and twist the fruit. Avoid pulling or yanking the fruit, as you could pull off the spur, taking with it next year’s flower buds.

Apples last the longest in home storage at standard refrigerator temperatures, about 33 to 38 degrees F, with about 85 percent humidity. Although garages, basements, and root cellars may provide adequate storage conditions, the best place to store apples at home is usually in a refrigerator. Warmer temperatures always shorten the storage life of apples. Apples stored near 33°F may last as much as 10 times longer than apples stored at room temperature.

High humidity helps reduce the shriveling of apples in storage. If the storage environment is low in humidity, as most refrigerators are, the fruit should be stored in a perforated plastic bag or a loosely covered container.

Although apples may be displayed in a fruit bowl at room temperature for a short period, such conditions will dramatically reduce their usable life.

Pears

The most common mistake novice pear growers make is to let the fruit 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. A pear fruit is ready to harvest when:

  • 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

To harvest a pear, gently take the fruit in the palm of your hand and lift and twist in a single motion. Alternately, use one hand to hold the spur and the other hand to lift and twist the fruit. Avoid pulling or yanking the fruit; such an action may well remove the small woody “spur” to which the stem of the fruit is attached, taking with it next year’s flower buds.

Harvested pears that will not be eaten within a few days should be promptly refrigerated. Place the fruit in perforated plastic bags or a loosely covered container. This will help increase humidity levels around the fruits while allowing the exchange of gases that accelerate ripening. To fully ripen the fruit, remove it from refrigeration and allow it 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.

The exception to these harvest guidelines is ‘Summercrisp’ which should be picked when still green with a red blush, and should not be ripened before eating.

Conclusion

The growing of apple and pear trees requires attention to detail in a number of areas—site selection, scion/rootstock selection, soil preparation, pruning, mineral nutrition and pest management. The reward, however, is high-quality, tree-ripened fruit unlike almost anything one can buy at the grocery store. For such a reward all the effort may be worthwhile.

The authors wish to extend a special ‘thank you’ to Jill MacKenzie, former Research Associate, and David Bedford, Horticultural Scientist, for their invaluable contributions to this publication.