Apples and crabapples for cold, windy sites
Cultivar class, rootstock, pollination, fire blight, and codling moth for apples where chinooks and late frost are normal.
Apples are the tree fruit most likely to repay a careful site in the high West, and they still fail when the site, the rootstock, or the bloom time is wrong. They bloom later than apricots and peaches, which is why they crop more often. They are not immune to a May frost, and they are on Colorado State University’s list of woody plants with high susceptibility to iron chlorosis.
A yellow apple tree in wet alkaline clay is a soil and water problem as much as a cultivar problem. Read chinooks and fruit buds for the two ways a crop dies, and alkaline soil before you decide the tree is “diseased” and needs a spray.
Buy a name and a rootstock
A tree labeled only “apple” from a big-box rack is a rootstock you do not know and a cultivar that may have been chosen for a milder warehouse, not for a Laramie bench. Buy from a nursery that will say both names. The cultivar is the fruit and the bloom time. The rootstock is the size, the anchorage, and a large part of the winter hardiness.
Dwarfing rootstocks keep a tree small enough to prune, spray if you must, and cover on a bad night. They also need a permanent stake or a trellis, and they are a poor choice in an exposed wind unless you build that support.
A semi-standard or a vigorous stock stands up better on a Wyoming or Montana site and takes longer to fruit and more space to prune. There is no universal “best” stock. There is a stock that matches the wind and your willingness to stake. If the seller cannot name it, shop somewhere else.
Cultivars with a long record in cold prairie and northern climates include Haralson, Goodland, Norland, and Parkland. Honeycrisp is hardy and widely planted, and it brings a known set of orchard problems: sunscald on fruit and wood, bitter pit, biennial bearing, and susceptibility to fire blight in a wet warm spring.
It is a reasonable Front Range tree if you accept those traits and thin the fruit. It is not a carefree tree. Early summer apples such as Lodi or Yellow Transparent are useful for sauce and do not store.
A late storage apple that needs a long, hot finish will not ripen in a high valley even if the tree survives. Match the ripening season to your first frost the same way you match a tomato’s days to maturity.
Crabapples are not only ornamental. A crab that blooms with your apple pollinates it, and some crabs, Dolgo among them, make serious jelly. An ornamental crab that is disease-prone and sterile of useful fruit is a different purchase. Ask whether the crab sets fruit and whether it blooms in the same window as the eating apple.
Pollination and pruning
Most apples need a second cultivar nearby that blooms at the same time. A single tree in a new subdivision, with no crab or apple within a bee’s easy flight, will flower and then drop tiny fruit.
Two trees of the same cultivar do not pollinate each other. A compatible crab counts. Bees do not work in a hard wind or a cold rain. A sheltered site is a pollination site.
Prune to a strong shape in late winter, on a dry day, and do not leave stubs. In wind, a wide, low tree beats a tall sail. Keep the leader or the open center, whichever system you chose, and stop.
Summer pruning is for water sprouts and for keeping a dwarf inside its space, not for removing half the tree in July. Paint is unnecessary on ordinary cuts. Tar dressings hold moisture.
Thin the fruit in June so the tree is not pulling itself into a biennial habit.
Honeycrisp in particular sets a heavy crop and then takes a year off if you leave every fruit. A thinned tree also builds better spurs for next year and is less likely to break in a wind or under wet snow on a leafy, loaded branch.
Fire blight, codling moth, and hail
Fire blight is a bacterial disease that blackens shoots so they look scorched, often with a shepherd’s crook at the tip. It is worse in warm, wet spring weather and on lush growth.
The cultural control you can do without a current spray guide is to limit nitrogen, prune out strikes well below the damage in dry weather, and choose cultivars that are not known for extreme susceptibility when you are replanting.
Disinfect tools between cuts if blight is active. Extension publishes the spray options and the timing. Rates go stale. This page does not print them.
Codling moth is the worm in the apple, and it is ordinary in Utah valleys and in many Colorado towns. Sanitation, picking up drops, and bagging fruit on a few trees are the home-garden controls that do not depend on a pesticide calendar. If you want a spray program, use the degree-day timing from USU or CSU for the current year. A spray on the wrong week is a wasted spray and a hit to the beneficial insects you wanted in the pollinator planting.
Hail ruins fruit and opens wood to infection. A small tree under hail cloth is more productive over a decade than a large tree in the open on the Palmer Divide. After a storm, pick damaged fruit, cut broken branches cleanly, and do not fertilize the tree to push soft growth. Water if the soil is dry.
Site and the first years
Full sun, drainage, and a position out of the frost pocket. The planting hole is wide and no deeper than the roots, flare at grade, the same rule as the tree page. Water deeply the first two or three summers.
Do not park a lawn sprinkler on the trunk. Mulch the soil and keep it off the bark, or voles will girdle the tree under the mulch in winter. A hardware-cloth cylinder around the trunk is the vole and rabbit tool.
Deer will browse a young apple to a stump. The fence is in deer, rabbits, and voles. An 8-foot deer fence around a small orchard is cheaper than replacing trees.
Do not expect a crop the year you plant. Dwarf trees may fruit in a few years. Larger stocks take longer.
Flowers the second year are not an obligation to keep every fruit. Pull them off if the tree is still small. The structure matters more than the first apple.
Checklist
- Buy a named cultivar on a named rootstock.
- Stake dwarfs. Prefer a sturdier stock on a windy bench.
- Plant a pollinizer that blooms at the same time.
- Site the tree out of a frost pocket, flare at grade.
- Limit nitrogen to limit fire blight and soft growth.
- Thin the fruit. Do not let Honeycrisp overcrop.
- Pick up drops for codling moth, and use extension’s current timing if you spray.
- Guard the trunk from voles, rabbits, sunscald, and deer.
- In hail country, plan the cloth when you plan the hole.
Sources
- CSU Extension, Iron Chlorosis of Woody Plants.
- USU Extension, Fickle Climate Keeps Gardeners Guessing, on bench sites.
- University of Idaho Extension, BUL 859, on variety hardiness mattering more for fruit than for most shade trees, and on choosing early-maturing, later-blooming fruit where frost at bloom is likely.
- CSU CO-Horts, hail aftercare.
- PlantTalk Colorado, iron chlorosis notes that include apple and crabapple.