Apple

Clear the fallen leaves before the first snow

Once the leaves come down, get them out from under the tree before the first snowfall. Rake and burn, bury, or compost them, or run a mulching mower over them to chop them up. Pick up dropped apples too, and store the fruit you keep well away from any windfalls. Diseased fallen leaves are the overwintering site for apple scab - the fungus survives in that litter and fires next spring's spores from it, so leaves left in place are the entire seed stock for next year's infection. Dropped fruit does the same job for codling moth larvae looking for a place to spin their cocoons.

Fertilize only if last year's growth was short

Before you feed anything, measure last season's shoot growth. A bearing apple should put on about 8 to 12 inches a year and a young non-bearing tree 12 to 18 inches. If the tree hit those numbers, add nothing. If it fell short, work compost around the root zone in early spring before the leaves come out. Nitrogen is normally the only nutrient an apple needs on an annual basis. Apples are one of the few fruit trees that are far more often over-fed than under-fed. Lush nitrogen-driven growth is soft, succulent tissue that fire blight infects readily, and it delays a young tree coming into bearing while keeping an older one from setting fruit.

⚠ Keep nitrogen to the window between bloom and the end of shoot growth in early summer; feeding after that pushes late growth that will not harden off before winter (University of Wisconsin Extension, Fertilization Guidelines for Mature Apple Trees). Base any fertilizer beyond compost on an actual soil test.

Thin apple fruitletsJun

Thin to one fruit per cluster about a hand-width apart. Bigger fruit and prevents biennial bearing.

Dormant-prune your appleFeb – Mar

Cut for an open center: remove crossing/inward growth water sprouts and one of any two competing leaders. Airflow and light cut disease and ripen fruit evenly.

Cut out fire blight cankers while the tree is dormantFeb – Mar

Walk the tree in late winter looking for sunken, dark, cracked patches of bark and for blackened shoots that held their dead leaves all winter. Cut through healthy wood at least 8 inches below the discolored bark of any canker, and burn or bury what you remove rather than leaving it in the row. The bacterium overwinters at the margins of these cankers and oozes out of them right as the tree blooms, so every canker you leave is the launch point for next spring's blossom infections. Late winter is the right time because both tree and bacteria are dormant, which means the cuts cannot spread infection and will not push a flush of soft sucker growth.

⚠ If you must cut out a strike during the growing season instead, sterilize the blades between every cut with 10 percent bleach or undiluted Lysol for at least one minute.

Watch the blossoms for fire blight strikes

Through bloom and the couple of weeks after, check flower clusters and shoot tips. Look for clusters that go water-soaked then droop, shrivel, and turn brown or black, and for young shoots that wilt into a downward hook with the dead leaves hanging on. Cut any strike out at least 8 inches below the discolored bark, sterilizing the blades between cuts. Bacteria ooze from overwintering cankers at the same moment the tree blooms, and bees carry them straight into the open flowers. The infection then runs from the blossom down into the wood, so a strike caught at the flower cluster is a small cut and one caught in August is a limb.

⚠ Copper, streptomycin sulfate, and Bacillus subtilis only protect blossoms and fresh wounds - they are completely ineffective against branch cankers, so no spray substitutes for cutting infected wood out.

Dormant oil on appleMar

Apply horticultural oil at green tip on a dry day above 40F. Smothers overwintering mites scale and aphid eggs.

⚠ Read the label and don't spray in freezing weather.

Apple scab: first fungicide at half-inch green tip

When the leaf buds have swollen and opened enough to show about a half inch of green tissue, spray captan or wettable sulfur. Repeat every 7 to 10 days through the week after petal fall, tightening the interval in rainy stretches and stretching it in dry ones. By mid-June look the leaves over: if you find no scab lesions you can stop, and if you find them keep spraying through the season. The fungus spends winter in last year's fallen leaves and shoots its spores into the air as the tree breaks bud, so the new leaves are infected before any spot is visible. The spores need several hours of continuous wetness to take hold, which is why spring rains drive the epidemic and why a fungicide applied after lesions appear cannot cure them.

⚠ Do not rotate captan and lime-sulfur close together - the combination injures leaves and flower buds. Follow the label interval on the product you choose.

Codling moth: first insecticide once the petals are down

Wait until most or all of the petals have dropped from the blossoms, then spray spinosad, carbaryl, malathion, or esfenvalerate. Make a second application 7 to 10 days later. Hang a pheromone trap first if you can - if it catches no moths, you may not need to spray at all. First-generation adults emerge from overwintering just before bloom and each female lays up to 100 eggs on the developing fruitlets. The larvae tunnel straight to the core to feed on the seeds, and once they are inside the apple no spray can reach them, so the only window that works is while the eggs and newly hatched larvae are still on the surface.

⚠ Never spray before the petals have fallen - it is both ineffective and lethal to the bees still working the blossoms. Every one of these products carries a legal pre-harvest interval: read the label and observe the required number of days between the last application and picking. If you want to combine an insecticide with a fungicide, use a pre-mixed all-purpose fruit spray that does not contain carbaryl.

Pick by background color and taste, not by the calendar

Watch the background color - the part of the skin not covered in red - and start checking once it shifts from green toward greenish-yellow. Then pick a few that look ready and eat them. An unripe apple is starchy and leaves a sticky film on your teeth. A ripe one has developed its aromatic flavor and lost that starchiness - it may still taste tart, which is normal for baking and cider varieties, so judge by aroma and the absence of starch rather than by sweetness alone. Keep tasting every few days rather than picking the whole tree at once. Red blush colors up well before the fruit is actually ripe, so it is a poor signal. What you are really waiting for is the tree converting stored starch into sugar, and the background color plus the taste of the flesh are the two things a grower can read without lab equipment.