Organic Winter Care for Fruit Trees

Picture this: a perfectly planted orchard with heavily laden trees. The fruit is just about ready to harvest. You scan the branches for evidence of ripeness–and that’s when you see them. Spots! Hundreds of tiny scabs signalling Venturia inaequalis (also known as apple scab) has taken hold of your crop and will soon transform your apples from delicious to devastated.

If you dream of growing your own fruit but worry about scenarios like this one, don’t give up before you begin. The solution to growing strong, healthy fruit begins long before apples start to form–during the dormant season of late winter and early spring. Taking a few steps now can set fruit trees up for success and safeguard your crop from pests and disease.

The importance of winter dormancy

During the cold temperatures that descend on much of North America in wintertime, fruit trees may appear asleep. Several important things are taking place, however.

Fruit trees are receiving chill hours, that crucial time spent in dormancy between 32°F and 45°F. Chill hours are necessary for fruits like apples, pears, peaches, plums, apricots and nectarines to eventually produce blossoms and fruit in the spring.

Different varieties require differing numbers of chill hours, which is why we recommend planting varieties known to do well in your region. Gala apples, for example, need a minimum of 500 chill hours, while D’Anjou pears need over 800. If trees don’t receive the minimum number of chill hours required, fruit abundance and quality will suffer.

Another thing happening during the winter is that your trees are receiving a break from pests and diseases that typically challenge them during the growing season. This is a boon for gardeners and orchardists, giving us the perfect opportunity to address problems that might develop down the road. Remember the dreaded apple scab discussed above? Late winter is the best time to prevent that from happening.

To proactively care for your fruit trees, complete the following important tasks when your plants are dormant.

Related: How to Select & Care for Fruit Trees To Ensure a Bountiful Harvest

1. Clean up from last season.

If any fruits remain on your trees, now is the time to remove them. That includes the ones you’ll never eat and those scattered on the ground. In the same way, rake up all leaves from beneath your trees if you didn’t do this in the fall and snow isn’t concealing them from view. Old fruit and leaves can shelter overwintering pests, whether through eggs or simply as mature adults.

Place them away from your trees, preferably in municipal composts where available. Dress the soil at the base of the tree with finished compost or fine mulch. Being meticulous will help minimize trouble come springtime.

Remove fallen leaves and leftover fruit to minimize places for overwintering pests and diseases.

Late winter or early spring is also a good time to consider planting short grass varieties or clover beneath your trees if you prefer coverage. Avoid shrubs or tall plants under apple trees that make raking difficult. If you’re eager to plant blooming companions for pollination and beneficial insects, plant nearby, not under.

2. Apply dormant sprays.

Dormant sprays treat a range of insect pests and fungal diseases that typically overwinter on fruit trees. Since treatment takes place in the cooler season, beneficial pollinators and spiders aren’t active on your trees. Some beneficial insects and larvae can still be harmed, but there are fewer present at this time of year. In addition, the treatment is an effective control for a large range of concerns.

Generally made from two ingredients–lime sulfur and horticultural oil–dormant sprays are easy to apply and safe for humans, which is why the United States Department of Agriculture’s (USDA) organic regulations permit their use. The horticultural oil targets mites, aphids, leafhoppers, mealybugs, leaf miners and more, while the lime sulfur controls scab, peach leaf curl, brown rot, powdery mildew, and other fungal diseases. We have found the combination to be particularly effective, as long as you follow a few rules of thumb when applying.

Apply dormant spray to coat the tree, branches and buds included, until it starts to drip.

That includes applying dormant spray before the buds on your trees begin to swell. Temperatures should be above 40 F for at least 24 hours and there shouldn’t be any rain in the forecast. Treat trees early in the day so they have a chance to dry out before nighttime. Using a pressurized bottle or hose end sprayer, spray trees from top to bottom, from at least two angles, including the undersides of leaves and branches, until everything is coated and begins to drip. Avoid treating on windy days or you may lose a good portion of your spray. Also consider protecting sensitive species that might grow nearby (such as maples and nut trees) and shielding siding and patios. Reapply one or two more times before buds break in spring, under similar conditions.

3. Prune your trees.

Late winter is pruning time for a few reasons. Pruning during the dormant period means minimizing exposure via cuts to fungal diseases and pests, which are less active during cold weather. In addition, some trees will weep sap if pruned when growth has already started. Pruning in late winter, while the tree is still dormant, helps avoid excessive sap flow. And finally, dormant winter pruning enables you to see the tree’s structure more clearly, without interference from leaves and fruit.

To prune in late winter, always begin by removing dead, diseased or damaged wood. Cut back to a healthy (outward-facing) bud or branch, checking for signs of life as you cut. Next, remove shoots or branches that are crossing or aiming towards the centre of the tree. As with most pruning jobs, you’re striving to increase sunlight penetration and ventilation. Branches that reach into the centre of the tree work against this strategy.

Pruning begins with removing dead or dying wood and crossing branches.

Finally, cut back last year’s growth at the branch tips by about one third. Trim to a strong, outward-facing bud just as you did above. This encourages the tree to form lateral branches that reach away from its center. Peaches only fruit on last season’s wood, so don’t overdo things in this area when pruning peach trees. If you’re using a pole pruner for standard or semi-dwarf sized trees, consider these tips on our pre-season pole-pruner checklist.

4. Add lime to soil if required.

Liming orchard soil every two to four years is one holistic practice that can help maintain a healthy growing ecosystem for your fruit trees. It’s important not to add too much, however. The best way to establish a schedule that works for your trees is to take a soil test for pH. Fruit trees typically thrive in soil with a pH of 6 or 7. Anything more acidic, and you may need to lime more frequently until the levels are reached. The amount will depend on your soil type. Most extension offices will recommend a set number of pounds of ground limestone per 1,000 square feet, added every two years. Follow the manufacturer’s instructions while being informed by your soil test.

Once the snow melts, spread lime evenly over the soil out to the tree’s drip line, avoiding direct contact with the trunk. Water lightly to help the lime penetrate the soil. Lime takes several months to affect pH, but will work more quickly if finely granulated and mixed into the soil surface. You can also lime in the fall for better spring availability.

5. Consider copper spray.

Copper spray can be effective for dealing with a number of pests and bacterial diseases like canker and blight, but given its potential for phytotoxicity, we use it sparingly on issues with few other alternatives. Canker, in particular, can hamstring a tree and cause it to produce little, if any, fruit depending on its location on the plant. A judicious copper treatment every few years can help control this challenge. Just remember: coppery sprays may accumulate in the soil if used too frequently, thereby harming the delicate balance of beneficial microbes.

6. Treat with probiotics.

This permaculture approach to fruit tree management involves adding activated microbes to the soil and tree canopy just as your trees are coming out of dormancy. The goal is to support a plant’s ability to absorb nutrients throughout the growing season. Treating your trees with probiotics will also help colonize the area with beneficial bacteria, thereby driving out the microbes you don’t want. We include this here, since dormant season is the perfect time to hunt down probiotics, so you have everything you need when the weather turns.

Final Tips

• Always plant disease-resistant varieties to minimize challenges. Look for recommendations specific to your region, since pests and diseases can be localized.
• Provide your trees with all the essential nutrients and moisture needed during the growing season for strong overall health.
• Keep the area around the base of your tree clean throughout the year. In areas prone to fungal diseases and overwintering pests, resist planting shrubs or other vegetation that will make raking difficult.
• Conduct formative pruning when trees are young to establish open centers that will help fend off pests and disease.
• Test your soil pH and nutrient levels every few years to ensure your trees have the best growing environment possible. Amend as needed.

Organic fruit tree management

Like many things done organically, cultivating fruit trees requires balance. A gardener that invests time cultivating healthy trees in a healthy garden ecosystem will have fewer problems in the long run. That’s because healthy trees are less susceptible to pests and disease and more likely to fend off challenges when they occur.

Adopting a year-round program of organic fruit tree management that includes dormant-season activities will prepare your trees for the year ahead. Organic methods for fruit trees have been around for generations, and they can fend off even the most aggressive threats. Add these methods to resistant fruit varieties, and you’ve got a winning combination.