Late-ripening apples face cold threat

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Farm Forum

You cannot bring a fruit tree into the house and most trees are too large to cover so the fruit will have to tolerate any upcoming cold snap without any more protection than the surrounding leaves in the canopy. Fortunately most fruits, cherries, plums and peaches, ripen in July and August so the fruit has long been picked.

Pear harvest usually starts in late August and many, but not all, pears have also been picked.

Apples are the real concern as many cultivars do not fully ripen until late September and even October. There are many trees still loaded with fruit and apple owners are wondering what to do.

First, apple fruit can withstand at least four hours of temperatures in the 28-30 degree Fahrenheit range without serious injury. The sugars and other constituents of the fruit lower the freezing point of the flesh and they can recover just fine.

You can tell if the fruit is frozen by a simple test: stick your finger nail through the skin of an apple. If the skin “pops” and juice comes out, it did not freeze. If the skin is hard and it feels like you are poking a Popsicle, then it probably is frozen.

If it is frozen, do not pick or handle the fruit. Instead allow the apples to thaw on the tree as temperatures warm. If the apples did not freeze they will continue to ripen and can be picked at their normal time.

There may still be some freeze injury so it might not be a bad idea to pick a few apples early this week and see if the flesh has turned brown. If oxidation has developed, the fruit received freeze injury and further ripening may not occur. Even if the injured fruit left on the tree continues to ripen, it may not store as well as it normally would.

Tree watering

If you have not yet watered your trees this year, you may want to consider doing it before freeze up this fall. Even if the leaves are turning color, the tree is still preparing itself for winter. Trees should be watered until late October unless cool, wet weather prevails. This moisture is needed to allow trees to prepare for winter and reduce the extent of winter injury or winter browning.

Following are some guidelines when determining how much water your tree would need in a 10-day time frame. These guidelines can vary depending on temperatures and other conditions. Be sure to include any rainfall into your calculations:

• Small shrubs (less than three feet): 3 gallons

• Large shrubs (more than three feet): 5 gallons

• Trees (Less than 1 inch diameter): 10 gallons

• Trees (1-2” diameter): 20 gallons

• Trees (2-5” diameter): 40 gallons

• Trees (5-10” diameter): 60 gallons

If your tree is less than two years old, be sure you are applying water only once a week. Be sure to water slowly giving the water time to soak down into the root zone.

Fall tree and

shrub planting

Fall is a great time to transplant many trees and shrubs. Surprisingly to some, fall is the best time to plant evergreens. The combination of warm soils and cooler temperatures are conductive for trees to begin establishing their roots.

The key is planting now while we still have a month or more of soil temperatures above 45 degrees Fahrenheit. This is the threshold for rapid root growth and once the soil temperatures slip below this point, root growth decreases and stops.

It is critical for the roots to become established before cold soil temperatures develop so here are a few tips to help the process.

First, be sure to water the plant throughout the fall, even when the air temperatures begin to cool down. Plants need moist soils to continue root growth. Moist does not mean wet, however, so check the soil to a depth of 6 inches or so before watering. Do not add any water if this zone is still moist.

Next, place a two-inch layer of a coarse, organic mulch down around the plant. Shredded pine or oak bark is the best and have the mulch extend at least two feet out from the plant. This mulch will help keep the soil temperatures warmed a little longer into the season. Be sure to pull mulch away from six-inch ring around the base of the tree or shrubs. If mulch is placed against the trunk it can provide a nice shelter for rodents to live and feed.

What should not be planted in the fall? The list is very short but the trees that are best planted in the spring are birch, hickory, magnolia, and walnut.

Bedding plants

brought indoors

Bringing in your bedding plants can be a great way to continue enjoying a bit of the beauty that was enjoyed in the yard into your home during the cold months. Often times it’s more than just the plant that’s being brought in.

Bringing in your geraniums, impatiens and begonias can bring along several insect pests and mites that can be troublesome inside the home. The most common problems are spider mites, aphids, and white flies. Be sure you check over all of the plants you are wintering in your home very carefully for signs of these pests.

Also examine the new shoots and undersides of leaves for any signs. There are a number of indoor pesticides that than be used in concentrate, ready-to-use sprays, and aerosol sprays. Read the label carefully before use. Some products may have a bad odor so you may consider spraying your plants in the garage and then bring them back inside once the spray has dried. Just be sure your garage is not too cold for your plant.

Insecticidal soaps or ultra-fine horticultural oils are less toxic alternatives. You may also consider isolating infested plants. Remember to check nearby household plants for signs of these pests. Once the furnace is running and humidity drops, certain pests like mites can develop very rapidly.

Canning / preservation questions

If you have questions about canning or preserving your garden vegetables, please contact SDSU Extension’s AnswerLine at 1-888-393-6336. There are some handouts also available at our office if you’d like to stop by and take a look. All handouts are free.