Protecting Indoor and Outdoor Plants in Cold Weather

William Hogan  |  12/8/2011 8:09:02 PM

For plants growing in the ground, mulch with a loose, dry material such as pine straw, shredded bark or leaves.

Large plants can be covered with cloth or plastic sheets during danger of freezing temperatures.

Bring patio or outdoor plants into the home. This is a good way to protect these plants from the cold weather.

Every winter is different from the previous winter. Recently we seem to have had quite variable weather in all our seasons. It probably just seems that way. We often have difficulty remembering how inconsistent our weather is from one year to the next. One thing is for certain-it will be cold in winter. Usually it will be cold enough to do damage to many plants that we grow. If you make preparations now, it will make plant survival more probable should we have another harsh winter this year.

Regardless of the temperature, we have been very dry for the past two years. The drought continues. Water is critical to all plants, even when they are dormant. If a hard freeze is predicted, water landscape plants prior to the freeze if the soil is dry. Strong, dry winds cause damage to plants by drying the foliage. Watering before the cold front will help to prevent this. Some people believe that wetting the leaves before a freeze will give cold protection. This is really not very effective. It is better to make sure the soil is adequately watered.

Provide mulch. For plants growing in the ground, mulch with a loose, dry material such as pine straw, shredded bark or leaves. Mulches will help to insulate the root area of the plant. This only works well if the mulch is applied while the soil is still relatively warm. Mulch also helps prevent the dry winds from removing soil moisture in the areas covered. Mulches will only protect the areas they cover. They are best used to protect below ground parts such as roots and crowns. Mulch can also be an effective protection for entire low-growing plants up to a height of four to six inches. However, don’t leave entire plants covered with mulch for more than three to four days. This method is best used for short term extreme cold. Complete coverage for longer periods of time can cause more injury from lack of sunlight. Mulch can also be used to protect the graft-union on fruit trees such as citrus. Be sure that you don’t leave the entire lower trunk buried in mulch all winter. Prolonged coverage could hold too much moisture against the bark and cause decay as the weather warms. Remove mulch from the trunk after the cold danger has passed.

Smaller individual plants can be covered for protection, again for a short period of time. Cardboard or plastic foam boxes can be placed over the plant. Large plants can be covered with cloth or plastic sheets. Stakes should be used to hold the covering away from the plant foliage. To be effective, make sure the stakes are taller than the plants. The cover should extend to the ground and be sealed with soil, stones or bricks to insure insulation. Again, remove these covers after the freeze danger has passed. Many plants have been “cooked” under plastic sheets after the temperature returns to the 60s and 70s. Covering tall plants with plastic should be temporary measure, not a permanent winter condition.

What about protecting small container or patio plants from cold? As we enter into the winter months, many people bring patio or outdoor plants into the home. This is a good way to protect these plants from cold or other adverse conditions that they might experience.

Bringing outdoor plants inside can create problems for some plants. Be sure that you provide adequate light. Light requirements will vary from species to species. If you aren’t sure about the light requirement for your plant, find a good reference book and familiarize yourself. Avoid placing any plant in a drafty area. Hallways and areas adjacent to doors will have natural air current movement. This can cause leaves to break off and the plant to dry out at a faster than normal rate.

Drying out can be a special problem indoors as well as outside. Even though the plants are in a warmer place, most are actually dormant and will require less water. However, heated air dries them out. Check the soil in the container often. It is usually best to allow the soil to dry out, then water thoroughly. Frequent watering with small amounts will often keep the roots wet and can lead to root diseases. This is just a general rule to follow. Like light requirements, it is best to know the water requirements of the type of plant that you have.

When you bring a plant indoors, we also bring in its pests. These pests can prosper and flourish indoors if conditions are good. The three most common pests are scale insects, mealy bugs and spider mites. All these feed on plants by sucking juice from the leaves and stems. All are very small in size and usually present in large numbers. The scale insect is usually dome-shaped and covered with a waxy shell. They don’t move around on the plant. Many people don’t even recognize these as being insects because of their immobility. They just look like a mass of small, raised dots on the plant. The mealy bug is similar to the scale, but often appears as a cottony mass or glob on the plant. Inside the cottony mass you will find small, oval, segmented bugs. Mealy bugs often congregate at the base of the plant stem. Spider mites are really tiny. They often look like someone has dusted the plant with fine red pepper. Sometimes the group of spider mites is brownish in color.

Without natural predators to feed on them, these pests can really build up indoors. There are several ways to control them. You can take the plant outside and wash them away with a vigorous stream of water. This works well on spider mites, fair on mealy bugs and not at all on scale insects.

Horticultural oils or ultra-fine oil emulsion sprays control all these pests very well. Premixed pyrethrum insecticides work well. Systemic insecticides control the pests while giving some residual control. Regardless of the method used, I recommend that you take the plant back outside to treat it. Wait for a warm day, treat the plant and bring it back in. This will avoid a mess and a possible unpleasant smell indoors.

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