How to Mulch Plants to Protect From Frost

Jeanne Grunert
Tropical plants need to be covered for winter.

Plants are adapted to the climates in which they are developed. People dig up plants in their natural environment and plunk them down in gardens throughout the world. As a result, some plants need winter protection. Tropical plants such as banana trees, cannas, and certain fruit trees may need to be wrapped or mulched against harsh winter conditions. Other plants need a thick bed of mulch. Before heading to the garden center to purchase supplies, know the basics on gardening zones and conditions and your plant's unique needs.

Check Gardening Zones First

The USDA Hardiness Zone or gardening zone refers to the general area in the United States that has a common spring last frost date or frost free date and fall first frost date. These dates can vary from year to year and place to place in any given year, but the average is what counts, and it's the average that's used to calculate the dates you see in any given gardening zone range. These dates guide when tender annuals can be planted and tell gardeners the date by which tender plants must be protected. They also provide guidance on the average cold temperature during the winter months. The lower numbers indicate colder winter temperatures and shorter growing seasons while the higher numbers reflect milder winter conditions and longer growing seasons. Most of 48 contiguous United States are between zones 3 and 9, with a large swath in the temperature path of zones 6 and 7. Why do you need to know your gardening zone? Remember that plants are adapted to thrive in the conditions under which they grow in nature. If your plant hails from a tropical zone and you're growing it in a New England zone 5 garden, you will need to provide winter protection. A plant from China, however, may naturally grow in zone 6-like conditions, so wintering it over in zone 7 isn't difficult and probably requires no special care.

Research Your Plant Needs

The next basic to understand is the plant's individual needs. There are too many plants to cover in one article on how to cover plants when cold outside, but certain plants almost always require some special care. These include:

  • Fig trees: In most gardening zones in the United States, fig trees need special protection against the cold.
  • Tropical plants: Banana trees, palm trees, cannas and other tropical plants should either be moved indoors or covered for protection.
  • Roses: In many gardening zones, roses benefit from a blanket of insulating mulch.
  • Perennials: Most perennials also benefit from a thick layer of mulch. This prevents the soil around the base of the plant from heaving, which occurs when soil freezes, thaws and freezes again, sometimes pushing the plant right out of the ground.

If you know the name of the plant, check resources online or seek help at your local garden center or county cooperative extension.

How to Mulch Plants When Cold Outside

Depending on the plant and zone, here are two basic techniques for covering plants during winter.

  • Mulch: Use wood chips, shredded pine or other mulch suitable for plants. Spread it around the plant from the crown out to the circumference of the leaves and a little beyond. You may also want to spread a thick layer of mulch all around the plants; this suppresses weeds and maintains a good amount of moisture in the soil.
  • Wrap or mulch inside a frame: For tropical plants that can't be moved indoors, you may need to create a frame and pack mulch between the tree and the frame. Stretch woven wire mesh around poles to make a circle around the tree's trunk, then pack it full of leaves or mulch.

Certain plants should be moved inside during the winter months and cannot be protected outdoors. These include ferns, often used to decorate porches during the summer months, spider plants, geraniums, and similar plants. Be sure to give them a good squirt with the hose before moving them inside to knock any insect pests off the plant.

Know When to Start

Whether you try to winter over plants in place with mulch or bring them indoors, the time to tackle this chore is in the fall before the first frost. Take good care of your plants now and enjoy them for many years to come.

How to Mulch Plants to Protect From Frost