Winter care for your plants

Temperatures are getting colder. We will likely soon face a killing frost. I generally consider this a cold snap below 28 degrees Fahrenheit. When that happens, things start to go dormant during the winter months. We often receive many inquiries this time of year regarding specific questions about how to prepare perennials such as trees, shrubs and other flowers for the winter here in ND and East Mt.

The big thing we usually remind people about is still water. Even though there is a great abundance of moisture in some years, we must ensure that we continue to provide it as the days go by. This should of course occur on an “as needed” basis.

We often receive a reprieve from winter temperatures during November and December. When this happens, we often do not receive any rain or snow that contributes to the moisture fall and the ground can become fairly dry before or as it begins to harden in the winter. This can be very dangerous for all perennials in our climate.

The reason for this risk is as follows.

Wet soil insulates from the cold, while dry soil does not. This can cause many problems for plants but I will summarize the two main problems. First, when plants store their energy in their root systems, they store it at a level that rarely reaches freezing temperatures. When the soil dries out and the cold can move further than usual, it can become a challenge for those plants. Second, dry soil does not retain temperature the same way as moist soil. This problem becomes especially critical in the spring of the year. As we begin to see warmer temperatures in April, the soil begins to warm with the heat of the sun. If the soil is dry it heats up much faster than if it is insulated and kept cold by water and ice. When this happens, many plants are tricked into thinking it’s time to wake up for the year when they have to “stay in bed” for a few more weeks. This can expose them to spring frosts that can damage young buds or flowers. Take care to ensure that the plants receive adequate amounts of moisture until the ground begins to freeze.

Other perennials such as perennial grasses, peonies, daylilies, etc. can be defoliated at any time after they have been exposed to frost. They will not produce leaves from the leaves they planted this year. New growth will emerge from the roots in the spring. Cut foliage to or near ground level.

Below I will outline some helpful tips for specific perennials.

Rose care:

Remember to allow roses to experience a killing frost of about 25 degrees Fahrenheit. After this happens, you can cut the leaves and stems to between 9 inches and 1 foot. Roses can and should be covered to provide a layer of protection from the cold. Do not add any mulch until air temperatures are rarely above freezing during the day. Adding mulch too early can create a warm environment under the mulch for mold and fungi to grow which may actually be more harmful than cold. In general, you should wait to cover anything until temperatures are above freezing during the day.

Caring for evergreen plants:

Some people often contact us in the fall with concerns that their evergreen plants are dying because they have needles that are turning brown and falling off. This is a natural process for all evergreen plants. Although they keep their needles throughout the year, they go through a period of time where they shed their needles in the third year and older. Often these needles have become too old, or are in a place on the plant that no longer receives the appropriate light for them to be useful and thus the plant discards them. Again, this is normal but usually occurs within the plant. If you see needles turning brown from the tips back toward the trunk, that’s a different problem. Winterburn is a common problem for evergreen plants in our climate, especially for young plants. We often do not receive the snow we need to protect them from the cold and so we can think of other ways to protect. Some wrap these plants in breathable materials such as burlap. You can also use a natural chemical product like Wilt Stop or Wilt Pruf. These natural pine resin products help cover the plant’s needles and protect against the cold. Monitor the weather with this chemical method because it generally requires a pleasant day with a temperature of 50 degrees Fahrenheit to be effective. I would love to see this implemented sometime in mid to late November as there is a chance it will last through the coldest part of the winter. These chemical applications are good for about four months, and applying them in November helps them last until the end of February, after which most of our severe colds pass.

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