Ask the Master Gardener: Protecting your plants from spring frost

If snow and freezing temperatures are in the forecast and going to persist for a few days, it would be a good idea to protect new and recently sprouted plants with a cover or keep them potted so you can move them to shelter.

Even frost-resistant plants may not be able to withstand extended freezing temperatures. Photo courtesy Metro Newspaper Service

Dear Master Gardener: With the early spring and plants coming up, what can handle a frost and what should we try to protect if we can?

Answer: The dates of the last freezing temperatures of spring and the first freezing temperatures of autumn are of great importance to home gardeners, farmers and commercial growers. These dates are often referred to as “last frost” and “first frost.” According to historical data for the Brainerd lakes area, there is a 20% chance of temperatures falling below 32 degrees on May 21 and a 10% chance on May 27. If you have plants in low areas where cold, dense air settles, frost damage is usually worse. Even frost-resistant plants may not be able to withstand extended freezing temperatures. If snow and freezing temperatures are in the forecast and going to persist for a few days, it would be a good idea to protect new and recently sprouted plants with a cover or keep them potted so you can move them to shelter. Mulch will also protect early perennial plants to keep them warmer.

The early blooming bulbs such as glory of the snow, daffodils, crocus, snowdrops, and winter aconite can withstand frosty temperatures. Some other cold-tolerant plants include: forget-me-not, sweet alyssum, primrose, viola, pansy, lily of the valley, nemesia, and snapdragon. Vegetables that are tolerant of frost include broccoli, cabbage, cauliflower, carrot, onion, turnip, parsnip, and some greens.

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Dear Master Gardener: I’ve been wanting to start a compost pile, but my husband thinks it will attract unwanted critters. Is he right?

Answer: Composting is a very important organic gardening practice that has been used for centuries to improve soil and help plant growth. It is a process that allows naturally occurring microbes to convert yard waste into a useful soil amendment. Most of the soil in this area tends to be sandy, so adding compost to sandy soil will aid in moisture retention and nutrition. There are two things to keep in mind when starting your compost. First, the microorganisms needed for decomposition require oxygen, water, and nitrogen. Second, the smaller the plant pieces, the more quickly they will break down.


According to Deborah Brown and Carl Rosen, professors at the University of Minnesota, many organic materials can be composted besides grass and leaves: non-woody shrub trimmings or twigs less than 1/4 inch in diameter, faded flowers, weeds, leftover plants at the end of the gardening season, lake plants, straw, coffee grounds, eggshells, fruit and vegetable scraps, shredded newspaper (black and white print), small amounts of wood ash, and sawdust. Sawdust requires the addition of extra nitrogen and wood ash raises compost alkalinity and may result in nitrogen loss from the pile. Never compost pet feces because it can transmit disease. Keep out any badly diseased plants.

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Ideally, grass clippings should be kept on your lawn, but if you decide to add them to your compost, mix them with other yard waste as they tend to pack down and restrict airflow, limiting the oxygen needed for decomposition.

It is best to locate your compost pile in at least part sun to help heat the pile. An active compost pile will heat somewhere between 130-160 degrees. Turn the pile to help speed decomposition and reduce any foul odors.

Do not compost meat, bones, grease, whole eggs, and dairy products because they attract rodents and other animals. As long as you don’t add the above-mentioned items, your husband can rest assured that you won’t be attracting unwanted critters and you will be creating free “gardener’s gold” which will reduce or eliminate the need for fertilizers. If you need some more ammunition for talking him into a compost pile, here is what the Environmental Protection Agency has to say, “Organic waste in landfills generates methane, a potent greenhouse gas. By composting food wastes and other organics, methane emissions are significantly reduced.” Hopefully you can talk him into it. Good luck!

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Dear Master Gardener: Are there any edible crabapples that are hardy in the Brainerd lakes area?

Answer: The Chestnut, Centennial and Whitney crabapple trees are all hardy to USDA zone 3. The Chestnut Crabapple tree was developed by the University of Minnesota in the 1940s. It is self-pollinating, vigorous, hardy, and adapts well to different soil types. It is an excellent pollinator for other apples. This crabapple tree produces large, russeted crabapples that ripen in early September. Its creamy white flesh is fine-grained and crisp with a sweet, nut-like flavor that is great for fresh eating, cooking or making jams. The fruit stores for 4-5 weeks.

The Centennial Crabapple, another University of Minnesota variety, was introduced in 1957. It is a compact tree that grows to about eight feet, and is fairly scab resistant. Like the Chestnut, it is also used as a pollinator for other apple trees. It produces heavy crops of oval, large, juicy, red-over-orange crabapples that are excellent for fresh eating, apple butter, sauces, and spiced apples. The fruit ripens in mid to late August. The crabapples do not store well though.

Another edible crabapple is Whitney, which was introduced in 1869. This tree produces beautiful pink and white blossoms in spring and is also self-pollinating. Whitney is moderately resistant to fire blight and intermediate in resistance to cedar-apple rust. It produces a large harvest of red, golf ball size apples that have been described as “approaching sweet” and ripens in late August or early September. The flesh is juicy and slightly yellow. The crabapples may be eaten fresh and are also perfect for canning, preserving, pickling and spicing.


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You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at and I will answer you in the column if space allows.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.
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