Dear Master Gardener: We have some trees along our road that have the bark eaten from them. I don’t think it is from porcupines because the small branches are eaten, too. Any information on this would be appreciated.

Answer: Although porcupines strip bark off trees, the damage along your road is being done by squirrels. A forester from the Minnesota Department of Natural Resources confirmed that they have been seeing a lot of trees stripped of bark from the top down in the past few weeks. Bark stripping is a common practice among many types of squirrels. According to Purdue University, the squirrels don’t actually eat the bark; they strip away the top layer to get to the sweet, phloem tissue underneath. They prefer to strip bark from small trees that have trunks less than 2.5 inches in diameter. Unfortunately, this can stunt a tree’s growth, make it more susceptible to insect or fungal problems, or even kill it.

Related: Ask the Master Gardener: Aloe vera plant grown indoors offers surprises

Dear Master Gardener: I was told I should buy zone 3 plants. What do “zones” mean? I think I put in some plants that didn’t say zone 3 on the tag - will they die?

Answer: The USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. Hardiness zones are based on the average annual extreme minimum temperature during a 30-year period in the past; not the lowest temperature that has ever occurred in the past or might occur in the future, and not the average low temperature. The majority of Minnesota is in Zone 3 and Zone 4. Almost all of Crow Wing County is in Zone 3b (-35 to -30 degrees Fahrenheit) with Zone 4a (-30 to -25 degrees Fahrenheit) starting at the southern border of the county. So, many Crow Wing County gardeners are able to successfully grow some Zone 4 plants, especially if they are hardy to Zone 4a.

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Related: Ask the Master Gardener: It’s rare but exciting for aloe vera plants to bloom indoors

There are other factors involved with a plant’s winter survival, such as snow cover. Snow is so effective at insulating the root system that some Zone 4 or even Zone 5 plants come through the winter unharmed if we have enough. A deep layer also protects the above ground plant parts from the most bitter cold. Several years ago, we had a winter with very cold temperatures and very little snow cover and I lost numerous plants -- even those that were labeled hardy to minus 40 degrees Fahrenheit. Survival rates can also be improved by taking advantage of the microclimates of your property, protected areas where plants may benefit from radiated heat and aren’t vulnerable to cold desiccating winds. On the other hand, highly exposed locations can increase plant stress and decrease survival rates. Gardeners should keep their zone in mind when selecting plants, but also keep in mind that other factors can affect plant hardiness.

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Dear Master Gardener: I just learned recently that oranges and lemons can be grown indoors in Minnesota. I would love to grow my own citrus fruit! How do I do it?

Answer: Yes, certain oranges and lemons can be grown as houseplants, but you will be disappointed if you expect to harvest large quantities of fruit such as you would find in a supermarket. Commercial fruit trees are too large to grow indoors and could not survive our Minnesota winters outdoors. The most commonly found indoor citrus trees are Calamondin oranges (Citronfortunella mitis) and Meyer lemons (Citrus x meyeri). Less popular but often available are tangerines (Citrus reticulata) and Satsuma oranges (Citrus reticulata Blanco), which are really very sweet tangerines whose blossoms are especially abundant and fragrant. Calamondin oranges are small and sour so are not particularly good for eating out of hand. They do, however, make good marmalade, and are colorful and fragrant plants. Meyer lemons are milder and sweeter than commercial lemons, are not abundant producers, and need annual pruning to keep their size manageable. All citrus trees grown indoors have similar growth requirements. Indoor temperatures should be around 65 degrees -- up to 10 degrees lower at night. They prefer a south-facing window with several hours of direct sunlight. They benefit from being set outdoors from about May-September, transitioning to a couple of weeks in the shade both going out and coming in. They are acid-loving plants so their soil requirements include plenty of peat moss. A mixture of one-third sterile potting soil, one-third peat moss and one-third perlite or vermiculite would be ideal. Fertilize plants at half-strength once or twice a month when they are actively growing (April through September) with a fertilizer formulated for acid-loving plants. They need regular watering and wilt easily. Make sure they do not sit in water. An indoor citrus tree makes an attractive houseplant and has the added benefits of fragrant blossoms and colorful, though not abundant, fruit. Sometimes a plant will have blossoms and fruit at the same time. Just don’t plan on sending boxes of Minnesota fruit to friends in Florida and California.

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.