Wally Peck: ‘Why can’t I grow that here?’
With the flurry of seed and plant catalogs we get every winter comes the nagging question every gardener has: I wonder if that plant will make it here? Many catalogs and nurseries are very good about clearly labeling their plants for zone recommendations; however, some are not.
With a little care and planning we have had good success with plants intended for zones south of us. Zones are based on long-term records but last Saturday at the Master Gardener workshop, Mark Seeley pointed out that the last decade is way off the charts in climate change. Zones are moving. But what is it that makes one plant survive and another freeze out?
Minimum temperature is one factor. Last winter we had at least one night that reached 30 below zero near Bemidji. Other years can range from a minimum of 20 below to 60 below. We live in an area with great variability of winter minimums, but the catch is – how cold does the plant get? A plant under two feet of snow will never reach the same temperature as the air. On the other hand, winters with little or no snow cover expose plant roots to extreme temperature variation. That’s when tender ones die.
Flowering shrubs and trees form their buds for spring in the fall and wait for the sap to start flowing to break dormancy. Some are susceptible to warm spells in January or February that get their juices flowing only to be followed by an icy blast. You may have noticed even our native trees and shrubs have a spring with few or absent blooms. We have a forsythia that tends to bloom up as high as the snow bank that covers it each winter.
Plants with tender roots can experience the same freeze and thaw cycles that interrupt their dormancy or simply cause the cells to explode during a cold snap. Tender vegetables like asparagus or perennials like roses and strawberries benefit from the protection of heavy mulching to keep them dormant until spring.
We often pay attention to watering during the growing season but don’t think much about moisture in the winter. Many perennials and shrubs are not tolerant of drought and need to go into dormancy well hydrated. Dry winter winds will desiccate many conifers and cause browning of needles in the spring, especially those not hardy this far north. Wrapping with burlap or spraying with a protectant helps with this problem.
Another strategy is to plant perennials as annuals and replant every year. Yes, it is expensive, but imagine the envy a giant elephant ear in your garden provokes! Tea roses are relatively inexpensive but many do not overwinter outdoors here.
So here in the north, stick to zone 3 plants to be sure, experiment with zone 4 especially in protected spots, and throw caution to the wind and try a zone 5 just to see if it will make it! Plant breeders from NDSU and Canada are always coming up with introductions for the northern grower. We have ordered a wisteria for a sheltered spot. Gardening is all about experimenting. After great success with sweet potatoes last summer, we have our eye on a hardy magnolia – maybe we can grow that here!
Master Gardeners will again be answering your gardening questions via a voicemail service. Call 444-7916, leaving your phone number, name and the nature of your question. A master gardener will give you a call to speak with you personally. Seek horticultural information on the University of Minnesota Extension website www.extension.umn.edu/gardeninfo/ Thank you all who supported the Master Gardeners at their Garden Party on Saturday. It was a good day to be a gardener.