Northern Plants for My North Dakota Garden: Cold-Hardy, Drought-Tolerant Perennials

When most people think of beautiful gardens, North Dakota is rarely the first state that comes to mind. While it's true that we don't have magnolia, jasmine, dogwood, or most of the other lovely plants that flourish in milder climates, plenty of flowers and flowering plants are cold-hardy and can survive in Zone 3, the coldest growing zone in the contiguous 48 states. Here, daytime highs can range from 30 degrees below zero in January to over 100 degrees in July and August. The state is also undergoing the worst drought in recorded history, even worse than the dust-bowl years of the 1930s. The wind is a constant for the northern plains, and blizzards have been recorded as late as June, and as early as October.

Despite our extreme weather, and the abrupt changes of seasons and sudden late or early storms, most people here do garden. It may be an attempt to fill the summer with as much color as we can, so the memory can keep us warmer through the long white winters. It may be the ingrained love of the land in native North Dakotans. Whatever it is, I learned about gardening from my grandmother and mother at an early age, and have continued to grow cold-hardy plants in my own yard.

Following are some of the plants in my own garden, along with what I do to keep them growing year after year.

Roses
If you know that all of today's roses (genus rosa) were originally derived from the wild rose, and that the wild prairie rose is the state flower of North Dakota, it should come as no surprise that there are roses in almost every garden in the state. From tree roses to climbing roses, hybrid teas to grandifloras, we grow them all. In my own garden, I tend to stick to floribundas (R.floribunda). The name, obviously, comes from the abundance of flowers on a single stem, as opposed to hybrid teas, that have a single flower on a long stem and are the roses used for cut flowers. Floribundas take much the same care as hybrid teas, but they are hardier at standing up to the north wind, and my garden has no protection on the north side. All roses need a mostly sunny location.

I've bought roses both as bare-root plants and in pots to plant in the spring. In either case, the rose should soak in water for at least 12 hours before being planted. I then dig a hole that is wider than the diameter of the root spread, and deeper than I want to plant it. I mix the garden dirt that came out of the hole with some peat moss, some compost, and some bone meal, the put some of it back in the hole. After making a mound in the center of the hole, I put the rose over the mound, so its roots can go down around it. If it's a hybrid rose that was grafted onto the rootstock, there'll be a knot at the point of attachment. I fill the hole back in with the amended soil up to the level of that knot, making sure all the roots are completely covered, tamp the earth down firmly, and add more soil if needed. Then I water the planted rose.

Roses do need more care than many other plants. First, they need to be pruned annually. The best time for this is in the early spring, just as leaf buds begin to show on the canes and when you're reasonably sure the last frost has passed. In North Dakota, the last hard frost might be in March, or it might be in June, when the bush already has flower buds. I usually prune in mid to late April, depending on the weather that year. I use good sharp pruning shears, purchased from rose experts Jackson & Perkins, that is ergonomically designed and takes less hand strength than some other shears. I remove wood or canes that look dead or weak, or that straggle out sideways from the base of the rose (suckers). Floribundas like mine should be pruned a little higher than hybrid teas, leaving at least 5 to 6 inches above the ground. The pruning cut should be made about a quarter of an inch above a bud (leaf, not flower) and at a 45 degree angle away from the closest bud. Pruning should shape the rose bush, and as I cut back over the summer, my intent is to give the rose a nice full shape with no suckers at the bottom and a cup shape at the top.

Roses also seem to attract more pests than many other plants. Insect pests include spider mites, aphids, psyllids, and a few others, and diseases include black spot and powdery mildews (both are types of fungus), among others. It's easy to spot insect damage: something has clearly been munching on your rose's leaves, and aphids tend to swarm all over buds. Black spot and powdery mildew attack the leaves, and look just like their name sounds. You can attack these problems in three ways. First, you could use a chemical pesticide/fungicide spray like Sevin TM; this can kill other types of insects, and is highly toxic. Second, you could spray your rosebush with a non-chemical spray such as the Safer TM line, which has two specific sprays just for roses, or you can make your own spray with a little mild dish soap mixed with water in a little mister. If you choose any of these sprays, you need to cover both the tops and bottoms of all the leaves. The third alternative, and the one I usually use, is a systemic treatment that both fertilizes and kills anything that tries to eat the plant. I apply it early in the spring for prevention of disease and to get the rosebush nourished before it starts to grow, and at six week intervals throughout the summer. You can find all of these products at garden centers and Home Depot TM type stores. You should also keep the base of the rose free from debris like leaves and sticks that make nice growing media for insect pests.

The final requirement for rose bushes up here in the great white north is winterizing. Since I keep the grafting spot above ground, I need to cover the rose with mulch or leaves up to and over that spot. Some people cover their roses with styrofoam "rose cones" over their roses for the winter months. If you do that, you need to take it off during warm spells, like the 60+ (above zero) days we had in January of 2007, or your rose will over-heat and die. I usually do a little pruning in the fall, and pile leaves and bark mulch over the rose, then removed it early in the spring. The mulch pile protects the rose from the cold, but doesn't cause it to over heat on the occasional warm days in winter. If you have a larger rose bed, try putting a chicken wire pen around the rose bed, then filling the pen with with leaves and mulch.

Delphiniums
Delphiniums (genus Delphinium) are a perennial flower species that grows well in cold northern climates. Like roses, they are typically planted in the spring, but are both cold and heat tolerant.. They come in colors including blue, white, pink, and lavender. They are tall plants (3 to 5 feet) that need staking as they grow; they should be staked early (I do it in late May, when they're about 6 inches tall) so that they'll grow up straight and won't be blown over by the prairie wind or pulled down by the weight of their flowers, which grow as tall spikes covered with small flowers, several spikes to a single plant. They like loose soil, and in my garden, I amended the soil before planting them just like I did for the roses They like a mostly sunny location. Like the rose, they can be attacked by mites and fungi, and I treat them with a systemic fertilizer and pest control just like I do for the rose. I don't spray them, because bees love them and I don't want to hurt the bees. In late fall, when the delphiniums look dead, I cut them back to a height of about three inches, and cover them with mulch for the winter. Miniature delphiniums also can thrive in the extreme climate of the northern states, and fare better in the wind because they aren't so tall.

Penstemon
Penstemon is a perennial native to North America, and different varieties grow wild in almost every state. A southern variety won't grow in the cold north, though, so be careful to choose the right variety for your area. I bought a local variety from a gardener about 20 miles from my home. I don't know the variety, but I know it's one of the cold-hardy ones. It too is planted in the spring, and first grows into a green mound, then in June it grows spikes that are covered with purple flowers (penstemon come in a variety of colors; P. x Mexicali, for example, has bright red flowers) shaped like small bells. They too are attractive to bees. Native penstemon are very drought-tolerant, heat-tolerant, and not too particular about their soil. When I planted the penstemon, I was in a hurry and didn't amend the soil, and I don't always remember to fertilize them. They like sun, but can handle part shade. They're the perfect plant for the northern gardener, because they're not demanding, they don't need to be babied, and they fight off both pests and diseases on their own. In the fall I cut back the flower spikes, but the remainder of the mound of narrow leaves stays green throughout the winter.

Hosta
Hostas, sometimes called plantain lilies in the south, come in a wide assortment of species and hybrid varieties, and there are hostas for every climate. I chose hostas because, like delphiniums and penstemon, they're perennials (in other words, I don't have to buy more and plant them every spring) and because they're shade lovers, and much of my garden is in almost full shade. I have five different species of cold-hardy hosta, and all of them bloom with high spikes bearing lavender flowers in mid to late August. I amended the soil with mulch and compost when I planted them, because they prefer a fairly rich soil, and I fertilize them in early spring and mid-July. They grow large leaves that can be solid green, blue-green, green edged in white or cream; and the leaves can be flat or have a corrugated texture. I have at least one of each that I've described. Like penstemon, they don't need to be babied too much. I cut the flower stems back when the bloom has died, but other than that, I don't cut them back in the fall, nor do I cover them. Their dead leaves protect the plant over the winter, and I remove them in the spring when the plants start regrowing as nubs coming out of the ground. Hostas do attract both deer and cottontail bunnies, so much so that in some areas they are called "deer lettuce." I don't have a problem with deer in my yard, but despite the fact that my Akita is fenced in about three feet from the plants, the bunnies come and have a little snack most evenings. I've tried rabbit repellant, but it hasn't worked. Nevertheless, they stay green all summer, as long as they are watered regularly, and thrive in my garden each year.

Astilbe
The astilbe, like many of these plants, is a perennial with many different species that do well in different areas, and there are a few that can survive both the North Dakota winter and the hot summer. They start as a small mound of green and silver leaves, then bloom in early summer. The blooms don't look like most people's definition of flowers; they seem to be feathery plumes from a distance, and only up close do you see the many little florets that make up the plumes. The foliage continues to look good throughout the summer. They thrive in shade, another reason I chose them for my garden, and spread out over time. They can be divided in either spring or fall, but they aren't self-seeding. They do need regular watering and aren't drought-tolerant, but are otherwise hardy plants for the northern garden. I cut off the blooms when they are faded, but don't usually cover them for winter.

Liatris
Liatris, another shade-loving perennial, is planted as a tuberous root, not a potted plant, and is usually planted in the fall in North Dakota. They bloom in late summer as a tall spike whose small flowers open first at the top and then gradually down the spike, until the whole spike is blooming. Their height varies by species; the tops of the purple spikes in my garden (Liatris scariosa) are about two feet tall; other species grow as high as 5 feet. They need watering, but not too much watering, as boggy soils can kill them. As with the penstemon, these are some of the favorite flowers of the local bees. In late fall, I cut them down, and if the winter is predicted to be especially cold, I cover them with a light layer of mulch. They're among my favorites because they are a blast of color when many other plants have stopped blooming, and because they are an easy-care plant. They also come in white and pale lavender varities.

Bellflowers
Bellflowers, or Campanula, come in two main types: tall ones (2-3 feet) and short ones (6-12 inches). I have the smaller type in my garden. Although they can be grown from seed, in North Dakota I would have had to grow the seeds indoors first, then plant the plant outside. Spring just comes too late for many seed-grown flowers here. I planted mine as small plants from a greenhouse, and they make a low mound of bright green leaves, and are covered with small blue flowers shaped like cups or upside-down bells throughout the summer. Although they are in my "shade garden" they receive enough sun in the afternoon to keep them thriving. The small bellflowers also look great in rock gardens, and can be divided in early spring or fall by taking cuttings and letting them root in water before planting. They derive from wild plants in the European alps, so are an excellent choice for northern gardens. By growing the shorter varieties, I avoid the problems of wind and staking. I do fertilize them lightly in spring and midsummer, but do nothing with them in winter (their mountain home made them strong).

Dianthus
Dianthus, sometimes called "Pinks," are related to carnations, and can be pink (mine are) but can also be red, coral, white or yellow. They have narrow long leaves that are silvery-green, and bloom most of the summer. They have a lovely cinnamon or spicy scent. They prefer sun and fertile soil, so in my garden I had to do some significant soil amendment with mulch, compost, and bone meal before I planted them. They need mostly sun, and probably don't get enough in my garden, but they get enough to stay alive and keep blooming, although not as profusely as they would in an area with more sunlight. Their soil needs to drain well, and to get the biggest flowers possible on the top of the plant, you need to pick off the buds from the sides, and continue to pick off the dead flowers to keep it blooming longer. In warmer climates, they can be grown from seed planted in the spring; in my northern garden, they need to be planted as small plants in our somewhat later springtime, or they won't grow enough to survive the winter. They survive the winter without being covered, and in fact covering them can kill them if they get too warm or too wet in the mulch or covering medium.

Coneflower
Coneflower, or Echinacea, are drought-tolerant, heat-tolerant, cold-tolerant, and crappy-soil- tolerant, and generally hardy plants. In fact, the only thing they seem to need to grow is sunshine. I grow them along the south wall of my house, rather than in the shade garden. Although their height is supposed to be 2 ½ to 3 feet, mine are easily 4 feet in height. They also have a habit of multiplying quickly. I started with 3 pink-flowering plants and 3 white-flowering plants about 4 years ago, and now have easily two dozen of the things. They will choke out any plant they find in their way. They also seem to be impossible to get rid of. The flowers top sturdy stems with rough-surfaced leaves. They would make wonderful cut or dried flowers, if I didn't break into a rash every time I touch them. (If it sounds like I regret having planted them, well, what can I say? At least they're reliable.) They are susceptible only to Japanese beetles, a pest we don't have in my northern garden. They die above ground in the fall, but they do it so late in the fall that I usually don't have time to cut them back before it snows. They grow up around the dead stuff in early spring, the time I remove all the dead stalks and flowers. I don't cover them at all in the winter, and they don't mind at all. Coneflowers are kind of like zucchini; they never come in ones or twos, they always come in lots.

Hollyhocks
Hollyhocks (Althaea) grow best as a border plant along a wall or fence. I have them against the south wall of my home, in the few spaces my coneflowers haven't yet invaded. Technically they are a biennial; a single plant only lives two years. But after it blooms, it drops seeds, so each year you have more plants. I chose the single-flower variety (each flower is a single flower, as opposed to the double-flowering hybrids, which have two flowers per flower), in the "Old fashioned" variety that I knew would be closest to the ones my grandmother grew. They grow from 5 to 8 feet high, and need to be staked as they grow. They have large leaves at the base, and a long spike with buds that produce the flowers. They can be grown from seeds, but I planted first year plants last fall so that I'd have flowering plants this summer, and I'm glad I did. They came in several different shades of pink, and provided color from June until mid-August. And they are a constant reminder of the grandmother who taught me to care for plants.

Asiatic Lilies
Asiatic lilies are considerably less expensive than daylilies, and thrive in part to full sun. They multiply each year, and seem to produce more flowers each year. My favorite lily is the Elodie lily, a double lily with beautiful soft-pink flowers, that grows to a height of about 4 feet. Their bloom time is in early summer, after the tulips but before the hollyhocks, coneflowers, and many other flowers in the garden. They start as bulbs planted in the fall, and must be planted at least 6 inches deep, but not more than or the bulb won't grow. They should be fertilized when you plant them, and again each spring. The Elodie is pollen free (but my garden does provide plenty of pollen for the bees on other plants) so they don't cause an allergic reaction in my nose, anyway, although they don't have a noticeable fragrance. Each plant seems to die in the fall, and should be cut down to the ground at that time. I put a light layer of mulch over the lily bed to protect them from snow. I haven't experienced any problems with pests or diseases in the several years that I've been growing Asiatic lilies, and they don't seem to mind the winter cold or summer heat. I do water them regularly, but not as often as the hostas. They can be dug up and separated every four to five years, and spread out a little or shared with a friend.

These are just some of the many plants that are hardy enough to not just grow but thrive in my northern garden. I didn't mention the climbing plants like clematis, the flowering bushes like lilacs, pyracantha, and peonies, or flowering trees like crab apple or Japanese flowering almond, or the many varieties of evergreens which, though not native to North Dakota, nevertheless thrive in rural shelter belts and suburban yards. While we can't match a place like Busch Gardens in Florida, we can certainly, with attention to the details, grow a lot more than wheat, corn and soybeans.

(Sources used for this article other than my own experience include the garden notebooks left me by my mother and my grandmother, the Burleigh County Extension agent, members of the Bismarck Garden Club, and The Readers Digest Illustrated Guide to Gardening, edited by Carroll C. Calkins, copyright 1975, 1989 edition.)