It used to be that when I heard the word “cactus,” one thing came to mind: a hot, dry desert. Cacti were fascinating plants, but aside from the occasional potted novelty from the discount store, I only expected to see them in picture books or botanical centers.
But I found out later that I was wrong. Most cactus species are sensitive to cold. But hardier ones grow well into Canada. It’s not difficult to grow cacti outdoors year round in your own garden.
With the right soil conditions, certain cacti are cold-hardy in at least USDA zones 6 to 9, and some to USDA zone 4. They’re all heat-tolerant in AHS zones 12 to 1.
Not all species in the groups that follow are cold hardy. If you see one in a nursery or catalog I don’t mention here, be sure to verify its hardiness zones from a reliable source.
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Here are a few of the more easily grown, cold-hardy cacti:
With some species native to as far north as Minnesota, these are usually the hardiest cacti. They make excellent rock-garden plants and can even grow in well-drained, grassy areas.
With the approach of winter, the fat, succulent “pads” of prickly pears begin to dry out and shrink. This is a way of dealing with freezing weather. They may even flop onto the ground, but will revive in spring.
The ‘Pink Parfait’ prickly pear is a good example of the medium-sized prickly pears. It will grow about 7 inches tall, with a spread of up to 3 feet. The spiny “pads” of these cacti grow in suc- cession, one coming out on the tip of another, with new ones sprouting from the bases. The flowers open from the tops of these pads in mid- to late spring, followed by oval fruit. Creamy-flowered ‘Crystal Tide’ and yellow-flowered Opuntia cymochila are shown in the insets above. All three of these prickly pears are cold- hardy in USDA zones 4 to 9.
The shrublike cactus is a tree cholla. The various cholla cacti belong to the same genus as the prickly pears, but they have cylindrical stems instead of flattened pads. They range in size and habit from small, ground-hugging creepers like devil cholla to shrubs or small trees that can reach up to 15 feet in their native habitats. Flowers are usually rose-pink to red. The tree, devil, Whipple and Klein’s chollas are cold-hardy in USDA zones 5 to 9. Although parts of the tops may die back in extremely cold winters, they’ll regrow from the roots.
All of these cacti have a globe or barrel shape, making them look a little like their namesake animal burrowing into the ground. There are about 45 species; the ones you see here are cold-hardy in USDA zones 5 to 9.
The color and shape of the late-spring blooms on the hedgehog cactus also earn it the name claret- cup cactus. Each flower stays open for several days. Plants slowly reach 12 inches tall with a 6-inch spread.
Because of the alternating bands of color, the clumping plant is also called rainbow cactus. There are a number of regional variations throughout its native range in the West and Southwest. Its flowers bloom in varying shades of yellow to near-white in midspring. Stems will eventually reach up to 12 inches tall with a 6-inch spread.
These are low- growing plants that form clustering colonies of rounded stems. Sometimes the stems are partly below the soil line, leaving only a small hump exposed.
The tiny pincushion cactus is Lee’s dwarf snowball. With a mature size of only a couple of inches across, it’s a good choice for a rock garden. It’s cold-hardy in USDA zones 5 to 9.
Clustering pincushion grows as far north as southern Canada. Different cultivars range in bloom color from deep purple to salmon pink. It eventually forms large clusters of stems up to 12 inches tall and wide and has a long bloom season lasting from late spring through early summer. It’s cold-hardy in USDA zones 4 to 9.
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The Missouri pincushion, is another prairie native. It can be found in many grasslands throughout the Great Plains and Upper Midwest. Occasionally, it will poke its head up through an established lawn. It can even survive being whacked with a lawnmower because there is enough of the plant left underground to grow new shoots.
Individual plants grow up to 4 inches tall and wide. The green-yellow flowers bloom in late spring. Missouri pincushion is cold-hardy in USDA zones 4 to 9.
Where to Plant Cacti
Although many species of cactus can be extremely cold hardy, they absolutely must have excellent drainage. They can’t stand to have wet feet, especially in winter when they’re not actively growing and taking up water. In cold, wet climates with frequent freezing and thawing, heavy soils can get soggy. That makes the ground vulnerable to frost heaving that can dislodge the shallow roots of cacti.
One good place to use cacti is in a gravelly rock garden, especially one built on a slope. Hillsides generally have better drainage than flat areas. The soil should be lean—a mixture of half coarse builder’s sand and half 3⁄4-inch pea gravel with only two percent organic material like compost will suit them fine.
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Even though cacti need careful placement to thrive, that doesn’t mean that they have to be kept away from other plants. The cacti have a lot of other companions. For example, pussy toes fill out the front and center of the bed, growing behind a large, flat rock. Their tiny, furry, silver-leafed base foliage, towering, slender stems and fluffy heads of pink flowers provide an interesting texture contrast to the cacti. Grasses and other plants help shelter the cacti in winter and also take up excess water in rainy spells.
You may want to have a bed with just cacti and other succulents. That’s OK, too. One good place for that is in a raised bed. White walls on the north and west sides give protection from desiccating winter winds and reflect sunlight onto the bed. The roof overhang shields the cacti from heavy rains.
Although it’s a cacti-and-succulent-only bed, there’s a lot of interest and variety in it. Using many different cactus species gives this planting plenty of variation in textures, heights, colors and shapes. Colorful rocks add to the show.
Many dry-plains, alpine and desert plants, such as penstemon, anise hyssop and basket-of-gold, grow naturally in the same habitat and have flower colors that go well with those of the cacti. The perky Sue makes a nice color and texture contrast to the Bailey’s lace cactus and likes the same arid, well-drained soil. Look in catalogs for plants that are listed as xeric, or low-water use, and that match your hardiness zones.
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Care and Culture of Cacti
I’ve already mentioned the high-mineral, sand-gravel soil “recipe” cacti like. If you have heavy soil, you’ll need to amend it. You can trench down to replace the existing soil with 18 inches of the amended mixture, but an easier way is to build up from the soil surface into a raised bed.
Larger rocks added to the bed are both ornamental and practical. You can place them to direct water away from some spots and toward plants that might want more. Rocks also absorb the rays of the sun in the winter, radiating heat on cold nights to create warm pockets for the cacti. Use larger rocks as windbreaks for plants that might suffer from cold winds. Plant cacti in as sunny a location as possible.
If you don’t have a natural area meeting all these criteria, you can still create a small one. I’ll show you how in “Building a hillside cactus bed” at far left.
If you want more cactus plants, they are generally easy to propagate. One method, which results in a clone, or exact replica of the parent plant, is by cuttings. I’ll show you how to do this in “Cactus propagation,” below. You can also start cactus from seed. This is an inexpensive way to get lots of plants but they’ll take several years to bloom. New, hardier cultivars are sometimes found among seedlings.
Cactus lovers are continually looking for more species and new cultivars that will grow in cold climates, and testing new methods for helping them survive. They also like to share what they find out with each other. You may not see the towering, many-branched saguaro of Western-movie fame jutting out of a Northern snowbank anytime soon, but it’s easy to experiment with the ones I’ve talked about. If you try just a couple of hardy cacti out of curiosity, you may find yourself “hooked” on these spiny characters.