How To Plant and Care For Cold Hardy Cacti & Succulents
By David Salman, High Country Gardens Founder & Chief Horticulturalist
Many gardeners don't realize that there are cold hardy cacti and succulents - plants that can grow outdoors even in sub-zero winter climates. These types of plants, when grown in the ground, do best in areas of the Western US and western Great Plains that get no more than 18 to 20 inches of annual precipitation.
Read on to learn more about how to grow and care for these special plants.
Cold-Hardy Cacti In Their Native Habitat
Our selection of succulents is extensive and includes many rare and unusual varieties from South Africa and the Americas. Cacti are simply a family, or sub-category, of succulents. Cacti are found as native plants only in the Western hemisphere.
Knowing how Cacti grow in their native habitat is a helpful step in growing them successfully in your garden. As more and more gardeners experiment with the various cold-hardy species, we can look to plant them more widely and expand their usefulness as garden plants into a much larger portion of the United States.
Although we think of cacti as being strictly low desert plants many species are found in some very cold, harsh environments. The habitats of most cold-hardy cacti are concentrated in the mountains of northern Mexico and the western United States. Additional cold-hardy species are also found in the mountains of southern-most Argentina and Patagonia. In the United States, several genera are native to the western Great Plains ranging from Oklahoma northward into Montana and the Dakotas. One species of Escobaria (also called Spiny Star Cactus) can even be found venturing into the southern edge of central Canada! The vast intermountain region is also home to numerous species. Many are found in both the mountains and the high, cold desert plateaus of this area.
The Chihuahuan desert in West Texas and southern New Mexico is also home to a treasure-trove of fascinating cold-hardy cacti. It is interesting that the cold hardiness of many species from West Texas and the Southwest exceed what we would expect. It seems that many of them retain their genetic cold hardiness from many thousands of years ago when those regions were much colder.
There are over 100 genera of cacti, but the majority of cold-hardy species are concentrated in a dozen or so. For the purposes of this article, I have defined “cold-hardy” as cold tolerance to temperatures of 0°F or lower. The most cold-hardy include Great Plains natives like Escobaria, the wide-ranging Opuntia, and mountain dwellers, such as Echinocereus and Pediocactus, which can withstand winters lows of -30°F and colder.
Watch: Planting Cacti & Cold Hardy Succulents With David Salman
How To Plant Cold-Hardy Cacti and Succulents In The Garden
In the garden, cold hardy cacti are not difficult to grow if you keep their basic requirements in mind. Tips for how to grow cold-hardy cacti:
- Drainage: First and foremost, cacti and succulents require excellent drainage.
- Soil Preparation: They like alkaline, mineral soils. They need lean soils that have not been amended with lots of sphagnum peat moss or compost, which retain moisture and can be too rich for cacti and succulents.
- Siting: They should be situated to receive full sun, especially during the winter months.
Cacti require a fast draining soil. This means no clay and no added compost, peat moss, or soil conditioners, as these make the soil too rich in nitrogen and humus. Drainage is critical to the health of a cactus plant’s root system.
- Planting cacti and succulents into water-retentive soils like heavy clays and rich loams will result in root rot.
- Excellent drainage is particularly important during the winter, especially in areas that receive frequent rains or snow. I recommend planting in raised or bermed (mounded) beds, especially where the native soils hold water and stay wet.
If your native soil is not sandy or rocky, then it will be necessary to improve the soil's drainage. A berm (low mound) or a wide bed can be created, or they can be planted in frost-resistant pots and containers.
To create a lean, fast draining soil for these raised beds, berms, or containers:
- Mix of 2 parts native soil to 1 part coarse sand and 1 part small gravel, porous red or black volcanic scoria (common in many western states), or expanded shale aggregate.
- Add the minerals that cacti crave by incorporating Planters II (a natural trace mineral fertilizer) and phosphate at recommended rates.
- Working larger rocks into the planting area also adds a pleasing landscape element. Well-placed rocks also create pockets of soil that duplicate spots where cacti are found growing in the wild.
Situating the planting area properly is also of critical importance. Most cacti prefer full sun and benefit from warm protected microclimates where rocks, buildings, or pavement absorb and hold heat.
- Locate planting beds in full sun against south- and west-facing walls, or in hot, dry areas surrounded by cement sidewalks and driveways.
- When looking for a planting spot, be sure that a garden bed in full summer sun doesn’t find itself in the shade as the sun drops lower in the winter sky.
- Low spots that collect water should also be avoided.
- Protect cacti from excessive winter moister. In moister climates (where you receive more than 18 to 20 inches of annual precipitation), move the potted plants under the overhang of the roof on the south or west side of the house or outbuilding to keep the soil dry from rain and snow.
When it comes time to plant new cacti, several techniques can be used to improve transplanting success.
- Most importantly, always plant cacti and cold-hardy succulents bare-root. Wait for the soil in the pot to dry out. Then gently loosen the potting soil in the root ball with your fingers and shake it off. You may see long, well-established roots. Once the soil is gone, trim the roots back by 1/3rd with sharp scissors or pruning shears.
- Plant into a shallow hole. Physically spread the roots out evenly. Backfill the hole holding the cactus so the crown (junction of root and stem) is just above the surrounding soil. Settle the soil between the roots by carefully vibrating the plant up and down.
- Mulch with crushed (not round) gravel to a depth of 1 to 2 inches depending on the size of the plant. Don’t worry when the gravel covers some of the spines up from the base of the plant. The mulch will settle a bit with time. Mulching will protect the plants from splashing soil (a significant problem in moister climates) and provide the roots with a more protected environment to become established.
- Water: Wait a day or two to water in the new transplants. This gives any cut roots time to callus over. At that point, I water thoroughly with a root stimulating mixture of seaweed and a dilute of high phosphorous fertilizer. When watering cacti, it is better to err on the side of dryness than to over water, especially in the colder months. However, during the heat of the summer, cacti will respond positively to a weekly soaking.
Maintenance Tips For Healthy Cacti & Succulents
Maintenance is the final component to a healthy cactus planting. A well-designed planting of cacti and companion plants should make for a low-maintenance garden. Always keep cacti mulched with gravel. I prefer crushed (angular) gravel to a depth of 2”. Remember to replenish gravel mulch annually; freezing winter weather causes the soil to contract and expand pulling the gravel down into the soil and thinning the layer above ground.
Established plants grow fastest when watered regularly, once every 7 to 10 days during the heat of the summer (when there is no rain). Stop watering by early September to let the plants dry down and shrivel in preparation for winter.
- In late spring or fall, Apply a single application of a granular fertilizer, such as Plant Success. I prefer organic formulations especially those with alfalfa meal, such as Yum Yum Mix. This should be supplemented with a dose of liquid sea kelp several times through the summer. I like to top-dress with Yum Yum Mix at the start of summer.
- Trim companion plants during the growing season as needed if they overgrow their cactus neighbors.
- With the arrival of fall, watering should be discontinued to allow the cacti to shrivel and harden off for winter.
- Fall clean-up is also important. Remove fallen leaves and prune back the stems of neighboring plants that have grown over or around the cacti. This helps to keep the cacti dry during the winter by facilitating maximum sunlight and air circulation around the plants. Remove all fallen leaves from around the cacti, and cut back any plants that create winter shade.
- In wetter climates that get a lot of winter or early spring rain, it is helpful to keep your cacti and succulents dry. Create an open-ended tunnel with plastic sheeting and bamboo hoops to shed water. Remove in mid-spring as the plants begin to wake up and grow.
Cacti benefit when grown with other plants as long as they’re not smothered by large and fast-growing companions. In wetter climates companion plants also help pull moisture from the soil and keep cacti drier. Clump grasses are particularly helpful in this way.
In the wild cacti are rarely if ever found growing only with other cacti. Unfortunately many cacti are relegated to cactus-only plantings. This “pincushion” look deprives the gardener of the opportunity to combine them in artful ways with non-cacti plant and thus extend the blooming season.
Learn more about incorporating cacti and succulents in your garden design, plus recommended companion plants, and why it’s important to protect cacti in the wild in our guide:
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