Cold Hardy Cacti for Xeriscape Gardens

When cold climate gardeners think of cactus, they most likely think of indoor plants. It may come as a surprise to many, that there are several species of cacti that can survive a northern winter outdoors. For the xeriscape gardener, cacti are drought tolerant plants of special interest in a northern garden.

Cold hardy cacti are able to survive freezing temperatures because they expel the water in the plant tissues as the weather gets cooler. Water expands when frozen and any water in plant tissue that is frozen would rupture and kill the plant.

Xeriscaping for Cold Hardy Cactus

If cacti are going to be useful garden plants, they must not only must survive the winter, but also flourish and flower during the summer months.

The two keys to growing cacti in northern climates are sunlight and excellent drainage. The planting area must be situated where it will receive direct sunlight all day long during the growing season. Overhanging tree branches may be trimmed back to assist with getting as much sun as possible onto the plants.

Like their southerly relatives, hardy cacti are drought tolerant plants and don’t require regular watering. During the growing season, cacti store water in their leaves, giving them their characteristic fleshy appearance. Too much water and the leaves will turn soft and their roots will rot. A cacti bed needs to be raised above ground level and the soil amended with sand and gravel to allow rapid draining.

On his website, Catci and Succulents, Rob Huntley of Ottawa, Canada recommends building a xeriscape garden bed for hardy cacti with a mixture of pea stone and coarse sand. Huntley layers in topsoil sprinkled with bonemeal a few inches below the final surface of the bed to provide the necessary nutrients for cacti roots.

Once established, cacti won’t require watering except in a prolonged drought and they don’t require fertilization. A thin layer of compost mixed with a bit of bonemeal spread over the garden in spring will be sufficient.

Cultivating Cold Hardy Cactus

Plant hardy cacti early in late spring or early summer. They root quickly and grow rapidly.

Cacti are commonly propagated from cuttings of mature plants started in pots indoors. When planting the be sure to position the plant so it is growing at the same depth as in the pot with the crown (where the stem meets roots) just on the surface or lightly covered with soil. Planted too deeply, the stem may rot and planted too shallow and the weight of the stem may cause the plant to topple.

As winter approaches and the days grow colder, cacti will begin shedding the water in their leaves. They will droop and shrivel up. Don’t water the cacti in fall, they can’t absorb the water and accumulated moisture may cause damage.

For the same reason, cacti should not be mulched for winter protection. An area with good snow cover will increase the survival rate but isn’t necessary. Fall maintenance should include removing any dead flower heads and tree leaves or other trash that may accumulate around the cacti. A pair of tongs will help protect hands from the thorny species.

In spring the cacti will appear dead. But the warm weather will revive them and they will inflate and rise within a few weeks.

A cacti garden may not be for everyone, but for the xeriscape gardener who wants to try something different, the eye catching shapes and colours of cactus might be worth the extra effort.

Sources

Winter Hardy Cacti

Cacti & Other Succulents