10 years ago most gardeners in Atlantic Canada would not have believed that you could grow Cactus outside, in the garden, through the winter in Nova Scotia. I certainly would not have. Even now, most people who come to my nursery or the Farmers Market comment 'but you need to take them inside in the fall?".... and are quite astonished to find out that you can leave them out.
Winter hardy Cactus are found in almost every US state and from Ontario to BC. It is not necessarily the hardiness that you need to look out for when selecting these plants but the conditions they are grown in. Many of them can take the cold. What they can not take is wetness, after all they are 'Cactus'. Some will even survive to Zone 2 temperatures.
One of the biggest things to consider, besides varieties (will get into in the next blog) is where will I put them. They need good drainage, a proper soil mix, sunlight and even though they are Cactus, they do need water.
If you are thinking about Cacti, you are probably thinking about a desert. They do need to be grown in well drained soil. They don't mind the wetness, what they can't take is sitting in any water. Ideally your Cacti should be on a slope where the water can flow away and the soil should be replaced or amened with course sand and rock. A good soil mix is 1/3 each compost, sand, pea gravel. If you want to just amend your existing soil then mix in sand and pea gravel or crushed rock.
Be careful of what you plant near them. Because it is the wetness that will do them in, don't locate them to close to perennials (or shrubs and trees that loose their leaves) that die back in the fall and their leaves and stems fall on the Cactus. This can rot them because the leaves will hold water and moisture. Make sure leaves and debris are removed before winter. Don't mulch them with anything. Don't cover them. The more exposed they are, the better they like it.
Having said that, last winter, when we had snow, and the Cactus bed is located at the edge of our parking area. Andrew is careful not to plow over it but because of the amount of snow it was piled up at least 6' over the bed. I crossed my fingers, toes and whatever else I could and waited. Most survived, two did not.
As the snow receded, Opuntia humifusa failed to thrive for the second year. It was clearly dead. I always kept a copy in the unheated greenhouse to keep trying. O. humifusa should survive and I am determined to get it to live. Other people who have bought this variety from me have had no problem at all.
This little barrel Cactus, one of four, turned to mush. You know when they look like a mass of jelly, they are not coming back.
They are so well worth growing and when they flower........
I have more to tell you......next time...why you need to be very careful when you lean over.