I have a succulent cinder garden outside in my backyard, here in Markham, ON. I’m wondering whether I should leave some of them outside through the winter or do I have to move them all inside. Please advise.
Cinder block makes an excellent container for succulents that enjoy hot sun, lean soil and the excellent drainage provided by the cinder block. Some succulents are hardy to zone 3 or 4 and can overwinter outdoors in Markham(zone 5), even in a container. Plants growing in containers should be a least 2 zones hardier than your zone to withstand winter conditions.
Many sempervivums (hens and chicks) and sedums may be hardy to zone 3 but other succulents, such as some of the beautiful echeverias, are not hardy enough to survive outdoors. Those plants can be repotted and overwinter indoors as houseplants or treated as annuals and replaced each year. If you can identify each of your plants or perhaps find the labels if you created the combination yourself, then you will be able to decide which plants must come indoors for the winter. For the hardy succulents position the container so that you can avoid soggy soil and protect it from drying winds.
Good luck with your garden!