Hardy Succulents

Credit: John Glover

In a village not far from where I grew up, there was an old cottage with a tiled roof that was almost covered with large, healthy clumps of Sempervivum.

My aunt told me they were called houseleeks and planted there to prevent lightning from striking the house. Believe it or not, from AD 768 to AD 814, Charlemagne, King of the Franks, required every homeowner to plant one houseleek on the roof of their dwelling as a safeguard against fire, war, hunger and pestilence. Since then, these little plants have been regarded as protection from evil spirits – an excellent reason to grow them!

Sempervivum grandiflorum

Sempervivums are known by the much more charming common name of hen and chicks in North America (or hens and chicks). It actually fits the plant perfectly: a healthy growing plant has a central tight rosette of fleshy pointed leaves from 3 to 8 cm (1 to 3 in.) in diameter, and surrounding it are many tiny offshoots, all tucked in like baby chicks. Growing in ideal conditions, these plants flower and hybridize freely, resulting in many named and unnamed cultivars. They are monocarpic, meaning that once a flower stem has appeared, bloomed and gone to seed, the rosette from which it sprang dies. But the plants are so clever that all those little chicks then grow and take over the space left behind. The flowers themselves are intriguing: little panicles of stars ranging in colour from greenish-white to yellow to pink. The other amazing thing about all the members of this genus is that they are hardy from zone 4 and up. I have seen incredible displays in Alberta and Saskatchewan. While they’re hardy and drought tolerant, they do need a rather specialized soil and full sun to really thrive. Get some good coarse grit or gravel and make up a mixture of two parts soil to one part grit/gravel, preparing the planting depth to about 15 cm (6 in.) deep. If it is on a slope facing south or west, so much the better, as standing water from heavy rains can be quite detrimental to these lovely plants. While they do well in pots, good drainage is integral and succulents absolutely hate being planted in those high-peat premixed potting soils. I speak from experience, having planted some in a shallow terra-cotta pan on my balcony table. The peaty soil stayed wet for too long and the plants actually shrank because their roots rotted! If you want to try some in a pot, they look really handsome growing out of the pockets of a strawberry pot. As a child I grew sempervivums in a trough garden and my very favourite was Sempervivum arachnoideum (spiderweb hen and chicks). The young rosettes are tight and quite tiny. The typical succulent pointed leaves have fine, silvery-grey webbing between them. The effect is quite stunning, especially if it is a large clump. I remember being taken to RHS Gardens in Wisley, where there was a dry-laid stone wall with these little plants growing in tight clumps in the cracks. I was entranced and just had to have some in my own garden. Sempervivum tectorum is the more commonly known species; it can be up to 8 cm (3 in.) or more in diameter, with bright-green fleshy leaves. There are many different cultivars of this plant, one being ‘Emerson’s Giant’, which has a lovely reddish tinge to the tips and edges of its foliage.

Sempervivum caucasicum

In the Alpine Garden at UBC, there are one or two good species to look for. Sempervivum caucasicum, as its name suggests, is native to the Caucasus Mountains. It has tight glaucous rosettes, with the outer mature leaves taking on an orange hue. Sempervivum grandiflorum forms a lovely mat at the base of a rock looking like a whole hen house. When you’re next at UBC Botanical Garden, stop by what was the old Alpine House, which has been renovated and is now the Intermountain Habitat House for plants that cannot tolerate coastal rain. The outside free-form stone wall houses the excellent collection of sempervivums, probably the largest public collection in Canada. Of course, not all hardy succulents are sempervivums; over 400 species of Sedum are native to many of the same regions. Probably the best known is Sedum spectabile. Its blue-grey foliage looks something like that of a jade plant, except the leaves are a little broader. It has long been a favourite for perennial borders as it blooms late in the summer with flat, cauliflower-like heads of tiny, dense pink flowers. It looks good at the front of a mixed border, as it grows to about 45 cm (18 in.) high and wide, and attracts bees and butterflies. Similar but more compact and looking like a little flower arrangement at the front of the border is Sedum spectabile ‘Hot Stuff’, about 30 cm (1 ft.) high, with stems in a nice tight cluster. Sedum ‘Herbstfruede’ is another of my favourites with lovely blue-green foliage and stunning salmon-pink blooms that age to a beautiful bronze as fall approaches, making it a great late-summer and early-fall garden plant.

yucca baileyi var. navajoa

Because most of these plants are low growing, readers on the south coast can add interest by interspersing clumps of yuccas, at least three per clump. Try Yucca baileyana var. navajoa, which has lovely, narrow, needle-like leaves up to 30 cm (12 in.) in length, forming an almost-perfect globe of see-through glaucous foliage. A notable beauty worth seeking out is Yucca filamentosa ‘Bright Edge’ because of its gorgeous leaf with a dark-green centre and wide gold edge. As you all know, I am a great believer in golden foliage to brighten those grey days of winter. Yet another radiant selection is Yucca rostrata ‘Sapphire Skies’, with a dramatic display of powder-blue leaves that fairly glow in morning or evening light. For more on yuccas, go to www.greatplantpicks.com for some wonderful possibilities, all hardy to zone 5.

Delosperma cooperi

Those who would like to add a riot of colour to the scene can try planting clumps of Delosperma cooperi, a succulent from South Africa that is covered with shocking magenta, daisy-like, double flowers in the summer. While this one is only hardy to zone 8, gardeners in chillier zones can display a planter of D. cooperi outside for a late-summer blast of colour and pull it inside during the cold months. In Latin, succos means juice or sap, and succulents from more than 60 families and 300 genera have evolved special water-storage tissues in thickened leaves, stems or roots as a way of surviving arid conditions. A carefully planted mixture of succulents can be the perfect answer for a drought-tolerant, low-maintenance garden. The range of colours and textures is amazing, and by interplanting largish clumps with complementary leaf colours and shapes, you can enjoy a truly spectacular show. n The following plants are hardy to the zone number indicated (turn to page 8 for our zone chart): Delosperma cooperi – zone 8 • Sedum ‘Herbstfreude’ (syn. Sedum ‘Autumn Joy’) – zone 3 • Sedum spectabile (everlasting, showy stonecrop) – zone 4 • Sedum spectabile ‘Hot Stuff’ – zone 4 • Sempervivum arachnoideum (spiderweb hen and chicks, cobweb houseleek) – zone 5 • Sempervivum caucasicum – zone 7 • Sempervivum grandiflorum – zone 6 • Sempervivum tectorum (hens and chicks, roof houseleek) – zone 4 • Yucca baileyi var. navajoa – zone 5 • Yucca filamentosa ‘Bright Edge’ (Adam’s needle) – zone 5 • Yucca rostrata ‘Sapphire Skies’ – zone 5 David Tarrant of the UBC Botanical Garden is a well-known gardening expert, author, and host of Spring, currently on HGTV. Additional photos: Terry Guscott: Sempervivum grandiflorum, Delosperma cooperi, Yucca baileyi var. navajoa, Sempervivum caucasicum