Cacti and succulents
There’s lots to love about the diverse family of succulents that do so well in New Zealand gardens. Mary Lovell-Smith takes in the wonderful world of this easy-care, hardy and adaptable tribe.
Our pick of the best for Kiwi gardens from this large and diverse plant family.
Credit Instagram. Or the millennials’ minimalist aesthetic. Or maybe it’s just their turn again in the cycle of fashions. Whatever the reason, succulents and cacti are returning to our houses and gardens in a big way – with their reputation for being easycare intact. Fabulous on a grand scale outdoors, they also make eyecatching houseplants, where their often intricate symmetry and patterning is more readily observed. The reason succulents and cacti make such hardy indoor and garden plants, in part, is because they can withstand sustained periods without water. Having evolved in dry environments, they can store water in their leaves, stems and roots. Other aspects of their physiology play their part too. Most plants open their stomata in daylight to absorb carbon dioxide for photosynthesis; succulents and cacti open theirs at night, when air temperatures are lower and humidity higher – reducing their water loss. Transpiration is also reduced by their having fewer stomata than other plants, and by the presence of thick skin, waxes, resins, hairs or deep ribs, needles and compact shapes.
However, dry environments are not only places with low rainfall – they also include places where water is precious. This could be in the mountains where it may rain often but the cold, strong winds and rocky soils let it slip away almost as fast as it comes. Or near the coast where brackish water discourages other plants. In tropical forests, epiphytic succulents have evolved in the treetops, taking their water from the host plants.
Cacti are often singled out almost as a separate category to succulents, but they are succulents too. The common perception that only cacti have prickles, spikes or spines is wrong. The hallucogenic peyote cactus ( Lophophora williamsii), for example, is spineless. And as any gardener who has battled with it can testify, most agaves have spines, yet they are not cacti.
What identifies a cactus are small, usually woolly or hairy, round “bumps” or structures on its surface. These areoles are found only in cacti, and not in other succulents, or any other plant family. Often described as a modified bud, the areole sprouts flowers, hairs and spikes, which themselves are believed to be vestigial leaves.
What also distinguishes cacti from other succulents is distribution. Succulents hail from right around the world, growing on every continent except Antarctica. New Zealand has some, including the trailing horokaka or New Zealand iceplant ( Disphyma australe) found on coastal banks and cliffs, and the Chatham Island iceplant ( Disphyma papillatum). Cacti are native only to the Americas, from Patagonia to Canada, with one exception – the mistletoe cactus ( Rhipsalis baccifera), which is also found in Africa, Madagascar and Sri Lanka.
The right succulent for you
From euphorbiacea and agavaceae to asteraceae and liliaceae, up to 60 plant families count succulents among their members. The diversity is huge, as are the conditions in which they flourish. Some like low temperatures, others high. Some prefer shade, others sun.
In your house
Apart from their obvious physical attractiveness, succulents are popular houseplants because they are easy to grow, most varieties being quite forgiving of neglect or of ill treatment through ignorance.
While those that like full sunlight will grow indoors, they tend to lose their colour. Red or orange ones may turn green, so as a rule, it is best to grow green ones indoors. Lack of sunlight can also affect a sun-loving succulent’s form, stretching it out in odd and unappealing ways.
One of the commonest ways to kill a succulent is by overwatering or giving them waterlogged soil which will rot the roots. This is easily avoided by ensuring their pot has a drainage hole and a free-draining growing medium. Allow the soil to become dry for a couple of days between waterings. Too much water causes soft wrinkled leaves, black rot on lower stems and leaves that fall off readily. Removing dead leaves will smarten up plants, enable better airflow and make them less susceptible to bugs, which love decaying plant matter.
In the garden
Outdoors, succulents are equally easy to grow, given similar attention to their needs. Ideally, the soil should be friable with good drainage but heavy soils can be improved with crushed pumice or coarse sand and compost. They suit sunny spots such as north-facing slopes and will happily grow in those dry places, including under eaves or in the rain shadow of a fence. Feed with a dose of low-nitrogen slow-release fertiliser in spring.
Christchurch landscape architect Eric Ellis has used large succulents in his designs for many years; initially in the warmer coastal hill areas, but more latterly on the flat and further inland as climate change has kicked in. “The tree aloes, Aloe thraskii, Agave attenuata, yuccas and the tall San Pedro cacti are beautiful, striking. They give great structural form to a garden, especially around modern, non-traditional architecture,” he says. “Look upon them as pieces of sculpture and you see them in an entirely different light.”
Get more for free
Few plants beat succulents for ease of propagation. The main methods are:
By leaf: Twist off some leaves, then let lie on the top of the soil for a few days for the ripped end to callous over (and avoid rotting) before watering.
Cuttings: Snip off an offshoot, remove some of the lower leaves and leave to dry before planting.
Babies: Some succulents send out chickens from the mother plant, which usually are already rooted. Remove gently and replant.
Seeds: Let the flowers shrivel, then cut it off to put in a paper bag in a dry place. Shake to dislodge seeds and sprinkle them on soil. Cover seed tray with clear plastic and keep in indirect sunlight. Misting is the best way to keep soil moist.
Ideally, the soil should be friable with good drainage but heavy soils can be improved with crushed pumice or coarse sand and compost.
Succulent varieties
From aeoniums, agaves, aloes and crassulas to echeverias, sedums and sempervirens, there are dozens of succulent families to choose from. Here’s a selection.
1Th e power of flower
Lampranthus spp are best known as iceplants, though its Latin name means shining flower. Indeed, a small-leaved lampranthus covered in daisy-like blooms is a stunning sight in spring. This South African native thrives on dry sandy areas and can be used as a trailing groundcover. Drape it over banks or in a rock garden. It tolerates light frosts but not prolonged damp.
2Get stoned
Lithops reach perfection in their simplicity. In the wild they avoid the attention of thirsty grazing animals by appearing as a pair of stones. Each year, a new pair of inner leaves grow and the old ones wither away. They prefer about five hours of pretty much direct sunlight in the morning and partial shade in the afternoon. Indoors, this means a spot by a north-facing window (second best, an eastern one). With their charming markings, subtle colours and diminutive size, they are best appreciated close up.
3Tall tails but true
Sedum morganianumaka burro’s tail or donkey’s tail hails from Mexico and the Honduras, and is best planted to show off its trailing habit, in a hanging pot or on a shelf, where its plaited-looking stems can drape up to 60cm long. Pink-red flowers appear in summer at the stem tips. While it relishes full sun, avoid too hot a spot indoors as it is prone to drying out. Outside, give it morning sun and some afternoon shade. It will not tolerate temperatures below 5 degrees.
4Th e big boys
Got time and space? Then try one of the big bad boy cacti, such as Echinocactus grusoni, commonly known as the golden barrel cactus. Originating from Mexico, it will
(eventually) grow to a 1m diameter ribbed globe. When it grows too big for indoors, plant it outside anywhere sheltered from winter rains.
Another impressive yet amenable cactus is the statuesque Euphorbia ammak, from Saudi Arabia and Yemen. It can soar to 10m, and puts out those classic Western movie arms. Plant it inside in a bright spot or somewhere warm and sheltered in the garden, such as by the northfacing wall of a building, preferably protected from winter rains.
5Fiercely cute
Ridiculously adorable with an excess of long prickles is the goat’s horn cactus ( Astrophytum capricorne) from Mexico. Growing to about 25cm tall by 10cm wide, its prominent ribs create an almost star-shaped ball or oval. Another plus: its beautiful pale yellow, red-centred flowers. It loves as much sunlight as it can get, but if outdoors, resents summer temperatures below 21 degrees Celsius. If spines don’t appeal, look at its less prickly cousins.
6First class
One of our most common genus of succulents are the echeverias, a large American family usually distinguished by their rosette forms. They owe some of their ubiquity here to their ability to withstand cold temperatures, but it is the sun that brings out their colours. And what a range – white, grey, green, mauve, orange, red, blue, brown, purple and even bicolour. Some are covered in wax; others, hairs or blooms. Extensively hybridised, an often bewildering array is available at garden centres. Echeveria agavoides ‘Waterlily’ has pointy leaves; Echeveria ‘Cinderella’ has frilled leaves; and those of Echeveria ‘Topsy Turvy’ are squared off. They make fabulous houseplants. Outside, the larger ones are great statement pieces. Use the smaller ones as groundcover.
With their charming markings, subtle colours and diminutive size, they are best appreciated close up.
7Flying high
No points for guessing why the South African Crassula falcata is called the aeroplane propeller or airplane plant. Its grey, 10cm long sickle-shaped leaves pile atop each other sculpturally, like a stack of abandoned propellers. Add a cluster of tiny scarlet flowers in summer, a potential height of 60-plus centimetres, a cold-tolerance to -6C, an ability to perform in full sun to part shade, and it’s a winner, indoors and out.
8Soft- hearted
The slowness with which Hoya kerrii grows is a downer for some, but others can see that it gives them all the more time to get soppy over the heart shape of its leaves (thus its popular name, sweetheart plant). Usually sold as a single leaf in a pot, it takes several years to get going, but then this charming Southeast Asian climber rockets away, growing to 4m long with waxy pale pink flowers with a deep pink centre star. Keep it inside, and somewhere bright. ✤