Gardening expert Maggie Barry knows all about indoor plants – she has more than 100 of them. She also knows a thing or two about keeping them alive. In this 2021 feature from the Listener archives, Barry shares her tips and tricks on the dos and don’ts of indoor gardening.
With a little basic knowledge, swapping and propagating can bulk up your plant collection and save you a fortune. For a start, there are fewer rigid rules than you might imagine about what can be grown inside and what belongs in the garden. Many garden plants can be invited in for their show-off flowering periods, then cut back and replanted outdoors. These temporary house guests will let you know when they’ve had enough. After flowering, and/or when their leaves droop or change colour and die back, their visit is over.
Even in an artificial indoor environment, plants tend to follow their usual seasonal patterns, so it’s natural for woodland flowers such as cyclamen to die back in the warmer months. They’ll be happy outside in some shade and, all going well, their corms will resprout in early autumn. If leaves are the plant’s main attraction never let it waste its energy on its - often- nondescript - flowers. Nip them in the bud. To encourage bushy growth, most herbs, perennials and flowering annuals will bush up pleasingly if their growing tips are pinched out or removed once they get to about 15cm.
As for display, behind every Instagram showstopper is a history of experimentation, but there are some useful general rules. For visual impact and health, flowering plants such as cymbidium orchids and cyclamen are best grouped together- in conditions that suit them- rather than dotted about. Odd numbers tend to please the eye better, and a restrained palette is safest for beginners.
Many garden plants can be invited in for their show-off flowering periods, then cut back and replanted outdoors. Minimalism is not usually associated with indoor plants, except bonsai and ikebana, the Japanese art of flower arranging. Lush is the key descriptor. Restaurants and hotels have popularised boisterous “living walls” - vertical gardens that can bring Henri Rousseau jungle paintings to life indoors. Given the risks of water damage, though, this is risky and best done only by professional installers.
Festooning a fence that can be seen from the house is a safer way to introduce a green wall, using hanging planter pockets. These can also cover unsightly features and save space, accommodating dozens of herbs, cuttings, flowering and foliage plants - provided they all like similar growing conditions. For an indoor-wall effect, layered shelves of plants, close to a sunny window, can be effective, with the help of grow-lights to provide substitute light for the higher, darker levels. It needn’t be flash. Recycled bookcases or (ideally, waterproof) metal stands will do, as the plants are the focus. The trick is to combine upright and trailing, leafy and succulent varieties to create interest and texture.
Any that fade or fail to flourish can be replaced by finer-looking specimens. By propagating and swapping plants with friends and family, a wall of plants can become an affordable, rewarding indoor feature.
There’s no mystery about why most houseplants die. The No 1 cause worldwide is overwatering. Less is more. I water when necessary, but check each plant at least once a fortnight - weekly in the summer. I carry a half-full bucket of water and scissors to snip vanquished bits. The key is knowing the various drinking habits of different plants. Orchids may only want a splash around their aerial roots once a month. Bromeliads like occasional top-ups directly into their crowns. Fleshy succulents need to dry out between drinks, although after that they don’t care if they’re given a thorough soaking. Ferns and leafy plants are much thirstier.
My “canary early warning plants” are Spathiphyllums - peace lilies. If their leaves are drooping, it’s time for a hands-on check on everyone. If a plant’s soil is damp to the touch, skip watering. If it’s dry past the base of your fingernail, water it thoroughly by fully immersing it in the bucket until the bubbles stop rising, signifying that air pockets are gone. Scoop up any escaped floating potting mix and push it firmly back to keep the shallow roots in place. A heavy mulch such as crushed shells can help, especially with cacti and succulents. Small pebbles, fine bark or sharp gravel also neaten pot displays, and succulents, in particular, thrive on the dry reflected heat and being raised above direct contact with damp soil. Ensure plants are robust and able to survive disease and predation by fertilising monthly in the growing season and sparingly in autumn and winter. Snip-groom and deadhead using sharp scissors to encourage fresh growth and remove dying leaves as they can harbour pests.
Plants also need MIQ. Any new plants should be isolated from your others for a few weeks to ensure they haven’t brought unwelcome hitchhikers with them. If heartbreak strikes - scale, mealybugs or aphids - the first treatment is to squash them. Follow that with a cotton wool bud dipped in a 50/50 solution of water and methylated spirits, a nip of vodka or any alcoholic spirit you can spare. Dab affected areas every few weeks to keep on top of the problem. Early detection, treatment and quarantine is the difference between losing a few leaves or potentially a slew of plants. Get into the habit of noticing changes so you can pounce early. Cut out damaged growth and wash the whole plant in cold, diluted dishwashing liquid, including under the leaves and on top of the soil. Disinfect all clips, ties and stakes and the sides of the pot itself, where bugs at various stages of their life cycles can lurk.
A great preventive is to pop leafy indoor plants out in the rain for a few hours or hose them down in the shower to freshen them up and help dislodge predators. Some plants don’t appreciate heating and air conditioning as we do. Standing pots on a layer of gravel, with water in their saucer, keeps the roots from rotting but humidifies their atmosphere. Houseplants have a reputation for being tricky to keep alive, let alone propagate. Yet even the much-ballyhooed fruit-salad/Swiss cheese plant - Monstera deliciosa - is pretty hard to offend, grows willingly from cuttings and has very basic needs.
Those who have invested three-to four-figure sums in a precious variegated specimen will be relieved that it’s among the most obliging of houseplants. In nature, it’s an evergreen tropical vine that can reach monumental proportions in the right habitat. When domesticated in small indoor pots, a monstera’s growth is limited to parlour-sized dimensions and it will take the hint if you prune its tips to keep it shorter. It appreciates extra humidity via misting or a gravel-and-water-saucer base. Like other fleshy-leaved plants, it also responds well to a regular “polish” - commercial leaf wipe or make one yourself: a glug of cooking oil and two squirts of washing-up liquid mixed with half a litre of water.
For those who swear they “always kill houseplants”, try succulents and cacti. Their needs are even simpler: more light and less water. Full-on sun magnified through the window would kill most plants, but not them. You could kill them with overwatering and darkness, but left to sunbathe and mind their own business, they’re highly unlikely to let you down.
Their leaves and stems will sprout roots just by being pushed lightly into soil, but not if it’s too damp. Some, such as the donkey tail (Sedum morganianum), sprout roots from the blunt end of each tiny leaf, which can be left sitting on the soil surface or pushed gently into the soil of neighbouring pots. “Burro’s tails” have been known to grow to more than double the expected 30-40cm. They need to dangle free of obstacles and disturbance, as the slightest knock can dislodge leaves.
The large subtropical philodendron family is also adaptable and hardy, giving an instant jungle effect with fast-growing long stems. The heart-leafed vines need a supporting structure, and rampancy is easily checked by removal of the growing tips. A 6-8cm cutting from below a leaf node will readily sprout roots in water. Rubber plants - rightly celebrated by Frank Sinatra as being unbudgeable, even by butting rams - are easily accommodated toughies, preferring a warm, draught-free spot with indirect light and watering only after they completely dry out. Sansevieria - formerly called “mother- in-law’s tongue” - bulk up readily. Rhizomes or “pups” develop around the base, which can be propagated, and an unwanted leaf can be angle-sliced to 5cm pieces, left to dry out for a few days, then planted into free-draining soil.
The ubiquitous spider plant (Chlorophytum comosum) could hardly be easier to grow or multiply. Neglect-tolerant, it sends out long shoots with ready-made plantlets with emergent roots that can be detached and water- or soil-sprouted. In full sun it will be more stripey, but in lower light it will be a darker green. Many plants, preferring low light and high humidity, would even love to live in your bathroom. These include African violets (Saintpaulia), which naturally grow under taller plants in the tropics. Much misunderstood, their needs are simply for moderation in all things. A little light, a little water and humidity, a smidgen of fertiliser and a small pot. If their modesty is respected, they’ll flower all year round. Happiest when pot-bound, they will eventually require thinning out. Branches snipped from the base can be stood in water for a month until they root, then planted up in high-fibre potting mix. Even a single leaf on a long stem will sprout roots in water provided it’s elevated above the water and can’t rot.
Still daunted? Air plants (Tillandsia) need neither soil nor water, getting all their nutrients from the air. A mere wisp of an air plant, with no help from me, made itself at home draped across a corner of the bathroom mirror frame where it quietly flourished into a lacy curtain in the five years it lived there undisturbed. Moisture-loving ferns will generally thrive in a bathroom, although maidenhair ferns are unforgiving if allowed to dry out.
The green filigree fronds of the swordfern, Nephrolepis, appear deceptively delicate but clothe a tough customer suitable for an anxious beginner. Colourful, velvety coleus - the first pot plant I ever bought, from my school fair - is an easy annual that can be made perpetual by taking small cuttings and rooting them in a glass of (regularly changed) water. So can perennial tradescantia, such as the striking, spiky sprawler, “Purple Queen”. Some cuttings, notably those from Pelargoniums and succulents, are prone to rotting.
Ideally, strip off most of the leaves and let the cut end dry out for a couple of weeks until a scar forms, then plant them to root in soil.
I won’t minimise the perils of repotting. It’s easy to damage delicate feeder roots. You must ask, is this plant’s journey to a new pot really necessary? If roots are growing out of the drainage hole, it might be. But remember that most succulents, cacti, pelargonium, orchids and bromeliads have small, fragile roots and don’t repot as robustly as palms or big leafy plants. For any transplant, the least root disturbance possible is essential. If you want classical, indestructible foliage plants with a proven track record going back hundreds of years, invest in an aspidistra or a kentia palm. The latter, in particular, will set you back. But it survived the overheated, dingy parlours of the Victorian era, so it’s bulletproof. Likewise, the aspidistra, which is often called the cast-iron plant, impervious as it is to insects and insults. Why, this heroic foliage even survived the verbal blowtorch of social critic George Orwell, who called one of his most coruscating social satires Keep the Aspidistra Flying.
This feature was originally published in the December 4-10 2021 issue of the New Zealand Listener. It has been edited for use here.
