House Plants
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All of us, gardeners and non-gardeners, have grown house plants and while the idea is very appealing it has to be admitted that the reality can be somewhat disappointing. To be successful with indoor plants you need provide the correct conditions for the plants’ survival and it is important to realise that conditions that we find comfortable are not necessarily those that plants most appreciate. The main points to consider are light, humidity, soil moisture, temperature and feeding.
Light
All plants need light for photosynthesis and even though most of the plants we use as house plants can tolerate reasonably poor light they will suffer if the light levels are too low. Plants suffering from inadequate light become leggy and lean towards the light. They will eventually become yellow and drop their foliage.
Areas away from windows are often very dark and may require supplementary lighting. Ordinary incandescent lights are not suitable for plant growth. Mercury vapour lamps, daylight fluorescent tubes (regular and compact) and the special plant growing fluorescent tubes (Grolux) all provide a more appropriate light for plants. One small spotlight or tube turned on for a few hours a day in the winter can make all the difference when trying to grow a plant in a dark corner.
Humidity
Most house plants come from the tropics and subtropics where the humidity often approaches that of a sauna whereas most houses have the humidity levels of a desert, especially in winter. Heating and air conditioning can dry the air to the point where few house plants can survive.
You can raise the humidity around your plants by sitting them on water-and pebble-filled trays. Regular misting of the foliage will also help offset the effects of low humidity.
Soil moisture
When to water is a question that faces every house plant grower. There is no hard and fast rule but bear in mind that more house plants die through overwatering than any other cause.
Watering is best done in the morning. Fill the watering can the night before and allow it to stand in the room with the plants. This will ensure that the water is at the same temperature as the soil and allows any chlorine to evaporate.
How often you water and how much water you apply depends on the type of plant and is largely a matter of experience. The plant will give you a few signs, the most obvious of which, wilting, indicates that water is needed immediately. The weight of the plant is another indicator: a light pot plant is probably dry.
The best guide is usually to check the moisture level by poking your finger a centimetre or so into the soil. If the soil is moist it will feel cool and damp, if not it will be dry and dusty.
Most plants can be watered from above using a small watering can. However, a few, such as African violets, cyclamen and cinerarias, may rot if regularly watered from above. These plants are best stood in a bucket of water and left to soak until thoroughly moist.
Temperature
Modern house plants generally thrive at normal room temperatures, but some prefer warmer or cooler conditions. Those that prefer cool temperatures and high humidity, such as maidenhair ferns, do best in bathrooms or rooms that are not regularly used or heated. Plants that prefer warmer conditions, such as Fittonia, are best grown in kitchens or living rooms.
Temperatures can vary markedly even with a heated room. Draughts from doors and windows can cause cold patches and any plants near large areas of glass will be colder than those in the centre of the room.
Feeding
Well-fed plants look more luxuriant and are better able to resist variations in temperature and humidity than starved plants. Liquid fertilisers and slow-release pellets are the most convenient to use. It is a good practice to add a well-diluted liquid fertiliser every time you water.
Types of house plants
Foliage
Apart from ferns and the few conifers treated as temporary house plants, all indoor plants have the ability to flower. However, many of them are grown primarily for their foliage and any flowers are simply a bonus.
Growing a plant for its foliage alone has some advantages. Flowering usually requires fairly bright light, while foliage tends to be more luxuriant in the shade. Consequently, if you’re not worried about the flowers, the foliage display often benefits. Rainforest plants such as Maranta, Calathea, Dieffenbachia, Aglaonema, Monstera, Pellionia, Peperomia, Philodendron, Pilea, Schefflera and Schismatoglottis can all get by in quite dark conditions, and even those with variegated foliage will maintain their leaf colour without ever seeing direct sunlight.
That said, some foliage plants, especially those with variegated leaves, need bright light to keep their colour. Caladium, Crotons (Codiaeum), Cordyline, Dracaena, variegated rubber trees (Ficus), Coleus (Solenostemon) and the fancy-leaved yuccas all need bright shade or a little sun for the best results.
Ferns are mostly natural shade-dwellers and, provided the humidity is high enough, they’re often the best choice for really dark places.
Flowers
While flowers have undeniable appeal, flowering house plants generally demand more care than those grown for their foliage alone.
The toughest flowering house plants are probably the arum-like species, such as Anthurium and Spathiphyllum. Begonias are also very reliable and easy to care for. Gardenias needs bright light and even warmth, but that scent is worth a little effort. Trickier, despite their popularity, are the African violets and their relatives. Known collectively as gesneriads, these plants often dislike overhead watering and frequently have a dormant period when they must be dried off. African violets (Saintpaulia) Columnea and Cape primroses (Streptocarpus) are easy enough, but keeping alive the likes of gloxinias (Sinningia) and Smithiantha requires more exacting care.
An alternative is to treat flowering house plants as temporary residents only. Tuberous begonias, Calceolaria, Impatiens, Pentas, cinerarias (Pericallis), Primula obconica, Schizanthus, Cape primroses (Streptocarpus) and Torenia all flower well indoors and often stay in bloom far longer than they would outdoors.
Special plants
Some groups of plants have attractions and demands that set them apart from the crowd. Orchids are probably the prime example. They are often very spectacular but may require precise attention to their requirement if they’re to bloom well. While the easier types, most notably the many Cymbidium cultivars, present no great difficulties, orchids tend to be plants for the enthusiast rather than the generalist.
Bromeliads too, particularly the air plants such as the Tillandsia species, have their enthusiasts. Once established they are undemanding, though their need for high humidity and specialist potting treatment rules them out for most houses.
One way around the humidity problem is to use terrariums and enclosed containers. The fad for bottle gardens may have died with the end of the 70s, but terrariums are still the best way to cultivate small numbers of bromeliads and tropical ferns without having to turn your house into a steam bath.
Cacti and succulents, on the other hand, are very undemanding and could be used more widely. Not all require full sun and many flower well indoors. They can be left without water for far longer than other house plants and will tolerate baking sun, cold draughts and low humidity.
Buying house plants
There are hundreds of different types of house plant on the market. Every garden centre stocks them and at first the choice can seem overwhelming. However, once you’ve eliminated those unsuited to your conditions and those that are too large or too small, the range diminishes rapidly. To avoid confusion, it’s important that you do your buying with a clear idea of what the plant is to do and the conditions under which it will be grown.
What to look for
Chose plants with compact growth and well-coloured lush foliage. If you’re looking for a flowering plant, buy one in flower, preferably with plenty of buds yet to open. If possible buy in the warmer months so that you can be reasonably sure the plant has been exposed to cold and draughts while in the shop.
What to avoid
Naturally you should avoid any plants with insect damage (or with pests present) and diseased foliage. But also look at the general shape and condition of the plant. Reject any with elongated stems, which indicates they’ve been grown in poor light or with improper temperatures. If it should be flowering and isn’t, don’t take it on trust that the plant will eventually bloom. Look at the crown of clump-forming plants, especially succulents and cacti, and reject any that show signs of stem softness or rot.
Pots
Pots come in all manner of sizes and designs so there are certain to be some that suit your decor. The design is up to you but the functionality of the pot as well as its visual appeal.
Make sure the pot has adequate drainage and can be fitted with a saucer to cope with the run-off. Ceramic pots are very heavy and prone to breakage. They are also very porous unless glazed. Plastic pots retain moisture but can be rather unattractive. Metal containers are best used as sleeves for other pots because they can corrode and may release toxins into the soil if used as pots. Wooden containers are more commonly used outdoors but if suitable they can be used indoors. Watch out for seepage and rotting with wooden containers.
Potting mixes
Most commercial potting mixes are perfectly satisfactory for a wide range of house plants, and specific mixes are available for fussier plants like cacti, orchids and African violets.
Potting mixes usually contain fertilisers but the supply is often inadequate. Mix in additional slow release granules and also add water holding crystals and/or wetting agents if they are not already present.
Repotting
If your plants are happy they’ll grow and you’ll have to repot them occasionally. It’s not a difficult procedure, but the question always arises: do you allow a plant to enlarge by moving it on to a bigger pot or do you cut it back and keep it in the same pot? Sometimes the plant answers the question for you. If it can be divided, you can break it up, return it to its original pot (with fresh soil) and have several spare plants. If it has a single trunk, as do some of the large dracaenas or Yucca elephantipes, it will have to go into a bigger pot. If it’s a shrub or a bushy perennial you can either pot it on or give it a foliage and root prune and repot it in the original container. Whichever method you chose just make sure you use fresh potting mix, water the plant in well and apply some mild liquid fertiliser.
Pests and diseases
Other than soft rots and mildew, house plants are really not that often affected by diseases, and the diseases they do suffer from are most likely to be signs of bad growing conditions than problems in their own right.
Pests are a different story. They’ll inevitably make an appearance and if you don’t keep a watch on your house plants they could be badly damaged. The most common pests are aphids, mealy bugs, mites, scale insects, thrips and white flies. Mild insecticides or removal by hand are usually effective for most of these, though bad infestations may need stronger sprays.
Mealy bugs and scale insects are the worst pests to deal with. The adult mealy bugs are easily killed, but the larvae live on the soil and only soaking the pots in insecticide will kill the larvae. Scales insects are protected by a waxy coating and live on the undersides of the leaves. You’ll need to add a spreader/sticker to your spray to make sure it adheres to the scale and you’ll have to ensure good foliage coverage to kill all the pests.
Propagating
Division and offsets
Tuberous-rooted, fibrous-rooted perennial and clump-forming house plants are usually propagated by division, most often in spring. Simply break up the tubers or the foliage clump and repot in appropriately sized containers.
Orchids are often grown from their rhizomatous roots, which are known as pseudobulbs. Their requirements differ and you should consult specialist advice.
Cuttings
Many house plants will grow from simple stem cuttings. Treat them just as you would cuttings of garden plants. Low, spreading house plants, such as Pilea will often self-layer as they grow. Any rooted pieces can be removed and grown on. Likewise, branches or stems with aerial roots can often be removed and potted up as ready-struck cuttings.
Leaf cuttings
Begonias and many of the gesneriads can be propagated by leaf cuttings. Remove a leaf, slice through some of the main veins on the underside of the leaf, then pin the leaf down on damp potting mix so that the cuts are in contact with soil. Cover the pot with a plastic bag to keep the conditions humid and within a month or two small plantlets should form where the veins were cut. Once large enough they can be removed and grown on.
Stem pieces
This method, which entails removing a length of stem with a leaf bud and treating it as a cutting, is most often used for Cordyline, Dracaena and Yucca. Even very woody pieces eventually strike if potted up and kept moist. Make sure you insert the stem the right way up.
Common indoor plants
The following are all readily available throughout the country. Most can be grown as house plants or cultivated in conservatories or greenhouses.
African violets
African violets (Saintpaulia species) have beautiful flowers and soft furry foliage. They prefer winter minimums above 12°C. They prefer a moderately rich, moist soil that is well drained. The furry foliage traps moisture and may rot if kept wet; watering by soaking from below is recommended. African violets like bright light but not direct sun.
Anthurium
Grown for their bold leaves and unusual arum-like flowers that have conspicuous red bracts. Anthurium prefers warm conditions, high humidity and ample soil moisture. Winter temperatures below 10°C are damaging. Regular feeding is important.
Aphelandra
The zebra plant has blackish-green foliage with starkly contrasting white banded variegations. It also has clusters of yellow flowers on stiffly upright stems. Best in warm humid conditions but capable of withstanding night temperatures down to 5°C. It is usually short-lived.
Aspidistra
A cast-iron tough foliage plant that forms a clump of strappy deep green leaves. It will grow under almost any conditions except extreme heat. It prefers regular moisture and feeding during the growing season. The small brown flowers are insignificant.
Begonia
Both tuberous and fibrous rooted begonias are often grown as garden ornamentals but evergreen forms are preferred as house plants. The fancy-leafed begonias, (such as the rex and iron cross styles,) the cane-stemmed and winter flowering cultivars prefer moderate warmth, around 15–18°C and fairly high humidity. There are many spectacular foliage forms and some also flower well. Water and feed regularly during the growing season but keep on the dry side over winter.
Bromeliads
Bromeliads are unusual plants that form a cup that often acts a moisture reservoir. Some are epiphytes and can be attached to tree fern slabs wired to the frame. Terrestrial or potted bromeliads should be treated in a similar way to orchids: use a coarse potting mix and provide high humidity rather than high soil moisture. Bromeliads vary considerably in their heat and light requirements: Aechmea, Billbergia and Vriesia are some the easier to cultivate genera.
Caladium
Spectacular foliage plants with large heart-shaped leaves in various shades of green, cream and pink. They prefer warm temperatures, above 20°C, and need regular watering and feeding during the growing season. They will suffer in low humidity. Most caladiums are herbaceous and will die back to a tuner in winter.
Cineraria (Pericallis)
Bedding cinerarias are frequently used to provide winter colour in the indoors. They require cool conditions, good light and moderate humidity. Plants are raised in autumn or bought in flower and they are discarded after flowering.
Croton (Codiaeum)
Crotons are brightly coloured foliage plants. Their leaves combine bright orange, yellow, cream and green in a bewildering array of combinations and patterns. They demand warm winter temperature, above 12°C, are moderate to high humidity. Feed and water well in summer. The leaves need frequent cleaning to keep the glossy.
Coleus (Solensostemon)
The fanciest coloured foliage forms of the bedding coleus are often used indoors. They are easily grown perennials that are often treated as annuals. Their leaves combine bright yellow, red and green tones with cream and darker greens, and are usually heavily puckered at the edges with a felt-like texture. Warm temperatures, good light and moderate humidity are essential or the foliage will drop in winter.
Columnea
These close relatives of the African violet are natural trailers that are usually grown in hanging baskets. They have long tubular flowers in shades of yellow, orange and red. The leaves are quite small and hairy, they are normally deep green but variegated foliage cultivars are available. Columnea requires warm night temperatures, above 10°C, and steady soil moisture.
Cordyline and Dracaena
The strongly upright Cordyline terminalis and Dracaena cultivars often have boldly coloured and patterned foliage. They are good long-term house plants that demand nothing more than regular watering and occasional feeding. Best with winter minimums above 7°C but capable of tolerating colder conditions for short periods.
Cyclamen
The florists’ cyclamen (C. persicum) is widely grown for winter colour. Ready-grown plants may be bought of you can start your own from seed. They need good light and just enough water to keep the soil moist. Too much water, especially on the foliage or around the corm, will lead to rotting.
Dieffenbachia
Dieffenbachia is a foliage plant with large heart-shaped to elliptical white, cream or yellow variegated leaves. It will grow well with average house temperatures but the leaf edges quickly brown if the humidity is too low.
Ferns
Many ferns are excellent house plants. They will tolerate low light levels but will suffer in low humidity. The leathery-leafed ferns, such as the stag’s horn fern (Platycerium) Polypodium and the various Polystichum ferns will withstand low humidity but Adiantum, Asplenium, Pteris and most of the other common ferns are best in bathrooms or unheated rooms.
Ficus
The large-leafed rubber tree (F. elastica) is the best known indoor fig but there are many other species that are also very attractive. They are grown either for their bold foliage, in the case of F. elastica, F. lyrata and F. macrophylla, or their growth habit, in the case of F. benjamina and F. pumila. Most species and cultivars are upright shrubs that eventually develop into trees. All Ficus will eventually become too large to keep indoors. However, some species are hardy enough to be grown outdoors in mild areas when they outstay their welcome indoors. Ficus are easily grown plants that will tolerate considerable neglect although they prefer ample moisture, bright light and moderate humidity.
Fittonia
Fittonias are attractively marked foliage plants that require a warm humid environment. They are ideal for terrariums and bottle gardens. F. verschaffeltii has pink-veined purplish leaves and F. v. ‘Argyroneura’ has silver-veined deep green leaves.
Gardenia
Gardenia jasminoides is overpoweringly fragrant. It has large glossy, green leaves and rose-like, creamy-white, double flowers. If the humidity falls too low or the night temperatures are erratic the flower buds may drop. Water and feed well from early spring to late autumn. Use a humus rich potting mix.
Gloxinia
The gloxinia (Sinningia speciosa) is a member of the African violet family. It has very large trumpet shaped flowers and is available in most colours except yellow and orange. The flowers and the large leaves have a velvety texture. Gloxinias have a dormant period in winter, during which just enough water to stop the tuberous rootstock shrivelling. Increase the water slightly as the plant comes into growth in spring, water and feed well while in the most active summer growth phase, then gradually dry the plant off from mid autumn. Use a humus-rich, well-drained, potting mix and grow in a bright position out of direct sunlight.
Impatiens
The common bedding Impatiens are seldom grown indoor but the fancy double forms and the larger New Guinea hybrids, such as the Butterfly series are popular house plants. They are easily grown in any moist well-drained potting mix with a well-lit position out of direct sunlight. They require a minimum temperature above 7°C to flower reliably through winter.
Monstera
The fruit salad plant (M. deliciosa) has very large, deeply lobed, dark green leaves and is usually treated as a foliage specimen. Under ideal conditions, however, it will produce fragrant, cream, calla-like flowers that are followed by pleasant tasting fruit that give the plant its common name. Established climb by means of strong aerial roots that emerge from the main stems. It is easily grown in any well-drained potting mix with a brightly lit position.
Palms
Most palms respond well to indoor cultivation. They vary considerably in their heat requirements but most do best with winter minimums around 12°C. They need regular moisture and moderate humidity. Chamaedorea, Howea and Rhapis are among the least demanding genera.
Peperomia
Peperomia are small clump forming perennials with heart-shaped leaves. Some have smooth foliage other are heavily ‘seersucker’ textured. The foliage may be green or silver variegated. The cream flower spikes are unusual rather than very attractive. They prefer moderate to warm temperatures, bright indirect light and high humidity.
Philodendron
There are many philodendrons ranging from small leaved shrubby species through to large leaved shrubs and climbers. Under ideal conditions they will produce calla-like flowers but they are primarily grown as foliage plants. Many foliage forms have been developed: some have deeply lobed or cut leaves, others have very bold variegations. The climbing species are usually trained up tree fern trunks or wire mesh columns filled with sphagnum moss. Water and feed regularly; these plants are generally trouble free if they can be kept growing steadily. They are best in a well-lit position out of full sun with moderate to high humidity.
Spathiphyllum
The peace lilies (S. wallisii and cultivars, such as ‘Mauna Loa’ and ‘Clevelandii’) are attractive white to cream flowered arum-like plants. The flowers, which are surrounded by a large bract, are often fragrant. The leaves are long, deep green, and glossy. Best in a fibrous, well-drained potting mix in bright position out of direct sunlight. Spathiphyllum prefers high humidity and regular feeding with temperatures above 12°C. Water regularly in summer but allow to become dry between waterings in cooler weather.
Streptocarpus
Cape primrose is an African violet relative, the foliage resembles the common garden primrose but the flowers, which are carried on 15 cm stems, are up to 75 mm long and trumpet shaped. It prefers cool temperatures (around 13 - 18°C), a moist well-drained soil, a bright position out of direct sun and regular doses of dilute liquid fertiliser.
Tupidanthus
Tupidanthus calyptratus is a large foliage plant that will eventually develop into a tree. It has broad, glossy, deep bronze green, digitate leaves and strongly upright growth. It prefers a well-lit position and regular feeding and watering in warm weather. The heads of small flowers are insignificant.
Copyright Geoff Bryant
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