How to water houseplants

There are two simple rules – water generously but ensure the pot does not remain standing in surplus water. It is no use simply splashing the surface of the compost with water and then going on to the next plant. Pour steadily until the gap between the compost and the rim of the pot is full, then wait until it drains through. If it’s all absorbed, apply more water and again wait until it runs through, [fit runs through immediately. the compost has probably become so dry it has shrunk from the sides of the pot (or in the case of a peat-based compost. the peat has dried out). If this has happened it will be necessary to place the pot in a bowl of water until the compost is thoroughly moist again. This is the best way of watering plants growing in a very peaty compost, such as azaleas.

A self-watering pot with a visual gauge showing the water level.

For plants with a low rosette of hairy leaves, such as sainlpaulias. or conns that may rot. such as cyclamen, it is best to add water to the saucer and allow it to be taken up by capillary action. This may take a little time. A good watering-can specially designed for indoor use is essential. Choose one with a long, narrow spout so that the water can be controlled accurately. If the spout is too short and the diameter too wide there will be a tendency for the water to shoot forward when the can is tipped, making it difficult to control. resulting in water over the window-sill and furniture as well as the plant. Because you don’t want the plants to stand in water, it is quite likely that surplus will have to be emptied from the saucer or container. However, a small bonus for this extra effort is that if a liquid fertilizer is being used, it may be possible to reuse some of the run-oil’ water and so economize. There are two situations where the excess water may be left with safety – if the pot is standing on a layer of pebbles and the water is not in direct contact, or if the plant is one of the rare exceptions that will tolerate wet feet. The umbrella grass (Cyperus altermfolius) is naturally adapted to marshy ground, while the Indian azalea (Rhododendron simsii) and mind your own business. Soletrolia soleirolli (better known as Ilelxiiw soleirolii), are examples of plants that will thrive in wet conditions.

‘Automatic’ watering

I lydroculture units apart. there are self-watering containers available that will take much of the guesswork out of watering. Individual systems vary, but most use wicks to transfer water from a reservoir to the compost. Even so. you still have to look at the water level indicator periodically and top up the unit as directed. There are many attractive plastic self-watering containers, but if these do not appeal there are also glazed pottery containers with a porous compartment that is filled with water which gradually seeps into the compost. Self-watering containers are useful for anyone with little time to spare, or if short stays away from home are a frequent problem, but they should not provide an excuse for neglect. Capillary mats are frequently used in greenhouses and good shops selling houseplants. and can also be bought for home use. These mats are most useful where many plants are grouped together on a tray but this is not how plants are generally arranged in the home. Capillary mats are. however, useful for placing in the long trays that can be bought for standing plants on a widow-ledge. If such a mat is used, it should not be assumed that regular checking is not required – the mat can dry out just as easily as the pots – but it does ensure that the pots receive a steady amount of water. The mat should be kept evenly moist, but not swimming in water, and the pots should be pressed well into the mat’s surface to ensure good contact.

Type of water

As long as the water is not loo hard. most houseplants will be perfectly healthy if given tap water, [fyou live in a particularly hard water area it is best to use a water softener or to boil the water first – but allow the boiled water to cool before use. Rainwater can be used, but an adequate supply is not always available, and unless it is kept as clean as possible it is likely to introduce and spread diseases. Rainwater is best reserved for those plants that respond adversely to lime, such as camellias. azaleas and blue hydrangeas. I lydroculture plants grown with an ion-exchange fertilizer, however, must be watered with tap water as the calcium is necessary to trigger the chemical reaction that will release the nutrients.

Going on holiday

Houseplants can be almost as much of a problem as pets at holiday time – knowing what to do with them for a week or two is always difficult. If the holiday is brief- less than about live days- it should be sufficient to water them well before you leave. In all except the hottest weather no permanent damage should be caused, although it makes sense to remove plants from a hot sunny window-sill to a cooler and more shaded environment. Hydroculture units and self-watering devices can be left for a fortnight without worry provided there is sufficient water in the reservoir. This is one instance where ‘topping up’ may be advisable if the level is getting low (but be sure to let the roots of hydroculture plants dry a little upon your return). Most cacti and succulents will survive a week or two without water if absolutely necessary, but alternative watering arrangements simply must be made for all other plants.

There may be a temptation to put some plants outside, on the basis that most of those outdoors manage to survive wilh the rain that nature provides. But there is no guarantee that it is going to rain at the right lime, and nature does not have plants growing in pots raised above the ground. Even if the pots are plunged in damp soil, most houseplants will not be able to withstand the sudden shock of being placed outdoors even in high summer. Try only those plants thai the A-’/ of Houseplants suggests can stand outdoors in summer -and even then provide a sheltered spot. The best solution is to arrange for an understanding neighbour or relative to care for your plants in your absence. If this is impossible you will either have to arrange your holiday to coincide with

the resting period of most of your plants (winter) or prepare them to last the siege as well as you can. in which case there are various techniques that can be tried. (.roup the plants together in a light place out of direct sunshine (or in a shady place for shade-loving plants), and arrange a reservoir of water at a slightly higher level (a large ice-cream container is suitable). By using wicks, which you should be able to buy from a good horticultural sundriesman. a steady supply of water can be applied to the pots. An alternative method is to run wicks from a reservoir and stand the pots on the wicks, allowing capillary action to transfer water to the pots. Always have a trial-run first, however, to be sure you have a system that works. If damp peat can be packed round the pots, so much the better. Do not apply a stronger dose of ’ccd before you leave the plants, to compensate for not feeding while you are away. It is better to miss a feed than to risk damage through over-feeding.

HUMIDITY

Plants are much more sensitive to humidity – or rather the lack of it – than humans. They lose water constantly through their leaves in the form of vapour transpired through minute pores, and if the atmosphere is dry the rate of loss will increase and often cause stresses within the plant. Obviously, plants vary in their tolerance and while cacti are well adapted to a dry atmosphere as well as dry roots, other plants from the rain forests of Peru and elsewhere, such as littonias and philo-dendrons. need humidity. Humidity produces a buoyant growing atmosphere that is immediately sensed as soon as one enters a greenhouse full of healthy plants.

Modern living, with its ever-increasing central heating and tendency towards a dry atmosphere, is unfortunately not conducive to this environment, and it is a constant battle of balance between an atmosphere that is right for the plants and one that is comfortable for us.

A start can be made by using humidifiers over radiators or near other forms of heating (taking into account safety aspects). which will prevent the air becoming excessively dry. failing anything more sophisticated, a few bowls of water will help.

There is no way that we can recreate the steamy atmosphere of a warm greenhouse in the living-room as a whole, so efforts are best concentrated on providing a localized environment. It is quite easy to provide moist air around small plants, by standing the pots on gravel or similar small stones to hold the bottom of the pot above the water in the base of the container. Another method sometimes used is to pack moist peat or moss between the pot and the outer decorative container. This is effective in producing a good micro-

Accssively dry air has a damaging effect on plants, and a humidifier, particularly in centrally heated homes, can help maintain a more humid atmosphere. They work by evaporating water.

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climate, but it is not easy to judge whether excess water is standing in the bottom – the consequences of which can be an overwatered and ailing plant. Spraying the leaves with a fine mist of water is very effective, but also time-consuming and not always good for the wallpaper and furnishings. In a bathroom it is simply a matter of placing the plants in the bath for their daily syringe, but in other rooms it may involve removing them to a more suitable place. It is a technique probably best reserved for those plants that will benclit immensely from this treatment, such as ferns, sela-ginellas and littonias. By grouping plants together the local humidity is increased and the plants lend to thrive better than they would as individual specimens. Never place a plant over a warm radiator or lire – apart from the safety aspect, the warmth will do them no good if the dry air kills them.

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