Growing Indoor Plants in the Greenhouse and Your Home

The point at which a greenhouse plant becomes a houseplant is difficult to define — much depends on the conditions that can be offered in the home, and for how long the plant is expected to last indoors.

A houseplant should ideally be able to spend the whole of its existence in the home, growing actively and healthily. Many other plants can be used, however, if they are treated as expendable after providing a useful period of decoration, or can be exchanged for other plants in a greenhouse where they can recover sufficiently to be used another day.

The decision of what to grow in a greenhouse is less difficult, for almost all plants grown in the home will grow equally well — often better — in a greenhouse, given sufficient warmth.

Generally speaking, plants for both home and greenhouse, whilst they are suitable for both situations, will benefit from a period in the more natural environment of a greenhouse.

Although most greenhouse plants benefit from good light, many of the green-leaved plants grown in the home are naturally adapted to shady conditions, and every effort should be made to provide the correct light intensity.

The temperatures provided in a greenhouse are minimum winter temperatures that should be allowed for houseplants - basically they are outdoors but indoors. Some plants will survive lower temperatures than those provided by a greenhouse, but they may suffer a severe check to growth. There is no precise temperature at which a tender plant will cease to remain healthy — much depends on other factors such as draughts, humidity and above all soil moisture. Many plants will survive surprisingly low temperatures if the soil is barely moist: it is a combination of wet roots and low temperature that frequently proves fatal.

Equally unsatisfactory for many plants is an excessively warm temperature in winter. Balanced, healthy growth is not produced by warmth alone, and without the accompanying light some houseplants will soon become sickly. Many cacti only flower well if subjected to a cold spell during the winter.

Lack of humidity is also a problem in most homes, and unless it can be provided by regular misting, by humidifiers, or by other means, it is best to avoid such plants which require high humidity.

Few plants require special composts, and most of them will grow happily in either a proprietary peat-based compost, or one based on loam, such as John Innes. 

Always bear in mind that plants in pots only have a limited root-run and the nutrients in the compost can soon become exhausted. For that reason most houseplants will benefit from regular feeding during the growing period.