Houseplant cultivation in the greenhouse

Houseplant cultivation in the greenhouse

Britain, unfortunately, still lags behind many Continental countries as far as indoor décor with pot plants is concerned. Many of the homes in Holland, for example, have large pictiure windows full of the most magnificent galaxy of plants one can imagine. Inherent appreciation over generations for all things which grow has, I feel, for a large proportion of the population, much to do with this philosophy. Nevertheless, it merely needs a start with pot plants, when, with a little ex-perience, I feel sure that many gardeners could emulate our Continental neighbours.

Much of the success in pot plant culture lies in a happy blend of patience and common sense. The greenhouse should be considered both as the production unit to provide a range of pot plants over the year for the home, and as an absorbing and attractive feature on its own.


A well situated, adequately ventilated, drip-free greenhouse, with a good clean water supply and a heating system capable of maintaining a temperature of around 50-55° F. is the first essential. There must also be a good system of benching, either on one level or tiered, not only to make more use of space, but to present a more attractive appearance. A convenient corner of a bench, either in the greenhouse or in a nearby shed, should be available for potting activities, and there must also be a storage area for the ingredients necessary for growing mediums, although these days, with easily bought, reliably formulated mixtures, this is not now so essential. There should also be suitable storage space for pots and seed boxes. It is also necessary to think of propagation facilities in the form of either a propagating case or a temporary or ‘permanent’ rooting bench.


Methods of propagation will depend upon what is considered to be the most effective technique. Where vegetative methods are used, it will be necessary to obtain stock plants or beg a cutting or two, while for seed sowing it is simply a question of deciding what to start with and making the necessary purchases. Some plan of action will, however, be necessary, preferably starting off at the appropriate time of year in the prescribed manner. The methods of seed sowing, cutting selection and rooting, leaf propagation, etc., are matters which were referred to earlier, as also were the appropriate composts for satisfactory growth.


Plants vary greatly in their growing habits, growing vegetatively and flowering at different times of the year. Success lies in sustaining healthy growth by choosing the correct size of pot, so that plants are neither over nor under potted, selecting the correct compost for each stage, and, perhaps most important of all, providing the necessary water and nutrients in a well controlled environment, liquid feeding being considered necessary every 10-14 days with most actively growing pot plants, except cacti and slow growing plants such as ferns. It would be foolish to pretend that one can start with pot plant culture and achieve 100% success with no set-backs. It would also be equally misleading to assume that there is any substitute for practical experience over a period. Nevertheless, if there is a common sense approach from the start, then I feel sure that success will far outweight failure.


The number of different types of pot plants which can be grown in a frost free greenhouse is legion, but I would suggest that in the beginning at any rate, the more simple types are selected. Plants such as primulas, pelargoniums, coleus, fuchsia, and many annuals, make excellent pot plants and are relatively simple to grow, while others such as tuberous begonias, cinerarias, or slreptocarpus can be a little more difficult. Many cacti are the essence of simplicity.

Annuals in pots

In addition to the flowering plants dealt with, a great many annuals can be grown in the greenhouse as pot plants, or in borders, to give a bright show of colour and provide cut flowers. Some of the best for these purposes are:

Acrolinum, Larkspur,

Antirrhinum (actually a perennial) Nasturtium,

Arctotis, Nemesia,

Calendula, Petunia,

Felicia, Ursinia,

Godetia, Zinnia.

Sow seed in March/April and pot into 3 in. pots. All merely require moderate heat.


There is great interest today in the cultivation of Orchids, many of which require merely a frost free greenhouse, as distinct from those which need almost stove conditions. Humidity and shade during the summer are essential for all types. The basic compost for Orchids is equal parts of sphagnum moss and osmunda fibre with a little bit of broken crock worked through to give good drainage. I would suggest that any gardener contemplating the culture of Orchids would do well to consult a specialist book on the subject, or become a member of one of the Orchid Societies.


As diverse a range of alpine plants as one could imagine will grow excellently in the cool greenhouse. This again tends to be a more specialised sphere and information on the culture of alpines in cool greenhouses is readily obtainable through membership of Alpine Societies or Rock Garden Clubs.


A wide range of Ferns can be grown in a greenhouse, prefer-ably cool, shady and moist, a north facing greenhouse being ideal. These can be propagated in a variety of ways from runners to seeds. The following is a list of some suitable varieties:

Adiantum cuneatum Pteris cretica major

Adiantum decorum Pteris wimsettii

Adiantum elegans Pteris cretica albolineata

Cyrtomium falcatum (Holly fern) Pteris tremula Ferns from bulbils (similar to small bulbs).

The only species grown as a pot plant is Asplenium bulbi- ferum.

Ferns from runners

The best type for this treatment is the Nephrolepis varieties, where the little plants are attached to a parent plant and are merely pegged down and allowed to root.


In addition to the plants so far mentioned, a vast range of shrub and herbaceous plants can be potted and induced to flower much earlier than they would out of doors. The list of these is endless and includes virtually every shrub and plant of reasonable size.

Wall plants and shrubs

Many tender wall plants and shrubs are ideal for a conser-vatory or lean to greenhouse, the best of which are as follows:

Cobaea scandens Jasminum

Ipomea rubro-caerulea Plumbago capensis Bougainvillea

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