If you like indoor plants, then having a greenhouse opens up a fantastic opportunity to be able to propagate your own. Aside of being able to increase your stock, it also offers the chance to replace individuals which have passed their best and preserve the genetic line of any particularly handsome examples you may have.
To be successful, propagating house plants demands clean conditions, warmth, light and appropriate levels of humidity – the ideal greenhouse environment, in fact. Small wonder so many greenhouse enthusiasts devote so much bench space to the activity – and for those of us who have a conservatory or sun-room too, there should never be a shortage of suitable specimens to adorn it.
Propagating by division is the simplest and most straight-forward way to produce new plants. Dividing the rootstock, for example, requires little more than pulling the root-ball apart by hand – or with the aid of a knife, if the plant produces rhizomes or the roots are particularly tough. Prune off any long, thick roots, retaining those which are attached to young, vigorous growth and then pot up in a suitable compost, water and place in good light – but not full sun – until the new plants become fully established.
Plants which are well suited to being propagated by rootstock division include:
Some plants, such as Calathea, Phlebodium, Pteris and Stromanthe, can be propagated in this way, but need much higher levels of humidity to establish themselves successfully.
House plants which spread by runners are also well suited to being divided – the runners of Saxifraga stolonifera for example, can be rooted individually and then eventually detached from the parent. Those which produce plantlets – small copies of the parent stock, attached to its leaves or stems – are also suitable candidates.
Once they are large enough to be handled, they need to be detached together with an inch or so of the surrounding parent material and inserted into a pot of appropriate compost and covered with a plastic bag to keep the humidity high. New roots should form in about 21 days and after about 8 weeks, the plant should be ready to pot on.
Leaves and Cuttings
Some of the most popular kinds of house plants can be propagated from whole leaves – including the likes of Saintpaulia (African violets) and Sinningia (gloxinias). The trick is to select healthy and undamaged fully-grown leaves and then cut them off close to the base of the stalk, with a sharp, clean knife. Either plant them in rooting compost and then pot-on the resulting plantlets they produce when they are large enough, or try rooting the leaf in water, although this can be a slower process, although it does seem to work well with African violets.
Most house plants can be propagated from cuttings and many of them – a list which includes Bougainvillia, Catharansus, Cissus, Gardenia, Hoya, Pelargonium and Schlumbergera along with some forms of Hibiscus and Tradescantia – by softwood cuttings. Usually done in early spring, healthy side-shoots are removed and dipped in rooting powder before being planted in a pot of rooting compost; several cuttings can share the same pot, just so long as the leaves do not touch one another.
Left in a warm, light part of the greenhouse – but out of direct sunlight – within six weeks new roots should have formed and the young plants can then be transferred to individual pots and allowed to grow on further. Alternatively, softwood cuttings can be started off in water, being planted directly into growing pots once the root system has formed.
For many people, half the appeal of the greenhouse is having the chance to grow things which would otherwise just not be possible and propagating house plants probably comes about as close to perfectly fitting that particular bill as you can get. Whether it’s the lure of producing something special, the fun of doing it for its own sake or simply the irresistible urge to get new plants for free, propagating house plants in the greenhouse is an absorbing hobby – and can rapidly become addictive!