An offset is a plantlet that has developed laterally on a stem either above or below ground: the stem arises from a crown bud and usually carries no other buds.
Most plants, such as sempervivums, that produce offsets first grow a miniature plant with only minimal roots. A root system will not fully develop until late in the growing season.
To speed up this process of propagation, pull away the offset from its parent, usually in spring. Either plant out in the garden or pot it up, using a cuttings compost with added grit, which will drain freely and so ensure good root development.
Where offset development is poor, it is possible to stimulate offsets by removing the plant's growing tip. This has the same effect as removing a terminal bud.
Although the term offset is normally used for a plantlet that is separated from its parent during the growing season, it is also used to describe slower-developing shoots that are produced by mainly monocotyledo-nous plants such as yuccas. Eventually these shoots should be sufficiently mature to be separated from the parent and planted on.
A pineapple plant produces offsets that can be used for propagation once its fruit is nearly mature. These offsets are variously described as slips, ratoons or suckers. Cut them off the plant close to the crown and plant out.
Many corm and bulb plants, such as fritillarias, each year produce miniature reproductions of themselves from the bases of the newly developing corms or bulbs. These are known as cormels (see page 45) and bulbils and bulblets (see page 47).
A runner is a more or less horizontal stem that arises from a crown bud and creeps overground. The leaves are normally scalelike, and rooting may occur at the nodes. The lateral buds develop as new plants, and eventually the stem of the runner deteriorates, leaving a new isolated plant. The classic example of this kind of natural vegetative reproduction occurs in the strawberry plant.
New plantlets usually root down and produce new plants quite successfully. However, unless controlled, a mat of new plants tends to develop, and these are not easily lifted and separated without damage, so thin out the runners regularly.
1 Thin out some runners in early summer to encourage strong growth.
2 Fill a pot with John Innes No. 1 compost. Firm to within | in of the rim.
3 Dig a large hole in the ground beneath a plantlet. Set the pot in the hole.
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1 Pull an offset away from the parent plant, preferably in spring.
2 Plant the offset in a pot filled with a cuttings compost with added grit.
Cut off pineapple slips close to the crown and plant out individually.
To produce large, well-established individual plants, dig in plenty of good compost for rooting; in early summer, thin out some of the runners, and pin down the rest into the compost, evenly radiating them around the plant. This method will induce early rooting, but the rate of development will not be quite as fast as for pot-grown runners.
These are obtained by placing a pot under each runner.
Dig a hole in the ground beneath a developing plantlet. Set a pot containing good compost into it and then push back the soil to keep the pot in position. Pin down the runner, using wire bent in the shape of a staple, so that the plantlet will root in the pot.
4 Pin down the plantlet in the middle of the pot, using a wire staple.
5 Pin down any other plant. Sever their plantlets in a star-shaped connecting stems once they pattern round the parent are fully established.
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