Plants in different period of their growth.

What You Need to Know About Seed Propagation

The production of seed is nature’s way of ensuring a continuing mix of genes to give strong, healthy characteristics.

Unlike plants that are grown from cuttings, which are clones of the parent, plants grown from seed can bear characteristics of ancestors going back several generations, rather than just the parents, so the exact appearance of the offspring is very hard to predict.

It is less common to grow indoor plants from seed than outdoor varieties, because so many more are produced than can normally be used, although the surplus can always be given away or exchanged. The attraction is the chance to grow something exotic, such as an avocado or citrus, from a seed which might otherwise be discarded, and this can be a fun way to interest a child in the process of growing. For the keen cook, it is also easy to grow sprouting beans, and herbs like basil and parsley, from seed in a succession of small usable batches to ensure a regular, manageable supply.

For the majority of seeds, germination is trig­gered as soon as they are sown into soil and begin to absorb moisture through the seed coat. However, some seeds have a particularly hard or moisture- resistant seed coat and need a little help before the process of germination can begin. The key is to carefully break through the outer layer of the seed bcoat without damaging the embryo inside. The easiest way to do this is scraping or “scarifying” the seed with an abrasive, such as sandpaper, or chip­ping away a tiny sliver of the seed coat with a clean, sharp knife.


Providing The Right Conditions

Some seeds germinate readily with little or no help, but others are more fussy and require the correct conditions to grow.

Humidity Temperature Light Soil mix
A moist environment

will prevent the leaves of young seedlings losing water, which cannot be replaced until a good root system has formed. A

propagation case is ideal, but a plastic bag sealed around the pot works just as well. When the seeds establish, you may need to support the plastic bag on short canes to prevent it touching the leaves

(which can lead to


Most seeds grow well in a temperature of about 65°F (18°C), but some require higher tempera­tures in order to germi­nate successfully. A heat­ed propagation case will maintain a constant tem­perature. These come in various sizes, according to how many seeds (or cut­tings) are to be grown. Wean the young plants before they leave the case by gradually lowering the temperature. Once germination occurs, the seedlings will need to be placed in a brighly lit position, out of direct sun. Too much direct sun­light will scorch the deli­cate new leaves, while too little sunlight will cause the seedlings to become tall, weak, and spindly. This is also a problem ‘if too many seedlings are left too close together in the seed tray for too long, because they are competing for light. Seedlings grow best in a light and free-draining soil mix that does not contain much fertilizer.

To sterilize pots of pot­ting soil (for example, for spore sowing, see page 102), fill a small pot with seed soil mix and firm gently. Lay a piece of paper towel on the sur­face and pour boiling water through until it comes out of the drainage holes at the base. Let cool before use.