Propagation – growing new plants for ‘free’ has to be my favourite part of horticulture. Even though I know the science behind how and why plants can reproduce, both sexually and asexually, it never ceases to amaze me!
The fact that pieces of stem, or even leaves, can grow new roots, or that we can cut roots up into sections and they will form entire new plants is, in my mind, quite amazing! Vegetative, or asexual, propagation, where the new plants are exact clones of their ‘parent’ is extremely important in horticulture, as many of our plants are named cultivars that can only be produced in this way. Variegated plants, in particular, have to be produced in this way, as seeds taken from these plants will normally revert to the original, non-variegated, species.
Reproduction by seed is nature’s way of survival. It is the way that plants have evolved, and are still evolving, to cope with changes in environment, or even natural disasters such as fires, floods or earthquakes which could kill the parent plant. Many offspring are produced, and all will be slightly different – just like us! The toughest will survive, and reproduce to form the next generation. Evolution. Survival of the fittest.
Man has been growing plants from seeds for thousands of years. Many of our crops have been developed by selectively choosing the parents for the next generation. Some of the crosses may have happened naturally, but far more would not have done so as the parents may have come from different areas, or continents. Nature would select for hardiness, we select for higher yields or bigger fruit. The Head Gardener would have selected his seeds for the next year from the biggest and best of his crop. Not from a seed catalogue. He knows which varieties have grown well on his site, in his soil, and over many years he would have, maybe inadvertently, improved on the original.
A little knowledge is needed, however, to understand which seeds are worth saving. Beans and peas are usually fine – they will grow ‘true to type’ as they often self-pollinate whilst still in bud.
Other plants, however, will cross pollinate and you cannot guarantee what you may get when you sow the seed the following year. The cucurbits, such as marrows, pumpkins and the various squashes, are one such group – you will get a ‘cucurbit’ of some kind. One of the students brought in a ‘marrowkin’, or was is a ‘pumpow’ this week, which she had grown from a saved seed of a pumpkin the previous year – which had been grown alongside her marrows. Interesting to carve for Halloween as it was more like a very fat marrow!
The Brassicas are another group of which the seeds are really not worth saving. Cabbages, kale, broccoli, sprouts are all the same species – but save the seeds and you do not know what the resulting offspring will be!
Last week I write about extracting seeds from fleshy fruits, such as berries by placing in a kitchen sieve and washing away the pulp. As well as the Blue Bean Fruit, we also extracted seeds from a lovely species rose we have here, Rosa pimpinellifolia, the Burnet Rose. This bears masses of charming, single blooms, up to 3” or so across, of a wonderful creamy white to pale primrose yellow in early summer, followed by very distinctive black hips.
Like most native plants, I prefer to sow some of the seeds immediately in order that they may have a winter chill to encourage germination. We save the remainder of the seed somewhere cool and dry, such as in an airtight container in the fridge until the spring.