How to clone a cabbage in your own garden
Why grow cabbages, and other brassica, from seed - when you can clone them! You simply dig up a cabbage root and split the stem lengthways in four, ensuring there is some root on each piece. Dip the pieces in a rooting compound and store them in slightly damp sand indoors over winter. In spring, plant out the cuttings. It yields an identical clone of the cabbage.
You shouldn’t do it for too many years, however, or you may face problems of ‘inbreeding depression’. That’s the result of growing on some species too often from their own saved seed, without refreshing the geneplasm eg. by mixing it with seed grown elsewhere. The plant grows more and more feeble. But, for serious gardeners like you and me, cloning is very useful.
Why? Root division by this method is a lot simpler than trying to collect the seeds when they are produced in year two (brassica are biennials). It’s also invaluable if you have a rare or heirloom variety of cabbage and want to grow it on perpetually. If you try doing this from seed you must go to great labour to avoid cross-pollination which will destroy the purity of the strain. Brassica will cross-pollinate with related varieties up to a mile away, even with wild turnip (rape).
Clone the plant instead. Don’t let it go to seed. And you have no problems.
Try it with any brassica
You can try this cloning process with almost any brassica - broccoli, cauliflower, cabbage, collards or kale. It doesn't work with kohl rabi or lettuce, however. But then, few people grow kohl-rabbi anyway and lettuces aren't brassica.
It’s odd that no modern textbook author seems to have heard of ‘cloning a cabbage’. The idea has been around for a very long time. Robert Thompson devoted a large section to this technique in The Gardener’s Assistant, 1871.
A leaf stem was cut from the brassica. They didn’t have rooting compound in those days, of course. Instead, the stem base was rolled in ‘newly slaked lime, dry wood ashes or powdered charcoal’ then sunk into the side of a clay pot filled with damp sand. The pot was covered and kept moist. If you were lucky, roots formed and you had a new plant, ready to set out again.
No gardening author has written about that idea since Thompson, so far as I can establish. Yet the friend who alerted me to this reference said, his grandfather had grown cabbages that way all his life. It was common knowledge in the Victorian era.
Did they clone cabbages in the Renaissance?
If cloning a cabbage is so easy, it might explain how new varieties of brassica like Brussels sprouts and Savoys were developed and stabilised in the 16th and 17th centuries. We simply don’t know how they did it. No records have come down to us.
But it seems implausible that, as soon as a farmer saw an interesting new mutation appear by chance, he would isolate it from other cabbages in a field one mile distant. Instead, he would grow it alongside his other cabbages. The seed of the mutated variety would then cross with that of other cabbages and the unique new strain would be lost. Yet, indisputably, we have Brussel sprouts. How come?
Suppose instead that the farmer took a stem cutting from that prototype Brussel sprout and he grew it on, year after year, without letting it set seed? In other words, he cloned it? It was well within the technology of the time. So, were the first Brussel sprouts and other novel cabbage varieties developed by cloning?
Today, we know that other types of plant - tomatoes, cucurbits and peppers – can also be propagated from stem cuttings ie. by cloning. Why do textbook authors rarely mention this? Perhaps they haven’t read the right gardening books!
Much more about this topic can be found at the Gardening Guild.