Monday, 5 November 2012

An important botanical principle



Named varieties of perennial plants usually do not ‘come true’ from seed.
I am using the genus Dicentra to illustrate the principle of seedling variation.
I will NOT be sowing these seeds!
As holder of the National Dicentra Collection, self-seeding dicentras are quite a problem. It is rather embarrassing when purple ones appear in the middle of a clump of  beautiful pink Dicentra formosa ‘Stuart Boothman’. If I did not pull them out they would take over! In February, Dicentra formosa seedlings germinate like ‘mustard and cress’ in my borders. The  seedlings are all different and are my worst weed! I cut away seed-pods in summer, but always fail to catch them all.
The interesting thing about this process is that some of these unwanted seedlings might grow into very fine plants. They may be even better than their parents and be worthy of growing on as a named variety (correctly called ‘cultivar’). I have often lifted seedlings, potted them up and grown them on. In my collection I have some very fine plants not quite worthy of wider distribution (or is it I prefer to keep them for myself?). All such plants if propagated vegetatively remain identical to their parent. They are described as a clone.

Dicentra formosa ‘Adrian Bloom’, like all dicentra cultivars, does not come true from seed
Seed pods of Dicentra formosa alba ‘Snowdrift’.
Its seedlings will be correctly named Dicentra formosa. If you only keep the white seedlings they are called Dicentra formosa alba. They will never be ‘Snowdrift’.
A plant I have raised from seed myself. When I vegetatively propagate this clone I can legitimately call it Dicentra formosa ‘Roger’s Pink’. 
Vegetative propagation of Dicentra formosa is either by division of the whole plant or by forking out root-like underground rhizomes and in my case potting them up to sell on Open Days. (These rhizomes are NOT root cuttings. I know of no dicentra propagated by true root cuttings. Certainly not Dicentra spectabilis, the wallpaper of this blog!  Eminent horticultural encyclopedias say you can!).


Seed pods of Dicentra macrocapnos. Self-sown seed of this species in the wild gives nearly identical plants. It is not helpful if a seedsman makes up a cultivar name when there is little natural variation.
And what is the significance of this variation to gardeners?
1). Hardy plant seedsmen and plant society seed distribution schemes often  offer seed collected from cultivars which do not come true.
2). Cultivar seed will often give plants unworthy of cultivation.
3). Most cultivars of vegetables and annual flowers offered by the ‘regular’ seed trade do come true from seed. Years of selective breeding has made them so. They will not be as identical as members of a clone. 
nb cultivar names of perennials offered by such seedsman are equally dodgy!
4). F1 hybrids come almost exactly true from seed. If you save F1 hybrid seed yourself, you will usually get very variable and unsuitable plants in the F2 generation.
5). Cultivars of some plants, Helleborus orientalis for example, will give  seed-raised plants similar, yet different, to their parent. Seeds collected from a cultivar such as Helleborus ‘Red Lady’ might be sold as the Red Lady strain. They will not be the clone ‘Red Lady’ but they will be fantastic!


Seed collected from this pink-spotted self sown Helleborus orientalis will germinate to give an attractive variable range of pink-spotted plants!
And what about those lovely black seeds in the picture? 
More myrmecochory!
I was fascinated by the information given in the comments column on my recent cyclamen post. When Sonja Hurst-Baird mentioned that dicentra exhibited myrmecochory, I rushed out and shelled a few pods. I think those white elaiosomes are absolutely beautiful.

2 comments:

  1. Such a grandiloquent title for an article about cultivars could be a worthy candidate for Private Eye's Pseud's Corner!

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  2. I like your style Harvey! I suspect your comment to be no compliment. The topic had been suggested to me by a very good gardener and scientist, who found that many of his erudite but none scientific colleagues do have difficulty with the idea I have tried to explain.

    ReplyDelete

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