Wednesday, 9 January 2019

Of leaf variation and other things

Chris went to her gym today, aiming to get back to pre-Christmas levels of fitness. I accompanied her as far as the entrance but then left her to it. I walked into town, also with fitness in mind.

I set off through the Southbrook area, noting beside the footpath a patch of Yellow Archangel, Lamiastum galeobdolon. It was the variegated form, subsp argentatum.

This variegated form of Yellow Archangel can be a real problem.
Southbrook, Daventry, 9 January,2019
It is an attractive plant, spreading via stolons (rooting overground stems) to quickly cover a considerable area - and therein lies the problem. So invasive is this subspecies that it is listed on Schedule 9 of the Wildlife and Countryside Act and it is an offence 'to plant or otherwise cause to grow this species in the wild'. Certainly my old friend Oliver Tynan was constantly tearing out clumps of it from his garden.

In some respects this situation is a little unusual. Variegated leaves often contain less chlorophyll than the 'normal' leaves and should theoretically be less vigorous. As a rule gardeners growing plants such as this Golden Japanese Euonymus, E.japonicus 'Ovatus Aureus' find they are constantly pruning away any fully green foliage to prevent it overwhelming the weaker yellow leaves. 

Any green foliage of this Golden Japanese Euonymus constantly has to be
 trimmed back lest it overwhelms the yellow leaves.The Dingle, Daventry
. 9 January, 2019.
A well-known species always bearing variegated foliage is Sowbread, Cyclamen hederifolium. The leaf borders are invariably pale and, to a considerable extent, the main part of the leaf blade is pale too.

Cyclamen hederifolium in our front garden.
Stefen Hill, Daventry. 9 January, 2019
Hederifolium means, of course, ivy-leaved. It is not surprising that horticulturalists have sought out ivies, Hedera, with unusual markings and even our common native species has distinctly pale venation, but generally this only applies to the leaves on non-flowering branches.
Leaves on the non-flowering branches of ivy commonly bear pale veins.
The Uplands, Daventry, 9 January, 2019

It was while I was stooping to photograph Cyclamen hederifolium in our own garden that I was reminded that the leaves of Eryngium bourgatii are also variegated. Like ivy, the pale areas are generally confined to the leaf veins.

Eryngium bourgatii leaves in our front garden .9 January, 2019

Does variegation confer any benefit or advantage to plants having foliage with this characteristic? I cannot think of any but I'll bet that someone, somewhere, has considered this matter. Perhaps even got a Ph.D out of it!

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