Lunaria annua ‘Alba Variegata’: works wonderfully in shade. Photograph: Gap Photos
I have fallen for variegation. I’ve grown ever so fond of stripes and frills, of silvers and whites, of chevrons and sploshes. Not a statement I would have made 10 years ago, but that’s the joy of growing older: you can slough away the hollow principles of youth because rules, particularly ones about taste, are largely pointless.
Variegation tends to be due to a mutation in plant cells. It’s a horticultural oddity that’s lovingly reproduced by cuttings. The variegation is caused by an absence of plastid pigments in the cell, causing a white patch in the leaf. Wherever there is a white patch, the leaf cannot photosynthesise, because there is no chlorophyll. This is a distinct disadvantage, because it lowers the plant’s potential. So why does this mutation appear in the wild?
Some variegation may actually protect the plant. The mottled variegation on large arum lilies (such as the giant arum) are thought to mimic the lichens growing on woody stems. Thus, a passing herbivore imagines the soft, fleshy stem is too hard to eat.
There’s an Ecuadorian caladium, elephant’s ear, with variegation that is thought to mimic the damage of the mining moth larvae. The adult moth confuses the pattern as a sign that the leaf has already been attacked, so flies on to look for another green leaf that hasn’t had eggs laid on it. This theory goes some way to explaining why variegation survives in the wild.
In the garden, meanwhile, the opposite can happen. Variegated plants are sports or mutations, so a change in temperature, too much shade or poor conditions can all cause the plant to revert to green. If you see a pure green shoot, chop it off, because once the plant remembers what full-throttle photosynthesis is like, it quickly resumes normal – in other words green – growth.
My favourite variegated plants are vegetables, mainly because they look so good on the plate. My first love is my variegated Daubenton kale – I’ll warn you now it is very, very hard to get hold of: ask Pennard Plants nicely. I like it now when it stands bravely alone in a battered winter garden. I like it when the frost makes it blush a little pink. And I like it in late spring when the honesty flowers and the Euphorbia polychroma join in the chorus.
I love the variegated nasturtium ‘Alaska’, with crazy cream marbling on its leaves. The same goes for the variegated American landcress, Barbarea vulgaris ‘Variegata’, which looks quite something when in flower. In that same vein, I love the variegated perennial wallflower Erysimum linifolium ‘Variegatum’; its mauve flowers are like confetti among the pale foliage.
I can see why pale variegation is often considered sickly. In a small garden, though, a little, carefully placed, adds to the texture and flow of a space, expanding darker corners. Take the variegated white honesty, Lunaria annua ‘Alba Variegata’, which works wonderfully in shade and self-seeds readily: that’s a rare thing in variegation.