Making Your "Black" Plants Really Dark
How Light Affects the Flowers and Foliage of Dark Plants
Jun 26, 2009
The purple colors that we see in leaves are the result of anthocyanins, which are plant pigments composed of, among other things, sugar. The more sugar a plant produces the more the anthocyanins are stimulated – and so the darker and deeper the leaf color.
Anthocyanins are also there to protect the plant from ultraviolet rays – and the more of those they get the more anthocyanins are stimulated. Start getting into shade and that purple color starts fading and the chlorophyll which accounts for the green color of most plant begins to dominate. But when conditions are right, the anthrocyanins in those plants that are called "black" predominate, and display not green but shades of deep blue or red.
Conversely, many dark, deep flowers bleach out in sunlight and so don't show their true depth unless given some shade. They too contain the anthocyanins, but because those pigments are unstable and water-soluble, the flower may water spot in rain or fade in an excess of light. So while dark leafed plants prefer sun, dark flowered ones do not – making the idea of a bed of deep, dark foliage and flowers problematic. So at best, most gardeners will find themselves compromising, creating gardens that may incorporate both the dark and the light, the bold and the delicate – that's what good garden design is about.
Good Sense in Good Garden Design
Good garden design also involves compromise.
Actually, Nature has a way of trying to force us into good garden design habits with the decree "right plant, right place." This means that no matter how badly we want to put that nearly all white hosta, 'Mostly Ghostly' next to that deep black mondo grass, we can't. The hosta would scald in the sun, spoiling the picture. It doesn't have enough chlorophyll to protect it from strong sunlight. Put the mondo grass next to the hosta in the shade and the mondo grass turns a distinctly greenish hue. It doesn't have enough sun to keep that same chlorophyll from dominating.
Kind of perverse, isn't it, that darkness is so light dependent? If you want a dark garden that depends on foliage – a wise move since leaves last longer than most flowers - then plant it in sunshine. – which is the enemy of white foliage.
Accustomed as we are of thinking of light as the property of goodness and angels and all that purity that white symbolizes – in the garden, it's just the opposite. The more light the closer to black the leaves will get.
Exceptions to the Sunlight Rule
So really extreme black and white gardens are scarce. In a part shade garden with white leafed plants in the shadiest spots some of the darker heucheras for your black element might work. The by-now trite 'Palace Purple' in part shade is very dark indeed but almost coppery purple in sunlight.
Heucheras are among the few exceptions to the rule of sun for deepest color. But even they demand at least morning sun to achieve really deep coloration.
Cimicifuga is another exception to the sunlight and darkness rule. This is a plant of the deep woods and so the foliage tends to burn and go crispy in sunlight even if given adequate moisture. So a part shade position is your best bet for getting a truly deep leaf color with these plants – which will then reward you by sending out racemes of white flowers - one of the few naturally black and white combinations to be found.
Nature has created her own sort of balance here and, with a few exceptions, gardens of extremes don't see to be part of the plan.
Here is a list of plants that can be darkened with proper planting.
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