Plant adaptations to deal with shade
Plants that prefer shade are adapted to make use of light from the red end of the spectrum (long wavelength) rather than the full spectrum of light utilised by plants that grow in bright conditions. Plants that are happy in shade often have leaves with a larger surface area so they can expose as much chlorophyll to the available light as possible. Leaves are often deeper green because the chlorophyll levels are higher, this is particularly noticeable on many shrubs. There are as always, exceptions to these findings in that some shade loving plants have pale, almost lime green or emerald leaves, such as some Hosta.
Plants in shady areas are to a degree, protected from sun scorch. The conditions can sometimes be quite still and humid which also makes it possible for them to thrive without losing excess moisture from the surface of the foliage. This is a process called transpiration. Think of the incredibly fine leaves of the pale green or white variegated Acers which have no waxy coating (cutin) on their leaves. These trees would quickly suffer in areas with high light levels or wind and their leaves would scorch, wither and die. Acers with dark red leaves can take much higher light levels because the red colour acts like a sunscreen and helps protect them from burning.
It is also interesting to note that plants which are adapted to shady conditions use more of the nutrients in the soil, making them very efficient users of all available sources of energy.
Other plants time their growth to make the most of the available light when many trees have lost their leaves. Think of Galanthus, Viola, Cyclamen and many more that flower in the winter when the light reaching the ground is much brighter. Then, as the new canopy of leaves starts to block the sun, they retreat back under ground. These summer deciduous plants are perfectly adapted to make use of the temporary shift in light levels.
Planting in shade. It is often the case that plants in shade take longer to establish. Rooting down and finding nutrients and moisture can be difficult, because these may not be as readily available in shady areas. So, it is always a good idea to take extra care of your new plants for double the time that you would for plants grown in sunny sites.
Plants for shade need never be boring or lacking in colour. In this springtime display is the newly emerging foliage of one of the purple leaved Actaea. Also included are the bright yellow foliage and mauve blooms of Polemonium 'Golden Feathers', the extraordinarily pure blue of Omphaloides 'Cherry Ingram', the purple jester's hat flowers of Epimedium grandiflorum 'Lilafee' and the heart shaped inflorescences of Lamprocampnos spectabilis.
Many, but not all plants can adapt to conditions outside of their ‘comfort zone’ if their other requirements like, moisture/humidity, shelter from strong winds, nutrient levels and pH are in place. So, it is always a good idea to know the nature of your soil, because this may allow you greater freedom in your selection of plants.
Shade avoiding plants. These types of plants cannot adapt well to shady conditions because they are unable to produce the nutrients they require without high light levels (blue light/shortwave). If placed in shadier sites they will behave in one or both of the following ways. The plants can become etiolated, growing quickly and stretching upwards trying to find the light, or leaning to the side for the same reason. Quickly running out of energy, they start to suffer and decline. They can also show nutrient stress when the leaves start to turn yellow or brown.
Shade tolerant plants. These plants will not stretch or discolour but may produce more chlorophyll, making the leaves look darker. Often they will produce larger leaves to enable them to make use of more of the available light.
Types of shade.
Full Sun. Areas in full sun receive 6 or more hours of direct sunlight in summer – weather permitting.
Light Shade. This describes a site that is open and not directly shaded by taller plants but it is shaded at some points of the day by an obstacle such as a building, wall, or nearby trees.
Part/Semi Shade. These areas get 3-6 hours of direct sunlight a day in summer, either in the morning or afternoon. If your site gets full illumination in the middle of the day, when the sun is at its strongest, then you would be more likely to have light shade.
Dappled Shade. This is a site that mainly has diffused or reflected light for most of the day. Areas near the edge of a wooded area or those that have a light canopy like silver birch are said to be in dappled shade. This can also refer to areas that receive reflected light from areas of water or other shiny materials.
Moderate Shade. These areas only get direct sunlight for 2-3 hours a day during summer. Again, if that light strongest at midday you can say it is more likely to be partial shade.
Deep or Heavy Shade. Usually this is found under the dense cover of trees or overhanging structures. These areas get less than 2 hours of direct sunlight per day and are usually dry as the cover creates a rain shadow.
It should be noted that many shade avoiders will do well in light-shade to semi-shaded positions, but may flower less due to the reduction of energy that the plant can generate using photosynthesis.
Many shaded areas can have less moisture from the rain, so it is a good idea to mulch in the spring to stop the winter moisture from evaporating and also help develop humus in the soil. Well-rotted compost is best suited to this particular area.
Almost all areas in the garden benefit from a yearly addition of suitable mulch.
Shade Tolerant plants
Brunnera macrophylla 'Alexanders Great'
Alstroemeria psittacina 'Royal Star'
You can find manner more plants suitable to your light conditions by using our filter Hardy's Filtered Search