I have two dogs and they have very different preferences when it comes to sunshine. One of them loves lying in the sun, while the other gets hot quickly and prefers the shade. Our plants, too, have preferences for sunlight or shade - but unlike the dogs, they can’t move into the spot they think looks most comfortable, so they are dependent on us to get their preferences right when we plant them!
Most often, the plant’s label or a garden book or blog will use symbols or terms to indicate whether a plant wants full sun, part sun or full shade. The next challenge is to work out what these terms really mean, and where those needs can be met in your garden.
The terms you will usually encounter relating to a plant’s light needs are full sun, part or partial sun (or part or partial shade), dappled shade and full shade. These requirements relate to the situation the plant would grow in where it evolved. For example, plants that grow in meadows need full sun, whereas a plant that comes from a forest prefers dappled light.
A plant that requires full sun needs a spot that gets lots and lots of sunshine each day - at least six solid hours. That period of sunlight exposure should begin from early or mid morning. Most vegetables, herbs, fruiting plants and flowers such as roses and annuals such as petunias and sunflowers do best in full sun. Some plants that need full sun (including vegetables) may grow best with a little shade from the hottest afternoon sunlight in summer, especially in hot climates.
Partial sun or partial shade
These positions are areas that get some sun during the day, but not full, uninterrupted sun. These locations may be overshadowed for some of the day. Many plants that need full sun can tolerate partial sun if it is only for part of the day. Plants that do best in shade may cope with partial shade if the spot is shaded for most of the day. Camellias and hydrangeas do well with partial shade.
This is a position that never gets lots of direct sunshine. Dappled shade is usually found under trees or in areas protected by a climbing plant on an arbour. If the area is overshadowed by a deciduous tree or vine, it will be in dappled shade from spring to autumn, but in full sun during winter. This is a good position to grow woodland plants including bulbs such as bluebells, some ferns and orchids and native understorey plants.
This is a spot that doesn’t get direct sunlight. It may be on the southern side of a wall or overshadowed by a solid structure such as roof, dense hedge or neighbouring property. The rear of a sunny balcony and positions indoors away from windows are often in full shade. Plants recommended for indoors such as spathiphyllum can usually be grown outdoors in a full shade situation (provided it is frost-free).
Consequences of mismatched light needs
When a plant and its light needs are mismatched, the plant suffers. It may fail to thrive and is usually attacked by pests or diseases. If the situation isn’t rectified (for example, by moving the plant to a better spot or changing the amount of sunlight or shade it receives by giving it more shade or by pruning overhanging branches to let in more sun), the plant may die.
Plants that need lots of sun but find themselves in a shady spot may not flower or fruit, can develop soft, lanky growth or may lose leaf patterning and variegations. A plant that’s in full sun but needs shade may wilt frequently, develop burnt leaves and be stunted.
Finding the sun
If you're unsure of your bearings, use a compass (there’s one on your smartphone) to work out where north lies. Or simply get up early to see where the sun rises in the morning, as that’s east. During the day the sun will travel across the northern sky and set in the west.
As a rule of thumb, in the southern hemisphere, the sunniest gardens face north but plants growing in a north-easterly or north-westerly position will also enjoy full sun. Positions facing south tend to be in full shade for most of the year.
That’s the rule of thumb, but at your place what’s around the garden will affect how much sunshine or shade your garden gets as well as the direction it faces. Overshadowing buildings, walls, neighbours' houses and trees can block the sun and may turn a normally sunny, north-facing garden bed into a partially or fully shaded spot. The amount of sunlight may also change over time as surrounding plants grow and nearby structures are erected or demolished.
The time of the year also affects the amount of sunlight or shade in different parts of a garden. This is because the sun rises and sets in different parts of the eastern and western sky, and travels in a higher or lower arc across the northern sky, depending on the season. Observe your garden at different times of the year to see how the patterns of sun and shade vary, and tailor your plantings to suit.