Sunlight is the first thing to get right with flowers, because no amount of feeding or watering will make a sun-loving flower bloom in shade, and no amount of care will keep a shade lover happy in blazing afternoon sun. A zinnia planted in shade grows tall, pale, and flowerless; a hydrangea planted in full sun in a hot climate scorches and wilts by midday. The plant label's sun requirement is not a suggestion — it is the single most important piece of information on the tag, and it is worth reading before you buy.
This guide explains what full sun, part shade, and shade actually mean in hours, which flowers belong in each group, and how to measure the light in your own garden, which is often very different from what you assume. The sunlight calculator can help you work out what your garden receives, and your local extension service can advise on the varieties that suit your climate.
What full sun, part shade and shade mean
The terms on a plant label have specific meanings, measured in hours of direct sun. Full sun means six or more hours of direct sunlight a day, and the plant will usually want the morning sun most of all. Part sun or part shade means three to six hours of direct sun, usually in the morning, with shade in the afternoon — the two terms are often used interchangeably, though part shade leans towards the shadier end. Full shade means less than three hours of direct sun, and usually means dappled light under trees rather than the deep shade of a north-facing wall. The catch is that the quality of the sun matters as much as the hours: six hours of gentle morning sun in a cool climate is very different from six hours of fierce afternoon sun in a hot one, and a flower that is full sun in a mild climate may need afternoon shade in a hot one. When a label says full sun, read it as full sun where you live, and watch how the plant responds in its first season.
Full-sun flowers: the sun lovers
The great majority of garden flowers are full-sun plants. Zinnias, marigolds, sunflowers, dahlias, lavender, roses, and most annuals need six or more hours of direct sun to flower well, and they will be leggy and shy of bloom with less. Our growing zinnias, growing marigolds, growing sunflowers, and growing lavender guides all specify full sun. Roses are the classic example: a rose in full sun flowers generously and the foliage dries quickly after rain, which reduces black spot, while a rose in shade flowers poorly and stays wet, which invites disease — our black spot roses guide explains the connection. Give full-sun flowers the sunniest spot you have, ideally with morning sun and good air movement, and they will reward you. In very hot climates, even full-sun flowers appreciate a little afternoon shade, and a light mulch helps keep their roots cool.
Part-shade flowers: the morning-sun group
Part-shade flowers want sun in the morning and protection in the afternoon, or dappled light through the day. Hydrangeas are the best-known example — they flower well in morning sun and afternoon shade, and they scorch in full afternoon sun, especially in hot climates. Our growing hydrangeas guide covers this in detail. Impatiens, begonias, fuchsias, and astilbe all do well in part shade, as do many woodland perennials such as hostas and hellebores. This is the group for the east-facing bed, the spot under a high tree canopy, and the bed that gets sun until midday and then shade. The common mistake is to plant a part-shade flower in full sun because the spot looks bright in the morning, and then to watch it wilt every afternoon. If a part-shade flower is wilting daily despite wet soil, the problem is almost always too much sun, not too little water.
Shade flowers: what grows where the sun does not reach
True shade flowers are fewer, but they are valuable, because every garden has a shady corner. Hostas, ferns, hellebores, astilbe, and lily of the valley all flower or look good in shade, and impatiens will flower in surprisingly little light. Shade under trees is a double challenge, because the tree roots compete for water and nutrients as well as blocking the light — dig in plenty of compost, water in dry weather, and choose tough plants such as hostas and ferns rather than delicate ones. Deep shade against a north-facing wall is the hardest spot of all, and even shade lovers will struggle there; use foliage plants and containers that can be moved into the light, rather than expecting flowers. Remember that shade does not mean darkness — a plant in full shade still needs light, just not direct sun, and a spot that is dark all day will grow nothing but moss.
How to measure the light in your garden
Most gardeners overestimate how much sun their garden gets, because they remember the sunny moments and forget the shade. Measure it properly: on a clear day, note each hour whether each bed is in sun or shade, and repeat the exercise in spring and in midsummer, since the sun's path changes through the year and a bed that is sunny in June may be shaded in April by a tree that has since leafed out. A tree that is bare in winter casts almost no shade, and the same tree in full leaf in July can shade a whole bed — this is why a spring bulb bed under a deciduous tree works so well, and why a summer flower bed under the same tree fails. Take photos of the garden at 9am, noon, and 3pm on the same day, and you will see the pattern clearly. The sunlight calculator can help you record and work out what each spot receives. Plant according to what you measured, not what you hoped, and move a plant that is clearly in the wrong light rather than waiting for it to adapt — it will not.
When a flower is in the wrong light
The symptoms are distinctive. A sun lover in shade grows tall and leggy, with long spaces between the leaves, pale foliage, and few or no flowers — it is stretching for light it cannot reach. A shade lover in full sun has scorched, brown leaf edges, wilts every afternoon even when the soil is wet, and its flowers fade quickly. Both problems have the same cure: move the plant. Flowers are far more forgiving of a move than gardeners expect, provided it is done on a cloudy day and the plant is watered in well, and our flowers transplanting guide covers the technique. A plant in the right light needs less feeding, less watering, and less pest control than the same plant in the wrong light, because a plant that is growing well can look after itself. Getting the light right is the cheapest form of flower care there is. If you are unsure about a diagnosis, a product, or a local rule, check your local extension service — its advice is tailored to your soil, climate, and the pests and diseases active in your area.
Frequently asked questions
How many hours of sun is full sun?
Six or more hours of direct sunlight a day. Part shade is three to six hours, usually in the morning, and full shade is less than three hours of direct sun.
Why won't my zinnias flower?
Usually not enough sun. Zinnias need six or more hours of direct sun; in shade they grow tall and pale with few or no flowers. Move them to the sunniest spot you have.
Can hydrangeas grow in full sun?
In cool climates, yes, with plenty of water. In hot climates they scorch in afternoon sun and do best with morning sun and afternoon shade.
What flowers grow in shade?
Hostas, ferns, hellebores, astilbe, lily of the valley, and impatiens all do well in shade. Avoid expecting sun-loving annuals to flower there.
How do I know how much sun my garden gets?
Note each hour on a clear day whether each bed is in sun or shade, and repeat in spring and midsummer. Photos at 9am, noon, and 3pm show the pattern clearly.