Full Sun, Part Shade and Indoor Light Explained
Plant labels use a small set of light terms. Here is what each one means in hours of sun, and how to measure your own space.
Outdoor light terms
Garden light is measured in hours of direct sun on a clear day in the growing season.
| Label | Direct sun per day | Typical plants |
|---|---|---|
| Full sun | 6 hours or more | Lavender, tomatoes, roses, zinnias |
| Part sun / part shade | 3 to 6 hours | Hydrangeas, lettuce, coneflowers |
| Shade | Less than 3 hours | Hostas, ferns |
Part sun and part shade cover the same number of hours, with a difference in emphasis. Part-sun plants need those hours to flower well and tolerate afternoon heat. Part-shade plants prefer gentle morning sun and need protection from hot afternoon sun.
Dappled shade is the shifting light under an open tree canopy. Woodland plants such as Japanese maples and hostas are adapted to it.
Timing matters as much as duration. Four hours of morning sun is far cooler than four hours after midday. In hot-summer climates, many full-sun plants appreciate light afternoon shade.
How to measure the sun in your garden
- Pick a clear day in late spring or summer.
- Check each planting area once an hour from 8 a.m. to 6 p.m.
- Note whether it is in direct sun, dappled light or shade.
- Add up the hours of direct sun.
Repeat in another season if you can. The sun sits lower in spring and fall, and trees leaf out, so a bed that is sunny in April may be shaded in July.
Indoor light terms
Light drops sharply as you move away from a window. A spot 6 ft (2 m) from the glass may receive less than a quarter of the light on the sill.
- Direct light: sun falls on the leaves for several hours. South- and west-facing sills. Suits cacti, succulents and herbs.
- Bright indirect light: a bright position just out of the sun's path, or behind a sheer curtain. Suits most tropical foliage plants, including Monstera and fiddle-leaf fig.
- Medium light: several feet back from a sunny window, or close to a north- or east-facing one.
- Low light: far from windows, or rooms with small or shaded windows. Bright enough to read by during the day. Snake plants, ZZ plants and pothos tolerate it.
These directions apply to the northern hemisphere. In the southern hemisphere, north-facing windows are the brightest.
A quick shadow test
Hold your hand 12 in (30 cm) above the spot at midday. A sharp, dark shadow means bright light. A soft but clear shadow means medium light. A faint or absent shadow means low light.
Signs a plant has the wrong light
- Too little: long gaps between leaves, small pale new growth, leaning toward the window, no flowers, soil that stays wet.
- Too much: bleached or scorched patches, crisp edges, leaves curling away from the light.
"Low light tolerant" means a plant survives there, not that it grows quickly. Every plant in a dim position needs much less water.