A south-facing window is the strongest light most homes have. University of Missouri Extension says south windows give the brightest light for the longest time, and are the right place for plants that need bright light and some direct sun. That makes it the place for cacti, succulents and a few sun-loving tropicals, and a risky place for shade plants in summer.
Window directions here are for the Northern Hemisphere. In the Southern Hemisphere, a north-facing window plays this role.
How much light a south window gives
University of Illinois Extension describes light by distance from the window. One foot-candle is about 10.8 lux, so a light-meter app reading in lux can be compared directly.
| Position at a south window | Illinois light category | Approximate light |
|---|---|---|
| Directly in front of the glass | Direct | 1,500 foot-candles (about 16,000 lux) |
| Up to 1.5 m (5 ft) back | High or bright | 300 foot-candles (about 3,200 lux) |
| 1–3 m (3–10 ft) back | Medium | 150 foot-candles (about 1,600 lux) |
| 4.5–6 m (15–20 ft) back | Low | 75 foot-candles (about 810 lux) |
Illinois gives these levels as the minimum a plant in each category needs. Missouri adds that overhangs, trees and nearby buildings cut what a window delivers, so measure your own spot.
Plants for a sunny south window
Light ratings come from the Illinois Extension houseplant chart where the plant is listed, and from NC State Extension or Clemson HGIC otherwise. Pet status is from the ASPCA unless noted.
| Plant | Light | Water | Size indoors | Cats and dogs |
|---|---|---|---|---|
| Desert cacti (Mammillaria, Opuntia and others) | Several hours of direct sun; south or west window (Clemson) | Dry slightly between waterings in growth; very dry in winter | Mostly a few inches of growth a year (Clemson) | Mammillaria fragilis non-toxic; spines injure |
| Jade plant (Crassula ovata) | High or bright, about 3,200 lux minimum (Illinois); four or more hours of direct sun (Clemson) | Moist, not wet, in spring and summer; dry between waterings in winter | Up to 1.5 m (5 ft) (Clemson) | Toxic |
| Aloe (Aloe vera) | Full sun to partial shade (NC State) | Let the soil dry completely | 30–61 cm (1–2 ft) | Toxic |
| Echeveria | Full sun; leaf colour improves with sun (NC State) | Little water | 3–30 cm (1–12 in) | Non-toxic |
| Burro’s tail (Sedum morganianum) | High light, a windowsill with at least partial sun (NC State) | Dry between waterings; less in winter | Trailing stems to 61 cm (24 in) | Non-toxic |
| Crown of thorns (Euphorbia milii) | High or bright (Illinois); full, direct sun (Wisconsin) | Let the soil dry | Under 61 cm (2 ft) as a houseplant (NC State) | NC State: problem for cats and dogs |
| Ponytail palm (Beaucarnea recurvata) | High or bright, about 3,200 lux (Illinois); sunny window (NC State) | Water deeply, then dry; much less in winter | 1.8–2.4 m (6–8 ft) in a pot; slow | Non-toxic (as bottle palm) |
| Bird of paradise (Strelitzia reginae) | Full sun preferred; tolerates a south window (Clemson) | Wet thoroughly, then let it dry slightly | 0.9–1.2 m (3–4 ft) (NC State) | Toxic |
| Citrus (calamondin, Meyer lemon) | Direct, about 16,000 lux (Illinois) | Moist, well-drained soil (NC State) | Grown in containers; 3–6 m (10–20 ft) outdoors (NC State) | Toxic |
| Croton (Codiaeum variegatum) | Bright light with some direct sun (NC State) | When the top 1.3–2.5 cm (½–1 in) is dry (Wisconsin) | About 0.9 m (3 ft) (NC State) | Not listed; NC State: sap irritates skin |
Notes on the main choices
Cacti. Clemson HGIC calls a south or west window with several hours of direct sun ideal for arid-climate cacti. In winter they are dormant: keep them at 7–13 °C (45–55 °F) if you can and water just enough to stop shrivelling. Waterlogged soil quickly rots the roots. See our cactus and succulent hub and soft or wrinkled cactus guide.
Jade plant. Clemson recommends 18–24 °C (65–75 °F) by day and 10–13 °C (50–55 °F) at night, and warns against letting leaves touch cold windowpanes in winter. NC State suggests a sunny spot with some afternoon shade. Drought causes leaf drop, so it is not a plant to forget. See our jade plant care guide.
Aloe and echeveria. Both want very well-drained, gritty mix and a pot with drainage holes; NC State prefers clay for aloe. If an aloe turns reddish, our aloe colour guide explains when that is stress. See the aloe vera hub and echeveria hub.
Crown of thorns. Wisconsin Extension notes it does well in low humidity and heated homes. Poor flowering can come from too much light at night, because it needs darkness to start flowering.
Ponytail palm. Not a palm but a slow succulent with a water-storing trunk. NC State notes it copes with dry indoor heat and prefers dry winters. It is hardy only to 10 °C (50 °F). See the ponytail palm hub.
Bird of paradise. Clemson warns that overfeeding gives lush leaves and few flowers. Feed every two weeks in spring and weekly in summer, and not at all in fall or winter. See our bird of paradise care guide.
Citrus. Missouri Extension says potted citrus want bright light to grow and fruit, though they can sit at medium light in midwinter. It names calamondin as the most popular, with Meyer and Ponderosa lemon also suitable.
Croton. Sources differ, which tells you something. NC State wants some direct sun for the best colour. Wisconsin says too much direct sun turns leaves grey and dull. Missouri considers crotons generally unsuited indoors because of their high light needs. A spot just to the side of a south window is a fair compromise. Wisconsin adds that sudden changes cause leaf drop. See our croton light guide.
How to choose for your south window
- Measure the spot at midday and again in late afternoon. A meter reading near 16,000 lux means direct-light plants; nearer 3,200 lux means high-light plants.
- Check for shade. An overhang, a tree or a building opposite can turn a south window into a medium-light spot.
- Think about winter cold. Clemson HGIC advises keeping jade foliage from touching windowpanes in winter; leave a gap between any plant and the glass.
- Plan for pets. If cats chew plants, choose ponytail palm, echeveria, burro’s tail or a Mammillaria.
- Keep shade plants back in summer. Missouri advises moving plants that do not need bright light to the side or interior of a large south window from late spring to early fall.
Acclimating plants to stronger light
A plant grown in a greenhouse or a dim room has leaves built for that light. Moving it straight into full sun can scorch it.
- Increase light in steps. Clemson HGIC advises gradually increasing exposure for plants kept in low light, to avoid sun scorch.
- Allow about two weeks. Iowa State gives 10 to 14 days for acclimating houseplants to brighter light outdoors. A similar stepwise move works at a sunny window: start at the side of the window, then move the plant closer every few days.
- Watch the leaves. Iowa State lists burning, discoloration and leaf drop as signs of too much light too fast. On succulents the damage to fleshy leaves and stems is permanent.
- Expect some leaf drop on sensitive plants. Iowa State notes weeping fig and tropical hibiscus often drop leaves after a move and regrow them.
- Keep shade lovers out of direct sun. NC State says spider plant is intolerant of direct sun, and that strong direct sun burns baby rubber plant (Peperomia obtusifolia).
For plants that need less light, see our houseplant light requirements chart and our guide to plants for dark and north-facing rooms. For pet safety across all light levels, see our pet-safe plants guide.
References
- University of Illinois Extension: Houseplants: Lighting
- University of Missouri Extension, D. H. Trinklein (rev. 2016): Lighting Indoor Houseplants, G6515
- Clemson Cooperative Extension HGIC: Indoor Cacti, HGIC 1502; Jade Plant, HGIC 1507; Bird of Paradise, HGIC 1562; End-of-Winter Houseplant Care
- Iowa State University Extension: Moving Indoor Plants Outside for the Summer; Growing Succulents Indoors
- University of Wisconsin–Madison Extension: Croton, Codiaeum variegatum; Crown of Thorns, Euphorbia milii
- NC State Extension Gardener Plant Toolbox: Aloe vera, Crassula ovata, Echeveria, Mammillaria, Sedum morganianum, Euphorbia milii, Beaucarnea recurvata, Strelitzia reginae, Citrus × microcarpa, Codiaeum variegatum, Chlorophytum comosum, Peperomia obtusifolia
- ASPCA Animal Poison Control Center: Toxic and non-toxic plant list