Pick the wrong window for your succulent and you get one of two failures: a soft leaning rosette starved of photons, or a brown necrotic patch where the cuticle gave up on a hot afternoon. South wins on raw light, east is gentle and forgiving, west is hot and sneaky in ways the meter does not show. The right answer depends on what you grow, and on where on the planet you live. Here is the rest of the picture.
Part of the Beginner's Guide to Succulents.
At a glance
Numbers below are clear-day readings at mid-latitudes (40 to 50° N), at the inside of a single-glazed sill. Substitute north for south if you live in the Southern Hemisphere; east stays east, west stays west.
| Direction | Direct sun (clear day) | Peak PPFD, summer | Peak PPFD, winter | Heat behind glass | Best for |
|---|---|---|---|---|---|
| South | 6-8 hours | 1000-1500 µmol/m²/s | 300-700 µmol/m²/s | High at midday | Sun-loving rosettes, Agave, most cacti |
| East | 3-5 hours (morning) | 600-900 µmol/m²/s | 200-400 µmol/m²/s | Low | Soft Echeveria, Haworthiopsis, Gasteria |
| West | 3-5 hours (afternoon) | 800-1200 µmol/m²/s | 200-400 µmol/m²/s | Very high, late day | Heat-tolerant Aloe, Agave, Mammillaria |
The non-obvious entry is heat. West and south read similar PPFD at the worst hour, but the leaf state at the moment those photons land is very different.
South-facing windows
A south-facing window is the gold standard for sun-loving succulents in the Northern Hemisphere. At mid-latitudes (the band running from Madrid through Berlin and on to Vancouver) it receives 6 to 8 hours of direct sun on a clear day, and clear summer noon delivers 1000 to 1500 µmol/m²/s of PAR at the sill. Winter cuts that to 300 to 700 µmol/m²/s, partly through shorter day length, partly through a sun angle low enough that any awning or window frame casts a longer interior shadow.
That band covers nearly every classic sun-loving genus: Echeveria agavoides, Aloe vera, Agave parryi, Mammillaria hahniana, Echinocactus grusonii, Trichocereus pachanoi, Cereus repandus. They will hold tight rosettes, push anthocyanin colour, and flower on a south sill that more shaded positions cannot match.
The catch is heat. Glass blocks UV-B but transmits most PAR and most of the near-infrared band that warms a leaf. A leaf 30 cm behind a south window in July can read 5 to 10 °C above ambient, and the substrate in a small black plastic pot can spike past 40 °C. Pair a south window with white pots or terracotta to dump some of that heat, leave 5 to 10 cm of air gap behind the pot for circulation, and water in the morning so the plant has full turgor before the sun crests. A small clip-on USB fan moving 0.3 to 0.5 m/s of air past the leaves at midday cuts the boundary-layer temperature by 3 to 5 °C, often the difference between colour and scorch.
East-facing windows
Morning sun is gentler than midday or afternoon sun for the same arithmetic reason that a March morning feels cool: leaf temperature starts low and rises slowly, so the xanthophyll-cycle protective pool keeps pace with the light it must dissipate. An east window receives 3 to 5 hours of direct sun, ending typically by 11 a.m. local time at mid-latitudes, with peak PPFD around 600 to 900 µmol/m²/s in summer and 200 to 400 in winter.
That makes east the safest position for two groups. The first is shade-tolerant species that scorch in stronger light: Haworthiopsis attenuata, Gasteria batesiana, Haworthia cooperi, soft Echeveria such as E. lilacina, E. cante, and E. laui. The pruinose bloom on the cante / laui group is a mechanical UV screen, and afternoon sun behind glass strips it faster than the plant can rebuild it. The second group is plants you want to keep green rather than colouring up: a green-form Echeveria pulvinata or Sedum morganianum stays its display form on east light, where the same plant on a south sill will pull bronze and copper.
The downside of east is winter. At 200 µmol/m²/s for four hours a day, the daily light integral falls below the etiolation threshold for nearly every succulent except the soft Haworthia group. East-window growers in temperate climates often need supplemental LED from October to March, on a 14-hour photoperiod that fills in the morning and evening shoulders.
West-facing windows
A west window looks similar to an east window on a sun-hours basis (3 to 5 direct hours), but the two are not interchangeable. West sun lands on a leaf whose internal water status is already running hot from the morning. Peak summer PPFD reaches 800 to 1200 µmol/m²/s, lower than south, but leaf-surface temperatures behind a west window in summer commonly run 35 to 45 °C, and on a closed sunroom or sealed apartment 50 °C is reachable. The cuticle dehydrates while the leaf is still receiving radiation, and the result is more sunburn than south at the same PPFD reading.
That is the trap on west windows: the meter says the position is gentler than south, but the plant burns anyway. The PPFD number describes light. It does not describe heat.
West works well for moderate-light tolerant succulents that handle heat: most Aloe (A. ferox, A. arborescens, A. striata), Agave (A. americana, A. parryi), and Mammillaria. These come from habitats where afternoon temperatures are part of the deal. It is risky for tender soft species, especially the cante / laui Echeveria group, the Haworthiopsis / Gasteria group, and any plant freshly arrived from a nursery whose previous light regime is unknown.
A practical fix on a hot west window is to step the plant 30 to 50 cm back from the glass during the worst weeks of summer, or hang a 50% sheer voile across the lower half of the window from late June through August. Both move the plant back into south-window light intensity without the heat layer. A 5 cm gap between pot and glass and a small fan blowing parallel to the window do roughly the same job for a single plant.
Northern hemisphere vs southern hemisphere
Every PPFD number above assumes the Northern Hemisphere. In the Southern Hemisphere (Australia, New Zealand, South Africa, Argentina, Chile), the equator-facing window is north, not south. Flip the geometry: north becomes the high-light position, south becomes the bright-shade position. East and west are nearly symmetrical across the hemispheres, since Earth's rotation (not its tilt) dominates morning and afternoon sun.
There is one subtlety that catches Northern Hemisphere growers visiting friends in Sydney or Cape Town. In the Southern Hemisphere a south-facing wall receives no direct sun all year, the equivalent of a Northern Hemisphere north window. This is the right window for Haworthia retusa, Haworthia cooperi, and Gasteria collections that want bright shade and would scorch on the equator-facing side of the house. Conversely, a north-facing window in Melbourne is functionally a Berlin south window with extra summer intensity, since Melbourne sits closer to the equator than Berlin.
Latitude effects
Latitude shifts every number above. Move closer to the equator and total intensity rises while seasonal variation falls. Move toward the poles and intensity drops while the seasonal swing widens.
At 30° N (Cairo, Houston, Delhi, northern Mexico), summer south-window PPFD reaches 1300 to 1800 µmol/m²/s, with leaf temperatures behind glass spiking well above 40 °C. South is too hot for many soft succulents in summer at that latitude. East becomes the better default for everything except hardened cacti and Agave; growers in Phoenix or Riyadh routinely treat west and south windows as winter-only positions and shift tender plants to east shelves from May through September.
At 55° N (Edinburgh, Moscow, Copenhagen), south is the year-round target. Summer PPFD on a clear day still reaches 1000 to 1300 µmol/m²/s, but winter drops to 100 to 200 µmol/m²/s with day lengths under 8 hours. That is below the etiolation threshold for nearly every rosette succulent, and supplemental LED from November through February becomes the difference between a tight Echeveria and a stretched one come spring.
Above 60° N (Reykjavík, Helsinki, Anchorage), winter solar gain on any window becomes negligible, and supplemental light is no longer optional for indoor collections. Summer compensates partially, but the seasonal collapse makes a permanent LED setup the practical baseline.
A working rule for unfamiliar latitudes: take the local solar noon altitude on 21 December (winter solstice) and on 21 June (summer solstice). If the winter solstice altitude is below 20°, plan for supplemental light through the dark months whatever the window direction. If the summer solstice altitude is above 75°, plan to shade or step back from south and west windows during the worst weeks.
What to grow where
The "best" window depends on what you grow. A single house with one south, one east, and one west window can hold three different collections happily, while the same plants moved between those windows would suffer in two of the three positions. Sort by genus and species:
- Soft Echeveria (E. lilacina, E. cante, E. laui, E. setosa, E. shaviana): east only. Pruinose bloom strips fast under west afternoon sun and burns on south in summer. Morning light at 600 to 800 µmol/m²/s is what these high-elevation Mexican species evolved into.
- Robust Echeveria (E. agavoides, E. nodulosa, E. derenbergii, E. pulidonis, E. harmsii): south or south-west. They pull strong red and copper edges between 800 and 1200 µmol/m²/s, and tighten visibly within two weeks of the move.
- Agave and columnar cacti (A. americana, A. parryi, Trichocereus pachanoi, Cereus repandus, Pachycereus pringlei): south. They want the maximum the window can deliver and tolerate the heat. A west window also works for mature plants whose epidermis has thickened.
- Mammillaria, Echinocactus, Ferocactus: south or west, at least 5 hours of direct sun. Below 600 µmol/m²/s sustained, spination loosens and the body greens.
- Haworthiopsis, Gasteria, soft Aloe (A. variegata, A. aristata, A. polyphylla): east only. South will scorch the leaf tips inside a week in summer, and west dries the cuticle of soft Aloe leaves before any meter reads "danger".
- Window-leaved Haworthia (H. cooperi, H. retusa, H. truncata): bright shade, which on a Northern Hemisphere north window or a Southern Hemisphere south window reads 100 to 300 µmol/m²/s. Direct east sun is acceptable for the first hour only; stronger light burns the translucent leaf windows that give the genus its display value.
- Lithops, Conophytum, hard mesembs: south, with no shade. Lithops elongates below 600 µmol/m²/s sustained, and even a south sill at 50° N is marginal in winter. Most growers of this group need supplemental LED regardless of window direction.
- Crassula, Sedum, Sempervivum (the cooler-climate Crassulaceae): south or south-west. They take the same light as robust Echeveria and colour reliably under it. Sempervivum can move to outdoor full sun in temperate climates from spring onward.
When in doubt and the species is not on this list, default to east, watch for stretching over the first three weeks, and step toward south if the rosette loosens. East undershoots safely. South overshoots painfully.
See also
- A Beginner's Guide to Succulents, for the broader framework on light, water, and seasonal change.
- North window succulent options, for genera that thrive at the lower PPFD bands without supplementation.
- Light acclimation protocol, for moving a plant between windows over a 14-day step schedule that avoids sunburn.