Quick Answer: Succulents want it cooler and drier than almost anything else you’d grow under cover — 68–74°F days (never below 48°F), 40–50% daytime humidity, and soil that’s allowed to dry out completely between waterings, per Michigan State University Extension guidance. That’s the opposite playbook from the humidity-loving crops in our other greenhouse guides: less water, more drainage, and a gritty potting mix instead of standard potting soil. Get the watering rhythm right and almost any of our greenhouse kit picks will keep a succulent collection thriving through winter.
If you’ve read our guides on greenhouse tomatoes, peppers, or cucumbers, succulents will feel like they’re breaking every rule those crops follow. The fruiting vegetables all want humidity somewhere between 65% and 90% and soil that never fully dries out. Succulents want the inverse: humidity capped around 40–50% during the day and soil that dries out completely before you water again. Run both groups in the same structure and the succulents — not the vegetables — are usually the ones that suffer from a well-meaning overwatering habit.
Greenhouse succulents by the numbers:
- 68–74°F — the average air temperature MSU Extension recommends for greenhouse succulents, with growth speeding up as the daily average climbs toward 70–75°F and cold damage becoming a real risk below 48°F.
- 40–50% daytime humidity — the target range for most succulent varieties, the lowest of any crop in our greenhouse guide series; sustained readings above that raise root rot and fungal risk.
- 60–85% nighttime humidity — a normal, harmless swing as temperatures drop overnight, distinct from sustained high daytime humidity, which is the actual problem for succulents.
- 50/50 gritty mix — the commonly recommended split between organic potting soil and inorganic drainage material (perlite, pumice, or coarse sand) that lets succulent roots dry out between waterings instead of sitting in damp soil.
How succulents compare to the rest of the crop series
The temperature numbers are close to what tomatoes and peppers want. Everything else is reversed:
| Factor | Tomatoes / Peppers / Cucumbers | Succulents |
|---|---|---|
| Daytime temperature | 70–80°F | 68–74°F |
| Humidity target | 65–90% (higher = better fruit set) | 40–50% (lower = healthier plant) |
| Watering rhythm | Consistent moisture, avoid drying out | Dry out completely, then water deeply |
| Soil type | Standard amended garden soil | Gritty mix, ~50% inorganic drainage material |
| Biggest failure mode | Blossom drop from heat or humidity swings | Root rot from overwatering |
| Ventilation priority | Manage fungal disease at high RH | Manage humidity buildup + heat scorching |
That watering row is the one that trips people up most. Growers who are used to keeping vegetable soil consistently moist tend to apply the same instinct to succulents on the same watering schedule — and that habit, more than cold or pests, is what actually kills greenhouse succulents.
Getting the soil right
Standard potting soil holds too much water around succulent roots for too long. Extension and grower guidance both point to a gritty mix — roughly half organic potting soil, half inorganic amendment like perlite, pumice, or coarse sand — so water moves through fast instead of pooling. Perlite is cheaper and lighter but crushes into powder after a few seasons of repotting; pumice costs more but holds its structure much longer and doesn’t break down the same way. Either works in a greenhouse setting as long as the pot itself also drains — a solid, unglazed clay or terracotta pot dries out faster between waterings than plastic, which matters more here than for any other crop in this series.
Pumice Soil Amendment for Succulents & Cacti
- Mixes 1:1 with standard potting soil to build the gritty, fast-draining blend succulents need.
- Holds its structure across repottings instead of breaking down into fine powder the way perlite does.
- Works in raised beds, greenhouse benches, or individual pots alike.
If you’re rebuilding trays of gritty mix or swapping pots across a whole succulent bench, that’s exactly the kind of recurring supply run Kindle Unlimited pairs well with — load up a field guide or two on succulent propagation for the slow winter dormancy stretch while you wait on amendments to restock. Sponsored link — we may earn a fee if you sign up. No extra cost to you.
Managing humidity the other direction
Every other guide in this series tells you how to raise humidity without inviting disease. Succulents flip that: your job is keeping humidity down without cooking the plants. Good roof and side ventilation does double duty here — it vents the heat that builds up in a sealed structure on a sunny day and it keeps daytime humidity from creeping into the 60%+ range where root rot and fungal issues become a real risk. A greenhouse thermometer/hygrometer that tracks both readings at once is worth running on a succulent bench specifically, since a “look and it’s fine” temperature check tells you nothing about whether humidity crept up overnight. If you’re in a humid climate, running a structure that pairs succulents with moisture-loving vegetables, a dehumidifier is generally the more targeted fix than opening vents wide enough to also drop the temperature.
Light and shade cloth
Most succulents want 6–8 hours of bright light a day, with full-sun desert varieties doing best under direct morning sun. That’s easy to deliver in most greenhouse structures — the more common problem is too much heat concentrated with that light, especially behind polycarbonate or glass in summer. Shade cloth in the 30–50% range knocks down peak intensity and heat without dropping succulents into the etiolated, leggy stretching that happens when they’re starved of light entirely. Watch the plants, not just a percentage on the cloth label — compact, colorful growth means the light level is right; stretching toward the light source means it’s time to pull the shade cloth back.
Dormancy changes the rules
Many popular succulents go dormant for part of the year, and the care rules shift with it. During dormancy, cut watering frequency by roughly half compared to active-growth months, keep temperatures on the cooler end of the range, and hold off on fertilizer — dormant roots aren’t absorbing nutrients efficiently, and feeding a dormant plant mostly just risks salt buildup in soil that’s already staying dry longer between waterings. Which season counts as dormant depends on the variety, so it’s worth checking care notes per species rather than assuming every succulent on the bench follows the same calendar.
How to choose
- Water on a “dry out completely, then soak” rhythm, not a fixed schedule — this is the opposite habit from every other crop guide in this series and the single biggest adjustment vegetable growers need to make.
- Build a gritty mix, not standard potting soil — roughly half organic material, half perlite or pumice, so roots never sit in standing moisture.
- Cap daytime humidity around 40–50%. Nighttime humidity climbing into the 60–85% range on its own isn’t the problem; sustained high humidity during the day is.
- Don’t skip shade cloth in summer. A structure that already runs hot for vegetables can scorch succulents even faster without 30–50% shade during peak sun.
- Cut watering roughly in half during dormancy, and skip fertilizer until active growth resumes.
The bottom line
Succulents are the low-maintenance crop in theory, but only if you unlearn the watering habits the rest of this crop-guide series teaches. Keep temperatures in the 68–74°F range, cap daytime humidity at 40–50%, build a gritty, fast-draining soil mix, and let the soil dry out completely between waterings — get that rhythm right and a succulent bench needs less day-to-day attention than any vegetable crop in a greenhouse.
Still shopping for the structure itself? Our best greenhouse kit roundup and best mini greenhouse picks both work well for a dedicated succulent bench.