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Learning how to grow cacti in a greenhouse is all about controlling the conditions. This guide covers what to do so your plants don’t just survive under cover, but grow strong and stay healthy. Let’s get started.
Cactus Greenhouse Planting
Greenhouse growing gives you more control, but a few things still need to go right for your cacti to thrive. Start with these:
Best cactus for an unheated greenhouse
Some cacti can handle temperature changes, which can happen even inside a greenhouse. Tougher varieties are your best bet if yours isn’t heated or insulated, such as:
- Opuntia (Prickly Pear)
- Echinocereus
- Cylindropuntia
- Escobaria
- Maihuenia
But if yours is heated, you can go for more warmth-loving types too, like:
- Strophytum myriostigma
- Ariocarpus
- Melocactu
Smaller cacti are also easier to look after. They take up less space, need less water, and are easier to move around if needed for light or airflow. Good options include:
- Gymnocalycium
- Rebutia
- Echinopsis
- Mammillaria
- Parodia
These are popular with beginners and tend to adapt well in most greenhouse setups.
Don’t plant in the wrong mix
Cacti need soil that drains fast. The best option is cactus-specific soil, which you’ll find in most garden centres. It’s made to dry out quickly and gives roots the air they need.
You can also make your own by mixing regular compost with coarse sand and horticultural grit. A rough mix of one-third each is a good balance. Just avoid any mix that holds water or stays damp for too long!
Water less
The golden rule is to let the soil dry out completely before watering again. When you water, give the soil a deep soak, then let the excess drain. Don’t leave the pot in standing water, though!
In warmer months, this might mean watering every couple of weeks. In winter, once a month should do it.
Tip: Always use pots with drainage holes. Without them, the roots sit in damp soil, leading to rot.
Give them sun, but not too much
Sunlight in greenhouses can be intense. Direct sun through glass can burn the plant’s surface, especially in warmer months. In that case, you might notice pale spots or yellow patches.
Ideally, plant them where they’ll get steady but not harsh light. A south-facing spot is a safe choice. Shade, such as shading fabric or netting, might be necessary for extra protection when the sun is high.
In colder months, the problem flips: there’s often not enough light. That’s when a grow light (or artificial light) is handy in stopping cacti from becoming stretched or weak. Adjust their spot or filter the light a little more if the colour starts to fade or they look washed out.
Greenhouse Temperatures for Cacti
During summer, aim to keep daytime temperatures between 18–29°C. Open vents or doors and use a fan (optional) to keep air moving should the temperature climb higher.
Around 10°C is a safe minimum for most types at night. Though cacti can handle cooler temperatures, avoid anything close to freezing. Use a small heater where insulation is lacking. A thermostat or timer can also help control the heater and prevent too much heat at night.
Remember, while cacti do well in warm and dry conditions, greenhouses can heat up fast. The key is balance. Keep the air moving, avoid stale pockets of heat, and give your plants time to adjust when the seasons change.
If you’re unsure what features to look for in a greenhouse model, check out our greenhouse buying guide for tips on choosing the right one for your space and climate.
How to Grow Cacti in a Greenhouse: Round-up
Cactus greenhouse planting gives you more control, but they do need the right conditions. Start by choosing the right cactus variety and planting it in suitable soil. Water less than you think. Give it sun, but not too much. And manage heat during the day and cold at night. Good luck!
Tempted to bring a few more into the greenhouse? These “Garden Greenhouse Ideas for Growing a Plant Paradise” are all you need.
Browse through our range of greenhouses, including wooden greenhouses, while you’re here!
