Do You Need a Mini Greenhouse for a Small Patio?
A mini greenhouse extends the season and shelters seedlings. When a small-patio greenhouse helps, and how to stop it blowing over in the wind.
A mini greenhouse - usually a tiered metal frame wrapped in a clear cover - is one of the cheapest ways to extend the growing season in a small space. It is genuinely useful for the right jobs, but it is oversold as a year-round grow room, and the lightweight ones have a well-earned reputation for taking off in the wind.
What is a mini greenhouse good for?
Its best jobs are at the edges of the season. In spring it warms the air around seed trays so you can start plants weeks earlier, and it hardens off young plants by sheltering them from cold nights and wind before they go outside. In autumn it keeps tender herbs and late salads going as temperatures drop. It is a season-extender and a seedling nursery, not somewhere to grow a full crop of tomatoes from start to finish.
Do mini greenhouses actually work?
Yes, for what they are designed to do. The clear cover traps solar warmth and raises the temperature inside by a few degrees, which is enough to protect seedlings from a light frost and to speed early growth. What they cannot do is create summer heat in the depths of winter or replace proper light, so treat the temperature boost as a buffer against cold rather than a growing climate in its own right.
How do you stop a mini greenhouse blowing over?
Anchoring is the single most important thing, because an empty tiered greenhouse is very light and a gust will send it across the patio. Tie the frame back to a wall, railing or downpipe with cord or bungees, weight the base shelf with bricks or paving slabs, and site it in the most sheltered corner rather than an exposed edge. On the windiest days, unzip or roll up the cover so the wind passes through instead of catching it like a sail.
Do you need to ventilate a mini greenhouse?
Yes. On a sunny day even in spring, a closed mini greenhouse can overheat quickly and cook the seedlings inside, and the trapped humidity encourages mould and damping off. Open or roll up the cover during the day when it is warm and sunny, and close it in the evening to hold overnight warmth. That daily rhythm of venting and closing is the main piece of maintenance a mini greenhouse needs.