Growing exotic plants under glass: greenhouses, polytunnels and conservatories
It can be incredibly rewarding growing tender plants and tender species under glass, opening up a whole new world of gardening. Think of tomatoes, chillies, bananas, palms… the list is endless! Unfortunately, investing in any structure – whether it be a greenhouse, conservatory, cold frame, polytunnel, mini-greenhouse, grow house or fold-up tomato house – can be fraught with difficulties.
If you need inspiration and want to assess what you can afford, there’s a huge selection of greenhouses, polytunnels, cold frames, mini-greenhouses, grow houses or tomato houses available at Primrose.
First, there are costs to consider. Budget options are usually called that for a reason. Lightweight push-together frameworks covered with PVC ‘tents’ have the nickname ‘blow-aways’ – not great for windy or exposed sites like mine. I had a bad experience with an 8’x4′ grow house, which retailed at nearly £100 and lasted just three days.
Tender plants – Greenhouse investment
In May 2015, I invested in an 8’x4′ lean-to aluminium greenhouse, with double doors down the long side to grow mostly tomatoes in summer and overwinter my exotic plants. It was the biggest I could afford and fit in the garden at the time. I’d recommend getting a professional to install one. Beyond me and the other half, we hired a builder to do it.
Pay the extra and invest in toughened glass, for safety’s sake. Storm Desmond was the first to wreak havoc with my greenhouse – five of the large panels blew out, although only one smashed (but that cost £62 to replace). Since then, I’ve spent about £500 on replacement glass and retrofitting glazing bars – the cost of the original greenhouse!
My conservatory has been great, but from March to October, you can barely enter the house without knocking something down. The colder months aren’t much better, with half-hardy perennials to overwinter. It’s also up a flight of stairs, meaning many heavy pots have to carried outside/back inside in spring and autumn.
The pros and cons of undercover structures
GREENHOUSE
PROS: Permanent.
Constructed to your specifications.
Successfully heated.
Toughened safety glass option – but more expensive.
CONS: Expensive, especially wooden framed models.
A base is needed for stability.
Difficult to build.
Requires time and effort to clean.
Wooden frames require treatment to prevent rot.
A danger of cheaper horticultural glass shattering.
POLYTUNNEL
PROS: Prices get more reasonable as the size increases. No glass to break.
Large areas can be covered.
Storm-resistant if installed properly.
Professional growers’ choice.
CONS: Not cost-effective on a small scale.
Manufacturers rely on you putting them up – I was quoted £700 to install a £400 model.
Cheaper covers need replacing.
Not as aesthetically pleasing as a greenhouse.
CONSERVATORY
PROS: Great habitat for exotic plants.
Sit and enjoy your plants.
Part of the house, so no cold journeys outside.
Temperature can be controlled.
CONS: If used as a sitting room, etc, not practical to have soil everywhere.
Using it as a greenhouse may upset family members. Really expensive.
Temperatures rise and fall dramatically if ventilation is not monitored.
GROW HOUSE
PROS: A cheaper but sizeable alternative to a greenhouse or polytunnel.
Easier to install.
CONS: Avoid if you live in a windy area.
PVC covers rip at seams easily.
Light intensity is poor.
MINI GREENHOUSE
PROS: Strength of those made of uPVCor glass with aluminium/wooden frames. Can be fixed to walls.
Excellent for hardening off plants.
CONS: Expensive.
Small size limits what you can grow.
COLD FRAME
PROS: DIY fixed version is cost-effective.
Excellent for hardening off crops.
Mobile versions are great for warming soil in spring for early crops.
CONS: Plastic versions are liable to blow away.
Heavier wooden types can be expensive.
TOMATO HOUSE/MINI GROW HOUSE
PROS: Cheap, easy to move.
Dismantles easily for winter storage.
CONS: Likely to blow away.
Not durable.
Shelves bow under the weight.
For more on choosing plants, visit my plant categories.
