Mini Greenhouses: Pros and Cons…

Do you want a greenhouse but not got the space for a standard version. Or you aren’t sure if a mini greenhouse is for you? Then read on.

You could opt for a Growhouse. `An aluminium or wooden construction with safety glass. There’s different sizes available; freestanding or designed to be against a wall. Costs vary, as does the design and heights.

Some retailers list mini greenhouses as Growhouses in their search options, which can be confusing. And there’s many variations on the height and internal layout of the mini versions too.

In a cool spot in your garden, you could even use it as a substitute cold frame- if needed.

My mini greenhouses are from the lower end of the price range. At the time of buying my choices were limited- due to ongoing trade disruptions caused by the pandemic and lockdowns.

Both of mine are an upright frame. Each section slots into place on top of the one below, then finally the two roof arches front and back. The plastic cover has ties at the corners, and access is via the zipped front opening. There’s a tie inside and out at the top of the front panel so you can roll it up and tie it in place to allow ventilation.

Spend time browsing the options available in your price range. Check if your local garden centre stocks them. Consider the size, and the materials, as they will require maintenance in a similar way to a standard greenhouse- washing inside and out being an essential, especially pre-spring.

Positioning. This will depend on your garden and the surrounding area. Are there large trees that cast shade? Tall buildings? Is the garden sheltered or exposed to high winds? The position of the sun across the day for what you want to sow and/or grow on will influence the positioning.

What surface will it be placed on? Avoid standing it directly on the ground unless you’ve got a solid base to place it on. And weight the greenhouse down to provide stability in windy weather.

As 2021 proved, summers can be wet and cool. Can you easily access it in sudden hot or bad weather to open or close the front panel?

Whichever type you install, take the time to fine tune your plant care regime. What additional things can you do to help your seeds and plants thrive rather than fail?

(I speak from experience on the fail side. Summer 2021, I opened the greenhouses in the morning, all was well. The day was dull and expected to stay that way. I went out, and later in the day the clouds cleared and blazing sunshine hit the greenhouses; the temperature inside rocketed and a tray of young lettuce seedlings died- I’d forgotten to apply the make-shift shading [a white net curtain]. I never forgot that, and my next sowing of lettuce was protected.)

Here’s the pros and cons for my type of mini greenhouse. You’ll see that some aspects appear in both.

PROS

a) Capacity: with three or four shelves you have flexibility. You can remove a shelf (and place it on top of one of the others temporarily) to give additional head room for a tall plant. There’s room for multiple seed trays and plant pots.

b) Easy to move. The light construction allows one person to move the greenhouse by themselves- always consider your personal health and safety when moving any structure or equipment.

c) They heat up quickly in the late spring/summer months.

d) Good light transmission- in the right location.

e) Positioning on lower shelves can help slow down the growth of excess seedlings. (Don’t neglect them, they need to be returned to the top shelf for maximum light and heat, but you may be able to slow them for a week or two to spread out harvesting times if you’ve sown too many seeds in one sowing.) See **

f) Size- If you only have a small space, a patio or balcony, it’s ideal.

CONS

a) Easy to move. You need to weight the greenhouse down to stop it getting blown over in high winds or gales.

(I have three to four bricks on the bottom shelf of each greenhouse- against a wall providing partial shelter. On top of the bricks I’ve created a shelf with a raised back and sides, which reduces the wind toppling the greenhouse from the base.)

b) After continual exposure to sunshine and rain the material ties you use to hold the rolled-up front flap open can break. (You can use plastic type pegs to hold the flap back, but make sure there’s no sharp edges that could rip the plastic cover.)

c) High temperatures inside and out in hot summers. In direct sunlight the plastic cover will get hot so be careful. As with a standard greenhouse, provide shading during hot summers.

(Old net curtaining allows light in but diffuses the burning effect on your tender plants- experiment to find what works for you. I also sprayed a fine water mist inside the roof of the greenhouse and over the net curtaining, when the sun was in direct line with them and the temperature was too high.)

d) A cold spring. The regular night-time minus temperatures experienced in spring 2021 in the UK, made extra protection for the plants inside the greenhouse essential.

(I used DIY propagator lids over the seed trays and pots. I used polystyrene packaging between the internal sides of the greenhouse and the trays to create another barrier between them and the cold external surface. Finally I covered the shelves with 30gsm fleece. The temperature inside- during April 2021- went down to -2 to -3 degrees on a number of nights, but the early plants were okay*.)

e) During the growing season you need to check your mini greenhouse daily- and more often during the height of summer.

*Any tender summer plants like tomatoes or peppers etc would be better indoors in the warmth.

** You need to regularly turn the trays of seedlings or plants to stop them growing toward the light and becoming lop-sided and leggy.

Conclusion

Still willing to give it a go?

There’s two items that I’d recommend you buy.

A greenhouse thermometer that gives you both day and night time temperatures, and humidity- it doesn’t have to be expensive.

And a notebook. Keeping a record of when, and what you’re sowing. How long has it taken to germinate. Temperatures, especially when frosts are due. You can adjust your sowing times for particular seeds next year, if needed.

If you’re not convinced you can start seeds and grow on plants in this type of mini greenhouse, then please have a look at my Gallery page.

I’ve been taking numerous photos during 2020/2021 to show what’s possible. I hope this small selection of images will encourage you to try growing flowers, vegetables and herbs in your own mini greenhouse…