There are – it seems – a few things that can be grown in an unheated greenhouse – with sufficient planning: Winter Lettuce, Potatoes, kale, cabbage, bok choy, Chinese cabbage, Spring onions, and Spinach.
Christmas potatoes will be grown in the potting shed.
Of the list above, I currently have seeds for:
- Spinach – Cello F1 (4)
- Chinese Kale (4) usually 60 days to germinate
- Lettuce – Winter Imperial
- Spring Onions – White Lisbon (estimate) usually 14-16 days
Also these seeds grow all year; the figures in blue are for spring/summer germination though this will be slower in autumn:
- Chives (16) 10-15 days
- Claytonia – Winter Purslane (16)
- Coriander (16)
- Cress – American land (estimate)
- Cress – curled (sow thinly on wet kitchen paper indoors) 5-7 days
- Dill (3)
- Mustard (sow thinly on wet kitchen paper indoors – 3 days after cress) 2-3 days
- Parsley – plain leaved (4)
- Pea shoots
- Radish – French Breakfast (16) 7-10 days and Black Spanish Round (9)
- Salad leaf – several varieties
- Watercress (not suitable for mixed planting)
How to Grow
In Square-Foot Gardening, we ignore the row spacing stated on the seed packet and concentrate on the seed spacing (after thinning where necessary -the figures in (xx) above), though we can usually squeeze a few more plants into the space available – but not too many.
A ‘square’ in this instance is 12 inches per side.
- 3″ plant spacing = 16 per square
- 4″ plant spacing = 9 per square
- 6″ plant spacing = 4 per square
- 8″ plant spacing = 2/3 per square (estimated)
- 12″ plant spacing = 1 per square
(It’s easier if you make something to help with the spacing. Home-made, but there are plastic versions on the market. Calculate how many plants you should have in your one-square-foot, lay the guide on the ground, and poke a stick through the holes to mark the compost. Sow or plant.)
Labelling of each container will be key. Which seeds were sown and when (and using a proper label that doesn’t disintegrate or fade).
I’m using potato growing bags as they become available (see earlier post regarding re-using spent compost) – which are 12 x 10 inches and 16 inches tall (I’ve turned the tops down to make them half-height. I’m not growing root crops so don’t need great depth). They have drainage holes at the sides – and I will do my best NOT to overwater them.
Examples of a Mixed Bag
The idea is to grow a mixture of crops in the same bag that look sufficiently different from each other that we don’t end up eating radish leaves by mistake, and that make the most of the space available to them.
12 x 10 inch Bag
More suggestions for greenhouse vegetables (Winter varieties if available)
- Brussels sprout
- Swiss chard