What you can still sow and plant

Here in Scotland, we’ve done most of our veg sowing for the year and precious few varieties are still worth planting out. The sun is weakening after the longest day and by mid September nothing other than our more vigorous weeds start growing.

This is much truer here than down south, so seed catalogues often give us overly optimistic timetables.

So, what’s the point of this article? Some quick-growing species, nearly always leaf crops, will still produce a worthwhile harvest and others put on enough growth to get established, letting them grow away quickly next spring.

But not only the sun matters. Soil temperature determines whether some varieties can germinate. Our cultivated lettuces, Lactuca sativa, were first cultivated in the Middle East when an Assyrian king reputedly introduced lettuces and other vegetables in 700BCE.

To survive, these lettuces had to develop a safety mechanisms to protect against high Assyrian temperatures that would make any germinating seedlings simply shrivel. This process is called thermoinhibition.

Thermoinhibition for lettuces kicks in when soil temperature rises above 26C, but when it’s cooler, seedlings germinate immediately. Fortunately during a Scottish summer, the usual soil temperature at a sowing depth of around 1cm is 20C or a little less.

So, this means the usual advice to avoid sowing lettuce in high summer only applies if you’re basking in a glorious heatwave. You’ll manage fine during a more normally dreich, Scottish summer. You can then go for cut and come again varieties or quick maturing ones such as Little Gem or Deertongue.

Like lettuces, several other vegetables, including celery and spinach, fail to germinate in heat. The ideal soil temperature for rocket, radish, dill and coriander is 15-20C. Endives and chicory prefer 20-22C, leaf celery 15C, and spinach 15-20C. During hotter, drier spells, if these crops do manage to germinate, being badly stressed, they’ll probably bolt and provide a pretty poor harvest.

Pak choi is also possible, producing tender spicy leaves in 45 days, provided the plants are kept constantly moist and you fend off our mollusc friends. And I prefer sowing beetroot in July, rather than earlier on.

As an investment for next spring, I sow one of my favourites, Swiss chard, about now. They can be sown direct or brought on in root trainers for planting out in August.

I put some in the open ground with a protective fleece covering and am lucky to have a polytunnel that I can use for others to extend the cropping season and hedge against what might be a fatally severe winter. For the same reasons, I sow spring cabbage next month and plant in the tunnel in September when it’s cool enough for brassicas.

Keep the fleece off the plants to allow for air circulation. You’ll probably need a mouse trap, checked daily, so you, not mice and voles, nibble your greens.

You could buy plants from mail order companies. But be careful. It shouldn’t be too late for planting leeks now, but I’d eat my proverbial hat if a savoy cabbage, delivered to you in September as one company promises, could give you a decent head in January. And, at £4.99, it’s a pricey cabbage.

But, I’m jettisoning wisdom and experience to try a broad bean, Luz de Otono, supposedly ready for harvesting in September/October. I’ve always found beans sown after the end of April rarely do well, but this new variety is apparently different. It’s not frost-hardy and probably won’t grow fast enough here, but broad beans top my list of favourites, so I’ll have a punt.

Plant of the week

Rose, Alba Maxima. Known as the Jacobite Rose, it’s strongly scented, very hardy, with pretty foliage and loosely double, white flowers. Beautiful and long lived, mine comes from a long line of local root cuttings.