September sowings

Is September really the most important sowing month?

Earlier this week I released my sowing guide for September, in which I claimed that September is the most important sowing month for the year round gardener.

I’m going to briefly explain here, why I make this claim and whether it’s really worth the effort. Here are the key points:

1. Most summer crops finish or stall in early October in unheated growing spaces, which for me includes my low tunnels, cold-frames and my polytunnel. October marks the end of the tomatoes, cucumbers and squash. A few summer fruits will continue to ripen through October, but yield reduces dramatically and by the end of October it’s essentially all over.

2. Most veggies take 3-5 weeks to be ready for planting out, which means that it you want to replace your under cover summer crops, you need to sow them during September, if you want all of your summer crops to be replaced by the end of October, that means all of your lettuce, Asian greens, spinach, salad onions need to be sown in September and planted in October.

3. Growth slows down noticeably in October, significantly in November and has stalled by mid December, it won’t really restart until mid-February, so early October is the key planting time for winter harvests, mid October for late winter harvests and late October for early spring harvests

4. Growth really restarts in March and September sown spinach and lettuce will grow very strongly in March and you will probably have too much of it, if you sowed enough for winter. So you need plants ready to replace your surplus of lettuce and spinach, September sown brassicas are perfect for this!

5. So you will likely have plenty of under cover space spare through March to May/June before you will want to plant your summer melons, tomatoes, peppers and squash in May (under cover) or June (outside)

6. In order to take full advantage of this very productive three month period between March and June you need to grow something other than lettuce, spinach, turnips and radish and the best option are hardy brassicas, especially cauliflowers, calabrese and cabbages. None of these will be ready for harvest in May unless you sow them in September and very early October. Sown earlier than this and they will need to be planted out in Autumn, displacing your winter veggies, sown later and they won’t be harvested in time. These brassicas will need to be grown in pots and over-wintered under cover, ready for planting in January/February under cover, your winter lettuces and spinach won’t quite be finished at this time, so they need to be interplanted into these beds (if you have 25 spinach plants/m2 harvest 5 of them and plant your cauliflowers in the gaps)

There are exceptions to everything in gardening, especially winter gardening, here are a few very important ones:

1. Brussels, Red Cabbages, Savoy cabbages and Kalettes need to be sown in spring to provide a secure supply of fresh winter veggies

2. Salad onions need to be sown in late July and August to provide a secure supply through winter and early spring

3. Lambs lettuce is very slow growing, so if you want to harvest it in winter it needs to be sown in August, if you want it in spring it can be sown in early September BUT it will soon go to seed in spring

4. Red cabbages sown in September won’t be ready until late May at the earliest and you will likely continue to harvest until July at the earliest (they will stand well into autumn) so don’t plant these where you want summer fruits but what a treat to have red cabbages two months early and they look beautiful!

5. Asian greens sown in September will go to seed in January/February so be ready to replace them, I like to replace them with September sown calabrese

6. Carrots for spring are best sown in late October, otherwise they will probably be too big in spring, accurately think they are in their second year and go to seed. Sown in late October they have just enough time to grow big enough (under cover) to survive winter but they think they are in their first year when they start growing again in late February. You benefit by having a 4-6 week head start and by not risking a failed sowing in February or early March

A few more tips:

1. In early March growth explodes under cover, so you will have too many spinach and lettuce plants, so make sure you have radish, turnips, Asian greens ready to go

2. If you like parsnips they do really well chitted and then interplanted into cold-frames full of spinach plants in early March (harvest every other spinach plant) and Zebrune or Long Red Florence shallots do nicely interplanted with the parsnips (in place if the remaining spinach plants in April). Harvest the shallots in August and the parsnips will be ready soon after, but you can leave them until winter if you like giants!

3. September sown spinach, grown under cover, will start to go to seed in early spring, so make sure you have a follow on batch ready to take it’s place, sown in October or February

Finally grow lights make life a lot more fun, allowing you to start almost anything at any time, but you need to balance heat and light, too much heat and not enough light means leggy plants, too much light and not enough heat means stunted plants, too long a day for brassicas and spinach accelerates them going to seed.

Used well though, grow lights it makes it easier to:

1. have Asian greens ready to plant in January and ready to harvest in March, when your September sown plants have gone to seed

2. plant your favourite spring lettuces out in November or February ready for an early spring harvest

3. sow baby savoy cabbages in January, so they are ready for harvest in May when you spring cabbages are finishing and your red cabbages are not quite ready

4. grow big strong peppers plants ready to set fruit in May or earlier if you have a heated greenhouse

5. grow early tomatoes, ready for harvest in May if you have a heated greenhouse or late June if you have a polytunnel

Interested in using lights, check out the Basic Growing Skills, section of by ebook, this chapter has you covered. As always for all of the details, check out my growing guides for each type of veg, these have all of the key dates, varieties and techniques. If you want more on the big picture of growing over winter the Monthly Growing Guides are a big help. If you want to only see content specific to growing in a particular environment, like a heated greenhouse, or a polytunnel or maybe just under fleece, these guides are the best place to start.

Wondering whether year round gardening is really worth the effort, this video is a good start.

or for winter specifically