When should I sow my seeds?

By Ben Heron

Most herb seeds – like vegetables – can be sown in the spring. But there are also many species that need to be sown in the autumn or the winter, or require some kind of treatment prior to sowing to break their dormancy [see post on stratification]. Other species, such as basil, are easy to germinate and – given the right conditions – can be sown at any time of the year.

The easiest way to check which herbs can be sown at a given time of year is to explore the ‘sowing time’ filter in the shop page. There is nothing more disappointing than buying lots of seed packs only to discover they were supposed to be sown three months earlier.

The correct sowing time will of course depend on whether you are sowing indoors or directly into a garden bed. Many seeds will only germinate once the soil reaches a certain temperature, which means that you might be able to germinate seeds in a greenhouse (or heated propagator) in March, but would have to wait until mid-April before it can be sown outdoors.

Another reason to delay sowing outdoors is that young seedlings can easily be damaged or killed by a heavy frost. If you do sow early, always keep an eye on the weather forecast and take measures to protect your plants if you can (pots can be moved indoors, or you can cover the plants in horticultural fleece).

There are certain seeds that can be sown in late summer or early autumn for ‘overwintering’. Basically, this means keeping young seedlings in a protected place – in a greenhouse or on a window ledge – until the following spring when they can be planted out. This is a common method for growing certain herbs such as milk thistle, giving them a head start so that they yield more flowers and seeds the following year.  

And finally, there are a few herbs such as angelica that can be sown outdoors in the autumn or early winter; the seed is exposed to cold and wet conditions over the winter, which is exactly what it requires to break its dormancy so that it will germinate in the spring. This method does come with the risk of losing some of your seeds to hungry rodents, birds and squirrels at a time when their food sources are limited; a safer alternative is to mix the seeds in damp sand or compost and leave them in a sealed bag in the fridge for a month or two prior to sowing. More on this in our post on stratification.

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