Start Sowing Early To Extend Your Growing Season

Here's how to get a head start on sowing seeds to get the most from your garden.

Pepper plants growing in an egg carton
Pepper plants growing in an egg carton. Shaun Roy / Getty Images

It is one of the big questions each gardening season – when exactly should you get started? When is the right time to sow seeds or plant out crops? The answer ultimately depends on where you live, of course – and the conditions to be found in your area. What you want to grow is also key to making these decisions. But there are ways to get started with sowing early and extend your growing season, even when you live in a colder climate zone.

I begin early in the year, but not outside in the garden. I start sowing in January or February indoors with the first tomato and pepper plants for my garden's polytunnel (also known as a high tunnel), which extends my growing season. I can grow in the polytunnel year-round, but I typically start to sow spring crops in March – both indoors for later transplantation, and directly into the growing areas inside the polytunnel.

I cannot typically direct sow outdoors until mid-April at the earliest. But taking the approaches mentioned above means that I can get started with sowing much earlier, and extend my growing season. It does not matter whether your last frost date is much earlier or later than mine, you could consider taking similar approaches in your own garden.

Sowing Early Indoors

Typically, a rule of thumb for short-season gardeners is to sow tomatoes and peppers indoors around six to eight weeks before the last frost date in your area. For me, this means that I usually sow these seeds in mid to late February. But because I am sowing for planting into my polytunnel, I can sow a few weeks earlier, since I can transplant into a space that is frost-free three to four weeks before outside conditions are reliably frost-free outside.

But there are a few things to consider when sowing early indoors.

  • First of all, tomatoes and peppers are both warm-season crops. They require relatively high temperatures for germination to take place. While not an absolute necessity, providing some gentle base heat, or using a heated propagator to increase germination rates is a good idea.
  • Secondly, these crops may suffer from the lack of light common when growing indoors, especially at this time of year. Seedlings that do not get enough light can become leggy and weak, and bend towards the light.
  • You can use foil to reflect and maximize light and turn pots or trays regularly. But I would recommend considering investing in LED grow lights should you wish to continue sowing early indoors.
  • Of course, there are plenty of other crops that you can sow early to get a jump start on the season. But tomatoes and peppers tend to be amongst the earliest sown. As spring approaches, the range of options increases, and so too do the daylight hours, so light and temperatures tend not to be as much of an issue.

Sowing early indoors does take a little more work than direct sowing. But it can be worthwhile for short-season gardeners because it can make it more likely that you will get a worthwhile yield of tomatoes, peppers, and other such crops before the end of your growing season.

Sowing Early Undercover

Exterior view of a poly tunnel in winter at Le Manoir aux QuatSaisons, Oxfordshire.
A polytunnel in winter at Le Manoir aux QuatSaisons, Oxfordshire, UK.

Mint Images / Getty Images

After the tomatoes and peppers, the next crops that I tend to sow are peas and fava beans. Where I live, these crops can also be overwintered in the polytunnel (as long as the right varieties are chosen). But I tend to sow some indoors in March to plant out in my polytunnel a few weeks later.

I could also consider direct sowing these in the polytunnel, but I find that they can disappear – eaten by mice and voles seeking out snacks. So I prefer to sow indoors and transplant seedlings; I then place cloches over them for protection while they are in the early stages of their growth.

Around a month before the last frost date in my area (around mid-April we are reliably frost-free most years) I can direct sow in the tunnel. This is when I will sow a number of spring crops undercover. Lettuces, Asian greens, radishes, early carrots, beets ... these are just a few examples of the early sowings I can undertake in the tunnel. Again, I will also often protect these early sowings with cloches to prevent harm from pests and cold snaps.

Sowing Early Outdoors

I tend to wait until April to sow outdoors. Amongst the first things I sow outdoors are parsnips and potatoes. I look at the weather conditions in a given year carefully before sowing or planting, since one spring can be significantly different from the last.

Since I have the tunnel for early planting, I do not tend to sow very early outdoors. But if you do not have an undercover growing area, there are a number of things you can do to make sure you can get started as soon as possible.

  • You can use row covers or cloches to warm a particular growing area before planting or sowing.
  • You can also use mulches to keep roots safe and soil unfrozen.
  • You could consider making a hotbed for some early sowing. This is simply a raised bed filled with composting materials. These materials give off heat as they break down, warming a layer of soil or compost on top.
  • Remember, raised beds in general will warm much quicker than ground-level growing areas.

Pick the right strategies for where you live, and you can begin sowing early. By getting a head start, you can extend your growing season and start getting the most from your garden.