Get growing – how and when to sow annual seeds

Cornflower 'Black Ball'

Now that you have a list of plants to grow in your cutting patch, it’s time to start thinking about sowing some seeds. Exactly when to start sowing depends on a number of things – the weather, soil conditions, and how much space you have indoors to grow plants until they are ready to go outside.

It’s been pretty cold (in the UK at least) so far this year, so there’s no rush to get seeds into the ground yet. Saying that, if you are planning to grow sweet peas and half hardy annuals, it would be a good idea to start them now.

Sweet peas

Sweet peas

You can sow sweet pea seeds directly into the ground later in spring but, if you have space on a windowsill, starting them now will give you stronger plants and earlier flowers. Sweet peas have a tough coating to the seed. Some people recommend making a small nick in the seed coat or soaking them overnight in water to help speed up germination. This year I’ve been using a trick I learned from Twitter, and have put the seeds on a piece of kitchen paper soaked in water, then folded it over to cover the seeds. I’ve found this a really useful way to see which seeds are going to germinate. As soon as the seeds show any signs of growth, I very gently move them to a pot of compost. Sweet pea plants have long roots, so find the deepest pots you can, or invest in some root trainers that are specially designed for sweet peas. It’s also possible to use the cardboard tubes from the inside of loo rolls. Stand them upright in a container (one with drainage holes in the base), fill them with compost and water well. Make a hole in the compost – about 2cm deep, and gently drop a single seed in. Sow one seed per cardboard tube or root trainer, more in a pot but keep them evenly spaced with room for the young plants to grow. Cover with compost and leave in a warm, mouse-free place. Mice love sweet pea seeds, so make sure they can’t get at yours.

Once you see green shoots, make sure the plants get plenty of light and the compost is watered regularly.


Half hardy annuals

Pink cosmos flower

Cosmos, rudbeckia, snapdragons and zinnias all make fantastic cut flowers. These plants can be sown indoors in March or April and grown on protected from frosts before you plant them out into the cutting garden in late May or early June. Fill a small pot with some finely crumbled, peat free multipurpose compost. The right texture is key – seeds like a fine soil so that the delicate new roots don’t come up against big lumps that they can’t grow through. Gently firm the top of the compost to level it and make sure there are no big air pockets. Water, again gently, to ensure the compost is damp right through but not soggy. Sow the seeds following the instructions on the packet, label the pot and put in a warm spot to germinate. If you have a propagator, put the pot in it to help maintain a nice humid environment. Depending on the temperature and the type of flower, you may see signs of growth in a few days or a couple of weeks.

As with the sweet peas, keep the growing seedlings in a light, frost free spot – a sunny windowsill is ideal, and check regularly to see if the young plants need watering.


Hardy annuals

Bee on a cornflower

Hardy annuals are a great choice if you have limited space for starting seeds indoors. They can be sown directly into the garden once the soil has warmed up in late spring. One word of warning though – don’t try sowing them too soon. Depending on the weather and where in the country you are, early April is the soonest you should be even thinking of sowing directly. The general rule is to wait until the weed seeds start to grow – a sure sign that the soil is warm enough to start seeds.

Prepare the soil by removing any weeds that have already germinated, and use a rake or hand fork to create a fine texture. Make shallow lines or zig zags in the soil, water if dry, and sow the seeds thinly into these. Sowing in straight lines makes it easier to spot which seedlings are meant to be there and which are weeds as the young plants grow. Cover the seeds with a little soil. You might need to protect the freshly sown area from the attention of cats or birds if they are likely to scratch up your seeds. This is easily done by laying some fine netting or thorny twigs over the soil. Watch for signs of growth. You will soon learn to recognise the flower seedlings and be able to remove any weeds that germinate alongside them. If the weather turns dry, water the flower patch using a watering can with a rose attachment.


In the next Jam Jar Cut Flower Garden post we’ll look at what to do with your seedlings when they get big enough to move to bigger pots (for indoor sown seeds) or thin out (for direct sown seeds).

Happy sowing!

7 thoughts on “Get growing – how and when to sow annual seeds

  1. janesmudgeegarden

    Thanks for this info. I’m a bit late planting sweet pea seeds (the general rule here is to have them in the ground by St Patrick’s Day) so I’ll use your kitchen paper method.


    1. Bee & Bouquet

      I’d recommend the kitchen paper method – it’s worked really well for me this year. Hope it does for you too. I’m trying it with sunflowers now – some old seed that may or may not germinate. So it’s going onto kitchen paper first to see if there’s any life left in it.

      Liked by 1 person

  2. tonytomeo

    Someone brought home one of those cheap big cans of wildflower mix from a big box store years ago. I really did not like the idea, but had to throw the seed out and about through the winter wherever there was any excavation. I was not at all careful about it. By this time of year, they were blooming everywhere, and the cosmos came back for many years. There is still some out there! Yes, it was cheap, but it looked great! Yet, I can not get bachelor buttons to look so good. Nor do sweet peas do well here. We grow them anyway, but the season is so short for them.


    1. Bee & Bouquet

      One of the great things about gardening is that you don’t have to spend a lot of money to get beautiful results. Sowing a seed mix is probably a good way to find out what does well in a garden, if a plant grows and seeds itself about then it must be happy. There’s a lot to be said for the ‘right plant, right place’ style of gardening!

      Liked by 1 person

      1. tonytomeo

        Well, if I had my way, we would not have spent the money on the seed mix (although it worked out nicely and was very cheap). I mean, we grow things! It is a nursery! I kept my front garden where I lived in town back then very nice with just things that grew from cuttings and seed from what I have been growing since I was a kid. I got my nasturtium seeds before I was in kindergarten, and they have been with me since. I got my pelargoniums when I was in junior high school, and then some more a few years later. They do not cost me anything.


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