Sunday 24 March 2019

Diarmuid Gavin: 'Give your summer flowers a head-start by sowing seeds indoors this weekend'


Cosmos flowers
Cosmos flowers
Sweet pea flower

Diarmuid Gavin

As the days grow longer and green shoots start to appear even through frozen ground, many of us are itching to get gardening again. While it's still too cold for outdoor sowing, there are some plants which you can get started indoors in February. Many of these will end up outdoors - either in the ground, in pots and containers, or hanging baskets - when the temperature climbs and risk of frost is gone.

It's a fun project and it's exciting to see your seeds first germinate and then develop. Seeds are a cheap way to raise plants and by choosing varieties you like now, you are not restricting yourself to what's on sale in the garden centre in May.

So, what do you need? Seeds want light and heat to germinate, so either a heated propagator or nice, sunny windowsill are the best spots. If you're using a windowsill, turn seedlings daily so they don't grow lopsided.

A word on watering: seeds will shiver and rot if compost is too wet and cold but won't germinate at all in dry soil. For best results, sow into damp soil and then water gently - recycling a kitchen spray bottle is ideal for this task. Use tepid water if you can.

Cover seeds with polythene until they germinate as this will help retain moisture and check daily until germination that soil is damp. Remove polythene or glass once germination has occurred.

Here's a taste of what you can sow this weekend - a home-grown selection of easy-to-grow bedding plants that will delight in summer:

Matthiola incana - Ten Week Stock

Fill your tubs and containers with this easy-to-grow cottage garden favourite. Immensely popular due to its delicious clove-like fragrance, it's also a great source of nectar for the bees. As the name suggests, it will take about 10 weeks from germination to flowering, so you could start a batch now and do another one in March. Sow in trays, only about ¼ inch deep, and cover lightly with either sieved compost or some fine grit or vermiculite. They will take a few weeks to germinate. When large enough to handle, prick out - this means gently (holding by the leaf, not the stem) removing the seedling with the help of a dibber (or pencil) and potting on individually. Keep growing on and gradually harden off for outdoor plantings in May.

os_219186204_Sweet pea.jpg
Sweet pea flower

Sweet pea

Sweet pea (above) is one of the best flowers for cutting in summer - the more you cut, the more they produce; and what beautiful flowers in gorgeous pastel colours and heavenly scent. Seeds are large enough to handle in singles and they can be sown singly in individual pots. Ideally you will grow them in root trainers - which are longer than usual pots - to allow good root development. A good trick if you want to avoid disturbing the roots next spring when you go to plant them outdoors, is to plant in biodegradable pots that will disintegrate in the soil. A handy household version of this is a loo roll or kitchen roll cut in two, which you can sit in trays. One seed per three-inch pot is sufficient and cover the seed with about half an inch of growing medium. Water with a fine watering can rose, cover with sheet of glass or plastic and leave to germinate. When large enough for transplanting in May, give them some support to scramble up - a simple teepee of bamboo sticks is ideal.


Cosmos (main photo, above) will reward you with tonnes of flowers in summer from white to pale pink to deep pink atop frothy foliage. Sow batches indoors from now until April. As the seeds are quite fine, just sprinkle them on the top of the compost and don't cover at all, or just lightly with some grit. You can also plant these directly into the soil outdoors in May but the flowers will come much later than if you get them going indoors now. For something very special, try growing the Cosmos atrosanguineus, which has lovely dark petals and an unmistakable scent of chocolate.


Lobelia flowers are a great trailing plant for hanging baskets. The seeds are very fine, dust-like, which makes them a bit tricky to sow thinly, but try your best and then just thin them out - you'll have way more seedlings than you need. You can also try mixing the seed with silver sand to get a more even distribution. Sow on the surface of the compost - don't cover with compost as they need light to germinate. Try to water from beneath to prevent damping off - a fungal disease they are prone to - and if growing in a greenhouse or propagator, let the air in regularly.

Top Tip

It's best to use fresh seed compost and pots or trays for sowing. If you are reusing last year's pots, give them a good scrub first to clean them out so there are no nasties, such as fungal diseases, lurking.

Weekend Magazine

Editors Choice

Also in Life