All across the UK we’re getting glimpses of Spring with warmer, longer and sunnier days! In my previous blog I covered sowing seeds indoors and this time we’ll be looking at how to sow seeds directly outdoors.
Now’s the time to get ahead of the game when it comes to growing your own, so use the tips from this article to help you plant out some seeds now and you'll be able to reap the benefits later on in the growing season. Whether you’re blessed with a large garden and raised beds or you simply have a small balcony, I will cover exactly how you can grow a delicious variety of vegetables to nourish you later this year.
What is Direct Sowing?
Direct sowing is the act of sowing seeds directly into the soil in which they will grow for the entirety of their life cycle. This is different to the process of starting seedlings indoors in trays (check out my last blog for what to plant indoors in Feb/Mar).
Direct sowing is ideal for gardeners who do not have the space to propagate seeds indoors in trays. This method also makes it easy to plant seeds in neat rows, which helps us manage the plants and any weeds later in the season. Not all types of vegetables are suited to direct sowing. Those sown at this time of the year need to be hardy to withstand the potential frosts and shorter days.
For those which need a little extra protection we can plant them in trays or the ground, under a cloche or cold frame, this keeps the soil temperature a little bit warmer for certain crops like parsnips, carrots and summer cabbages.
How to sow your seeds outdoors
1. Find out what hardiness zone you live in
When it comes to direct sowing at this time of year, you want to make sure that you live in a ‘mild’ area, by this I mean the hardiness zone of the UK in which you live. It goes without saying different parts of the UK have different temperatures, here you can find what zone you live in. If it is any colder than 8b or 9a (H4) then it’s best to delay sowing outdoors until the temperatures warm up around April. You can also make more use of cloches and fleeces to keep seedlings warm.
2. Source your seeds and compost
Next you will need to source your seeds, you can order online from a multitude of suppliers, I find the variety on “realseeds.co.uk” is really good. Large hardware/gardening stores have a good variety of seeds too.
Any of the following can be sown directly now (March) in milder areas: beetroot, broad beans, carrots, kohlrabi, lettuce, leeks, onions, parsnips, peas, radish, spinach, summer cabbage, summer cauliflower, swiss chard and turnips.
You will also need a good quality compost. I find Melcourt’s Sylvagrow is a great all round compost. It is peat-free and will provide all of the nutrients your plants need. For planting into containers, you will find perlite or horticultural sand is worth getting too, it will improve the drainage of your compost.
3. Prepare your growing space
If you’re planting directly into a raised bed in the garden it is a good idea to mulch your patch with a liberal amount of quality compost. It is unnecessary to cultivate (or dig up your soil), this only disturbs and destroys the soil and its organisms by exposing them to oxygen and light. The natural process of plants roots growing and rotting will cultivate the soil for us, along with the efforts of earthworms and the billions of other soil biota in a healthy soil.
If you’re planting into plant pots/containers, ensure that you have sufficiently large and deep ones (around 25cm deep for most plants, although spinach and lettuce can grow in smaller pots).
This is especially important if you're growing plants with extensive rhizomes and roots like parsnips, carrots and turnips. Once you have some appropriately sized pots, fill them up with compost and some perlite/horticultural sand at a ratio of approximately 5:1.
4. Sow according to each plant’s needs
Top tip 1: use a ruler to make seed spacing easy!
Top tip 2: if you want to grow a great variety of these plants it’s worth investing in a few cloches and some horticultural fleece so your seedlings will survive the cold.
Beetroot (grows well in containers) Sow three seeds at 10cm spacings, 2.5cm deep. If planting multiple rows, space them 30cm apart. You can sow small batches from March to July every 2 weeks to get a constant supply of Beets! If you’re growing in containers choose one which is at least 25cm deep.
Broad beans (grows well in containers)
Sow seeds 5cm deep and 20cm apart. They are best planted in double rows, with the parallel rows planted 20cm from each other. Dwarf Varieties can be sown 15cm apart.
If planting in containers, only choose dwarf broad bean varieties.
Sow the seeds as thinly as possible, 1cm deep, in rows 15–30cm apart. Thin out seedlings if necessary, aiming for plants 5–7.5cm apart. Ensure you grow any early cultivars under a cloche or fleece. Any maincrop cultivars can be grown without protection from Late March to July. You can find this information out on seed packets.
If planting in containers, choose short-rooted varieties or you will need a container around 45cm deep.
Kohlrabi (grows well in containers)
Sow seeds 1cm deep in rows 30cm apart continuing until mid-August in warmer zones. Sow a little and often, every two to three weeks, for a constant supply. If growing in a container, thin out to the strongest seedling per pot.
Lettuce (grows well in containers) Sow seeds thinly, 1cm deep, in rows 30cm apart. Sow a short row every fortnight for a constant supply of Lettuce from late March to late July.
If growing in a container, each Lettuce head needs 15-30cm to grow out.
In March-April, sow Leek seeds thinly, 1cm deep, in rows 15cm apart. If you don’t have much space in your vegetable patch, plant your leeks to one side and you can transplant them at a later date when crops like lettuce have been harvested.
Sow onion seeds 1cm deep in rows 20cm apart. Thin out first to 5cm and later to 10cm, leaving the strongest plants. The closer the plants are to each other, the smaller the bulbs will generally grow.
Parsnips Sow thinly or sow three seeds 1cm deep at 15cm intervals in rows 30cm apart.
Warm the soil before sowing with cloches and leave these in place until the seedlings have developed two true leaves. If you don’t have a cloche or dome, plant your seeds from mid April - early May when it is warmer.
Peas Peas generally grow well during a cold spring but it is advisable to never sow into cold, wet soil. Wait until you have a few days of warm weather or you can warm up the soil with a cloche first, then sow. Make a flat-bottomed trench 5cm deep and sow seeds 7.5cm apart, cover with soil, then lightly firm. Cover with horticultural fleece.
If growing in containers, choose containers which are at least 25cm deep.
Radish (grows well in containers) Sow seeds in short drills, 1cm deep and about 2.5cm apart. Sow them every two to three weeks from now till the end of summer for a constant supply. From March to mid August, you will want to sow summer cultivars of radish as winter cultivars will tend to bolt.
If growing in containers, for summer varieties any pots from 12-25cm deep should be fine.
Spinach (grows well in containers)
Sow outdoors directly where they are to grow. Make a drill 2.5cm deep, then add seeds thinly along it, space rows 30cm apart. Summer cultivars can be planted unprotected from Mid-March to Late May.
Spring Onion (grows well in containers) Sow thinly 1cm deep in rows 10cm apart. Sowing every 2 weeks until September will give a continual harvest. Thin seedlings out until they are around 2.5cm apart.
Ensure you have bought a summer cabbage variety before planting. Sow in early March under a cloche to keep warm, transplant to your raised bed or large container from May to June.
Between March and May, sow thinly, 2cm deep in a seedbed. Seedlings and rows should be 15cm apart for dwarf cultivars or around 60cm for larger cultivars.
Swiss chard (grows well in containers)
Sow seeds 1cm deep and 2.5cm apart. Once seedlings have emerged, thin out the plants to 5-8cm apart.
Swiss Chard is perfect for growing in containers, use the planting density as described across a container which is at least 25cm deep.
Sow seeds 1cm deep thinly with rows spaces 25-30cm apart. You can sow specifically early cultivars of turnips between March and June.
So that’s a simple guide on what to sow outdoors in March in your garden or in containers in a balcony garden. Ensure that you keep the seeds and seedlings well watered, especially when in containers.
Follow the spacing and depth advice for each plant to make sure you won’t have overcrowded growth later in the season. Don’t forget that some plants need extra protection from the cold between March and May.
Some of the crops can also be regularly planted every two to three weeks so you have a constant supply throughout the summer - so if you think you will eat lots of a particular plant like Lettuce or Beetroot, be sure to save some seeds to plant regularly through the growing season!
Once you've planted your seeds, why not take a picture and post it in our Urban Growing Community on Facebook. We'd love to know what you've chosen to grow this year. If you have any questions you can also post them there too to get advice from our Head Grower and our network of urban growers.
Dish is Square Mile Farms’ Head Grower. He’s on a mission to reconnect people with their food by helping them grow it themselves! Square Mile Farms bring vertical, urban farming to city dwellers in their homes and in the workplace. We aim to bring people closer to food production and help to create a culture of healthy, sustainable living. Find out more about our offering and get in touch here with any queries. Sign up to our newsletter for tips on a healthy lifestyle and a round-up of relevant news. You can also follow us on social media to stay up to date with our journey, find us on Instagram, Twitter and Facebook. Why not join our online Urban Growing Community for advice on growing at home and much more!