Seeds to Sow in March

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Seeds to Sow in March

March is a month of hope and change, the beginning of spring and, for most gardeners, the start of the growing season, with many early bulbs in bloom and spring shoots bursting open. The increasing number of sunlight hours means that this is a key month for sowing many seeds indoors on warm sunny or in heated glasshouses.

Outdoors, the worst of the cold is hopefully behind us and we can begin planning and tidying gardens after winter, although spells of frosty or wet weather will probably still limit what gardeners can do at times. Growing conditions across the UK in March vary dramatically. Given some decent weather by mid-March the soil might be starting to warm up and it may be worth sowing a few of the toughest plants directly outdoors; check your soil temperature with a soil thermometer before you get started. Using a cloche or cold frame will help to protect seeds from the worst cold spells.

To see all seeds that can be sown in March, take a look here.

Top Seeds to Sow in March

Sweet Peas

March is a great time to start off your sweet peas indoors: they are the ever-popular climbing annuals that no garden is complete without.


Sweet peas provide displays of sumptuous blooms over many months, scenting the air with enticing perfume and flowers in a range of shimmering colours. These are blooms that can be enjoyed as garden plants or grown for cutting and bringing indoors.


We highly recommend our Unwins Sweet Pea Old Fashioned Selection. Try planting Sweet Peas in deep root cell trays.


For pots and summer borders, nicotiana are valuable bedding plants.


Their showy, trumpet-shaped flowers appear for weeks, often until the first frosts, and some selections have a sweet jasmine-like scent in the evening, perfect for enjoying during those long, balmy summer nights.


They are easy to grow and need little care other than watering and feeding. March is the perfect time to sow them indoors on a warm, sunny window sill.


If conditions are mild, lettuce are good seeds to try planting outdoors this month, as long as soil is workable and not too cold.


To help ensure reasonable germination you can cover seeds with a cloche which will protect from the worst of the weather.


We recommend Unwins Lettuce Allsorts Seeds and Unwins Organic Lettuce Looseleaf Salad Bowl

Other seeds to sow now


Sow outdoors from mid-March using a cloche or cold frame
  • Brussels sprouts
  • Summer cabbage
  • Beetroot
  • Cauliflower
  • Leeks
  • Onions
  • Peas
  • Spring Onion
  • Carrots
  • Turnips

Vegetables & Salads

For sowing indoors on a bright windowsill, or in a propagator or greenhouse
  • Celery
  • Celeriac
  • Kale
  • Swiss Chard
  • Tomatoes
  • Cucumbers
  • Chilli peppers
  • Rocket
  • Marrow
  • Radish

Half-Hardy Annuals

  • Cosmos
  • Verbena
  • Rudbeckia

Caring for Plants

Sweet pea plants raised from seed the previous autumn can be planted out towards the end of this month, as long as conditions are relatively mild. Keep them somewhere cool and bright until conditions are right; prepare the planting site by digging in organic matter and provide climbing support. Keep an eye on plants and don’t let them go short of water if the spring is dry.

Tomato seedlings that have recently germinated can be pricked out and potted-on, once they have the first pair of true leaves. Do this carefully and keep the recently potted plants moist, somewhere bright and warm.

Broad beans sown in pots under glass can be planted out under cloches towards the end of the month; if you direct-sowed in February, keep cloches over the seeds, removing in spells of sunny, mild weather after they germinate.


Those vegetables that were grown the year before and are still in the ground – broccoli, cauliflower, Brussels sprouts, leeks and spring cabbage – are all usually ready to be harvested in March

Thinking About Next Month

April sees the start of the main seed-sowing season. Ornamentals such as cosmos, tagetes, dahlia, lupins and snapdragons are among the many you can sow indoors in April. There is still time to sow tomatoes while many other tender vegetables such as squash, courgettes and peppers should also be started under cover. Outside, peas, leeks and parsnips can be planted, and a wide range of hardy annuals such as nigella, nasturtiums and calendula, not to mention many wildflowers, can also be sown.

Other Seeds to Sow in March

Nature's Haven Achillea Cassis Seeds

Unwins Ageratum Red Sea Seeds

Unwins Ageratum Timeless Mix Seeds

Unwins Alpine Armeria Morning Star Deep Pink Seeds

Unwins Alpine Dianthus Arctic Fire Seeds

Unwins Alpine Dianthus Little Maiden Seeds

Unwins Alpine Saxifraga Floral Carpet Seeds

Unwins Alpine Saxifraga Purple Robe Seeds