What to do in your allotment in March

Purple sprouting broccoli

Written by Lee Senior

March is an exciting and pivotal month in the allotment calendar, and the start of the busy seed sowing season. There are many vegetables that can be started in gentle heat this month, but only sow your seeds if you can provide the correct conditions for growing on. It’s important to exercise caution as snow is still a realistic possibility! At the time of writing, a cold snap is forecast for much of the UK. 

The good news is that the March sun is strong enough to heat the greenhouse to significant daytime temperatures. Providing adequate ventilation and shade for seedlings is now a key consideration. Conversely, the temperature can plummet at night so frost protection is essential. Cabbage is a favourite crop of mine but, like all brassicas, it does need a little care after germination. Try not to subject the young seedlings to bright sunshine and hot greenhouse temperatures. South-facing windowsills might also be a bit too much. Happy growing!

Allotment flowers in March

  • Summer-flowering bulbs like gladioli can be planted this month. 
  • Lilies, although often planted in autumn, can also be planted in early spring. If you’re using containers, move the bulbs out onto the allotment when they’ve finished flowering for future years.
  • This month, colourful crocus flowers linger on and are supplemented by daffodils and muscari. Snap the spent heads from daffodils to maintain their vigour by preventing them from setting seed. 
  • There are a number of miniature daffodils, perfect for containers. I like the dwarf variety ‘Tete a Tete’. For something different try the double-flowered, multi-petalled, ‘Rip Van Winkle’.
  • The blue muscari ‘Armeniacum’ looks great under trees or in semi-shaded areas and flowers towards the end of March into April.
  • Sow sunflower seeds into modular seed trays and pop them on a sunny windowsill to germinate ready for potting-on next month.
  • Lime-haters such as azaleas, camelias and rhododendron should be fed this month with a slow-release ericaceous fertiliser.

Allotment vegetables in March

  • There’s still time to plant a few garlic bulbs to provide a respectable crop at the end of summer.
  • I like to start off my spring-planting onion sets in a cold greenhouse at the beginning of this month. The root development is quicker than direct planting at this time of year.
  • Parnsips need a long season and if the soil is warm enough they can be sown directly at the end of month. Don’t worry if the weather is inclement – they can be sown as late as the end of April.
  • Sow Brussels sprouts F1 ‘Brenden’ or F1 ‘Crispus’ in a cold greenhouse or on the windowsill.
  • In a heated propagator, sow Cucumber F1 ‘Delistar’.
  • From the middle of March, make some early carrot seed sowings to help to avoid carrot fly. Only sow seeds in pre-warmed soil, or sow in a polytunnel.
  • I’m a huge fan of purple carrots and my kids love them too. At the end of the month and into April, direct sow F1 ‘Purple Haze’ into well-drained, freshly prepared ground that has been pre-warmed with a membrane. 
  • At the end of the month, early Beetroot ‘Boltardy’ can be direct-sown.
  • I prefer to sow early pea seeds in gentle heat indoors and then transplant later in spring. This maximises germination potential. The second early variety ‘Hurst Greenshaft’ is ideal.
  • Sweet corn needs a relatively long season and seed should be sown in March in gentle heat. Take care not to overwet the compost as the seeds can be prone to rot. Protect from frost. 
  • Lettuce ‘Unrivalled’ is perfect for spring sowing in trays for transplanting. At this time of year I sow under glass but as the soil warms up the seeds can be sown directly.
  • Courgettes are one of my favourite crops. They have many uses and are easy to grow. Sow the seed in March and April in gentle heat and protect from frost.
  • In mild, sheltered areas, early varieties of chitted potatoes can be sown in well-drained ground. Alternatively, early varieties work well in larger containers and can mature within 10-12 weeks. They grow well in greenhouses and polytunnels if it isn’t too hot, but please do keep an eye out for frost.

Allotment fruit in March

  • Blueberries are a super fruit to grow. Unless your soil is naturally acidic, plant the bushes in large pots of ericaceous compost.
  • The end of March signals the end of the bare-root fruit planting season. Pot-grown fruit trees can be planted all year round.
  • Bare rooted gooseberries and all currant plants including whitecurrants, redcurrants and blackcurrants can be planted out until the end of the month if the soil isn’t frozen or waterlogged. 
  • Prune established autumn-fruiting raspberries almost to ground level before new growth commences.
  • Clear out any dead strawberry plant foliage to encourage a good air flow to the base of the crowns.
  • Keep an eye on the blossom belonging to apricots, peaches and nectarines. It can be damaged by frost so it’s worth covering the tree with fleece if you’re worried. Alternatively, if you’re lucky enough to have the space, why not grow a dwarf peach tree in a pot in a polytunnel, like my neighbour does?

Crops to harvest in March

  • Purple sprouting broccoli is now cropping heavily and the young heads are so full of flavour. Use netting to protect your plants if pigeons are a problem.
  • Kale, winter cabbage, Jerusalem artichokes and spring onions are in season.
  • You can still get good crops of winter lettuce, under glass. 
  • I’ve now run out of leeks after a bumper crop, but I plan to sow even more this year to remedy this.
  • My Brussels sprouts have just about finished now and what a wonderful crop it has been! The flavour of modern varieties is far superior and less bitter than older varieties.
  • Parsnips are still going strong but it’s noticeable the tops are starting to grow just a little. When this happens they should be okay for another two-to-three weeks before they start to become unusable.

General March allotment jobs

  • Try to stay off waterlogged soil but, if you have to access the allotment, use planks to spread your weight.
  • If you’re transplanting seedlings this month be careful to handle them by the leaves and avoid contact with the stem. Damage to the stem is irreparable whereas a damaged leaf is not so calamitous.
  • Prepare your raised beds for direct sowing seeds at the end of March. Cover the soil surface with black plastic to warm the soil underneath.
  • Invest in a cloche to advance outdoor sowing and improve the germination rates of outdoor sown seeds.
  • Remember to carefully dispose of any spent winter crop plants. If they show any signs of disease like club root, don’t add them to the compost heap or you’ll spread disease around the allotment.
  • Prepare all your beds for planting by digging in some good quality compost. If you use well-rotted manure, make sure it’s properly rotted down so it doesn’t damage the delicate roots of your seedlings. 
  • If it’s still very cold in your area, you could always insulate your greenhouse with horticultural bubble wrap. Or, invest in some fleece to cover seedlings.
  • Protect your containers from impending slug and snail attack with copper tape.
  • Put a feeder out for the birds to attract them to your allotment. Birds eat pests and should be a welcome sight around the plot. 
  • Use shading fabric in the greenhouse if the weather’s unseasonably sunny and warm. This protects seedlings from sun scorch.

Planning ahead

  • Plan to start watering next month by cleaning or installing water buts and checking watering cans. 
  • Check you have plenty of potting compost and containers for potting on all your thriving plants and seedlings in April.
Lead image: Purple sprouting broccoli from Suttons
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About Lee Senior
Lee Senior is an experienced horticultural writer, RHS Yorkshire in Bloom judge and horticultural consultant. He has also had an allotment for over 30 years. After initially spurning horticulture as a career option, to pursue his boyhood dream of becoming a train driver, Lee soon realised he couldn’t resist getting his hands dirty to make a living. Horticultural College training led to getting an allotment at the tender age of 18 (in the days when you could actually get a plot quickly). “My gardening hero is Geoff Hamilton” says Lee. “It was Geoff who convinced me that you didn’t have to spray everything that moved in the garden. Watching him on Gardeners’ World in the late 1980’s and early 1990’s was a revelation. I was lucky enough to meet Geoff and I’ve also had the pleasure of meeting BBC gardener, Joe Swift. Now, over three decades of practical experience has taught me to work with mother nature, not to fight against her and don’t try to tame her, as so many gardeners seem to be on a mission to do. I feel strongly that we should all respect nature and do our bit txwo help our ailing planet. Small-scale food growing is my passion and I can’t wait for my two daughters to hopefully pick up the baton in the future. Nothing beats the flavour and satisfaction of growing your own food. You simply cannot buy the same quality and freshness. Everyone can have a go at growing something, no matter where they live and it is great to see how growing food in containers is taking off now,” says Lee. When he isn’t writing for the gardening press, Lee runs his own Allotment Consultancy business, advising individuals and organisations and Councils on how to get the best from their land, either in person or remotely. Lee’s website is: https://allotmentsandgreenspaces.wordpress.com or you can email him directly at: allotmentsguru@gmail.com. Away from horticulture, Lee is a keen walker and he has written a number of successful walking books which are available at his online bookstore: https://www.etsy.com/shop/WalkingintheAire/