What to do in your allotment in May

Leek plants ‘Autumn Mixed’ from Suttons

Written by Lee Senior

It’s May, and we’re now in one of the busiest months of the year when the allotment threatens to take over your life! The next few weeks are exciting and pivotal – helping to define the allotment gardening year ahead. One of the main jobs is to nurture and prepare young plants for life outdoors. Hardening off takes 2-3 weeks and should be completed by the end of this month. By then, the risk of frost is almost eliminated in most parts of the country.

But what happens if you don’t properly prepare your plants for outdoor life? Over the years I’ve occasionally bypassed hardening off my young plants, due to lack of time. The plants didn’t die, but they did refuse to grow for weeks, looking somewhat dishevelled. A month of valuable growing time was lost. Hardening off is time consuming, but it is essential. And once the plants are out on your plot, cloches, fleece and portable ‘easy’ tunnels can all be used for extra protection if the weather is cold at night.

A hapless mouse entered my shed just before Easter. My knee pads were nibbled and a roll of fleece is now partly shredded. Ironically the mouse also discovered my spare stash of rodent bait… On the plot, the weeds are growing and pests are increasing. This is a great time of year to use nematodes as a natural defence against slugs. These natural living organisms deal with the slugs in the soil in your chosen area and protection lasts up to six weeks. Happy growing!

Image: Lavender ‘Hidcote Blue’

Allotment flowers in May

  • Plant out your sweet peas this month, after hardening them off.
  • Lavender ‘Hidcote Blue’ seeds can be sown until early June. It makes a wonderful border plant in a well-drained, sunny position, and is equally happy in containers.
  • An allotment wouldn’t be complete without nasturtiums. Try ‘Little Gem Mix’ for an easy-going striking display – it may even help in the fight against cabbage white caterpillars as they’re part of the brassica clan.
  • There’s still time to sow annual flowers such as Afro-French Marigold ‘F1 Zenith Mix’. As well as looking great, they help to deter whitefly from crops such as tomatoes.
  • The tall varieties of sunflowers are a great way to attract children to the joys of allotment gardening. For something a little different why not try the bushy Sunflower ‘Total Eclipse’. Easy to grow, they reach a height of around 60cms and the blooms can be cut to fill vases.
  • With an eye on next year, Sweet William seeds can be sown directly between now and July.

Allotment vegetables in May

  • May is at the heart of the direct sowing calendar. The soil should be warm enough to sow beetroot, carrots, kohlrabi, parsnips, radishes, turnips and swedes. Try Kohlrabi ‘Purple and White Vienna Mix’ for pretty stems, and Beetroot ‘Rainbow Mix’ for a good selection of multi-coloured beets.
  • Brassicas such as cabbage, broccoli, cauliflower and kale can also be direct sown into the ground, or into trays for transplanting. Make sure you net them to prevent cabbage white butterflies from laying their eggs on the leaves.
  • There’s still time to sow French beans and runner beans directly into their final positions. I must admit that I prefer to start them off in cells or trays to reduce losses.
  • Early to mid-May is the final period when broad bean seeds can be sown until late autumn.
  • Plant leek seedlings out in May, making sure they’re deep in the planting hole (up to half the height) to encourage a long, straight. blanched stem. Water well.
  • Plant out hardy varieties of cucumber. Use cloches to protect the young plants from cool weather and water them well until they establish. In the greenhouse, there’s still time to sow cucumber seeds. ‘F1 Baby’ is fast growing and can be harvested from August-October.
  • If the risk of a late frost has completely passed where you are, now’s a good time to plant outdoor tomato plants. Provide canes if they need support and keep them moist.
  • Make sure your growing pea plants still have plenty of support. You don’t want them to blow over in windy conditions.
  • May is a busy month in the potato calendar. An allotment friend recently gave me some spare first early ‘McCain Premiere’ seed potatoes which I gratefully accepted! I’m looking forward to big things from this much vaunted variety. All potatoes are susceptible to frost. I tend to earth up (cover) the young shoots with soil or a temporary fleece covering to protect those vulnerable young shoots during cold snaps. If the worst happens and the plants get ‘frosted’, they should recover if they’re otherwise healthy, albeit with a loss of valuable growing time. There’s still time to plant all maincrop seed potato varieties before the middle of the month.

Allotment fruit in May

  • It’s an exciting time of year as we discover just how successful fruit tree pollination has been as the flowers begin to set. Check the rootstocks of your fruit trees this month as they put on fresh growth. If you see any growth from the base (roots) of your grafted fruit trees, cut it away at the base with a clean, sharp pair of secateurs, cutting at an angle.
  • Look out for codling moths on your fruit trees. Hang out moth traps towards the end of May to catch the male moths and prevent caterpillar damage to leaves.
  • Keep blueberries well watered with lime-free water if the ground is dry or they’re grown in containers.
  • Cover your strawberry plants with a bird protection net once the fruit has set after flowering.

Crops to harvest in May

  • May is a relatively quiet month for harvesting compared to much of the allotment calendar. Winter/early spring stalwarts such as broccoli, kale, parsnips and leeks have all come to an end. Leeks and parsnips make fine flowers for insects if you let them continue their lifecycle.
  • Asparagus is in its main cropping season this month.
  • Rhubarb is also plentiful and at its peak for harvesting.
  • Spring (overwintered) cabbage is in season now, after sowing last July/August.
  • Early spring sown radishes are now ready to harvest along with overwintered lettuce and spring onions for a tasty mini home-grown salad.
Runner Bean Support Frame Kit

Image: Shutterstock

General May allotment jobs

  • For the first half of May, focus on hardening off all seedlings before planting out. Move the pots or trays outdoors during the day for a week or two but bring them in every night.
  • Don’t worry if you’re behind, or don’t have enough space for indoor seed sowing! Vegetable plug plants are a very convenient alternative.
  • Stay vigilant for late frost – especially if you’re growing first and second early potatoes.
  • Put out slug control in wet weather to protect young plants.
  • If you don’t have time to weed properly, remove the flower heads from weeds like dandelions to stop them from going to seed and spreading.
  • When you’re clearing bindweed from your allotment beds, make sure you remove as much of the plant material as possible. This weed will sprout new plantlets from even 1cm of root or stem left in the soil.
  • Construct supports ready for planting out your climbing beans.

Planning ahead

  • Plan for the higher temperatures in June by checking your water supply. Make sure you have water butts and consider setting up irrigation systems.
  • Remember to take plenty of photos of your allotment over the next few months while growth is shooting ahead. This helps with planning later in the year.
Lead image: Leek plants ‘Autumn Mixed’ 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/