May is always looked forward to as the first month of summer but it also marks the end of spring. It is a month when gardeners can get caught out by mini droughts and heat waves and even the last, late frosts.
The biggest threat is young plants that have that have recently been transplanted into the open ground and any freshly emerging seedlings. So be sure to keep all of them well watered and if the young transplants look as if they are flagging give them some shade protection from the heat of the sun or drying winds.
On the other hand May can bring damaging frosts, cold winds with heavy rain, so be prepared to take steps to protect plants if it is necessary.
Stay vigilant on weed watch
Pesky weeds will be popping up faster than your crops as the soil warms up. Check under leaves of crops as well as between rows and gently remove with a weeding fork.
Catch weeds while they’re small by hoeing borders and the vegetable garden once a week. Paths, drives and patios can be kept weed-free by spraying with a path weed killer. Many of these prevent weeds returning for several months after they are applied. Perennial weeds, such as dandelions, have roots that will regrow if you just kill the leaves. They will eventually weaken over time if you hoe them off, or you could try to dig out the roots.
Earth up potatoes
Spuds planted in March or early April should be showing long healthy shoots above the compost. By earthing up your potatoes, you can increase the number of potatoes grown from each tuber and protect your spuds from damaging sun exposure.
Earthing up is the name given to the process of covering shoots with additional compost. When shoots are showing 10cm above the compost, cover them with more compost to leave just four cm shoots showing at the tip.
Repeat this process every time shoots reach 10cm tall.
How to beat a cold spring
The cold start to the season has delayed the planting and slowed the development of many vegetables. Some varieties need a long growing period in which to mature, so it can be helpful to find ways of chivvying them along.
Where small numbers of plants are required, planting indoors in modules or pots can protect young, vulnerable plants and enable them to be grown on and planted out as soon as the weather allows. Larger plants are also less susceptible to slug damage than seedlings and so losses are fewer.
Cloches will not only keep the soil beneath drier, but also retain the heat from the sun, transforming cold, wet, and claggy soils into warm, crumbly soils that are suitable for sowing into directly.
Simple mulches or coverings also warm the soil and can be used with advantage as permanent mulches on certain crops.
Carrots, for example, will benefit from the shelter and warmth created by fleece, and will naturally raise the cover as they grow. Tucking in the sides of the fleece also prevents the carrot root fly from entering, minimising crop damage.
Potatoes can be planted through a black plastic mulch. This will aid tuber development as well as helping to prevent the soil from drying out. No earthing-up is required, as the tubers will form beneath the black plastic and be shielded from the light.
As they develop on the surface, harvesting them merely requires rolling back the plastic, and since the plants can be left in situ, smaller potatoes can often be left to increase in size.
Sow and plant into warm soil
Warm up your vegetable plot with a ground preparation fleece before sowing or planting out. When temperatures rise during May, seeds and plants will grow rapidly, however when temperatures drop, plant growth grinds to a halt.
A gardening fleece will keep temperatures up, whilst being permeable enough to allow air and moisture through, ensuring healthy growth. The added bonus of a gardening fleece is it will help diffuse strong light, providing shading and preventing damaging scorching.
Plant in pots or trays under glass, dwarf and climbing French beans, runner beans, sweet corn, outdoor cucumbers, courgettes, pumpkins, squashes, outdoor cucumbers – all which can be planted out next month.
Savoy cabbage, winter cabbage, endive, kale and sprouting broccoli can be sown in the open ground now, ready to be planted out next month.
This is also your last opportunity to sow peas and parsnips this year.
Cut perennials with the ‘Chelsea Chop’
The ‘Chelsea Chop’ in the week of the famous flower show (or thereabouts) helps to keep the taller, late-flowering perennials from leaning. Pinch out asters, Helenium and Eupatorium at knee height and they will re-branch to provide you with stockier plants.
Make a bean wigwam
Use canes or hazel stems to make a support for growing beans. Either tie the tops together to form a wigwam or else arrange the supports in long ’X s’ that cross either half way up or close to the top. Sow a couple of beans to each cane and a few at the ends of the row, as replacements for any that don’t come up. Beans are greedy plants so they’ll enjoy being grown above a trench filled with rotted manure or kitchen compost (even part rotted will do). Cover the trench with soil and then plant the beans. Once the beans are up make sure that the slugs cannot get to the growing tips because they’ll destroy the plant.
Thin out seedlings
Seedlings sown in rows can quickly grow into each other’s space, taking up vital water and nutrients, effectively reducing your harvest.
Use a dibber to gently remove excess seedlings whilst protecting their roots and transplant healthy seedlings elsewhere. Once you have thinned out your seedlings, water your remaining seedlings to allow the surrounding compost to re-settle.
Set up a safe haven for garden wildlife
Butterflies and bees are valuable pollinators that are always more than welcome in the garden. You can attract these beneficial bugs by sowing colourful wildflower seeds and providing them with food and a safe place to stay. With May’s unpredictable weather, a butterfly house or bee log is brilliant for these bugs’ survival, as it will provide a safe place to hide from the rain.
Watch the temperatures around your tomatoes
Tomatoes originate from South America and suffer as soon as temperatures drop below 10°C. Keep them under cover until you can be sure that the weather is warm enough to plant them outside, and then find the warmest spot to give them all the help they can get. If you are growing in the ground, keep well away from the potatoes, as blight can travel from one to the next. Try to keep the plants in a position that is warm but with air movement, as the blight favours humidity. Bush varieties are great in pots on the terrace.
Time to repot pelargoniums
Tough as old boots they may be, but last year’s pelargoniums appreciate repotting and new soil to set them up for the summer. For best results, pick off dead foliage, prune back to healthy new shoots and give them all the sun they can get.
Cut evergreen hedges
May is a good time to trim evergreen hedges, such as Lonicera, box and yew; it will get their edges looking crisp and neat. Small hedges can be trimmed with shears. Larger hedges are best tackled with a hedge trimmer. It is illegal to disturb nesting birds, so be sure to check the hedges for signs of nests before you start the job.
- Keep sowing seeds in small batches roughly fortnightly so that you avoid having a glut but give yourself a longer more manageable harvest.
- Repot supermarket herbs, dividing them into smaller pots, a couple of stems per small pot should do for starters. You can use this trick on mint, coriander, basil, thyme – pretty much anything.
- Pinch out the tops of chillies to encourage new branches to grow and create a bushier plant.
- If you haven’t started growing yet now is the perfect time to get in young plug plants or buy young plants from garden centres and nurseries. There is so much to choose from to grow in raised beds and allotments.
- Keep hoeing between crops to control weeds and also create a ‘dust mulch’ to conserve precious soil moisture. Try to water in the cool of the evening if possible using a watering can to direct the water around the root area of the crops.
- If you can get it, put some straw underneath the developing strawberry fruits to keep them off the soil and try to avoid watering overhead to reduce any problems with mildew.
The month in brief
- Watch out for late frosts. Protect tender plants
- Earth up potatoes, and promptly plant any still remaining
- Plant out summer bedding at the end of the month (except in cold areas)
- Collect rainwater and investigate ways to recycle water for irrigation
- Regularly hoe off weeds
- Open greenhouse vents and doors on warm days
- Mow lawns weekly
- Check for nesting birds before clipping hedges
- Lift and divide overcrowded clumps of daffodils and other spring-flowering bulbs
- Watch out for viburnum beetle and lily beetle grubs