April proved to be a particularly cold, dry month. As a result a lot of plants have been held back. For example, fruit trees are flowering about two weeks later than we would normally expect. So, if you have delayed planting or sowing because it has been too cold, don’t worry. May is likely to be a warmer month and Mother Nature will give us all a chance to catch up.
The cold weather has meant that daffodils and tulips have flowered later and have given a good display for longer. The lack of bad weather has allowed them to prosper. To guarantee a good display next year, however, now is the time to deadhead them. This stops them forming seeds and instead direct their energies into creating strong bulbs. Pot grown bulbs can be knocked out and laid out to dry in a cool place. Once the leaves have died back they can be removed and the bulbs stored to be replanted in early autumn.
You will find nurseries and garden centres selling tomato plants in May. Buy sturdy plants for planting out in your greenhouse. Don’t buy too many as you will be tempted to cram them in. Tomato plants need space and good ventilation to thrive. An 8ft x 6ft greenhouse can happily accommodate 6 plants. There are some interesting varieties of tomato available, and you might like to try new ones. Stalwarts like Moneymaker and Alicante continue to be good if you just want a plant or two for your own supply. You can also plant cucumbers now. Choose a female-only variety like Femspot to save the chore of picking off male flowers. You can also grow chillies and peppers in your greenhouse. Plants will be available soon. Whatever you decide to grow in your greenhouse, stake them when you plant them. Staking after the plants have grown larger will cause damage to their roots.
Keep your greenhouse well ventilated, especially on warm days. With the nights continuing to be cold, make sure you close all ventilation late in the afternoon. This will trap the day’s warm air into the night.
May is also the best month to begin successional sowings of beetroot. You can also sow carrots, radish, kohlrabi, turnips and salad leaves. Salad leaves can be grown really successfully on a windowsill if you don’t have any outdoor space. If you decide to sow sweetcorn, remember that they need to be in a square to enable pollination by the wind. Many gardeners prefer to sow sweetcorn in cells and then plant them out into a square when they are large enough to handle. Courgettes, squashes and pumpkins can be sown in May indoors or under cover.
May is also a good month to take cuttings of rosemary and a range of tender perennials like asters. Hebe cuttings can be taken now. It is also time to plan ahead by sowing biennials like sweet williams and wallflowers. A range of perennials can also be sown in May ready for next summer’s display.
Roses will be growing strong shoots this month, ready for another superb display of flowers in the summer. Climbing and rambler roses might need you to tie in any wayward stems. This helps to keep the roses tidy and also stops the wind from damaging the stems.
Keep up with the weeding in both the flower garden and the vegetable plot. Lightly fork around plants in the flower beds and borders. This discourages weeds and also lets you see where you have spaces to plant your hardened-off seedlings. It is really important to harden-off tender plants that have been grown in the greenhouse or on a windowsill. In the vegetable garden hoe between the rows of vegetables regularly to kill weeds and keep the soil in good health.
Brassicas can now be planted out. Once planted provide protection from pests like cabbage root fly. Cover the plants with fleece keeps pest at bay and also deters pigeons who have a taste for young brassicas. In June you will need to take the fleece away and replace it with netting to prevent the cabbage white butterfly laying its eggs on the underside of the leaves. Talking of pests, remember to check under pots for snails and remove any you find. Don’t ignore under the rims of your pots. It is really easy to miss a couple of small snails hiding there. If you don’t like using slug pellets, try nematodes instead.
You might have found your lawn growing less quickly in the dry, cold spring. However, the inevitable rain combined with higher temperatures will boost the grass and mowing will become a regular job. If you have space try to leave an area of grass unmown. A wild area, even a small one, will provide cover for insects and pollen for bees.
Finally, keep an eye on your potatoes. As soon as shoots are seen earth them up. This applies whether the potatoes are in rows in the vegetable bed or in some form of container. Keep earthing up container grown ones until the container is full. This effort should reward you will a good crop of tasty new potatoes next month.