May can be warm but tends to be unsettled until about the third week, when prolonged periods of sunny and dry weather arrive.
This year May began with unusually warm conditions, and then it turned unsettled! Despite the cold snap in April some of the more tender plants managed to avoid a check in growth, although northerly winds damaged new shoots and emerging flowers.
May is a beautiful month – the best in the gardening calendar for sheer variety of trees and shrubs in bloom. All plants are putting on fresh new vibrant growth. It seems that everywhere the air is full of perfume from Choisya, Lilac, Ceanothus, Wisteria and Cherry laurel. Some of the most impressive Rhododendrons and Azaleas also start to flower during May. Typical spring displays in parks and gardens contain a profusion of tulips, wall flowers and forget-me-nots.
Lightly prune shrubs such as Rosemary once flowering is finished, also trim Forsythia and the evergreen Viburnum. Vinca (Periwinkle) known for its spreading habit, can be cut back to contain growth, otherwise it is likely to take over the garden.
This is a good time of year to get your herb collection organised. Herbs are incredibly versatile and essential in any garden. They can be grown for cooking, used as refreshing herbal teas, and most are hugely beneficial to wildlife – whether in the garden or window box.
Many herbs are easily grown from seed (except Parsley, Rosemary and Lavender), but plants are readily available so start with small specimens for window boxes/containers and use larger plants for the garden. Once established the shrubby varieties like Rosemary and Sage will grow for many seasons. Herbs can be dried or frozen and surplus leaves can be used to make deliciously flavoured oils. The best herbs for wildlife are mints, thyme and marjoram – the latter will be covered in bees for the duration of the flowering season. Old English Lavender is also a favourite for bees.
The most spectacular flowering tree is Horse chestnut, and it blooms during May. It grows to 80 ft with a spreading canopy making it unsuitable for most urban gardens. The Horse chestnut has huge palmate leaves made up of 5 leaflets; it produces white flowers with a splash of red which grow upwards above the branches. In autumn, the familiar spiky seed pods are produced containing dark glossy chestnuts. This beautiful tree is in decline due to a fast spreading disease called ‘bleeding canker’, which is caused by bacteria and fungus. Affected trees show a dark red-brown sticky liquid seeping from cracks in the bark. This disease weakens; causes die back and can kill young trees.