Hypericum is often known as St John’s wort – wort being an old English name for a plant, quite often of value in herbal medicine. The feast-day of St John is 24 June, which is the time when the flowers open, both before and after. The name St John’s wort is usually applied to all kinds of hypericum, but especially to the wild plant hypericum perforatum – the perforate St John’s wort – still used in the treatment of anxiety and depression.
Hypericum is often known as St John’s wort – wort being an old English name for a plant, quite often of value in herbal medicine.
The feast-day of St John is 24 June, which is the time when the flowers open, both before and after. The name St John’s wort is usually applied to all kinds of hypericum, but especially to the wild plant hypericum perforatum – the perforate St John’s wort – still used in the treatment of anxiety and depression.
It is effective enough to warrant being a prescription-only drug in this country, although it is sold in other countries over the counter.
The perforate St John’s wort is a perennial with a tough woody rootstock. The perforate part of the name refers to little translucent spots on the leaves, not quite perforations but looking like them.
There is another wild hypericum that frequently turns up in gardens called tutsan as a common name, or hypericum androseanum.
It can make a pretty little shrub to 60 to 80cm, dotted over with small bright yellow flowers followed by red cherry-like seed capsules, these eventually turning black, drying out and shedding copious amounts of tiny seeds.
Garden types
There are many garden kinds from Southern Europe and Asia. These are mostly better garden plants because flowering is more impressive.
The flowers of all kinds of hypericum have an unusual and very distinctive structure of five petals, some narrow or broad according to the species, with a large central boss of fine-thread stamens that explodes around a central flask-shaped ovary which becomes the seed capsule.
The flowers of hypericum are yellow, and, although the colour varies somewhat, they all have a sunny quality about them that brightens a garden in summer. They are not star plants but can play a very useful role as exciting fillers.
The best-known in gardens is the tall shrub hypericum ‘rowallane’, which originated as a chance seedling in the garden of the same name in Co Down.
It can make a big bush to over two metres tall and wide and needs no attention or pruning and flowers over a long period.
Another very well-known variety is called ‘hidcote’, named after the famous English garden of that name. It has flowers similar to those of rowallane, although it is a smaller grower and considered hardier than rowallane, which can get a touch of frost damage, but this is usually very slight, and does no great harm. It flowers much more profusely in full sunshine.
Commercial landscaping
Most widely used in past decades was hypercium calycinum, also called “rose of Sharon”, widely planted in commercial landscaping to cover areas of ground, especially banks and slopes, but it becomes badly damaged by rust and is now not worth growing.
Although somewhat taller, hypericum moserianum ‘tricolor’ has variegated and red margins, but it is too artificial for a rural setting.
Another shrubby kind, hypericum ‘elstead’ is grown for its decorative berries rather than the flowers, which are smallish but carried in groups at the ends of the twigs.
Later, the upright conical berries turn red as the leaves colour and it is a very pretty shrub of medium size.
There are several kinds of small hypericums, usually grown as rock garden plants, although many are big enough for use in flower beds and borders.
The most common of these is hypericum olympicum and hypericum empetrifolium. They both make a broad, flat bun of a low bush, sparkling with yellow flowers. Any kind of hypericum is a valuable addition to the garden.
If you have the time and energy to pick off the leaves of plants affected by leaf miner, it is beneficial to do so.
Removing the leaves before the miners have pupated to become adults reduces the number of adults there are to lay fresh batches of miners.
The harm is not great to ornamental plants, but vegetables such as spinach (shown) can spoil. Different species of leaf miners affect various plants, such as celery, apple, lilac, cherry, spinach, parsnips and beetroots.
The adult wasps, moths or flies lay a few eggs near the leaf mid-rib. When the tiny larva hatches, it feeds on the tissue between the upper and lower skins of the leaf, a tiny space, as little as one millimetre.
Trees, shrubs and roses
Continue to spray roses against blackspot disease after wet weather. Check young trees and shrubs for signs of drought, as it often happens they do not get a great start, are slow to root out and are then very vulnerable to drought.
They do not die right away but fail to make enough reserves in summer to survive the winter and die at that time. Tie in climbers as they grow.
Fruit, vegetables and herbs
Make repeat sowings of fast-maturing vegetables and herbs, such as lettuce, radish, coriander and rocket. Thin out and transplant vegetables that have reached suitable size and control weeds early. After periods of rain, spray apple trees for apple scab and potatoes for blight.
Liquid-feed sweet corn and other tender vegetables if they have been slow to get moving.
Lawn
Less mowing is required as the peak of grass growth declines. If grass growth is poor, apply a dressing of high-nitrogen fertiliser or lawn fertiliser.
Ideally this should go on when rain is on the way and the ground is already damp after rain. Otherwise there is a chance of scorching. Keep lawn edges trimmed and apply lawn weedkiller in good growing weather if needs be.
Flowers
Snails can destroy bedding plants in a single close, wet night. Feed all containers if they have not had slow release fertiliser pellets added to the compost.
Watch for greenflies on bedding plants and container plants. Patio plants such as petunias, osteospermums and marguerites are widely available in garden centres and can be planted out now.
Greenhouse and house plants
Continue to feed greenhouse plants and water freely to maintain strong growth. Use a shading material if the greenhouse gets too hot.
Check greenhouse plants for scale insects, greenflies and red spider mites, all of which can build up very rapidly at the time of year with soft growth on most plants.
Read more
Gardening: Dazzling azaleas to fill your garden with colour
Gardening: Mexican beauty brings an exotic touch to the garden
This is a subscriber-only article
SHARING OPTIONS: