Hypericums all have bright golden yellow flowers of a distinctive angled shape, and they have a great habit of flowering over a long period. The hypericum best known in gardens is the tall shrub Hypericum ‘Rowallane’.
This fine plant originated as a chance seedling in the garden of the same name in Co Down. It can make a big bush more than two metres tall and wide, and it is often seen as part of a shrub border. This kind can flower from summer well into early winter in a mild year. The flowers are large, up to 8cm in diameter and carried in a group well displayed at the end of the shoots.
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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’. The latter can get a touch of frost damage, but this is usually very slight and does no great harm, because it shortens the stems.
Both of these shrubs can be allowed to grow and fill the space available or they can be grown as stooled bushes, cut back in later winter and allowed to grow out and flower in summer. Sometimes the plant is given the name St John’s wort, the saint’s feast day being in June.
The hypericum most widely used in recent decades is the ground-covering Hypericum calycinum, also called ‘rose of Sharon’. It spreads rapidly by suckering, but can be too invasive for a garden without adequate space. However, it has proved to be a very good plant for a country garden, where it could be used in a semi-wild setting and at boundaries.
Unfortunately, some years ago, it began to be badly affected by hypericum rust disease, which causes all the leaves to fall prematurely and leaves the plants looking very bare in late summer. For this reason, it is not now planted so much, but could be used in odd corners where this would not be noticed.
Although somewhat taller, Hypericum moserianum, a French variety, has Hypericum calycinum as one of its parents and can be used as an alternative. There is a form of this called ‘Tricolor’, which is variegated and has red margins, but it is too artificial. Another shrubby kind is Hypericum ‘Elstead’, which 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 are carried in the same groups. These turn red as the leaves colour and it is a very pretty shrub of medium size.
There are some wild hypericums, notably the tutsan, Hypericum androsaemum, which has smallish flowers and rounded seed pods, red turning almost black. The seeds are tiny and easily spread and this wild plant often turns up in gardens – too pretty to be a weed and yet appearing all by itself.
Very often, these plants are left in place and treated as garden plants. It is usually only when the first plant generates more seedlings nearby that its wild nature is suspected.
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, the first smaller than the second.
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