Hypericums are a wide range of garden shrubs, but generally fall into two groups as far as pruning is concerned. St Johns Wort and Rose of Sharon types.
The shrubby varieties of Hypericum such as Hypericum 'Hidcote' should be pruned in spring - March or April depending upon area and weather conditions. The low growing Hypericum calycinum - better known as St John Wort - should be pruned hard in late winter or very early spring. (See below)
Pruning later in the season may rob you of flowers for that year - although pruning St Johns Wort even as late as end of May will still give you plenty of flower - but later in the summer.
This type of Hypericum flowers on the ends of new shoots, so the more new shoots you can get the plant to make, the more flowers you will get.
Left - Hypericum calycinum - Low growing : St John's wort
The best way to prune Hypericum shrub varieties, is by cutting all growth back to within a few inches of ground level. It will soon grow back to near its original size within one season. This will ensure that you get a well shaped shrub, with plenty of new healthy shoots that will be a mass of flower later in the year - normally starting July. Alternatively, simply trim off last season's flowered growths.
Dead heading the flowers should not be carried out with the varieties that have attractive fruits such as H. x inodorum 'Elstead', Hypericum androsaemum.
See also - Hard Pruning
A shrubby Type
- is also a shrub - but low growing and often seen in roadside plantings - that can be pruned back hard. There is no finesse needed in pruning this variety. If you have a large swathe of them as groundcover, simply run a rotary mower over then - set at the highest setting. Or you can use a heavy duty strimmer. Hedge clippers - shears - will also do the job. The aim is to get rid of all the existing growth by pruning down to ground level or just above.
It will not be a pretty sight once done, but within a week or so, the bright green new growth will start from the base and soon giver the ground cover plant that St Johns Wort is known for.
Hypericum calycinum should be pruned in late winter - or early spring - and is a great start to the gardening year! It can either be pruned this way each year, or every two years.
The shrub section of Hypericum has a few useful and accommodating varieties which will flourish in a wide range of garden situations. (There are also a few ‘perennial’ types which we deal with elsewhere.)
Hypericums are often seen in public areas as ground cover plants and not too well cared for. However, as a garden shrub, they can make a useful contribution - and spectacular display - in almost any garden soil, or in sun or shade. In fact, there is almost certain amount tk be a Hypericum for any of the many difficult places which most of us tend to have somewhere in the garden.
All shrub types of Hypericum have golden yellow flowers, some with spectacular masses of protruding stamens, and some with attractive seed fruits - gold, red or black.
There are two basic forms in relation to growth habit and height. One type being low growing and rapidly spreading by underground stems, and the other being the clump forming shrubby types, that will grow to a height of one metre with a similar spread.
As with their varied wild habitats throughout the world, Hypericums are suitable for planting in either slightly acid, neutral, or alkaline soils and will not baulk at being planted in areas of moderate shade, slightly damp areas, or hot sunny banks.
All of the shrubby types are suitable for planting in borders, woodland, beds, or at the base of dry walls. The lower growing variety we include here - Hypericum calycinum - is best used as a mass planting ground cover subject; a use for which it has no equal in the right situation.
Hypericum is used (as St John’s Wort) in herbal medicine. It is extracted from one species – being Hypericum perforatum – a perennial type. The herbal preparation is sometimes packaged as ‘Hypericum’ rather than, or as well as, St John’s Wort. This information is simply to prevent you thinking that all Hypericums are herbs. They are not, and certainly not the shrubby types we talk of here.
The growing conditions previously listed are suitable for most Hypericum, and in particular, either full sun or partial shade. The varieties mentioned here are all fully hardy in most winters, especially once matured and settled in for a few years.
Seed of Hypericum is generally available for sale, but it is also possible to collect and save your own seed. Collect the seed as soon as ripe - but NOT before, or it will not be viable.
In this case, the seed should be surface-sown in pots or containers as soon as harvested – early autumn. Overwinter in a cold frame or unheated glasshouse.
Germination will probably take place before the onset of winter, or in the following early spring.
The low growing Hypericum calycinum freely roots underground stems which can be removed and potted up in bunches. The shrubby types can also be layered into the soil, by means of pegging down a few of the stems in early summer and severing once rooted.
Care needs to be taken in the first year as young plants, but afterwards they are relatively easy to grow on.
No pests worth mentioning, but Hypericum calycinum is prone to leaf rust – which is unsightly, but not normally lethal. Prevention with a fungicidal spray is best. Some of the shrubby types also suffer from rust to a lesser extent, and Hypericum x inodorum in particular can be spoiled.
Hypericum calycinum – is superb as a ground cover plant, and best in full sun or partial shade.
Hypericum x inodorum ‘Elstead’ is well planted, and has broad leaves, and upright growth, bright golden yellow flowers, and pink to red fruit held above the foliage in late summer.
Hypericum x inodorum ‘Ysella’ has golden foliage – lime green if too shaded! 1.2m max
Hypericum kouytchense. Sometimes sold as Hypericum Sungold. Arching shoots with golden bowled flowers, giving way to almost pyramid shaped red fruits in late summer.
Hypericum Hidcote - Bushy normally evergreen, and with large attractive flowers. No fruits to speak of. A good variety
Hypericum patulum ‘Henryi’ is an old well tried and tested favourite – having cupped yellow flowers, and semi-evergreen or fully evergreen foliage. 1.2 meters normally though older specimens maybe 1.5m.
Cornus alba, stolonifera and sanguinea