Hypericum is commonly known as St John's wort. Most varieties are deciduous or semi evergreen and summer flowering with lovely bright yellow flowers and followed in autumn by attractive berries. There are many varieties but those commonly sold and grown in gardens are H.x hidcoteense 'Hidcote' and H. calycinum 'Brigadoon'.
Hypericum is easy to grow being tolerant of most growing conditions and it tends to be vigorous with a tendency to self seed. It is very tolerant, Hypericum will put up with drought and shade, (although flowers best in sun) but dislikes waterlogged, damp soils. Hypericum has a long flowering season and carries a profusion of blooms as the image top right illustrates.
There is no need to prune other than to remove any dead wood in the spring.
There are also dwarf varieties suitable for front of the border or rock gardens such as Pallens
Another plus point of Hypericum is that it is ideal to have as a cut flowers both the blooms and later the berries are attractive and frequently used in flower arrangements.
Between 2015-2018 the RHS undertook a trial of Hypericum assessing varieties for shrub shape, flower quality and lengh of flowering, autumn fruits and disease resistance.
Hypericum Calycinum retained its AGM, and it is a low growing, spreading type, only 60cms high and is good for grown cover. It will spread quickly, quite vigorously, and is bordering invasive and each plant will spread up to 1.5.
Hypericum Hidcote image left is a very popular variety which also retained its RHS garden merit award and grows up to around 1.2m so suitable for the back of the border and even for hedging.
Also H. x moserianum is a dwarf variety growing up to .5m with reddish stems and very hardy H5.
Hypericum kouytchense is another short variety up to .5m with large flowers and good autumn berries. Most of these varieties are readily available.
For an explanation about frost hardy