How to grow Hypericum

Rust on hypericum

Hypericum at a Glance

  1. Easy to grow, vigorous considered by some to be invasive
  2. Tolerates semi shade
  3. Do not require pruning
  4. Can be prone to rust- see image left
  5. Can be deciduous, semi-evergreen and evergreen
  6. Height varies from tall shrubs to dwarf  and ground cover varieties

Hypericum is commonly known as St John's wort and also Rose of Sharon. 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'.

Before planting Hypericum, be aware that all parts are toxic to animals and should be handled carefully as contact with the leaves can cause skin irritation. That said, Hypericum is easy to grow and is tolerant of most growing conditions. Hypericum will put up with drought and shade, (although flowers best in sun) but dislikes waterlogged soils. Hypericum has a long flowering season and carries a profusion of blooms as the image top right illustrates.

It is vigorous with a tendency to self seed, and is considered by some to be invasive because of its self seeding.

There is no requirement 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 flower both the blooms and later the berries are attractive and frequently used in flower arrangements. 

Rust and hypericum

Hypericum has a tendency to develop rust, illustrated top left. It is not fatal to the shrub, but makes it very unsightly. It will not spread to other neighbouring plants, but it spoils the look of the shrub.

Personally, if I was planting Hypericum again, rather than go for one of the traditional varieties (see below) which I have currently have planted such as H. hidcote, I would take a punt at the more recently developed varieties labelled as "rust resistant."

Illustrated is Hypericum inodorium magical beauty ('Kolmbeau') which has salmon coloured berries with numerous yellow flowers, and grows to around 1m.

It is available from Crocus along with H. Hidcote. (this is an affiliate link) 

Hypericum inodorium magical beauty ('Kolmbeau')
Hypericum inodorium magical beauty ('Kolmbeau')

Recommended varieties of Hypericum

Between 2015-2018 the RHS undertook a trial of Hypericum assessing varieties for shrub shape, flower quality and length of flowering, autumn fruits and disease resistance. If you are looking for a variety to grow, this is a starting point.

New AGMs were awarded to H. beanii 'Precious Sun' which grows up to 1.5m; H.x dummereri 'Peter Drummer' a ground cover variety growing to 45cms, H. Henryi subsp hancockii ' September Sun' a taller variety growing to 2m; H. lancasteri growing up to 1.2m; H. oxyphyllum 'Golden -Ness' which is compact with coppery new growth up to 1.2m and H.pseudohenryi up to 1.8m. Flowering times vary a little starting the earliest in June to late flowering on October all with yellow flowers.

Those which retained their AGM are H.forrestii, H.x hidcoteense 'Hidcote' and H. Kouytchense. 

Hypericum Hidcote image top left is a popular variety readily available which 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.

How to prune Hypericum

It is not essential to prune Hypericum, but if needed, spring is the time to take the shears to it.

A light prune in early spring if you want to restrict size or tidy up. Some Hypericum are prone to rust and pruning in the spring is one way to remove rust tainted branches. Hypericum also self seed, which is a plus or minus depending on what you want in your garden.

To reduce the problems with rust, the shrub can be cut down at the end of summer and all the rusty leaves removed for a fresh start in the spring. It will still flower and produce berries as Hypericum flower on the current year's wood. In particular, H. calycinum which is vigorous and can be prone to rust so will enjoy being cut back annually to the ground in around February /March time. Hypericum flowers from July to October.

Fully ***hardy and easy to grow. Most Hypericum need little or no attention and grow in almost any conditions.