Hypericum olympicum f. uniflorum - St John's Wort, Rock Garden Plant

Hypericum olympicum f. uniflorum (sold as Hypericum polyphyllum 'Grandiflorum') is a small St John's wort that forms a neat, low mound of small grey-green leaves. From June to August it carries bright yellow flowers, each with a central tuft of golden stamens.

Olympic St John's wort at a glance

Botanical name	Hypericum olympicum f. uniflorum (sold as H. polyphyllum 'Grandiflorum')
Common name	Olympic St John's wort
Plant type	Low, mound-forming subshrub
Height and spread	Up to about 20 cm tall, 10–50 cm wide
Flowers	Bright yellow with a tuft of golden stamens, June to August
Position	Full sun
Soil	Well-drained soil of any type; dislikes winter wet
Pond depth	None – not for wet ground or water
Hardiness	RHS H4 – hardy in an average UK winter (-10 to -5°C)
Native to	Not UK native

Is it a pond or bog plant?

No. It is a dry rockery plant. In the wild it grows in sandy, stony places among rocks, and the RHS advises protecting it from excessive winter wet. It will rot in wet or waterlogged ground, so do not plant it at the pond margin or in a bog garden. At most, it suits a dry, sunny raised bank or rockery near a pond.

Where to plant it

Rockeries and raised beds with sharp drainage
A dry, sunny bank above a pond
Full sun

Is it poisonous?

The RHS lists it as potentially harmful. Do not eat any part of it, including the fruit, keep pets from eating it and wear gloves when handling it.

Which size should I buy?

Bare-root plants (7 cm, 9 cm, 1 litre and 3 litre) arrive without a pot or compost and are the most economical way to plant a group. Potted plants (9 cm, 1 litre and 3 litre) arrive growing in our peat-free compost and give a faster display. Packs of 3 come in 7 cm, 9 cm, 1 litre and 3 litre bare-root sizes and cost less per plant. The 2x Pot & Compost option is two plants supplied with pots and compost.