Grow St. John's wort in full sun and well-drained soil. St. John's wort is Hypericum — the garden shrub, not the herbal capsule.
Give it full sun and well-drained soil
| Factor | Recommended | Avoid |
|---|---|---|
| Sun | Full sun; light shade is tolerated, with fewer flowers | Deep shade that opens the plant and cuts bloom |
| Soil | Average, well-drained ground; lean soil is fine | A ponded crown, or a rich bed that pushes leaf over flower |
| Water | Regular water the first season; then only in a long drought | Standing water around the roots |
| Mulch | A few inches of bark or compost kept off the stems | A wet mound piled against the bark |
St. John's wort is a sun shrub. Full sun packs more flowers; light shade is fine, deep shade is not. [1] Well-drained soil is the usual bed — dry, rocky, or sandy ground works once the plant is in. A wet low spot rots the crown. [2] A landscape shrub such as Hidcote wants that same drain. So does Sunburst. [3]
Does St. John's wort need full sun?
It flowers best in full sun. Light shade is tolerated. Deep shade makes a thin plant with a weak bloom.
Will St. John's wort grow in shade?
Light or part shade is fine. Full shade cuts bloom and opens the outline. Give it at least a few hours of sun.
Water the first season, then only in a long drought
New plants need regular water through the first growing season. Once roots take, the shrub tolerates dry spells. Extra water in a wet summer is the usual rot. [4]
- Soak after planting, and keep the root ball moist through the first season.
- Water in a long drought. Do not wait for the leaves to wilt in July heat.
- Mulch the root zone, and keep the mulch off the stems so the bark stays dry.
- Do not leave the crown in a puddle. Moist the first year is the aim, not standing water.
How often should I water St. John's wort?
Keep a new plant moist the first season. Then water only in a long drought. Do not leave the crown in standing water.
Plant at the same depth as the pot, and leave room to spread
Set the crown even with the surrounding soil. Burying it invites rot. Give a landscape shrub room to the mature width — these are 3- to 4-foot mounds, not a 12-inch edging plant. For a groundcover or a berry shrub, see Types of St. John's Wort.
- Dig a hole as deep as the root ball and about twice as wide.
- Set the ball at the same depth as the nursery pot. Leave the crown even with the soil.
- Space landscape shrubs about 3 to 4 feet apart, measured to the mature spread, not the pot.
- Backfill, firm, and water in. Mulch the root zone and keep it off the stems.
- Plant in spring or fall while the soil is workable.
How far apart should I plant St. John's wort?
Leave about 3 to 4 feet between landscape shrubs. Measure to the mature width, not the nursery pot.
Cut it back in late winter — it flowers on new wood
Flowers form on this year's growth. A summer cut removes the bloom you wanted. In a cold winter the top may die back; new shoots from the base still flower the same year.
- Wait until late winter or early spring, before new growth starts.
- Cut winter-killed stems to live wood, or to the ground if the top died.
- Shorten the remaining stems by about one-third.
- Do not shear the plant like a hedge in summer.
Kalm's St. John's wort is the exception: do not cut that shrub to the ground. A groundcover kind can be sheared or mowed in late winter to renew the mat.
When should I prune St. John's wort?
Late winter or early spring, before growth starts. It flowers on new wood. In a cold winter, cut dead stems; new shoots still bloom.
Not the weedy herb, and not Rose of Sharon
Common St. John's wort is Hypericum perforatum — a weedy herb with translucent dots in the leaves when you hold them to the light. That is the plant in herbal capsules. It is not the landscape shrub. Choose kinds on Types of St. John's Wort. Rose of Sharon in U.S. nurseries is Hibiscus syriacus, a late-summer hibiscus, not Hypericum. That job is on How to Grow Hibiscus.
Is St. John's wort the same as Rose of Sharon?
Not in U.S. garden centers. Rose of Sharon is Hibiscus syriacus. St. John's wort is Hypericum.
If the shrub is thin and woody, cut it in late winter — do not add water to a soggy bed.
FAQ
Can I grow St. John's wort in a pot?
A compact berry kind can sit in a large draining pot. Open ground is the usual home. Water when the top few inches are dry. Do not leave the pot standing in a saucer of water.
Can I start St. John's wort from a cutting?
Named kinds are usually started from cuttings, not from seed. Buy a plant if you want a named shrub this season.
Is the herbal capsule the same plant?
The capsule is made from common St. John's wort, Hypericum perforatum. Growing the landscape shrub is not a how-to for that supplement.
Does St. John's wort get rust?
Rust can speckle the leaves, especially on a crowded groundcover. Cut out affected stems. Spray recipes belong on pest hubs, not this page.
Is St. John's wort toxic to pets?
The sap and foliage can cause photosensitivity if eaten. Keep pets from chewing the leaves.
Related guides
Recommended plants
References
- [1] NC State Extension Gardener -
https://plants.ces.ncsu.edu/plants/hypericum-frondosum/ - [2] Oregon State University Landscape Plants -
https://landscapeplants.oregonstate.edu/plants/hypericum-hidcote - [3] Plant Addicts -
https://plantaddicts.com/st-johns-wort-care/ - [4] UT Gardens -
https://utgardens.tennessee.edu/september-2013-plant-of-the-month-st-johns-wort/
This note is part of Hypericum Guides.
More first-season notes by plant are gathered in How to Grow Guides.
Updated: Reviewed by Bosquelle Editors