Hypericum

( hye - PEHR - ik - um )

At-A-Glance Information

Also called St. Johnswort or Goatweed, this genus of evergreen, semi-evergreen and deciduous shrubs and perennials thrive in partial shade in the hottest climates, but can take full sun elsewhere. These plants need moderate to regular water, and produce yellow flowers with pronounced stamens. Use these shrubs as ground or bank covers, in woodland gardens, as border shrubs for lawn areas, or to fill in amongst other similarly sized shrubs in landscapes. Take care when planting these shrubs in the landscape, as ingestion of plant parts, especially berries and flowers, is toxic for humans and pets.

Hypericum Species and Varietals

The genus Hypericum includes over 490 species and is a member of the plant family Hypericaceae. Hypericum ideal growing zones vary by species. See the descriptions below for more information. To find your zone, click here: Zone Map.

Hypericum aegypticum (Shrubby St. John's Wort, Egyptian St. John's Wort)
Native to the eastern Mediterranean, these plants form shrublets that reach up to 6.5 feet tall with a crowded branching pattern. They have a somewhat spreading habit, and tiny leathery green leaves. Flowers are small and yellow.

Hypericum androsaemum (Shrubby St. John's Wort, Sweetamber)
This semi-evergreen shrub grows well in zones 3b-24. Native to Northern Europe, this plant is shade-tolerant and has somewhat arching stems. Leaves are green above and pale beneath. Yellow flowers bloom in clusters in summer followed by inedible berries that start red and age to purple-black. Great as a tall groundcover. Varieties include 'Golden Tutsan', 'Albury Purple' (2 feet tall and wide, with purple new growth) and 'Glacier' (pink new leaves that mature to green variegated with cream).

Hypericum calycinum (Aaron's Beard, Creeping St. Johnswort, Great St. John's Wort, Jerusalem Star)
Evergreen to semi-evergreen, this shrub is native to Bulgaria and Turkey, and grows to 1 foot tall with a spreading habit. Grows best in zones 2b-24. Will invade other plantings unless confined. Medium green leaves in the sun are yellow-green in shadier areas, with yellow summer blossoms. The tops of this plant are often killed by cold weather, but will grow back. Clip or mow during the dormant season.

​Hypericum crux-andreae (St. Peter's Wort)
These shrubby plants are native to eastern areas of North America, and is mostly found in the sandy ground of coastal plains. They are considered wildflowers.

​Hypericum frondosum 
This deciduous shrub can be evergreen in mild climates, and grows best in zones 2b-24. Native to the south-eastern United States, these shrubs get 1-3 feet tall with a mounding habit. This plant has blue-green leaves and bright yellow flowers bloom from mid-summer to early fall. Variety 'Sunburst' forms a dense mound 3 feet tall and wide.

Hypericum foliosum (Shining St. John's Wort, Malfurada, Furalha)
This species is endemic to the Azores, and produce golden-yellow flowers. The species forms a bushy shrub to a little over three feet tall with green pointed leaves. Blooms pop in August.

Hypericum gentianoides (Orangegrass, Pineweed)
This species is native to eastern areas of North America, and  is unique in that leaves are typically pressed up against stems, and are a bit scale-like. These plants produce yellow flowers. They prefer to grow in disturbed areas and wetlands.

Hypericum grandiflorum (Large-Leaved St. John's Wort, Malfurada, Corazoncillo)
This species is native to the Canary Islands and Madeira, and is considered invasive in California. It produces a 6 foot tall shrub with green foliage and yellow flowers. Branches typically grow upright from the base of the plant.

​Hypericum 'Hidcote'
Evergreen to semi-evergreen shrub or a perennial planting in the coldest areas. Prefers zones 3-9 and 14-24. 4 feet tall and 5 feet wide, though in cold weather freezes will keep the plant more compact, to just 2 feet tall and 2.5 feet wide. Dark green leaves with yellow flowers that will bloom all summer long.

Hypericum hircinum (Goat St. John's Wort, Stinking Tutsan)
These plants are native to the Mediterranean and the Middle East, and reach up to 5 feet tall. Flowers are yellow with very conspicuous stamens.

Hypericum maculatum (Spotted St. Johnswort, Imperforate St. John's Wort)
This species is native to Europe and Western Asia, where it grows in moist meadows. It produces upright stems that hold green foliage and are topped with yellow flowers. There may be black dots on leaves, petals, and sepals.
 
Hypericum montanum (Mountain St. John's Wort, Pale St. John's Wort)
This species is native to Eurasia and Morocco, and reaches up to 32 inches tall at maturity. Flowers are yellow, and bloom from July through August. 

Hypericum x moserianum (Gold Flower)
Evergreen shrub in most areas, though treated as a perennial in coldest zones due to dieback. This mounding plant prefers zones 3-9, 14-24 and H1. Gets 3 feet tall and wide, and leaves are green above, blue-green underneath. Golden flowers can be single or bloom in clusters and pop in summer and fall. Should be cut back in early springtime to rejuvenate foliage for the next season. Variety 'Tricolor' (pictured) has gray-green leaves edged in white and tinged pink.

Hypericum perforatum (St. John's Wort, Perforate St. John's Wort, Common St. John's Wort, Klamath Weed)
These perennials reach up to 3.3 feet tall and produce many yellow flowers with long stamens. These plants are native to Eurasia and North Africa, and have naturalized in many temperate areas of the world.

Caring for and pruning Hypericum shrubs

Plant Hypericum shrubs in full sun exposure in well-draining, moist, fertile soil. These plants are not picky about soil pH, and can tolerate alkaline, acidic, and neutral soils. Provide these shrubs with some afternoon shade if they are grown in a particularly warm climate. Once established, these plants are relatively drought-tolerant but do appreciate some waterings during the warmer months of the year. For groundcover species, prune to rejuvenate in late winter or early spring each year (or every other year) by cutting plants back to the base. For taller, shrubby species, prune every two or three years to shape and control size. They can be pruned hard, but may not flower in the following year if too much wood is taken. Fertilize St. Johnswort yearly in early springtime with a balanced, slow-release fertilizer to support blooming and fruiting for that season.

Propagation

Hypericum can be propagated by using cuttings, through division or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting or division methods. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your shrub, follow the instructions below:

Propagating Hypericum by Cutting
  1. Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
  3. Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots. 
  4. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Hypericum by Division
Division is probably the easiest way to propagate these plants. The idea behind this method is that you are taking an existing clump of live plants and breaking it into smaller segments. Division should be attempted only when the plant is not in its blooming period during fall or early spring. To use this method, you will need a clean shovel, clean pruning saw, extra pots if you are not going to immediately plant your divisions in the ground, and well-draining soil to fill the pots (again, if you will not be planting your divisions directly into the ground). To propagate by division, follow the instructions below:
  1. Identify the area of plants you're going to divide. Start by loosening the soil around the plant with your shovel, working your way inward to avoid causing damage to the roots. Once you've gotten your clump out of the ground, lay it out on its side.
  2. Divide the clump into segments, either with your shovel or with a pruning saw, as many as you'd like as long as there are at least three 'shoots' per segment. Lay them out on the ground.
  3. If you will be planting your shrub in the ground, this is when you'll prepare your new hole. Dig a hole (large enough to accommodate the root ball of the clump you are planting) in the ground with your shovel in a sunny location with soil that is well-draining. If you have issues with drainage in your garden, amend with loamy soil before planting. Backfill and water generously.
  4. If you are transporting your division elsewhere, or hanging on to it until you're ready to plant it, you'll need your pot filled with soil. Dig a hole large enough to accommodate the root ball of your division, and place your new plant in the soil. Water generously, ensuring that adequate drainage is occurring. Place the pot in a sunny location until you are ready to plant it in the ground.

Propagating Hypericum by Seed
  1. Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
  2. Harvest your seeds. The seeds are contained in dried flower heads after flowers fade. In early fall, cut the seed pods off of the plant and place them in a paper bag. They'll continue to dry and open, releasing the seeds inside. Store seeds in a cool, dark and dry place until you are ready to use them.
  3. Anywhere from the middle of spring to early autumn, water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 1-2 months from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
  4. Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Seeds are contained inside seed pods that are left behind after flowers fade.
Hypericum seeds.

Problems and Pests

Hypericum shrubs suffer from the following issues:
  • Thrips
  • Scale
  • Anthracnose
  • Rust 
  • Leaf Spot
  • Aphids
  • Whiteflies
For information on these issues, see the following links:

​Many species are considered invasive, though those listed below have low invasive ratings.
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Gallery

Low-growing Hypericum species are wonderful woodland-area groundcovers.
Hypericum shrubs are at home in cottage-style and informal gardens.
Smaller species of Hypericum are wonderful in rock gardens or in front of larger shrubs.

Videos

How to grow these shrubs in your garden.
How to prune Hypericum shrubs.
All about Hypericum 'Hidcote'.
It's time to prune!

Resources

How to Grow & Care for Hypericum: St. John's Wort
Fertilizing St. John's Wort
Hypericum St. John's Wort Care
Wikipedia: Hypericum
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 369 - 370, Hypericum (St. Johnswort)
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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