Hypericum

( hye - PEHR - ik - um )

At-A-Glance Information

Commonly called St. John's Wort or Goatweed, this genus includes species of evergreen, semi-evergreen and deciduous shrubs and perennials. These plants thrive in partial shade warm climates, but can take full sun elsewhere. They need moderate to regular water in the garden, 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. 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 USDA hardiness zones 5-8 or Sunset growing 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). This species is considered invasive in Oregon and California in the United States as well as New Zealand and Australia.

Hypericum calycinum (Aaron's Beard, Creeping St. Johnswort, Great St. John's Wort, Jerusalem Star, Rose of Sharon)
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 USDA hardiness zones 5-9 or Sunset growing zones 2b-24. It 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. This species is considered invasive in California and the Pacific Northwest region of the United States and the United Kingdom.

Hypericum crux-andreae (St. Peter's Wort, St. Andrew's Cross)
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. This species thrives in USDA hardiness zones 5-10.

Hypericum frondosum (Cedarglade St. John's Wort, Golden St. John's Wort, Blueleaf St. John's Wort)
This deciduous shrub can be evergreen in mild climates, and grows best in USDA hardiness zones 5-8 or Sunset growing zones 2b-24. Native to the south-eastern United States, these shrubs reach 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, Leafy St. John's Wort)
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. This species thrives in USDA hardiness zones 4-8.

Hypericum gentianoides (Orangegrass, Pineweed, Gentian-Leaved St. John's Wort, Orange-Grass St. John's Wort)
This species is native to eastern areas of North America and grows well in USDA hardiness zones 3-9. It is unique in that leaves are typically pressed up against stems and are a bit scale-like. These plants produce yellow flowers and they prefer to grow in disturbed areas and wetlands. Stems and leaves have a citrusy fragrance when crushed.

Hypericum grandiflorum (Large-Leaved St. John's Wort, Malfurada, Corazoncillo, Large-Leaved Hypericum)
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. These shrubs thrive in USDA hardiness zones 8-11 and are considered invasive in the Bay Area, California (United States).

Hypericum hircinum (Goat St. John's Wort, Stinking Tutsan)
These plants are native to the Mediterranean and the Middle East, and grow well in USDA hardiness zones 5-9. They can reach up to 5 feet tall at maturity. Flowers are yellow with very conspicuous stamens. This species is considered invasive in western Europe, the British Isles, Italy, Greece, and Portugal.

Hypericum maculatum (Spotted St. Johnswort, Imperforate St. John's Wort, Dotted 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. Best in USDA hardiness zones 5-8.

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 in the plant's native range. Mountain St. John's Wort grows well in USDA hardiness zones 5-9.

Hypericum x moserianum (Gold Flower, Hybrid St. John's Wort, St. John's Wort, Variegated St. John's Wort)
Evergreen shrub in most areas, though treated as a perennial in coldest zones due to dieback. This mounding plant prefers USDA hardiness zones 6-9 or Sunset growing zones 3-9, 14-24 and H1. Plants reach 3 feet tall and wide, and leaves are green above, blue-green underneath. Golden flowers can be single or bloom in clusters. Plants should be cut back in early springtime to rejuvenate foliage for the growing 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. The species is considered invasive in regions across North and South America, Australia, New Zealand, and Africa.

Caring for Hypericum

Take care when planting these shrubs in the landscape, as ingestion of plant parts, especially berries and flowers, is toxic for humans and pets. 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.

Plant Hypericum, or St. John's Wort, in a space in the landscape that receives full sun; ideally, they appreciate between 6 and 8 hours of sun each day for the best blooms. Provide some afternoon shade when temperatures are at their warmest. When these shrubs are grown in less light, they will not flower as profusely and become leggy. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.0 and 7.5 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, these plants are considered moderately drought-tolerant, able to get by on rainwater alone for most of the year with supplemental irrigation during extended periods of dry weather.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. Deadheading will also discourage plants to spread and lessen their invasiveness. If growing these shrubs for their decorative berries, make sure to not deadhead shrubs. Hypericum plants are herbaceous perennials that can survive for decades in the garden before needing to be replaced.

Caring for Hypericum in Containers
Hypericum shrubs are wonderful in the ground, but can also be grown in containers. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Hypericum plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

Harvesting Hypericum
Hypericum plants produce berries that are popular in cut flower arrangements. The best plants for cut berry stems are high-yielding hybrids like Hypericum x inodorum or Hypericum androsaemum varieties. The berries are produced from mid-summer to late fall and range in color from deep red, burgundy, and pink to ivory, yellow and green. Stems are ready for harvesting when 80% to 90% of the berries are fully colored and most of the petals and foliage have dropped from the plant. The berries themselves should feel firm to the touch. The best time of day to harvest is in the morning, after dew has dried but before the heat of the day sets in. Make a cut at the base of the stem and drop it into a bucket of cool water. Hypericum berry stems have a vase life of between 7 and 21 days.

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

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. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
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.
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.
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:

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.
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.
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.
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

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. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
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.
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.
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 are tiny, black to brown, and cylindrical with a slight curve.

Problems and Pests

Certain Hypericum species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Hypericum shrubs can be susceptible to developing issues with the following pests and diseases in the landscape: