St. John’s Wort Guide: How To ID, Plant, and Grow St. John’s Wort Plant Varieties

Image Credit: Nicky ❤️🌿🐞🌿❤️ (NickyPe)²²

How To Identify St. John’s Wort

When it comes to how to identify St. John’s Wort, remember that there are almost 500 species.¹ Generally, though they have similar characteristics, some may not fit the below descriptions.

The size can vary, with some growing no more than a foot, while others can grow up to 4 feet, sometimes more.

St. John’s Wort Leaves

Leaves are generally oblong in shape and a deep blue-green in color. They have sheer dots that you can see when held up to the light.

Leaves are smooth at the edges and grow opposite, meaning there are pairs of leaves directly across from each other all along the stem.

St. John’s Wort Flowers

St. John’s Wort flowers are typically yellow but some species may have other shades. Generally, they have five petals that have black dots around the edges.

The flowers have a large number of stamens that are bundled together in numerous groups. They kind of look like pom-poms

St. John’s Wort Fruit

St. John’s Wort fruit makes its appearance in the late summer and grows through the fall. They are soft and fleshy and start off red but eventually turn black.

The berries can remain on the bush throughout the winter, giving a nice splash of color to your backyard garden or other outdoor space during a time when it may not have much else going on.

St. John’s Wort Seeds

St. John’s Wort seeds are numerous, one single plant can produce about 100,000 a year! They are black or brown and very, very small.

These seeds can remain viable in the soil for at least a decade.

When To Plant St. John’s Wort

As for when to plant St. John’s wort for the best yield, spring or early summer is best. This applies to both seedlings you have been growing yourself or a more mature plant from a nursery.

Best Growing Conditions for St. John’s Wort

While this plant is one of the hardest around and isn’t particularly precious about its care, knowing the best-growing conditions for St. John’s Wort is just as important as any other plant. Here are some of the most important planting tips for St. John’s Wort.

When reading the below, keep in mind the wide variety of species. While much of what you read typically applies to the Hypericum genus generally, it is best to read up more thoroughly on the particular species you want to use.

It is possible some would have different needs or recommendations.

Spacing Needs for St. John’s Wort Shrub

So, how far apart to plant St. John’s Wort shrubs? Most species grow between one and three feet tall and about one to two feet wide.

Given their average height and spread, it is best to plant them about 24 to 36 inches apart.

Watering

During the first growing season, regular watering is required. Roots will develop more extensively with longer watering a few days a week rather than more frequent shorter watering, which leads to a more shallow root system less tolerant to dry conditions.

Aim for an inch of water spread over two to three sessions. If there has been a lot of rainfall during this time, you likely don’t need to water it.

The watering needs for St. John’s Wort plants are minimal once the plant has been established. It is pretty tolerant to drought at this point.

If you live somewhere that gets regular rainfall in the summer, you probably won’t have to do anything watering-wise. But if you live somewhere with drier, hotter summers, you may want to give it some an inch of water every seven to 10 days.

The most important times to pay attention to its watering needs are when the flower buds are starting to form in the spring and when the berries start growing later in the summer. Signs the plant is in need of water are drooping leaves, blooms not opening or falling off the tree before opening, or berries being smaller than usual.

Sunlight Needs

So how much sunlight does St. John’s Wort need each day? Too much sun and the leaves will scorch.

Too little sun and it won’t produce the prolific blooms for which it is known. The sweet spot is an area that gets plenty of morning sun and some shade during the hottest parts of the day.

Generally, it will do perfectly fine with full sun in more temperate regions, but in really hot areas, it will need some shade.

Soil Composition Requirements

One of the most hardy aspects of St. John’s Wort is its ability to thrive and adapt to some of the poorest soil conditions.⁴ It can also grow equally well in rocky soils, sandy soils, clay soils, or loamy soils.

But generally, it will thrive best in soils that are well-draining and consistently and evenly moist. As for the ideal soil pH,⁵ it is pretty flexible here as well.

It doesn’t appear to have a strong preference and can grow just fine in acidic, neutral, or alkaline dirt. If you live somewhere with lots of rain, well-draining sandy soils are best to protect the plant from root rot.

This is a common issue for shrubs in areas with high amounts of precipitation.

Temperature and Humidity

St. John’s Wort does best in more temperate areas where the average temperature falls between 60 and 80 degrees. Like it was mentioned earlier, in hotter climates, it will do best where it is protected from the sun during its peak strength.

In areas where it drops below 40 degrees, the plant will go dormant for the winter, but as a perennial, will bounce right back in the spring. To keep the plant from dying during this time, cease watering when the ground starts freezing and make sure the soil is not soggy.

If the plant is stuck in really wet conditions during this time, it may die of root rot. It is not particularly sensitive to humid conditions, but if it is really humid, it may develop root rot or other fungal diseases.

Fertilizer

While this plant does not require the highest quality soil to grow normally, like many plants, it will do best in fertile soils. So if you want the highest quality version of your variety, add compost to the soil every year.

It does not need fertilization of any kind, however.

Growing St. John’s Wort From a Seed Cutting or Seedling

If you are interested in growing St. John’s Wort from a seed, cutting, or seedling, here are some tips on how to do that:

Seed and Seedling

Growing a new plant from a seed is the preferred way to propagate St. John’s Wort because it is the easiest way. Start germinating your seeds about six to eight weeks before the last frost is expected in your area or you can plant them directly in the ground once you are sure the threat of frost has passed.⁷

If growing indoors, here are the steps to germinate the seeds and grow a seedling:

1. Get a small container with a high-quality potting mix
2. Press the seeds into the soil but keep them uncovered
3. The seeds of this plant require light and a relatively warm temperature to germinate. They should be somewhere that is at least 60 degrees and gets ample sunshine.
4. Seeds should germinate in about 10 to 20 days
5. You can plant the seedling in a larger container or outdoors once it reaches at least two to three inches long

Cutting

If propagating via a cutting, you will need a softwood stem about 4 to 6 inches long. Be sure it comes from a healthy part of the plant and it is taken from above a leaf bud.

Take all the leaves off the lower section and dip them in some rooting hormone. Place the treated stem in a pot filled with a potting mixture of compost and perlite.

Water the cutting before putting a plastic bag over it. The pot needs to be in a warm area to facilitate root growth, and the soil must be uniformly moist during this time.

Roots should become established in about 10 weeks. When the plant appears hearty enough, you can put the cutting in a new pot or plant it outside.

St. John’s Wort Growing Zone

When it comes to the optimal St. John’s Wort growing zone, it will ultimately depend on the variety you choose to plant.³ Generally speaking, the proper growing zones for St. John’s Wort span from 4 to 10.

It produces the most flowers in full sun but too much in hotter weather can damage the plant. So in warmer areas, you should only plant it somewhere that offers partial shade.

St. John’s Wort Growth Rate

When it comes to how long it takes to grow St. John’s Wort, know it is a generally slow-growing plant. It will grow about a foot a year.

So depending on the variety you plant, it can take anywhere from one year to several for it to reach its full height.

Companion Plants For Growing St. John’s Wort

There are a number of companion plants for growing St. John’s Wort.

Plants That Go Well With St. John’s Wort

St. John’s Wort attracts many pollinators and birds, so planting them along with other perennials popular with wildlife can encourage frequent visits.

Some good choices include:

• Black-eyed Susan
• Bee balm
• Mike Jensen
• Alpine strawberry
• Bleeding hearts
• Ornamental grasses
• Columbine, and
• Coneflowers

Some good choices for annuals include:

• French marigolds
• Sunflowers
• Calendula, and
• Zinnias

Other shrubs that go well with this plant are yew, Chinese holly, and mountain laurels.

St. John’s Wort Plant Varieties

Here are some of the more common St. John’s Wort plant varieties you are likely to see in the average garden:

This plant is actually considered a noxious weed in many countries as well as several states in the US including Indiana, Oregon, West Virginia, California, Wyoming, Washington, Utah, Montana, and Nevada.²

In Alaska, it is considered an exotic plant.

It grows one to three feet tall and has smaller, oval-shaped leaves. It will produce the most flowers when grown in full sun but in very hot climates, placing it in such areas may scorch the leaves.

It can be grown in partial shade just fine. It can spread very quickly, and once established, can be difficult to get rid of.

The stamens are particularly bushy and may even obscure the petals, which are the typical bright yellow most of the species has.

They are particularly attractive to pollinators like bumblebees and other types of bees. It tolerates a wide range of soils and works well as a hedge or border.

Its foliage is particularly attractive, it has a very fine texture and turns a beautiful gold color in the fall. The copper-colored bark is particularly attractive in the winter.

Most commonly used as ground cover, it typically only grows one foot high and two feet across. Its leaves are on the longer side, at 4 inches and turn a nice shade of purple in the fall.

The yellow flowers are also large compared to the overall size of the plant. This species can also grow very aggressively and be difficult to remove, its vertical roots can go as far as 5 feet deep into the ground.

Its yellow flowers are very small, about ½ an inch across. Its most distinguishing feature is its black dots and spots can appear anywhere on the petals, whereas most other species only have these markings on the edges of the flower.

Its flowers are a particularly bright shade of lemon-yellow. Leaves are more of a pale green shade.

It only has four narrow petals which are arranged in an X shape. Its stems are reddish-brown and have branches.

While many of these plants will produce the most flowers in the sun but will still bloom in the shade, Orangegrass flowers will only bloom in full sun. Its branches are very wiry.

This species is considered endangered or vulnerable in several US states.

Because of its native habitat, it does better in wetter soils as compared to other types.

‘Sunny Boulevard’ is one of the more cold-hardy species and can do well as low as zone 4.

St. John’s Wort Ground Cover Pruning

If you live in colder climates where the branches die back in the winter, pruning until there is only live wood in the spring will contribute to the optimal regrowth of this perennial plant. Pruning in the early spring will also significantly increase this shrub’s flower production.

Every three or four years, the plant may benefit from an extensive ‘renewal’ pruning.⁶ This involves cutting back the plant to half its height, which will lead to healthy, dense new growth.

This more extensive pruning will also help it retain a nice shape.

How To Stop St. John’s Wort Disease

If you are wondering how to stop St. John’s Wort disease, the good news is this plant is pretty hardy and not super susceptible to any particular disease. When it comes to St. John’s Wort disease prevention, the biggest worry is probably the aforementioned root rot,⁸ which can be prevented by avoiding overly wet and waterlogged soil.

In super-humid conditions, it may be vulnerable to fungal diseases. But they typically aren’t super problematic and can generally be controlled well by removing the infected parts of the plant.

As for common pests of St. John’s Wort plant, there really aren’t any that are particularly drawn to it. So when it comes to chemical or natural pest control for St. John’s Wort, you really do not need to worry too much about that.

St. John’s Wort Benefits for Health

St. John’s Wort benefits, medicinally speaking, are only available from Hypericum perforatum. All the other species offer nothing more than ornamental value.

Growing St. John’s Wort for Medicinal Purposes

So, what are the medicinal uses of St. John’s Wort? It has been used as a medicine since the time of ancient Greece, and the most common purported uses include treating depression, anxiety, menopausal symptoms, somatic symptom disorder, insomnia, ADHD, and obsessive-compulsive disorder.

It is also used topically for things like wounds and bruises, and a variety of skin conditions. Historically it was also used to treat kidney and lung problems, but these don’t appear to be modern-day uses.

It is probably best known as a natural treatment for depression and it has been studied extensively in this context, according to the National Center for Comprehensive and Integrative Health (NCCIH).⁹ This herb appears to work better than a placebo when used for mild to moderate symptoms up to periods of 12 weeks.

Whether it maintains this benefit beyond then is unknown, as is whether it would benefit people suffering from severe depression. The NCCIH also states there is not enough evidence to determine if it offers any meaningful benefit for the variety of other conditions for which it is recommended, such as menopause or somatic symptom disorder.

Considerations For Taking St. John’s Wort Plant

St. John’s Wort plant contains substances that interfere with your body’s ability to metabolize numerous medications. And if the body can’t process them properly, their effects will be weakened.

If you take any of the following types of drugs, you probably should not use this herb:

• Oral contraceptives
• Antidepressants
• Heart medications such as ivabradine and digoxin
• Cyclosporine
• The blood-thinning medication Warfarin
• Statins such as simvastatin
• Certain cancer drugs such as imatinib and irinotecan
• Certain HIV drugs such as nevirapine and indinavir

If you consume this plant while already taking antidepressants or other drugs that affect your serotonin levels it increases your risk of side effects from too much serotonin production. Other side effects may include increased sensitivity to the sun (when taken orally or applied topically), anxiety, dry mouth, trouble sleeping, stomach problems, fatigue, headaches, and sexual problems.

Do not use St. John’s Wort while you are pregnant as it could cause birth defects. Taking it while breastfeeding could make infants drowsy, fussy, and colicky.

St. John’s Wort is a very attractive shrub that can add some cheer to your outdoor space with its abundant amount of yellow flowers and striking red berries.

Frequently Asked Questions About St. John’s Wort