How to Grow St. John's Wort Herb Plants

About Growing St. John's Wort Plants in Your Herb Garden

Growing St. John’s Wort plant is easy to grow. There are over three hundred varieties. It is used primarily for medicinal purposes. St. John’s Wort herb is believed to have been named after St. John the Baptist. It originated in Europe where it grew wild in woods, fields, and along roadsides. Quickly spreading, To be sure, its popularity spread and now it is found in herb gardens all over the United States and the world. Yet, to many farmers, it is a weed they try to keep out of their fields.

St. John’s Wort is a perennial herb that grows into a small shrub if allowed. With attractive leaves, this herb has clusters of bright yellow flowers, that bloom from July through August.

Did you Know? St. John’s Wort was used to ward off evil spirits and witches. I think it works, as I have not seen evil spirits in my herb garden.

Medicinal Uses

St. John’s Wort herbs are used to treat anxiety and depression. This herb has also been used for kidney ailments, incontinence, and pulmonary problems.

A tincture is made from the active ingredient “hypericin”. You can easily make it yourself, or buy it in stores. The leaves are also used in teas.

St. John's Wort Plant Specifications

Flowers Bloom: July – August.

Flower Colors: Yellow

Days to Harvest: Before and during the flowering stage.

Plant Height: Most varieties grow one to three feet tall. A few varieties can grow up to four feet high or more.

Light Needs: Full sunlight. Partial shade in hot regions.

Ideal Soil pH: 5.5– 7.3.

Plant Hardiness Zones: 5 – 9.

Ideal Growing Temperature Range: Daytime: 60 to 70° F.

Plant Type: Perennial. The plant normally lives 3 to 5 years or more.

Number of Varieties: It is one of over 900 varieties of Salvia.

Deer Resistant? Yes.

Native To: The Mediterranean.

Botanical Name:

Flowers Bloom: Late Spring to Summer before the flowers bloom.

Flower Colors: Pink, purple, red, violet, red.

Days to Harvest: Late spring to summer.

Plant Height: Most varieties grow two to three feet tall. A few varieties can grow up to four feet high or more.

Light Needs: Full sunlight.

Ideal Soil pH: 5.5– 6.5.

Plant Hardiness Zones: 4 – 9.

Ideal Growing Temperature Range: Daytime: 60 to 80° F.

Plant Type: Perennial. The plant normally lives 3 to 5 years or more.

Number of Varieties: Over 900 varieties.

Deer Resistant? Yes.

Native To: Europe.

Botanical Name: Salvia Officinalis

St. John's Wort Plant Propagation

St.John’s Wort plants are started from seed. Start seeds indoors, 6 to 8 weeks before the last frost in your area.

Note: For indoor starts, we recommend using a heated germination mat, to increase the speed of germination. And, it, results in a higher germination rate.

Growers also start plants from cuttings.

Seed Planting Depth: Sow seeds 1/4″ deep or less. Or, sow them on top of loose soil and lightly water them in.

Ideal Soil Germination Temperature: 60 to 70° F.

Final Plant Spacing: Space seedlings, or thin plants 10 to 18 to 24 inches apart.

Days to Germination: 10 – 21 days.

How to Grow St. John's Wort Herb Plants

Planting and Soil Needs

Almost any area of your garden or flower bed is good for growing St. John’s Wort. They grow well in full to partial sun, tolerating shade. They prefer moist, and light soils. Sandy and coarse soils are fine, too.

Being a perennial, St. John’s Wort is hardy. To assure a good start, sow seeds outdoors after the last frost in your area. When seedlings are about two to three inches tall, thin or transplant them. Different varieties will require varying amounts of space. Of course, you can start them indoors if you prefer.

When planting them for the first time, mix plenty of compost into the planting site. Additionally, add in a high-nitrogen fertilizer because the nitrogen gives them a fast early start.

The plants can suffer from root rot in extended periods of wet or soggy soil. Hence, do not grow it in low areas. Instead, plant them in slightly elevated soil.

Once started, these plants grow well with little or no attention.

Light Requirement

Select a location in your garden where they will receive at least six to eight hours of bright, direct sun. For optimal growth and flavor, grow them in a location that receives full sunlight from sunrise to sunset.

In hotter areas of the country, St. John’s Wort plants benefit from a little light shade to protect the leaves from scalding in the rays of the hot sun. However, too little sunlight results in leggy plants, less vigorous plants with less oil content in the leaves.

Fertilizer Needs

St John’s Wort plants are not heavy feeders. Rather, they grow best in average soil with little or no extra fertilizer. Give them a high-nitrogen fertilizer once at the start of the season to promote quick growth. Then, do not add fertilizer to this plant.

But if the soil is poor, then add a little balanced, general-purpose fertilizer once or twice during the season.

Water Needs

St. John’s Wort plants are quite tolerant of droughts. Thus, they do not require water during most times of the year. But add water if they appear to wilt during extended periods of drought.

Their roots grow deep. So, water the plants deeply at the roots. Then, allow the soil to dry out between watering.

Other Steps

Weeds rob valuable water and soil nutrients. Therefore, keep young plants well-weeded. Then, after they have grown several inches, apply a layer of mulch. This helps to retain soil moisture and gives the plant a neat and tidy appearance.

Pinch back the growing tips of the plant to promote bushier growth.

Prune away dead, damaged, or diseased leaves or stems. At the end of the season, cut the plants back by 1/3 to 1/2.

The plants overwinter with little or no extra care in most areas.

Insect and Plant Disease Problems

Insect and disease problems are uncommon. Yet, problems sometimes occurs.

Aphids, caterpillars, and spider mites are an occasional problem. Treat aphid and spider mite infestations with an organic insecticidal soap. Do this only if problems arise.

Pick caterpillars off the plant by hand whenever you spot them.

Foraging animals do not bother these herbs.

St. John’s Wort herbs can suffer from fungal diseases. Prune plants to improve air circulation. Then, use organic fungicides only if needed.

Root rot occurs in prolonged periods of wet or soggy soil. So, grow the plants in well-draining soil. And, increase drainage.

Also, see: Plant Problems – causes and cures

Harvesting and Drying St. John's Wort Leaves

You can harvest St. John’s Wort leaves as soon as there is enough to use. Do not pick more than 1/3 of the foliage. First, allow the dew to dry of the leaves. Then, pick the leaves in the morning, when the oils are at their maximum.

Harvest the entire plant in the fall before the first frost. Cut the stems near the ground. Hang plants upside down to dry, in a well-ventilated area.

After the leaves are dry, remove the leaves and flowers. Finally, place St. John’s Wort leaves in an air-tight container and store them out of sunlight.