St. John’s wort, sometimes known as St. Joan’s wort, (Hypericum perforatum) is one sign that summer has indeed arrived. It typically blooms very near to the summer solstice, which is a useful identifier as to the best time to harvest the aerial parts with their sunny yellow flowers. The harvest season of St. John’s wort is short, lasting from late June to early July.
In the article below, I’ve outlined some tips to help you identify and forage St. John’s wort this summer.
St. John’s wort (Hypericum perforatum) is a popular flowering shrub known for its cheery yellow blooms that appear in late spring through summer. Getting St. John’s wort to bloom abundantly at the right time involves understanding its ideal growing conditions.
When to Expect the First Blooms
Gardeners eager to see the bright yellow flowers of St. John’s wort generally need to wait until late May or early June for the first blooms to appear. This lines up closely with the Feast of St. John the Baptist on June 24th, which is how the plant got its common name. The shrub requires the warmer temperatures of late spring to trigger the initial flowering.
While other flowering shrubs like lilacs and viburnums begin blooming in early spring, St John’s wort starts a bit later. Have patience for those vibrant yellow blossoms Once they start up, you’ll get to enjoy them for months to come.
The Peak Bloom Period
One of the best features of St. John’s wort is its long bloom time. While some flowering shrubs only last for a couple weeks, St. John’s wort flowers persist for 2-3 months on average.
The peak bloom period runs from late May through July and August. During this time, the shrub will be completely blanketed in cheerful yellow blossoms that persist nicely in summer heat. Deadheading spent blooms as they fade keeps the flowering going strong for months.
Maximizing Flower Production
To get the most blooms out of your St. John’s wort shrubs during the peak bloom period, keep these tips in mind:
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Site in full sun. St. John’s wort thrives in a spot receiving at least 6 hours of direct sun per day. Morning sunlight is particularly beneficial.
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Prune in early spring. Pruning out old wood in early spring helps promote the fresh new growth that will be covered in flowers.
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Provide consistent moisture Water regularly to keep the soil evenly moist but not saturated, Let it dry out slightly between waterings
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Fertilize lightly. One application of balanced organic fertilizer in early spring gives St. John’s wort the nutrients it needs for abundant flowering.
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Allow adequate space. Give St. John’s wort room to spread out. It can reach over 3 feet wide at maturity.
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Propagate new plants. Growing St. John’s wort from seed or cuttings lets you add more plants for a bigger floral display.
Caring for St. John’s Wort After Blooming
Once the long bloom period winds down in late summer, St. John’s wort requires a bit of care to prep it for next year:
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Deadhead spent blooms. Pinching off faded flowers keeps the plant looking fresh and prevents self-seeding.
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Water regularly. Supply ample moisture until the first frost to keep it healthy going into dormancy.
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Cut back in late fall. After the plant goes dormant, cut all stems back to about 6 inches to remove old wood.
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Apply winter mulch. Place 2-3 inches of bark chips or chopped leaves around the base to insulate the roots through winter dormancy.
With proper care after blooming, your St. John’s wort will return even better next year!
Troubleshooting Lack of Blooms
If your St. John’s wort fails to bloom well, here are some common causes to check:
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Insufficient sunlight – St. John’s wort needs full sun to flower abundantly. Increase sunlight if possible.
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Excess shade – Nearby trees and shrubs may be blocking too much sun. Prune or relocate the St. John’s wort.
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Overpruning – Blooms form on new wood. Pruning at the wrong time removes flower buds.
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Transplant shock – Allow newly transplanted shrubs time to establish before expecting flowers.
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Irregular watering – Too much or too little water can prevent good flowering.
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Immaturity – Young shrubs may take a couple years to start blooming well. Be patient.
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Poor soil conditions – Improve drainage and nutrient levels if needed to support blooms.
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Pest damage – Insects or disease can weaken plants and reduce flowering. Treat any issues promptly.
With the right growing conditions and care, St. John’s wort will reward you with an abundance of golden summer blooms year after year. Time those first blossoms for late spring, and enjoy the long peak bloom period all summer long in your garden!
Pruning St. John’s Wort To Help It Bloom
Since St. John’s Wort blooms on new growth every year, the plants will only flower at the branch tips if it is not pruned back every year. Cutting back to the woody growth early in the spring will help St. John’s Wort to remain compact and dense. Shrubs that have been neglected for a few seasons are easily rejuvenated with a hard cut back into the woody growth. New shoots will quickly develop, and if rejuvenation is done early in the spring, blooming will not be sacrificed.
St. John’s Wort Identification
It’s likely that once you successfully identify St. John’s wort, you will have an easy time finding it again. Knowing what to look for, having confidence in your plant identification skills, and using resources as needed is important when learning to identify wild plants.
However, before you are comfortable foraging for St. John’s wort in the wild on your own, I would recommend that you take a botanical key with you into the field. William A. Weber has a useful key that I always bring with me on botanical and foraging adventures called Rocky Mountain Flora. This book, and other keys, give detailed information about altitude, habitat, and other special characteristics of plants. Keys are meant to bring you discernment and confidence about the plant you are learning to identify.
Learn more about our favorite books to help you identify and harvest plants in our post, 5 Foraging Guide Books To Help You Identify & Harvest Plants.
St. John’s wort is a perennial that grows around 3 feet tall. It can often be found near meadow drainages, creeks, and foothills. It likes plenty of sun and dry soil. Finding St. John’s wort in cities, in parking lots, and in places where you wouldn’t think much would grow, is a testament to the fortitude of this plant and its ability to come through adversity to be of service.
When foraging for St John’s wort, look for its opposite-patterned leaves and branches. The leaves and sepals are oblong in shape and three times longer than they are wide. The leaves are stalkless, and if held to the sky, light will shine through the small dots. There are many long stamen that come together in three bunches and pop out of the center of the flower. St. John’s wort has a reddish, woody stem base.
St. John’s wort flowers have five distinct petals with a rose-like stamen. The yellow petals are oval to round, about 1 inch across (Ells, 2011), and the buds or new flowers have a reddish tint.
There are tiny pinhole dots—tiny oil glands—on St. John’s wort leaves as well as on the petals, sepals, and leaf margins (Moore, 2003). These perforations are why Hypericum perforatum gathered its name.
In the Rocky Mountains, there is a native species called Hypericum scouleri. This species is slimmer and a little more delicate than H. perforatum (Wiles, 2018). Harvesting this local species will take more tenderness and care on your part.
St Johns Wort groundcover Hypericum calycinum – pollinator friendly flowering evergreen groundcover
FAQ
How long does St. John’s Wort bloom?
Shrubby St. John’s wort has a rounded, compact growth habit (hence the common name) and often blooms with pom-pom clusters of yellow from June through August.
Does St John’s wort like sun or shade?
John’s-wort is a small, spreading shrub growing 4–20 inches tall and forming mats. This plant is slightly salt tolerant. It requires a moist well-drained site in sun to partial shade although it tolerates most soil types, including dry soil, and full sun will maximize blooms.
Why does my St. John’s Wort not bloom?
The three most common reasons for lack of blooms and berries are improper pruning, lack of sunlight, and nutrient deficiency. St. John’s Wort blooms on new wood and responds well to pruning early in the spring. As surrounding trees and shrubs grow and mature, they may create too much shade for the St.
Does St. John’s Wort spread?
Common St. Johnswort spreads both by underground rhizomes, above-ground creeping stems, and by seeds that are dispersed by wind and animals. One plant can produce up to 15,000 to 34,000 seeds per year that are viable for up to 30+ years.