Shrubby St. John’s wort (*Hypericum prolificum*) is a flowering shrub native to the eastern United States and Canada. It grows in woodlands, swamps, and near rivers and streams. This plant is known for the numerous pollen-producing organs its flowers contain.
I. Appearance and Characteristics
Hypericum prolificum, known as shrubby St. John’s wort, is a deciduous shrub in the genus Hypericum. It was named for its “prolific” number of stamens. Hypericum prolificum is native to the central and eastern United States and Ontario. Habitats include riparian areas, slopes, thickets, swamp edges, and oak woodlands.
Hypericum prolificum is a shrub growing up to 2 m (6 ft 7 in) tall with elliptic leaves up to 70 mm (2.8 in) long and 15 mm (0.59 in) broad. The flowerheads have between 1 and 9 flowers, each 15–30 mm (0.59–1.18 in) across with 5 golden yellow petals and numerous stamens. The ovary is usually three-parted, though may have up to five parts in some individuals.
II. How to Grow and Care
Sunlight
Shrubby St. John’s wort needs sufficient sunlight but doesn’t tolerate direct light. Grow the plant in the shade of other plants or on a balcony away from strong, hard light. Expose it to more sunlight in the spring and fall to help it grow, but in the summer, place the potted plants in half-shaded places and mist them with water to cool the temperature and increase humidity. Otherwise, symptoms like drying leaf tips may appear.
Temperature
plants of the Hypericum genus are widely distributed. They like warm, moist environments; the best temperature range for the plants is 20 to 26 ℃, but they can tolerate temperatures as low as -10 ℃. They require little water and endures drought, but don’t tolerate waterlogged soil. Avoid watering so frequently that the soil gets waterlogged.
Watering
Shrubby St. John’s wort can withstand drought but is intolerant of waterlogged soil. In the first year after planting, about 2.5 cm of water every week will be enough. In areas with plentiful rain, no additional watering is needed. From the second year on, shrubby St. John’s wort doesn’t need any additional watering, as normal precipitation will meet its needs for water. If over-watered, its roots are likely to rot due to waterlogging, and leaves will wither and dry up.
Soil
Shrubby St. John’s wort can adapt to a wide range of soil types. It grows well in most common soils (except for heavy clay) and prefers sandy loam with good drainage. A slightly acidic loam with a 5.5-7.0 pH value is ideal. Shrubby St. John’s wort is tolerant of barren soil and drought, but if the soil can’t drain water well, waterlogging can cause the roots to rot.
Fertilizing
Shrubby St. John’s wort requires very little fertilizing. Usually, no additional fertilization is needed after the initial planting, unless obvious symptoms of slow growth appear. If that happens, apply some low-concentration balanced compound fertilizer (10-10-10 NPK ratio).
Planting Instructions
Plant shrubby St. John’s wort in the early spring or early fall. Choose a cool, shaded place, such as within tree shade. Remember to clear the soil first and remove weeds. Dig a planting pit slightly shorter than the diameter of the root ball and 3 times wider. If you’re planting more than one sapling, avoid planting them too close, or low light and poor ventilation may result in powdery mildew. Pile some soil around the root collar (the juncture of trunk and roots) to form a gentle slope, and this helps disperse water.
After planting, press the soil firmly and water thoroughly. Note the distance between each
Some plants in the Hypericum genus have subterraneous rhizomes that tend to expand in all directions. To prevent excessive expansion, it’s a good idea to fence the planting spots or set brick perimeters around them to control their growth.
Pruning
Shrubby St. John’s wort doesn’t need much pruning. To promote more lush growth, trim 1/5-1/4 of the total branch length by the end of spring or early summer, which promotes new branches to sprout. Shrubby St. John’s wort buds and leaves both grow in pairs. Generally speaking, cutting one branch off promotes the pair of buds beneath the incision to develop into two branches.
For shrubby St. John’s wort with robust growth and branches crossing inward, winter is the time for an overall pruning. As perennial herbaceous plants, you may just clip them flat with a sickle and they will revive. Shrubby St. John’s wort has a short life span, so you can also consider getting new seedlings to replace the old ones once they start to decline.
Propagation
Shrubby St. John’s wort can be propagated by seeding, cuttage, or plant division. To sow seeds yourself, sow them in a sand bed. Dust a thin layer of soil on them, water once, and sprout the seeds in temperatures of 10 to 12 ℃. Keep the potting soil moist. Transplant seedlings when they grow to 5 to 10 cm tall.
For St. John’s worts with dense branches, propagation is usually performed at the end of summer by soft-branch cuttage. Choose some robust, soft branches that sprouted in the current year. Cut 10 to 15 cm-long from the tip, making sure to keep at least 2 full leaves on each branch. Insert the cut branches into the soil and keep half the length aboveground. Keep the soil and the environment moist. When the seedlings reach 20 cm tall, transplant to pots. Seedlings need to grow to 70 cm tall to move outdoors or wait until the end of the next summer.
Transplanting
For best results, transplant shrubby St. John’s wort during late summer to early fall (S2-S3), as new root growth can happen before winter. Shrubby St. John’s wort thrives in sunny or semi-shaded spots with well-drained soil. Always ensure the roots are well-watered before transplanting to reduce stress.
Pests and Diseases
St. John’s wort has very few (if any) pest problems. However, in areas with wet winters (or if overwatered), it may struggle with root rot. If wet winters are a challenge in your area, be sure to plant your St. John’s wort in well-drained, sandy soil.
Seasonal Precautions
Shrubby St. John’s wort begins to flower at the end of spring. You can extend its flowering by giving it some shade. Especially potted, it needs as much sunlight during the day as possible in spring and fall.
When shrubby St. John’s wort is planted without a brick perimeter or fence, remove overly lush-growing parts before the frost every fall to prevent it from growing too fast and expanding too wide. Eradicating this hardy plant requires multiple applications of 2,4-D herbicides.
III. Uses and Benefits
Consider planting shrubby St. John’s wort as a hedge or mass planting in wildlife and pollinator-friendly gardens. The showy blossoms are highly attractive to pollen-seeking bumblebees, halictid bees, and syrphid flies, and the foliage is a food source for grey hairstreak butterflies and certain moth species. This dense, flowering shrub also works well on the edges of cottage gardens, planted along roads, and in low-maintenance garden sites.
