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Smooth-bark St. John's-wort

Hypericum lissophloeus

Also called smoothbark St. John's-wort, silverbark St. John's-wort.

A Florida Panhandle rarity for pond edges, with silvery bark that peels like a birch's and bright yellow flowers from May until frost.

RareEvergreenShowy flowersTolerates wet soilWildlife value

Type: Shrub
Mature height: 6–10 ft
USDA zones: 7–10
Growth rate: Medium
Sun: Full, Part
Soil moisture: Average, Wet
Grows wild in: Sandy barrens, swamps and wet flats
Native range: Florida See what is native in your state

Hardiness zones Find your zone by ZIP code

Smooth-bark St. John's-wort grows wild only around the sinkhole ponds and sandhill lakes of Bay and Washington counties in the Florida Panhandle, where it often rings the shore as the main shrub. It is the tree among the St. John's-worts, a narrow evergreen on one trunk with needle-like, gray-green leaves. Its smooth, chestnut-brown bark turns metallic silver and peels in thin, curling sheets like a birch's. Florida lists it as endangered, and NatureServe ranks it imperiled. Plant it at the wet edge of a pond or rain garden, where its silver trunks and yellow flowers show above the water.

Size, growth and what to expect

No source rates its growth, so our growth estimator uses the middle rate, about a foot and a half a year. It makes a narrow, upright shrub 6 to 10 feet tall and 3 to 5 feet wide, and some reach 13 feet. It grows on a single trunk with a bushy crown. Its needle-like, gray-green leaves run half an inch to an inch long.

Bright yellow flowers half an inch to three quarters of an inch across open from May until frost, each with about 200 stamens. Small capsules follow, each holding many tiny seeds. In the wild a bank of seed in the soil lets stands come back after a drought.

It grows wild only in Bay and Washington counties, Florida, on the rising and falling shores of sinkhole ponds and small lakes set in longleaf pine and scrub oak sandhills. There it may stand in water in wet years and on dry sand in droughts. Clearing lakeshores for beaches is its main threat.

How to grow Smooth-bark St. John's-wort

Smooth-bark St. John's-wort grows best in full sun and takes light shade. It wants a moist to wet, acid, sandy soil, and it stands periods of flooding. In the wild the water can rise over its roots to 5 feet deep. Once rooted it rides out a dry spell, but the long drought of 1999 to 2003 killed many wild plants, so keep it moist. Set plants 3 feet apart and 3 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and keep the mulch clear of the stem. Seed is hard to raise. In one trial only 8.5 percent of fresh seed and 21 percent of frozen seed sprouted. Press it onto damp, peaty sand without covering it, since other St. John's-worts need light to sprout.

Water weekly through the first summer unless the ground stays wet. Plants standing in water grow woody prop roots at the base, which is normal. It needs little pruning.

Each flower carries both male and female parts, so there are no male and female plants to pair. Bees work the flowers, and birds and mammals eat the leaves and seeds. Watch for rust, and powdery mildew may turn up.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (9)