Hypericum prolificum (Shrubby St. Johnswort)


Botanical Information

FamilyHypericaceae
GenusHypericum
Speciesprolificum
CategoryWoody
TypeShrub (deciduous)
OriginIntroduced into cultivation in 1750. Native to New Jersey and Iowa.
Pronunciation

Details

USDA Hardiness Zone5 - 9
USDA Hardiness Ref.
Canadian Hardiness Zone9b - 5a
Canada Hardiness Ref.
RHS Hardiness ZoneH4 - H7
RHS Hardiness Ref.
Temperature (°C)-30
Temperature (°F) -20 to (-30)
Height1.3 m
Spread 1.3 m
GrowthSlow
Flowering PeriodJuly

Description and Growing Information

General DescriptionA loose formed, but low mounded shrub with delicate branching and linear leaves. Flowers are bright yellow and quite prolific.
ID CharacteristicA small shrub with opposite leaf arrangement, and small linear leaves. Bright yellow flowers with a post persistent capsule fruit.
ShapeDense, rounded form, small.
LandscapeBest suited to mass planting for full effect. Ideal for large scale commercial plantings since it is relatively care free.
PropagationSoftwood cuttings taken in June - July root easily if treated with 1000ppm of IBA and placed in sand undermist. Seed germinates without pretreatment.
CultivationLoosen up soil, remove rocks and weeds, does well in dry soils, full sun.
PestsHypericum rust can damage some species and cultivars otherwise it is a relatively problem free plant.
Notable SpecimensThe Gardens of Fanshawe College, London, Ontario.
HabitatNew Jersey and Iowa to Georgia.
Bark/Stem DescriptionOlder stems are light brown and exfoliating and tend to become gnarled with age.
Leaf DescriptionOpposite leaf arrangement. Simple, narrow oblong to oblanceolate, 2.5 - 7.6 cm long, 0.6 - 1.2 cm wide. Obtuse, dark lustrous green or bluish green above, no noticeable autumn colour.
Flower Description1.91 - 2.54 cm in diameter, bright yellow, flowers late June to August, borne on auxiliary and terminal flowered cymes.
Fruit DescriptionDry, dehiscent 3 valve capsule, persistent all winter, brown, offers a good identification feature, could be used for dried arrangements.
Colour DescriptionDark lustrous green in summer, possibly considered bluish green. There is no noticeable autumn colour. Bark is light brown, flowers are clear yellow.
Texture DescriptionMedium.

Photographs