Heartleaf skullcap (Scutellaria ovata) is part of the mint family. The plant gets its name because part of its bloom looks like a medieval skullcap and because it has heart-shaped leaves. It’s indigenous to North America.
I. Appearance and Characteristics
Scutellaria ovata, commonly known as the heartleaf skullcap, is a member of the mint family (Lamiaceae). Its range in the United States is from Minnesota to Florida, and from Texas to the Atlantic coast. It is also native to Mexico.
The stem of heartleaf skullcap is characterized by its distinctive green coloring and the presence of whitish hairs that give it a slightly fuzzy appearance. The square shape of the stem is notable, with each side measuring roughly 1/4 inch (0.6 cm) in width. The texture is fairly rigid, supporting a moderately dense branching pattern. These stems, with their unique combination of color and texture, are key identifiers for heartleaf skullcap.
The leaves of heartleaf skullcap are heart-shaped, reaching up to 4 inches (10 cm) in length and 3 inches (7.5 cm) in width. The margins are created to serrate, with the upper surface potentially displaying hairs while the lower surface is lighter and can have dense to sparse hairs. The petiole is characteristically hairy. These features, including the leaf shape, margin type, and presence of hairs, are crucial for identifying heartleaf skullcap.
The flowers of heartleaf skullcap are 2-lipped and lavender-colored, blooming from May to July. The upper lip of the flower is hooded, while the lower lip features a distinctive white patch. Flowers typically measure about 1 inch (2.5 cm) in length. The arrangement lends a unique, almost orchid-like appearance, making them easily recognizable. These flowers are usually found in small clusters, providing a striking contrast against the plant’s green foliage.
The fruit of heartleaf skullcap is a distinctive 2-parted capsule, readily apparent from June to September. It encases nutlets and has a unique mechanism, where the upper part detaches to release the seeds, while the scooped lower section remains attached to the plant. This functional design ensures effective seed dispersal. The fruit is small in scale and, when mature, may have a color change that signifies ripeness, aiding in identification. Textural changes can also occur, offering subtle clues for precise identification.
This species is highly variable across its range, with local races expressing distinct phenotypes. Numerous varieties and subspecies have been described, with wide variation of on what constitutes the best taxonomic treatment. In two extremes, botanist Carl Epling recognized twelve subspecies in his 1942 treatment, while T.M. Lane described S. ovata as a single polymorphic taxa with no distinguishable varieties in a 1986 publication.
A numerical analysis published in 1988 indicated that at least three subspecies showed statistically significant morphological separation. Some modern floras have recognized these three subspecies:
- S. ovata ssp. bracteata
- S. ovata ssp. ovata
- S. ovata ssp. rugosa
Scutellaria ovata has been ranked as globally “secure”, the lowest level of conservation concern. However, it becomes locally rare at the edges of its natural range. It is currently listed as threatened in Minnesota. In Michigan, it was considered “probably extirpated” until in 2007 it was found in The Nature Conservancy’s Ives Road Fen Preserve in Tecumseh, Michigan. This was the first documented occurrence of the species in Michigan since 1918.
II. How to Grow and Care
Heartleaf skullcap thrives in well-drained soils and partial shade, preferring consistent moisture without being waterlogged. Special care points include pruning to shape and encourage bushier growth, along with potential division every few years to maintain vigor. Overall, heartleaf skullcap has an easy care profile, suitable for both novice and experienced gardeners.
Sunlight
Heartleaf skullcap thrives best in full sun conditions, where it can receive at least six to eight hours of direct sunlight daily. Optimal light supports vigorous growth and enhances the plant’s ability to produce robust foliage and vibrant flowers. When subject to less than ideal light, such as partial shade, heartleaf skullcap’s growth may be less compact, and flowering could be reduced. This species is resilient and can tolerate some deviation from full sun but performs best when planted outdoors in sunny borders, rock gardens, or open areas that receive ample sunlight. Heartleaf skullcap’s leaves might exhibit slight changes in texture or coloration to reflect the intensity of light exposure.
Watering
Thriving in its native woodland settings, heartleaf skullcap is accustomed to the consistent moisture found under the canopy. This species exhibits a preference for evenly moist soil conditions and demonstrates moderate drought tolerance once established. For optimal health, heartleaf skullcap should be watered every week. Indoors, where heartleaf skullcap is often grown due to its attractive foliage, ensuring adequate humidity is key to mimic its natural environment. Particularly during the growing season, maintaining soil moisture becomes crucial to support its vigorous growth and lush leaves.
Fertilizing
For heartleaf skullcap, apply a balanced fertilizer in early spring, prioritizing slow-release formulas to support steady growth. Monthly doses during the growing season foster robust flowering while ensuring plant vigor. Less is more—avoid over-fertilization, which can harm heartleaf skullcap’s roots and natural habitat balance. As growth slows in fall, reduce feeding to prevent unnecessary stress. Practical tip: Dilute to half-strength to safeguard against nutrient burn.
Propagation
Heartleaf skullcap thrives when propagated through division, which involves carefully separating the root ball into smaller sections during its dormancy period. Ensure each new section has an adequate amount of roots and shoots for independent growth. After separating, plant these divisions in well-draining soil, maintaining consistent moisture without overwatering to encourage establishment. With attentive care, the divisions will grow into healthy, individual plants that retain the parent’s characteristics.
Transplanting
Transplant heartleaf skullcap from the thaw of winter into the promise of summer for the best root establishment. Choose dappled light locations, and for thriving growth, add compost to the soil during the transplanting process.
III. Uses and Benefits
Heartleaf skullcap is used in borders, meadows, cottage gardens, native plant gardens, open woodland areas and naturalized areas.
