Origin and Common Names
Physostegia intermedia (Nutt.) Engelm. & Gray, commonly known as the slender false dragonhead, is a species of flowering plant in the mint family (Lamiaceae). It is native to North America, specifically found in the central and eastern United States and southern Canada. It can be found growing in tallgrass prairies, fields, meadows, and along stream banks and ditches.
General Appearance
The slender false dragonhead can grow up to 3 feet in height and often forms dense colonies with its rhizomatous roots. It produces numerous erect, unbranched stems that are square-shaped and covered in fine hairs. The leaves are lance-shaped, with a pointed tip, and arranged in opposite pairs along the stem. From late summer to early fall, the plant produces spikes of tubular flowers that are white, pink, or lavender in color, and surrounded by prominent leafy bracts.
Uses
Physostegia intermedia has several uses in traditional medicine. It was historically used by Native American tribes to treat various ailments, including coughs, colds, fevers, and sore throats. The plant contains several compounds that have been found to exhibit antimicrobial, anti-inflammatory, and antioxidant properties. In addition, it is often cultivated as an ornamental plant for its showy flowers and attractive foliage, and can be found in many gardens and landscapes.
Light Requirements
Physostegia intermedia thrives best in full sun. However, it can withstand partial shade and even grows as an edge plant in woodland areas. Therefore, the plant requires at least six hours of direct sunlight daily for optimal growth, development, and flowering. Although it can tolerate some shade, the enough light enables it to produce more vibrant flowers.
Temperature Requirements
Physostegia intermedia is drought tolerant and can survive in moderately dry soils. It is adapted to USDA hardiness zones 3 through 8, which means that it can handle extreme cold and hot temperatures. The ideal temperature range for the plant's growth is between 60-75°F (15-24°C). In warmer temperatures, it requires frequent watering to maintain healthy foliage and flower growth. During winter, the plant dies back to the ground, and its below-ground rhizome survives until the next growing season.
Soil Requirements
The ideal soil for Physostegia intermedia is moist, well-drained loamy soil with a pH range between 5.0 and 7.0. The plant thrives in rich soils with moderate to high fertility and adequate organic matter. Poorly drained soils or soils that are too alkaline will lead to root rot and damage to underground rhizomes. It is recommended to amend soil with compost or organic matter to improve soil structure, moisture retention, and fertility. Lastly, the plant prefers soils with good aeration and does not tolerate waterlogged conditions.
Cultivation Methods
Physostegia intermedia is a hardy perennial that can be grown from seeds or propagated from cuttings. For seed germination, sow the seeds in a well-draining soil mix and keep the soil moist until the seeds sprout. Once the seedlings have grown a few inches tall, transplant them into the garden.
For propagation through cuttings, take stem cuttings in the summer and root them in a rooting hormone and well-draining soil mix. Keep the soil moist and transplant the cuttings into the garden once they have developed new roots.
Watering Needs
Physostegia intermedia prefers moist soil, especially during its growing season. Water the plant regularly to keep the soil moist but not waterlogged. If the soil is heavy and poorly draining, reduce the frequency of watering to prevent root rot.
Fertilization
Physostegia intermedia is not a heavy feeder and can grow well in most soils. However, adding compost or well-rotted manure to the soil can improve soil fertility and enhance plant growth. You can also apply a slow-release fertilizer in the spring before new growth appears.
Pruning
Physostegia intermedia does not require frequent pruning, but you can pinch back the tips of the stems during the early growing season to promote bushier growth. Remove any dead or damaged stems in the spring or fall to encourage healthy growth and rejuvenation of the plant.
Propagation of Physostegia intermedia (Nutt.) Engelm. & Gray
Physostegia intermedia (Nutt.) Engelm. & Gray, commonly known as intermediate obedient plant, can be propagated through different methods, including seeds, cuttings, and division.
Propagation by Seeds
The seeds of Physostegia intermedia can be sown directly in the garden bed or in pots filled with potting mix. Sow the seeds in spring, covering them lightly with soil. Keep the soil moist but not waterlogged until the seeds germinate, which usually takes about 3 to 4 weeks.
Transplant the seedlings into their permanent locations once they are large enough to handle and have developed a good root system. The plants may take two to three years to flower when propagated by seeds.
Propagation by Cuttings
Take softwood cuttings of Physostegia intermedia in spring or early summer when the new growth is still tender. Cut a 4- to 6-inch stem that does not have any flowers or flower buds, and remove the lower leaves. Dip the cut end in rooting hormone and plant it in a pot filled with a moist potting mix. Place the pot in a bright but indirect light and keep the soil moist until the cutting roots, which usually takes about 2 to 3 weeks.
Transplant the rooted cuttings into individual pots and grow them until they reach an appropriate size for transplanting into the garden bed. The plants propagated by cuttings may flower in their first year.
Propagation by Division
Physostegia intermedia can also be propagated by dividing the clumps in spring or fall. Dig up the clump and use a sharp knife to cut it into several smaller sections, making sure that each section has some roots and a few shoots. Replant the sections immediately in a prepared garden bed or in individual pots, and water well.
The plants propagated by division may flower in their first year depending on the size of the divided sections.
Disease and Pest Management for Physostegia intermedia (Nutt.) Engelm. & Gray
Physostegia intermedia (Nutt.) Engelm. & Gray, commonly known as obedient plant, is a hardy perennial that is generally resistant to pests and diseases. However, under certain growing conditions, the plant may fall prey to a few diseases and pests.
Common Diseases
Rust: Rust is a fungal disease that appears as powdery brown spots on the lower leaves of the plant. To manage rust, it is important to remove and destroy infected leaves. Applying fungicides at the first sign of the disease can also help control the spread.
Leaf Spot: Leaf spot is another fungal disease that appears as brown, irregular patches on the leaves. To manage leaf spot, it is important to remove and destroy infected leaves, avoid overhead watering, and apply fungicides.
Common Pests
Aphids: Aphids are soft-bodied insects that typically feed on the underside of the leaves, causing them to curl and distort. To manage aphids, it is important to regularly inspect the plant for infestations. You can spray the plant with insecticidal soap or neem oil to control the population. Ladybugs are a natural predator of aphids and can help control the population.
Spider Mites: Spider mites are tiny insects that feed on the plant’s sap, causing the leaves to yellow and fall off. To manage spider mites, it is important to regularly inspect the plant for infestations. You can spray the plant with water to wash off mites, or use insecticidal soap or neem oil to control the population.
Slugs and Snails: Slugs and snails are common pests that feed on the plant’s leaves. To manage these pests, you can use physical barriers like copper tape around the plant’s base, handpick them in the early morning or evening, or use iron phosphate-based baits.
Overall, proper care and maintenance of Physostegia intermedia can help prevent diseases and pests. Regularly inspecting the plant for any signs of infestation and taking prompt action can also help minimize damage.
