Overview: Physostegia virginiana (L.) Benth.
Physostegia virginiana (L.) Benth., commonly known as obedient plant or false dragonhead, is a perennial herbaceous plant belonging to the mint family (Lamiaceae). The plant is native to the eastern and central regions of North America, but has been introduced to other parts of the world as an ornamental plant for its attractive, showy flowers.
General Appearance:
The plant typically grows to a height of 2-4 feet and spreads up to 3 feet wide, forming a clump of leaves on erect stems. The leaves are lance-shaped, with serrated margins, and grow alternately along the stem. The flowers are arranged in dense spikes at the end of each stem and appear in mid to late summer. Each flower is tubular, about 1 inch long, and has 5 petal-like lobes that are pink, white, or lavender in color.
Common Names:
The plant is commonly known by several names, including obedient plant, false dragonhead, and lion's heart. The name "obedient plant" comes from the unique characteristic of the flowers, which can be bent and will remain in the position they are placed, hence giving the perception of being obedient.
Uses:
The plant has several uses, including medicinal and ornamental purposes. The root of the plant was historically used in traditional medicine to treat various ailments such as headaches, fever, and rheumatism. The plant is also popularly grown in gardens as an ornamental plant due to its attractive flowers. The obedient plant is drought-tolerant and attracts pollinators such as bees and butterflies, making it an excellent choice for gardens and landscapes.
Light Requirements
Physostegia virginiana requires full to partial sunlight. The plant needs at least 6 hours of direct sunlight. In shaded areas, the plant may grow, but the flowering is not as abundant as in full sunlight. Hence, it is recommended to plant the Physostegia virginiana in areas that receive full sunlight for most of the day.
Temperature Requirements
The optimum temperature range for the growth of Physostegia virginiana is between 18°C and 30°C. If the temperature falls below 15°C, the growth rate of the plant may decrease, and the leaves may turn yellow. On the other hand, the plant may not survive if the temperature goes above 35°C. Hence, it is important to maintain an optimum temperature range throughout the growth period of the plant.
Soil Requirements
Physostegia virginiana thrives in well-drained soils that are rich in organic matter. The plant prefers loamy soils that are slightly acidic to neutral with pH ranging from 6.0 to 7.5. The soil should be moist but not waterlogged. The plant may tolerate short periods of drought, but excessive dryness can affect its growth and flowering. Therefore, it is advisable to water the plant regularly, especially during the hot and dry seasons.
Cultivation methods
Physostegia virginiana, also known as obedient plant, is a herbaceous perennial that can thrive in most garden soils. It can be grown from both seeds and root cuttings. To grow from seed, plant in the early spring in well-draining soil and keep the soil consistently moist until germination occurs. Root cuttings should be taken in the fall and planted 1-2 inches deep in the soil.
Watering needs
Physostegia virginiana prefers consistently moist soil, so irrigation may be necessary during dry spells. However, be careful not to overwater as this can lead to root rot. It is best to water deeply once a week rather than several shallow waterings throughout the week.
Fertilization
Fertilize obedient plant in the early spring with a balanced fertilizer, following the instructions on the package. Fertilization can be repeated in mid-summer, but be careful not to over-fertilize as this can lead to excessive vegetative growth at the expense of flowers.
Pruning
Physostegia virginiana can become leggy and flop over without adequate support. Pruning can help to maintain a compact form and promote bushier growth. In the early spring, cut back the stems to 6-8 inches above the ground. Pinching back the growing tips in early summer can also help to encourage branching and a fuller plant.
Propagation of Physostegia virginiana
Physostegia virginiana (L.) Benth can be propagated through different methods such as seeds, division, and stem cutting.
Seed Propagation
The easiest and most common method of propagation is by seed. The seeds can be sown indoors or outdoors, depending on the preferences of the grower. If sowing outdoors, the seeds should be sown during the fall, as they require a period of cold stratification to break their dormancy. Indoors, the seeds should be sown in a seed tray and kept in a warm place of around 70°F (21°C). The seeds should be kept moist until they germinate.
Division Propagation
Division is a straightforward method of propagation. The plant can be dug up and divided into smaller sections using a sharp spade or knife. Each section should have a few stems and roots. The divided plants should be replanted in their original soil or a new one, and they will establish new roots within a few weeks.
Stem Cutting Propagation
Propagation by stem cutting is a more reliable method of producing plants that are genetically identical to their parent plants. The cuttings can be taken during the growing season, usually in the summer. A stem tip of about 4-6 inches long can be cut off. The bottom leaves should be stripped off, and the stem should be dipped into a rooting hormone before being placed in a potting mix or soil. The cutting should be kept moist and warm, and in a few weeks, roots will start to form.
Disease Management for Physostegia virginiana (L.) Benth.
The plant Physostegia virginiana (L.) Benth. is susceptible to a number of diseases that can cause significant damage to the plant. Some common diseases that affect this plant are:
- Anthracnose: This disease is caused by fungal pathogens and can cause symptoms such as leaf spots, stem cankers, and blight. To manage anthracnose, it is recommended to remove and destroy infected plant material and ensure the plant is not stressed due to environmental factors such as drought or over-fertilization.
- Root Rots: Root rot is caused by fungi that typically thrive in wet soil conditions. Symptoms include yellowing leaves, wilting, stunted growth, and eventual death. To manage root rots, it is important to ensure proper drainage and avoid over-watering or watering the leaves of the plant. Additionally, improving soil quality and using fungicides can help manage this disease.
- Powdery mildew: Powdery mildew is caused by a fungus that commonly appears as a white or grayish coating on the leaves, stems, and flowers of plants. It can cause decreased photosynthesis, stunted growth and wilted leaves. To manage powdery mildew, it is recommended to remove and destroy infected plant material and use a fungicide if necessary, making sure not to overspray as it can lead to the harm the plant.
Pest Management for Physostegia virginiana (L.) Benth.
Physostegia virginiana (L.) Benth. is also susceptible to pests that can cause significant damage to the plant. Some common pests that affect this plant are:
- Aphids: Aphids are tiny insects that feed on the sap of the plant by piercing it with their mouthparts. This can cause yellowing of the leaves, curling and eventual defoliation. To manage aphids, it is recommended to use insecticidal soap or insecticides that are safe for this plant. Also, maintaining proper hygiene practices and cultivation of predator insects such as ladybugs can help manage aphids.
- Spider Mites: Spider mites are also tiny insects but instead of feeding sap, they scrape and feed off the surface of the leaves which cause light speckling, yellowing, and eventually leaf loss. To manage spider mites, it is recommended to mist plants regularly along with using insecticides or miticides that are safe for this plant. Drought or water-stressed plants attract spider mites, ensuring moist soil can help manage this pest.
- Japanese Beetle: Japanese beetles are a pest that can severely damage this plant as they eat various parts of the plant, risking defoliation and death. To manage Japanese beetles, it is recommended to use insecticides that are safe for this plant and destroy any found beetles. Cultivating plants such as geraniums and tansy that repel Japanese beetles can help manage this pest.
