Origin
Silphium laciniatum L. var. robinsonii Perry, commonly known as the Compass plant, is a perennial herb that is native to the central part of North America.
Common Names
The plant is commonly referred to as Compass plant due to the tendency of its basal leaves to align themselves north-south. Other common names include Coulter's compass plant, Rosinweed, and Polar plant.
Uses
The plant has been traditionally used for medicinal purposes, particularly by Native Americans. It was used to treat a variety of ailments such as respiratory infections, coughs, and fevers. The plant has also been used for its diuretic and laxative properties, and it was believed to help increase urine flow. Nowadays, Silphium laciniatum is considered to be an important forage crop for livestock as it provides a good source of high-quality forage.
General Appearance
Silphium laciniatum L. var. robinsonii Perry is a tall, upright plant that can grow up to 10 feet tall. Its leaves are large, reaching up to 2 feet in length, and deeply lobed, with the lobes, or teeth, pointing towards the base of the leaf. The plant has small yellow flowers that bloom in the summer and typically grow in clusters at the top of the stem. The stem of the Compass plant is covered with fine hairs and is generally smooth. The plant is well adapted to survive in harsh environments, such as prairies, and can tolerate drought and periodic fires.
Light Requirements
Silphium laciniatum L. var. robinsonii Perry requires full sun exposure for optimal growth. It needs at least 6 hours of direct sunlight per day. The plant can tolerate some shade, but it may not flower as prolifically.
Temperature Requirements
The plant thrives in warm temperatures with mild to moderate humidity. It can withstand cold temperatures if the soil is well-draining. Silphium laciniatum L. var. robinsonii Perry grows best in hardiness zones 5 to 9, where the average temperature ranges from 18 to 29 degrees Celsius.
Soil Requirements
The plant prefers well-drained, fertile soil with a pH range from 5.5 to 7.5. It can tolerate slightly acidic or alkaline soil conditions. The soil should be rich in organic matter and have good moisture retention capacity. Silphium laciniatum L. var. robinsonii Perry can grow in clay, loam, or sandy soil types.
Cultivation Methods
Silphium laciniatum L. var. robinsonii Perry can be grown from seeds. It is recommended to sow them directly in the garden where they are to be grown in spring when the soil temperature reaches at least 60°F. The site for planting should be well-drained and exposed to full sun. It is important to space the seeds 18-24 inches apart, cover them with 1/4-inch soil, and water them thoroughly.
Watering Needs
It is essential to keep the soil consistently moist during the germination period. After the plants are established, they can tolerate some drought, but it is still necessary to provide them with regular watering during prolonged dry periods. The frequency of watering depends on the soil type, climate, and plant size. It is recommended to apply water directly to the roots rather than overhead to avoid wetting the foliage.
Fertilization
Silphium laciniatum L. var. robinsonii Perry is a native plant that grows well in poor soil. However, if you want to boost its growth and blooming, you can apply a balanced fertilizer in early spring. Use a slow-release granular fertilizer, following the manufacturer's instructions. Avoid overfeeding the plant, as excessive nitrogen can promote vegetative growth at the expense of flowering.
Pruning
Silphium laciniatum L. var. robinsonii Perry does not require extensive pruning. However, you can deadhead the faded flowers to encourage the plant to produce more blooms. You can also cut back the stems by half in the fall or early spring to promote bushier growth and prevent the plant from becoming too leggy. If the plant becomes too large or unsightly, you can also cut it back to 6 inches above the ground in early spring. The plant will resprout from the roots and produce new growth.
Propagation of Silphium laciniatum L. var. robinsonii Perry
Propagation of Silphium laciniatum L. var. robinsonii Perry can be done through seeds or root cuttings.
Propagation with Seeds
The most common method of propagating Silphium laciniatum L. var. robinsonii Perry is through seeds. The best time to collect the seeds is in the fall, once the seeds have matured and turned brown.
To plant the seeds, scarification is necessary to break the seed coat and allow water to penetrate. Soak the seeds in water overnight or use a file or sandpaper to slightly nick the seed coat before planting.
The seeds should be planted in loose, well-draining soil about ¼ inch deep and kept moist until germination, which should occur within a few weeks. Once the seedlings have established their second set of leaves, they can be transplanted into larger containers or directly into the garden.
Propagation with Root Cuttings
Propagation of Silphium laciniatum L. var. robinsonii Perry can also be done using root cuttings. This method is best done in the late fall or winter when the plant is dormant.
Choose a healthy plant with strong roots and dig it up carefully. Cut several sections of the root, each about 2-3 inches long. Make sure the cutting has a few buds on it.
Plant the cuttings in a suitable rooting medium, such as coarse sand or vermiculite. Make sure the cuttings are vertical and barely buried. Keep them moist but not overly wet and place the container in a cool, dimly lit location. After about four to six weeks, the cuttings should start to develop new growth. Once they have established a strong root system, they can be transplanted into larger containers or directly into the garden.
Disease and Pest Management for Silphium laciniatum L. var. robinsonii Perry
Silphium laciniatum L. var. robinsonii Perry, commonly known as the compass plant, is a native perennial forb that is drought-tolerant, easy to establish, and provides important habitat for wildlife, especially in prairie ecosystems. While Silphium laciniatum L. var. robinsonii Perry is relatively pest and disease-resistant, there are some potential problems to be aware of.
Common Diseases
Fungal Leaf Spot: One common disease that can affect Silphium laciniatum L. var. robinsonii Perry is fungal leaf spot, which can cause circular or irregular brown spots on leaves, and if left untreated, the leaves can turn yellow and fall off. The best way to manage fungal leaf spot is to remove infected leaves and dispose of them. Avoiding overhead watering, improving air circulation, and keeping the area around the plant clean can also help prevent the spread of fungal leaf spot.
Rust: Rust is another fungal disease that can affect Silphium laciniatum L. var. robinsonii Perry, causing small yellow spots that turn into small red pustules on the undersides of leaves. Severe rust infestations can cause the leaves to yellow and fall off. Treating rust can be challenging, as fungicides may not be effective. However, removing infected leaves and maintaining proper plant hygiene can help prevent the spread of rust.
Common Pests
Aphids: Silphium laciniatum L. var. robinsonii Perry can also be affected by aphids, soft-bodied insects that suck sap from the plant and can cause stunted growth and curling leaves. To manage aphids, regularly inspect the plant and remove any aphids by hand or using a strong jet of water to dislodge them. Insecticidal soaps or neem oil can also be effective.
Spider Mites: Spider mites are another pest that can affect Silphium laciniatum L. var. robinsonii Perry, particularly in hot and dry conditions. These tiny arachnids live on the undersides of leaves and can cause yellowing and stippling of the leaves, as well as webbing. Spraying the plant with a strong jet of water, regularly misting the foliage, and introducing natural predators like ladybugs can help control spider mites.
While Silphium laciniatum L. var. robinsonii Perry is relatively resistant to pests and diseases, it is important to monitor the plant regularly and take action if any problems arise. By practicing good plant hygiene, including removing infected leaves and maintaining proper watering and fertilization practices, gardeners can help prevent many common issues.
