Origin
Descurainia obtusa (Greene) O.E. Schulz ssp. obtusa is a herbaceous, perennial plant native to western North America, ranging from Alaska to California, and east to Colorado and New Mexico.
Common names
Descurainia obtusa is commonly known as blunt-fruited dwarf agoseris, blunt-fruit tansymustard, or blunt-fruited tansy mustard.
Uses
Descurainia obtusa has been traditionally used by Native Americans as a medicinal plant for treating respiratory ailments. The entire plant can be used as an expectorant, or the leaves can be chewed to alleviate sore throats and coughs. The plant also has antibacterial properties, making it useful in wound care. In addition to its medicinal value, Descurainia obtusa is occasionally used for erosion control in restoration projects.
General appearance
Descurainia obtusa is a low-growing plant with a woody base and slender stems, typically less than 30 cm tall. The leaves are deeply lobed and smooth, ranging from 1-4 cm in length. The small, pale yellow flowers bloom in late spring to early summer and are clustered in a terminal raceme. The fruits are small, round, and flattened, measuring less than 3 mm wide. The plant has a distinctive pungent odor and grows in dry, rocky soils in the open areas of foothills and mountain slopes.
Light Requirements
Descurainia obtusa generally require full sun exposure for healthy growth. The plant can also tolerate partial shade but in such cases, it may lead to elongated stems and reduced bushiness. Therefore, it is advisable to have the plant in an area that receives full sunlight which should last for at least six hours daily.
Temperature Requirements
Descurainia obtusa grows well in a wide range of temperatures. However, the ideal temperature range for growth is between 15°C to 25°C. The plant can survive in temperatures higher or lower than this but might either grow slower or exhibit slower growth or die if the temperature is too extreme.
Soil Requirements
The plant is generally adaptable to different soil types. However, for optimal growth, the soil should have proper drainage and high fertility. The soil should contain a high percentage of organic matter and should have a pH range of 6.5 to 7.5. Additionally, it is essential to ensure that the soil does not become waterlogged since this can lead to root rot and eventual death of the plant.
Cultivation Methods
Descurainia obtusa is a cold-season annual or biennial and usually grows to be around 30 cm high. It prefers full sunlight or partial shade and can tolerate almost any soil, as long as it is well-draining. This plant is often grown from seed, and the best time to plant is in the spring or early fall in moderate climates.
Watering Needs
Descurainia obtusa requires moderate watering, and it is crucial not to allow the soil to become too wet or too dry. Plants that have been established can usually tolerate some drought, but young plants require frequent watering to help establish a strong root system. It is important not to soak the soil since this can cause root rot and other diseases.
Fertilization
Descurainia obtusa requires a minimal amount of fertilization. Overfertilizing can lead to bushy and weak growth and is strongly discouraged. Prior to planting, incorporating some well-decomposed organic matter, such as compost or manure, can improve soil fertility and reduce the need for additional fertilizer.
Pruning
Descurainia obtusa doesn’t require pruning, but it is good to remove dead or diseased leaves when necessary. Since it is a small plant, it also doesn’t require staking. As the plant reaches maturity, it ultimately sets seeds and dies every year.
Propagation of Descurainia Obtusa
Descurainia obtusa, commonly known as blunt-fruited Lepidium or bluntpodded pepperweed, is a wild flowering plant native to North America. Having a low maintenance and drought-tolerant nature, it is an ideal choice for gardening enthusiasts.
Seed Propagation
The most common method of propagating Descurainia obtusa is through seeds. Seeds can be collected from the plant's matured pods during the fall season. These seeds should be thoroughly cleaned and stored in a cool, dry place until they are ready for planting.
After three months of stratification in moist soil, the seeds can be sown in flats or directly in the ground. The ideal temperature for germination is 20-25°C, and the seedlings should receive partial sunlight. Transplanting should be done when the seedlings reach a height of 5-7 cm.
Cuttings Propagation
Descurainia obtusa is a plant that can be propagated by cuttings. Stem cuttings are the preferred method of propagation. To propagate through cuttings, a 10 cm long stem cutting with 2-3 nodes is selected and treated with rooting hormones before planting.
The cutting should be planted in a well-draining medium and kept moist until the roots develop. The cutting should be kept in a shady area until the roots develop and then gradually exposed to sunlight to prevent scorching.
Disease Management
Descurainia obtusa is typically resistant to most plant diseases. However, given the right environmental conditions, some diseases may still develop and cause problems for the plant. Here are a few common diseases that may affect Descurainia obtusa and suggestions on how to manage them:
Fungal Leaf Spot
If the plant is infected with fungal leaf spot, you may notice small brown spots with yellow halos on the leaves. To manage this disease, keep the plants well-ventilated and avoid overhead watering. Apply a copper-based fungicide at the first sign of infection.
Black Stem Rot
Black stem rot causes wilting and death of the plants. The disease is caused by the fungus Leptosphaeria maculans. To manage this disease, practice crop rotation and avoid planting Descurainia obtusa in areas where cruciferous crops have been grown in the past. Remove infected plants immediately and destroy them.
Virus Diseases
Descurainia obtusa is susceptible to several virus diseases, including turnip mosaic virus and cauliflower mosaic virus. Symptoms of virus infection include stunted growth, leaf curling, yellowing, and mosaic patterns on the leaves. There are no cures for virus diseases. To manage virus diseases, use disease-free seeds, maintain good sanitation practices, and control insect vectors.
Pest Management
Descurainia obtusa typically attracts a variety of insect pests. Here are some pest management strategies to consider:
Black Cutworm
The black cutworm is a common pest that feeds on the leaves and stems of Descurainia obtusa. To control this pest, handpick and destroy the cutworms and their eggs. Use a bacterial insecticide, such as Bacillus thuringiensis, to control heavy infestations.
Cabbage Looper
The cabbage looper is a caterpillar that feeds on the leaves of Descurainia obtusa. The insect can be identified by its looping, inchworm-like movement. To manage this pest, use row covers to exclude the cabbage loopers from the plants. Handpick and remove any visible loopers and destroy them.
Aphids
Aphids are small, soft-bodied insects that suck the sap from the leaves and stems of Descurainia obtusa. They excrete a sugary substance that attracts ants and causes a black, sooty mold to grow on the leaves. To manage aphids, use a strong stream of water to wash them off the plants. Use insecticidal soap or neem oil to control heavy infestations.
