Overview
Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz, also known as hoary cress or whitetop, is a perennial herbaceous plant from the Brassicaceae family. It is native to Europe and Asia and has been introduced to other parts of the world, including North America, where it is considered a noxious weed.
Appearance
The plant can grow up to one meter tall and has a shallow, fibrous root system. It has round, white to grayish-green leaves that are hairy and toothed. The inflorescence is a dense cluster of small white flowers on top of a tall, erect stem. The seeds are small, flattened, and dispersed by wind, water, or animals.
Uses
Cardaria draba has been used in traditional medicine for various purposes, including treating indigestion, coughs, and skin rashes. However, it is not recommended to consume this plant due to its potentially toxic compounds. The plant is also used as a forage crop for livestock, but its low nutritional value and bitter taste make it less desirable than other forage options. In some areas, the plant is considered a valuable source of nectar for bees.
Invasion and Control
Cardaria draba is considered an invasive species in many regions, including North America, where it has become a significant problem. It outcompetes native plants for resources, reduces biodiversity, and can even alter soil chemistry. Biological control agents, such as insects and fungal pathogens, have been introduced to control the plant's spread, but the effectiveness of these methods varies depending on the specific region and environmental conditions. Other methods of control include physical removal, herbicides, and prevention of seed production.
Overall, Cardaria draba is a highly adaptable plant that can thrive in a variety of conditions, making it a challenging invasive species to control.Light Requirements
Cardaria draba ssp. chalapensis is a plant that can tolerate a wide range of light conditions. It can grow in full sun or partial shade. However, it does not do well in complete shade, as the lack of light can inhibit its growth and development.
Temperature Requirements
This plant is native to regions with a Mediterranean climate, which means it prefers mild temperatures. The ideal temperature range for Cardaria draba ssp. chalapensis is between 15-25°C (59-77°F). However, it can tolerate temperatures as low as -9°C (16°F) and as high as 40°C (104°F) for short periods of time.
Soil Requirements
Cardaria draba ssp. chalapensis is a plant that can grow in a variety of soil types. It can tolerate both sandy and clay soils, but it prefers well-draining soils that are rich in organic matter. The pH range for optimal growth is between 6.0-8.0. While this plant can tolerate drought conditions, it does better with consistent soil moisture.
Cultivation
Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz is a hardy plant that thrives well in a wide range of soils, including clay and loamy soils. It tolerates both acidic and alkaline soils and can grow in moderate saline conditions. The plant can be grown from seeds, but it is best propagated by root cuttings taken from the parent plant during the dormant season. The cuttings should be planted in the late fall or early spring after the last frost has passed.
Watering Needs
The plant requires moderate watering, and care should be taken not to overwater it. Overwatering can lead to root rot, which can eventually kill the plant. The frequency of watering can be reduced during the winter months, when the plant goes dormant. It is advisable to water the plant at the base to prevent wetting the foliage, which can cause fungal diseases.
Fertilization
Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz does not require excessive fertilization. A slow-release, balanced fertilizer can be applied in the spring to encourage healthy growth. Organic fertilizers, such as compost and well-rotted manure, can also be used to improve the soil structure and provide essential nutrients.
Pruning
Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz does not require regular pruning. However, pruning can be done to control its size and shape at the beginning of the growing season. Deadheading can also be done to prevent the plant from producing seeds, which can lead to self-seeding and invasion of neighboring areas. When pruning, it is advisable to use clean, sharp tools to prevent the spread of diseases.
Propagation of Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz
Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz can be propagated through different methods depending on the needs of the grower. Here are some of the most common propagation methods used with this plant:
Seed propagation
The easiest method of propagation for Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz is through seeds. Seeds can be collected from the plants during the Fall season after the flowering and seed set periods have ended. The seeds must be air-dried and then stored in a cool and dry place until planting. During the Spring season, the seeds can be directly planted into the soil or started indoors using trays. Seeds require good soil moisture and warmth to germinate, usually taking about 7 to 10 days. Once the seedlings have grown their first true leaves, they can be transplanted into individual pots.
Vegetative propagation
Another method of propagation for Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz is through vegetative propagation. This method involves taking cuttings from a mature plant and rooting them in water or soil. After selecting the ideal plant, new shoots or stems can be cut, leaving at least a node on the stem. The cuttings should be about 4-6 inches in length. They should be planted into a potting mix that is well-draining, lightly watered, and kept in a warm and humid location. The cuttings can root in approximately 4 to 6 weeks, after which time they can be transplanted into individual pots or into the ground outside.
Division
If you already have Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz growing, then propagating by division is an excellent method. This method entails dividing the mature plant into sections and planting them into individual pots or directly into the ground. Use a sharp, sterilized tool to divide the plant carefully. Make sure each piece has several roots and leaves. Once the sections are separated, they can be planted in rich and well-draining soil and watered regularly. Division should be carried out during the Spring or early-Fall seasons.
Disease Management
Several diseases can affect Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz, including:
- Blackleg caused by the bacterium Xanthomonas campestris can cause wilting and stem rot of the plant. Infected plants should be removed immediately and destroyed to prevent the disease from spreading. Crop rotation, sanitation, and using disease-resistant cultivars can help prevent the disease.
- Clubroot caused by the soil-borne fungus Plasmodiophora brassicae can result in stunted growth, yellowing, and wilting of the plant. Infected areas should be removed, and the soil should be disinfected before planting. Liming the soil can be helpful in preventing clubroot.
- Downy mildew caused by the oomycete Peronospora cardariae can result in yellowing and death of the plant. To manage downy mildew, proper spacing of plants, avoiding overhead irrigation and maintaining good air circulation can be helpful. Fungicides may also be applied.
Pest Management
Several pests can affect Cardaria draba (L.) Desv. ssp. chalapensis (L.) O.E. Schulz, including:
- Aphids can suck the sap from the plant and cause wilting and stunted growth. Natural predators, such as ladybugs and lacewings, can be introduced to control aphids. Insecticidal soap and neem oil can also be effective.
- Cabbage loopers and cabbage worms can feed on the foliage and cause severe defoliation. Handpicking can be effective for small infestations. Bacillus thuringiensis (Bt) is a microbial insecticide effective against caterpillars.
- Root maggots can damage the roots and kill the plant. Crop rotation, keeping the soil free of debris, and using floating row covers can aid in controlling root maggots.
