Origin and common names
Arabis platysperma Gray var. howellii (S. Wats.) Jepson, also known as Howell's rock cress, is native to the western United States. It can be found growing in many different habitats, including rocky slopes, meadows, and forests, at elevations ranging from 3,000 to 10,000 feet. This plant is named after Thomas J. Howell, an American botanist who collected specimens of this plant in the late 1800s.
General appearance
Howell's rock cress is an herbaceous perennial plant that can grow up to two feet tall. It has a woody base and produces numerous stems that are covered in small, dark green leaves. The leaves are pinnately divided and have toothed margins. The flowers are small, white, and clustered at the top of the stems. The plant blooms in the spring and attracts bees and other pollinators. The seeds of the plant are small and have a distinctive flattened shape.
Uses
Howell's rock cress is primarily used for ornamental purposes, as it is a beautiful addition to rock gardens or as a groundcover in sunny areas. It also has some medicinal value, as it has been traditionally used by Native Americans to treat various ailments such as colds, coughs, and fever.
In addition, the plant is also edible, and the leaves can be added to salads or cooked like spinach. However, as with any wild plant, it is important to be sure that you have properly identified the plant before consuming it.
Light Requirements
Arabis platysperma Gray var. howellii requires bright, direct sunlight to grow successfully. It is recommended to place the plant in an area that receives at least 6 hours of full sun per day. Without sufficient light, the plant may become leggy and weak.
Temperature Requirements
This plant is native to California and can tolerate a wide range of temperatures. However, it grows best in moderate temperatures between 60-70°F (16-21°C). During the winter months, it can tolerate temperatures as low as 20°F (-7°C), but prolonged exposure to freezing temperatures should be avoided.
Soil Requirements
Arabis platysperma Gray var. howellii grows well in well-draining, slightly acidic soils with a pH ranging from 5.5 to 6.5. The soil should also be rich in nutrients and organic matter to ensure optimal growth. It is recommended to add compost and other organic materials to the soil before planting.
Cultivation
Arabis platysperma Gray var. howellii (S. Wats.) Jepson is a low-growing perennial plant with a mat-forming habit. It thrives in well-draining soil and full sunlight. The plant is tolerant of different soil types and can grow in rocky or sandy soils, as long as there is good drainage. It is best to plant the Arabis platysperma Gray var. howellii in the spring or fall.
Watering needs
The Arabis platysperma Gray var. howellii requires moderate watering and can tolerate drought-like conditions. It is essential to water the plant thoroughly when planting to help establish its roots. After that, it is best to water the plant moderately, allowing the soil to dry out slightly before the next watering. Overwatering can lead to root rot and damage to the plant.
Fertilization
The Arabis platysperma Gray var. howellii does not require frequent fertilization. A light application of a balanced fertilizer, such as a 10-10-10, in the early spring can help encourage blooming. It is best to avoid over-fertilizing the plant, as this can lead to excessive foliage growth and reduced blooming.
Pruning
The Arabis platysperma Gray var. howellii requires minimal pruning. Deadheading the spent blooms can help prolong the flowering period and keep the plant looking tidy. It is best to prune back any dead or damaged stems in the early spring before new growth appears. If the plant becomes too leggy, cutting it back by one-third can encourage new growth and a compact habit.
Propagation of Arabis platysperma Gray var. howellii (S. Wats.) Jepson
Arabis platysperma Gray var. howellii (S. Wats.) Jepson, commonly known as Howell's rock-cress, is a low-growing perennial plant that is native to California. The plant produces beautiful white and pink flowers, making it a popular choice among gardeners. Here are the methods recommended for propagating Arabis platysperma Gray var. howellii.
Seed propagation
Seed propagation is the easiest and most effective method of propagating Arabis platysperma Gray var. howellii. The best time for sowing the seeds is in spring, when the soil is warm and moist. Choose a site that has well-draining soil and full sun exposure. Sow the seeds on the surface of the soil and cover them with a thin layer of sand or compost. Keep the soil moist but not waterlogged until the seeds germinate, which usually takes around two weeks. Once the seedlings reach a height of 3-4 inches, thin them out to avoid overcrowding and encourage healthy growth.
Cuttings propagation
Propagation through cuttings is another way to grow Arabis platysperma Gray var. howellii. Take cuttings in summer or early fall when the plant is in its active growing phase. Cut 4-6 inch long stems from the parent plant, making sure each cutting has several leaves. Remove the lower leaves and plant the cuttings in a pot filled with moist potting soil. Cover the pot with a plastic bag to create a humid environment and place it in a shaded area. Once the cuttings develop a good root system, transplant them to individual pots or to the garden.
Division propagation
Propagation through division is a useful method for rejuvenating old or overgrown Arabis platysperma Gray var. howellii plants. It is best done in early spring or fall when the plant is not in its active growing phase. Dig up the parent plant and tease apart the root ball into smaller sections, each containing a set of leaves and a small portion of the root system. Plant each section in a hole that is twice as large as its root ball and water well. Make sure to keep the soil moist until the new plants establish a healthy root system.
Disease Management
Arabis platysperma Gray var. howellii (S. Wats.) Jepson is generally a hardy plant species, but it can still be affected by several diseases. The common diseases that affect this plant species include:
- Downy mildew: It is mainly caused by the Peronospora parasitica fungus. The symptoms are yellowing and curling of leaves. Proper ventilation, good airflow, and appropriate water management (avoiding overhead watering) are some of the ways to control downy mildew.
- Powdery mildew: It is caused by the Erysiphe cichoracearum fungus. It appears as white, powdery growth on the leaves, stems, and flowers. Pruning the affected leaves, improving air circulation, avoiding overhead watering, and using sulfur-based fungicides can help control powdery mildew.
- Black Spot: It is characterized by leaf spots that are circular, with a dark-brown or black ring surrounding a lighter center. It can be caused by the fungus Alternaria brassicae. Pruning affected leaves, maintaining good air circulation, and using appropriate fungicides can help control black spot.
Pest Management
Arabis platysperma Gray var. howellii (S. Wats.) Jepson can also be affected by pests that can damage the plant's leaves, flowers, and roots. The common pests that affect this plant species include:
- Aphids: They feed on plant sap and can cause yellowing and curling of leaves. Insecticidal soap and neem oil are effective in controlling aphids.
- Spider Mites: They cause tiny yellow or white spots on leaves and can cause webbing. Pruning the affected leaves, improving air circulation, and using miticidal soap or oil can help control spider mites.
- Cabbage loopers: They feed on leaves and can cause large holes in them. Handpicking and using Bacillus thuringiensis can help control cabbage loopers.
Regularly checking the plant for signs of disease or pest infestation can help in early detection and control. Maintaining good hygiene, watering the plant properly, and providing appropriate fertilizers can help to minimize disease and pest problems.
