Description:
Achillea millefolium L. var. californica (Pollard) Jepson, also known as California yarrow, is a flowering perennial herb in the Asteraceae family. It is native to California, specifically in the Sierra Nevada mountain range, as well as some other western states in the United States.
General Appearance:
The plant grows up to 1-3 feet in height, with fern-like, finely divided, and aromatic leaves. Its stems are erect and covered with fine hairs. The flowers are small, white to pale pink, and arranged in clusters on elongated, flattened-topped inflorescence. They bloom from late spring to early summer.
Common Names:
The plant is commonly known as California yarrow, western yarrow, or white yarrow. It is also known by various Native American tribes as a medicinal plant and for ceremonial purposes, including blood-staunching and wound-healing.
Uses:
Achillea millefolium L. var. californica has various uses, including as an ornamental plant in gardens, for medicinal purposes, and for erosion control.
Medicinally, the plant has been traditionally used to treat various ailments such as indigestion, menstrual disorders, skin conditions, and respiratory infections. It is also used externally as a poultice for wounds, cuts, and bruises due to its astringent and antiseptic properties.
In addition to its medicinal properties, the plant is used in erosion control measures due to its extensive root system.
Light Requirements
Achillea millefolium L. var. californica requires full sun exposure for optimal growth. The plant can tolerate some shade, but it leads to decreased growth and blooming.
Temperature Requirements
The ideal temperature range for the growth of Achillea millefolium L. var. californica is between 15°C and 22°C. The plant can tolerate some frost, but it is not suitable for extremely cold temperatures. In hot summer regions, the plant may require additional watering to prevent dehydration.
Soil Requirements
Achillea millefolium L. var. californica prefers well-draining soil, preferably with a pH range of 6.0 to 7.5. In addition, the soil should be rich in organic matter to support healthy growth. The plant can tolerate slightly acidic to slightly alkaline soils.
Cultivation methods:
Achillea millefolium L. var. californica (Pollard) Jepson requires full sun to partial shade for optimal growth and should be planted in well-draining soils. The plant is generally propagated through seeds, cuttings, or division of the root system.
Watering needs:
The plant is moderately drought-tolerant and should be watered deeply once a week, especially in dry weather conditions. It is essential to avoid overwatering as excessive moisture can cause root rot and fungal diseases. The soil should be checked for moisture content before watering, and water should be applied at the base of the plant.
Fertilization:
Achillea millefolium L. var. californica (Pollard) Jepson generally does not require fertilization, but a balanced fertilizer can be applied once a month during the growing season to promote robust growth. Organic fertilizers are preferred, and fertilizer should be applied at the base of the plant and should not come into contact with the leaves and stems.
Pruning:
Deadheading the flowers after blooming can help promote continuous flowering and prevent self-seeding. Pruning the plant to the ground is recommended in early spring to stimulate new growth and maintain the plant's overall health. Cutting back the plant by a third of its height after the first blooming can also encourage a second round of flowering.
Propagation of Achillea millefolium L. var. californica (Pollard) Jepson
There are several methods for propagating Achillea millefolium L. var. californica, including seeds, cuttings, and division.
Propagation by seeds:
Seeds of Achillea millefolium L. var. californica can be sown indoors in early spring or directly outdoors in late spring. The seeds should be sown on well-draining soil, covered lightly with soil, and kept moist until germination occurs, which usually takes 2-3 weeks.
Propagation by cuttings:
Achillea millefolium L. var. californica can also be propagated by stem cuttings taken in summer. The cuttings should be 4-5 inches long, taken from the tips of the plant, and dipped in rooting hormone before planting in a well-draining soil mixture. The cuttings should be kept moist and out of direct sunlight until roots form, which usually takes 4-6 weeks.
Propagation by division:
Another method for propagating Achillea millefolium L. var. californica is by division of established clumps in spring or fall. The clumps should be carefully dug up and divided into smaller sections, each with several roots and shoots. The new plants should be planted in well-draining soil and kept moist until established.
Disease Management
Achillea millefolium L. var. californica is susceptible to a few common fungal diseases. Powdery mildew, rust, and Septoria leaf spot are diseases that may affect this plant.
Powdery mildew appears as a white coating on the leaves, reducing the plant's ability to photosynthesize. To manage this disease, remove and destroy affected plant parts, maintain adequate space between plants, and avoid overhead watering. Fungicidal sprays may be necessary for severe infections.
Rust is a fungal disease that appears as small, yellow-orange spots on the leaves. As the disease progresses, the spots turn into rust-colored pustules. To manage rust, remove and destroy infected plant parts and provide good air circulation. Fungicides can also be used to control severe infections.
Septoria leaf spot presents as small, circular lesions on the leaves, which will eventually turn yellow and fall off the plant. The disease can weaken the plant, making it more vulnerable to other pests and diseases. Septoria leaf spot can be managed by removing and destroying affected plant parts and applying fungicides if necessary.
Pest Management
Achillea millefolium L. var. californica is relatively resistant to pests. However, some occasional visitors may cause damage to the plant.
Aphids are common pests that may colonize Achillea millefolium L. var. californica. These tiny insects can cause distorted growth, damage to leaves, and the buildup of a sticky substance called honeydew. To manage aphids, spray the plant with water to dislodge them, introduce natural predators like ladybugs, and use insecticidal soaps.
Spider mites are another pest that can attack this plant, especially in hot, dry conditions. These pests are difficult to see with the naked eye, but their damage - stunted growth and yellowed leaves - is quite apparent. Managing spider mites involves keeping the plant well-watered and maintaining good humidity levels. Insecticidal soaps and predatory mites are also effective treatment options for spider mite infestations.
Finally, snails and slugs are pests that may enjoy feasting on Achillea millefolium L. var. californica. Look for slime trails on leaves and remove any visible snails or slugs by hand. Keeping the area around the plant free of debris can also help to reduce their numbers.
