Origin:
Polygonum douglasii Greene var. microspermum (Engelm.) Dorn, also known as Douglas' knotweed, is a herbaceous perennial plant species native to North America. The plant is commonly found growing in California, Arizona, and New Mexico in the United States as well as in Mexico.
Common Names:
Douglas’ knotweed is also commonly referred to as small-seeded knotweed due to its small and tiny seeds.
Uses:
The plant has been used for medicinal purposes as it contains tannins that have astringent properties. Traditional practitioners use it to treat bleeding gums, diarrhea, and dysentery. The plant is also used to make a yellow dye. In addition, it serves as a food source for wildlife, including small mammals and birds.
General Appearance:
Polygonum douglasii Greene var. microspermum is a low-growing plant with a spreading or tumbling growth habit. The plant can reach a height of up to 1 meter. The leaves are lance-shaped and green, and can grow up to 10 cm long. The flowers of Douglas’ knotweed are small, pinkish-white or light pink, and are borne in clusters at the end of the stems. The plant produces small seeds that are rounded and black, measuring about 1.5 mm in diameter. The root system is fibrous and shallow.
Light Requirements
Polygonum douglasii var. microspermum typically prefers full sunlight to partial shade. It can tolerate some shade but growth and flowering tend to be reduced in these conditions.
Temperature Requirements
The ideal temperature for Polygonum douglasii var. microspermum growth is between 20°C-30°C. It can tolerate extreme temperatures, such as heat waves, but cannot tolerate prolonged frost or freeze. In colder climates, plants can be grown as annuals or cultivated in greenhouses where the temperature can be carefully controlled.
Soil Requirements
Polygonum douglasii var. microspermum prefers well-drained soil. It can grow in sandy, loamy, or clay soils. The plant requires a soil pH between 6.0 to 7.5 and does not tolerate alkaline soils. Fertile soils that are rich in organic matter are best for growth and flowering.
Cultivation of Polygonum douglasii Greene var. microspermum
Polygonum douglasii Greene var. microspermum is quite hardy and can be grown in various types of soil. However, it thrives best in well-draining soils that are rich in organic matter. Planting should be done in fall or early spring, depending on the climate of the area.
The seeds or cuttings should be planted at a depth of 1 to 2 cm, about 15 to 30 cm apart. The plant needs full sunlight and can tolerate partly shaded conditions, especially in hotter regions. Be sure to keep weeds away as they compete for nutrients and water and stunt the plant's growth.
Watering Requirements of Polygonum douglasii Greene var. microspermum
Polygonum douglasii Greene var. microspermum requires moderate watering and can withstand drought conditions. However, the plant should be watered frequently during the initial growing period to encourage root growth.
Once the plant is established, it does not need much watering, except during prolonged droughts. Plants grown in pots should be watered more frequently than those grown in the ground as they tend to dry out much faster.
Fertilization of Polygonum douglasii Greene var. microspermum
Polygonum douglasii Greene var. microspermum does not need a lot of fertilization. Adding compost or well-rotted manure during planting or once every year provides enough nutrients for the plant. The organic matter also helps to improve soil quality and drainage.
It is recommended to avoid excessive use of chemical fertilizers as they can harm the plant and alter the soil's pH level. In case of any deficiencies, you can apply a balanced fertilizer at half-strength.
Pruning Polygonum douglasii Greene var. microspermum
Polygonum douglasii Greene var. microspermum requires minimal pruning. It is mainly done to remove dead, damaged, or diseased leaves, stems, or branches. Pruning is also performed to control the plant's size and shape or to rejuvenate older plants.
The best time to prune this plant is in late winter or early spring, before new leaves emerge. You can use clean and sharp pruning tools to make clean cuts and avoid tearing the plant's tissue. Remember to remove any debris or pruning waste to avoid attracting pests or diseases.
Propagation of Polygonum douglasii Greene var. microspermum (Engelm.) Dorn
Polygonum douglasii Greene var. microspermum (Engelm.) Dorn, commonly known as the small-seeded knotweed, is a herbaceous perennial plant that belongs to the family Polygonaceae. Propagation of this plant can be carried out using either seeds or cuttings.
Propagation by seeds
The propagation of Polygonum douglasii Greene var. microspermum (Engelm.) Dorn using seeds involves the collection of mature seeds from the parent plant, which should be done in the fall. The collected seeds should be sown in a well-draining soil mix in the spring after the danger of frost has passed. The soil should be kept moist, and the seedlings should be kept under partial shade until they are well established.
Propagation by cuttings
Propagation of Polygonum douglasii Greene var. microspermum (Engelm.) Dorn can also be done using stem cuttings. To carry out this method, the stems should be cut from the parent plant in the spring or early summer. The cuttings should be around 5 to 6 inches long and should be taken from healthy and mature stems. Afterward, the lower leaves should be removed, and the cuttings should be dipped in rooting hormone before being planted in a well-draining soil mix. The cuttings should be kept moist and under partial shade until new roots and growth appear.
Disease Management
Polygonum douglasii Greene var. microspermum is susceptible to a few diseases that can affect its growth and productivity. The common diseases that might affect the plant include powdery mildew, rust, and root rot.
Powdery mildew is caused by fungal infection and appears as a white powdery substance on the surface of leaves, stems, and flowers. Rust is caused by fungal infection too and appears as yellow or brownish pustules on the undersides of leaves.
Root rot is caused by soil-borne fungi that attack roots and damage the root system, thus affecting the plant's ability to absorb nutrients and water. To manage these diseases, you can incorporate cultural, biological, and chemical control measures. Cultural controls include planting healthy plants in well-draining soils, avoiding overhead irrigation, and removing infected debris from the garden.
Biological control involves introducing natural predators into the garden to feed on the pests that cause these diseases. For example, introducing lacewings can help control aphids, which spread powdery mildew. Likewise, introducing ladybugs can help control whiteflies, another common pest that leads to these diseases.
Chemical control involves using pesticides and fungicides to kill the pests and diseases. However, the use of pesticides and fungicides should be the last resort and must be done according to the manufacturer's instructions.
Pest Management
Polygonum douglasii Greene var. microspermum is susceptible to a few pests that can cause significant damage to the plant. The common pests that might affect the plant include aphids, whiteflies, and spider mites.
Aphids are tiny insects that suck the sap from the plant's leaves, making them curly and distorted. Whiteflies are another tiny insect that sucks the sap from the plant's leaves and secretes a sticky substance that attracts ants. Spider mites are tiny arachnids that feed on the plant's leaves, leaving behind yellowed and stippled leaves.
To manage these pests, you can use cultural, biological, and chemical control measures. Cultural controls include removing infected plant debris, avoiding over-fertilization, and keeping the plant healthy and well-watered.
Biological control involves introducing natural enemies of the pests into the garden. For example, introducing ladybugs, lacewings, and parasitic wasps can help control these pests.
Chemical control involves using pesticides and insecticides to kill the pests. However, the use of pesticides should be the last resort and must be done according to the manufacturer's instructions.
