How to Grow Dahlia pinnata? A Detailed Guide to the Latest Cultivation Methods

Dahlia pinnata is an excellent groundcover plant, also known as dahlia and xiaolihua, etc. It is a perennial bulbous herbaceous plant of the genus Dahlia in the Asteraceae family. The plant is low-growing with a long flowering period, representing hope and longing. It can be used in flower beds, flower borders and other places, and can also be grown in pots for ornamental purposes or used as cut flowers. It has extremely high ornamental value. Let us take a look together at the cultivation methods for Dahlia pinnata!

Growth Habits of Dahlia pinnata

Dahlia pinnata likes sunlight and prefers a mild climate. The optimal growing temperature is 10-25°C. It fears both heat and cold; the tuberous roots freeze at 0°C. In areas with high summer temperatures and frequent rain, plant growth stalls and the plant enters a semi-dormant state. It is neither drought-tolerant nor waterlogging-tolerant, and dislikes heavy clay soil. After being waterlogged, the tuberous roots rot. It requires loose, fertile, well-draining sandy loam soil, and should not be planted in low-lying waterlogged areas.

Propagation Methods of Dahlia pinnata

1. Bulb division: The underground parts of Dahlia pinnata have bulbs or corms, tubers, tuberous roots, etc. After growing underground for one year, these bulbs or corms, tubers, tuberous roots, etc. will produce small bulbs around them. Simply separate these small bulbs and plant them. The operation is simple and management is convenient. Just note that when planting, do not plant the small bulbs too deep; usually the thickness of the covering soil should not exceed twice the bulb diameter.

2. Division: The best time to divide Dahlia pinnata is after the soil thaws in early spring. Remove the mother plant from the pot, shake off excess potting soil, separate the tangled root system as much as possible, and cut it into two or more plants with a sharp knife. Each divided plant must have a substantial root system, and its leaves should be properly trimmed to help it survive.

3. Cuttings: After the terminal buds, axillary buds and basal shoots of Dahlia pinnata sprout, they can all be used for cuttings to root. Basal shoot seedlings have the most vigorous growth and strong resistance to pests and diseases. Generally, in early March, plant the tubers in a pot of plain sand, keep it moist, and place it at a room temperature above 15°C to force sprouting. When the basal shoots grow 2 true leaves, snap them off from the tuberous roots, insert them into plain sand to force rooting, spray water 2-3 times a day, and roots will form in just over 20 days.

Cultivation Methods for Dahlia pinnata

1. Potting: The potting soil for Dahlia pinnata is made by mixing 5 parts garden soil, 3 parts fine sand or cinder, and 2 parts composted manure. Broken tiles should be added to the bottom of the pot as a drainage layer. Use a 10 cm pot for small seedlings. After the seedlings recover, water once with dilute cake fertilizer solution. Before the seedlings reach 20 cm in height and before flower buds appear, repot twice, adding new leaf mold each time and filling the edges of the pot.

2. Light: Dahlia pinnata likes sunlight. Sufficient light is beneficial to its growth. Ensure 6-10 hours of light per day. If kept in shade for a long time with insufficient light, growth will be poor, with few flowers and susceptibility to disease.

3. Temperature: Dahlia pinnata prefers cool conditions and fears heat. In northern China, the temperature is relatively suitable, and it will bloom from summer to autumn. In the Yangtze River basin, however, summer temperatures are high, and the plant enters a semi-dormant state. Leaf shading and water spraying to lower the temperature must be carried out.

4. Watering: Dahlia pinnata has lush branches and leaves and consumes a lot of water. If it lacks water and is exposed to strong light, the leaf edges will scorch in mild cases, or the leaves will drop in severe cases. If there is too much water, the tuberous roots rot easily, so the potting soil should be neither dry nor wet. During the flowering period and in summer, watering should be increased; in spring and autumn, less. On rainy days, prevent waterlogging by elevating the pot. Before harvesting the tubers in early autumn, water less or not at all.

5. Fertilizing: Dahlia pinnata likes fertilizer. In addition to applying sufficient base fertilizer, during the growing period except midsummer, apply 10% cake fertilizer solution every 10-15 days. After flower buds appear, apply 1-3% potassium dihydrogen phosphate to promote vivid flower colors.

6. Training: When growing a single-stem Dahlia pinnata, remove the side buds and keep the main branch. For pot cultivation, control the height. Remove all axillary buds from the base, picking them as they grow, leaving only one flower on the terminal bud. When growing a four-branch Dahlia pinnata, when the seedling is 10-15 cm tall, pinch the base leaving 2 nodes to form 4 side branches. Keep only one terminal bud on each side branch, which can produce 4 flowers.

7. Pruning: If you want Dahlia pinnata to bloom on National Day, you can do renewal pruning after flowering in early July. First twist and break the branches to be cut, leaving about 20 cm in height. After they wilt, cut them. After cutting, control water appropriately and pinch according to cultivation requirements. Generally, with careful cultivation for 2 months, it can bloom on National Day.

Pest and Disease Control for Dahlia pinnata

1. Powdery mildew

[Damage] Powdery mildew affects leaves, flower stalks and flower buds. Initially, nearly circular white powdery spots appear, which expand into mottled white powdery patches. Leaves become distorted and withered. The pathogen overwinters in diseased plant debris and spreads through airflow. The disease is severe from September to October.

[Control] In the early stage of the disease, use 2% antimycin 120 aqueous solution at 100-200 times dilution or 40% sulfur-based suspension concentrate at 800 times dilution, spraying once every 10 days for 2-3 consecutive sprays.

2. Brown spot

[Damage] After leaves are infected, pale yellow small spots first appear, then enlarge and sink, finally forming nearly circular spots with a grayish-white center and dark brown edges, with concentric rings, 1-5 mm in diameter, and a pale black moldy substance on the surface. The pathogen overwinters in diseased leaf debris. The disease is severe from June to August.

[Control] Use 1% Bordeaux mixture or 75% chlorothalonil at 600 times dilution for control.

3. Viral disease

[Damage] Shows symptoms such as mosaic, chlorosis and stunting. The viral agents include Dahlia mosaic virus, cucumber mosaic virus, tomato spotted wilt virus, tobacco streak virus, etc. Leafhoppers and aphids transmit the virus.

[Control] For control, select virus-free propagation material and control virus-transmitting insects.

4. Dahlia pinnata moth

[Damage] The larvae are pale yellow or pale red. It occurs 2-3 generations per year. The larval damage period is from June to August.

[Control] Spray 50% fenitrothion at 1000 times dilution. If the insects bore into the stems, inject omethoate at 100-200 times dilution.