How to Grow Coleus from Seed? A Detailed Guide to the Latest Planting Methods
Coleus is brightly colored, comes in a great many varieties, and is easy to propagate, making it a widely used foliage plant. Besides being displayed as a small foliage plant, it can also be used to create patterned flower beds, and can serve as foliage accents in flower baskets and bouquets.
Indoor displays are mostly small to medium potted plants; choose a cachepot that is light in color and smooth in texture to set off the gorgeous leaf colors of coleus. To keep the plant's shape beautiful, the unopened flower spikes are often cut off, and the plant is placed on a low table or windowsill for enjoyment. For courtyard cultivation it can be used in flower beds or as a plant border. Several pots of coleus can also be arranged into patterns to decorate a meeting hall or a theater lobby, creating a mass of blooms.
So how is it done? Usually seed propagation can maintain the superior traits of a variety; for those that cannot maintain their varietal traits through seed propagation, cuttings propagation is required.
1. Applicable types
Seed propagation can maintain the superior traits of a variety, and this type is suitable for the following 5 leaf-type varieties:
[Large-leaf type] Has large ovate leaves, tall plants, few branches, and an uneven leaf surface.
[Colored-leaf type] Leaves are small, oblong, with pointed tips and a smooth surface; leaf colors include red, orange-red, yellow-green, and green with white spots.
[Crisped-edge type] Leaf margins are split and wavy, with great variation in the splits and waves, and many leaf colors.
[Willow-leaf type] Leaves are slender and willow-shaped, with irregular splits and serrations along the margins.
[Yellow-green leaf type] Leaves are small and yellow-green; plants are short with many branches.
Sowing is generally done in March. Mix fully decomposed humus soil and plain sandy soil in equal halves, blend evenly, and put the mix into a seedling pot. Place the seedling pot containing fine sandy soil in water to soak thoroughly, then sow as for small seeds, cover with a thin layer of soil, cover with a glass pane or plastic film, and keep the potting soil moist. The suitable germination temperature is 25°C to 30°C, and germination occurs in about 10 days. After seedlings emerge, thin them 1 to 2 times, then prick out and pot up. The seedlings from seed vary in leaf color, so at this point you can keep the best and discard the poor ones.
2. Seed preparation
Coleus seeds are relatively expensive, so you can collect them yourself. Before flowering, select plants with bright colors to save seed. When they flower, use a brush to dip pollen and brush it onto the stigma for artificial pollination, then bag the plant with paper to isolate it and prevent hybridization and degeneration. Before flowering, apply some phosphorus and potassium fertilizer to ensure the nutrients needed for seed set, so the seeds produced are plump and have a high germination rate.
Generally, after flowering and fertilization, as long as there is sufficient sunlight and no pest or disease damage, coleus will set seed. The seeds mature one month after setting, and can be harvested plant by plant, dried in the sun, and stored for sowing the following year.
Because coleus seeds are rather small, they can be dried in their pods at harvest. Seeds collected yourself will show some degeneration and variation when sown the next year, so weak seedlings should be culled from the seedling stage to ensure the seedlings are neat and uniform.
3. Seed propagation
With a high-temperature greenhouse, pots can be sown in all four seasons; it is generally done in a greenhouse in March.
Mix fully decomposed humus soil and plain sandy soil in equal halves, blend evenly, and put the mix into a seedling pot. Place the seedling pot containing fine sandy soil in water to soak thoroughly, then sow as for small seeds, cover with a thin layer of soil, cover with a glass pane or plastic film, keep the potting soil moist, and water and tend as needed.
The suitable germination temperature is 25°C to 30°C, and germination occurs in about 10 days. After seedlings emerge, thin them 1 to 2 times, then prick out and pot up. The seedlings from seed vary in leaf color, so at this point you can keep the best and discard the poor ones.
Seed collection for seed propagation takes considerable labor, growing seedlings from seed takes a long time, and potting up is also labor-intensive, so cuttings propagation is used relatively more in production.
The sowing medium is a mix of 1 part peat soil and 1 part fine sand; just broadcast the seeds. Coleus seeds are light-loving seeds, so no soil cover is needed after sowing. The suitable germination temperature is 20-25°C; keep the substrate moist, and germination occurs in 8-10 days. Cuttings can be taken in all four seasons, rooting in about 1 week at around 20°C, and water rooting is also very easy.
When seedlings from seed grow 1 pair of true leaves, pot them up. The potting soil is 2 parts peat soil, 1 part loam, and 1 part river sand, with enough base fertilizer added. During the growing period, fertilize frequently, including topdressing with superphosphate and bone meal. Keep the temperature above 20°C. During the seedling stage, decide whether to pinch based on the cultivation goal: if you want to grow a plant with a full, bushy shape, pinch off the main stem to promote side-branch growth. If you want to grow a conical plant shape, do not pinch off the main stem.