Cultivation, seed collection and propagation methods of coleus

[Aliases] Five-colored grass, foreign perilla, painted nettle.

[Family and genus] Lamiaceae, Coleus genus.

[Morphology] Tender perennial herb or subshrub, often grown as an annual. Plant height 30-50 cm, few branches, stems four-angled. Leaves opposite, rhombic-ovate, thin in texture, up to more than 15 cm long, with deep coarse teeth, long pointed, in different colors such as yellow, red and purple. Verticillasters numerous, arranged into panicles up to more than 30 cm long, flowers small, blue or light purple. Flowering in summer and autumn. Nutlets smooth, 1000-seed weight 0.15 g.

[Varieties, forms and cultivars] The main leaf colors of the varieties include green ground, with the midrib and its two sides yellow, and the rest of the leaf surface with yellow blotches; deep red, dark brown or light brown with pale yellow-green margins; rose-red ground with

yellow halo, outer side green; bright red ground with yellow halo, outer side green, etc. Curly-leaved variety (var.

verschaffeltii Lem.) leaves red-purple, plants relatively robust, more branches, leaf margins appear wrinkled and creped when viewed.

[Origin and distribution] Native to Indonesia.

[Habits] Prefers warm, sunny and moist fertile soil, minimum overwintering temperature 2-30°C, can self-sow in a cold room.

[Propagation] By sowing or cuttings. Sowing can be done indoors in pots in February-March, germinating evenly. For cuttings, after the weather turns cool in autumn, cut off the stems or upper parts of branches, trim off some leaves, about 6-8 cm long, insert into an indoor sand bed, cover with glass, maintain humidity and temperature. If using the middle two nodes of the stem, leaving some leaves on the upper node, or taking only one node with some leaves, it can also be used as a cutting. The sand bed is best slightly lower than ground level; after November, provide appropriate heating, and the rooting rate can reach 95%.

[Cultivation] After the cotyledons of sown seedlings unfold, transplant once in a flat pot, then pot into 3-inch pots. After cuttings root, pot into 4-inch pots. Use 3 parts loam, 1 part leaf mold, with an appropriate amount of sand added for the potting soil. Young seedlings should be pinched to encourage branching and form clumps; generally 5-6 inch pots can be used for growing and viewing. If you want to grow large plants, continue repotting into 8-10 inch pots, and they can be trained into a round-headed or conical shape; for the latter, the main branch must not be pinched, and bamboo stakes should be used for support. Plants kept for seed must not be placed outdoors in summer, to avoid damage from heavy rain and strong wind, and should be shaded when sunlight is intense. If used for flower beds, the 3-inch pot seedlings can be topped and then planted in the ground at a spacing of 25 cm, and inflorescences should be removed as soon as they form. (This article is excerpted from the complete book "Rural Breeding Industry")

[Seed collection] The nutlets can fall off when mature, so when most of the calyces on the inflorescence turn yellow, pick the entire inflorescence, dry it and thresh the seeds.

[Uses] An excellent potted foliage plant, it can also be used for summer and autumn flower beds; the colors are vivid and very beautiful. In addition, branches and leaves can be cut for use as cut flowers or to decorate flower baskets and wreaths.

Coleus cultivation and propagation

    Coleus is a plant of the genus Solenostemon in the Lamiaceae family, also called variegated-leaved foreign perilla and painted nettle. Coleus leaves are bright and vivid, with extremely varied leaf colors; the leaf surface may be green, red, yellow, dark red, purple, etc., and has spots of various colors such as yellow, red and purple, with different shades, appearing as irregular blotches. Most coleus currently cultivated are excellent hybrids of various colors, hence called hybrid coleus. Coleus is an excellent foliage plant, can be grown in pots for viewing, and can also be arranged in flower beds; the branches and leaves can be used as cut flower material, with relatively high ornamental value.

    Growth habits

    Coleus is native to Indonesia, likes warmth, is not cold-tolerant, and the suitable growth temperature is 20°C-25°C; it likes sufficient sunlight; it likes loose, fertile, well-drained soil; it likes moisture and dislikes waterlogging. It was originally a perennial herb or subshrub, but in most areas of China it cannot overwinter outdoors, so it is often cultivated as an annual.

    Propagation

    Because plug seedling raising saves seeds, is easy to manage, produces robust growth, has a short recovery period, a high seedling rate, a short production cycle and high seedling efficiency, in recent years coleus propagation has mostly used the plug seedling method. According to the propagation material, it can be divided into two types: plug sowing seedling raising and plug cutting seedling raising.

    Plug sowing seedling raising method

    (1) Seeds: It is advisable to choose seeds that are plump, highly vigorous and have a high germination rate. Before sowing, disinfection treatment is needed: put the seeds into warm water at 50°C-60°C and stir for 20-30 minutes. Soak in water for a period, skim off the shriveled seeds, then rinse clean with clear water, filter off the water, and air-dry for use. They can also be soaked in 40% formalin solution, 0.5% potassium permanganate solution or 0.3%-1.0% copper sulfate solution, then rinsed and air-dried before use.

    (2) Substrate: The basic requirements for the substrate are sterility, no insect eggs, no debris and no weed seeds, with good water retention and air permeability. Substrates such as peat soil, coconut coir, perlite and vermiculite can be selected; peat soil and vermiculite are commonly used, mixed at 2:1 and sieved before use. Before sowing, the seedling substrate is best disinfected once with a 600-1000 times solution of carbendazim or chlorothalonil. Note that inorganic fertilizer must never be mixed into the sowing substrate, otherwise it will cause failure to emerge or death after emergence.

    (3) Plug trays: Plug tray specifications include 288-cell, 200-cell, 128-cell and 50-cell. Because coleus seeds weigh 3300 seeds per gram and the seeds are relatively small, 288-cell or 200-cell plug trays are commonly used. If used plug trays are to be reused, they must be cleaned, disinfected and dried before use; commonly use 600 times solution carbendazim, 800-1000 times solution of fungicides such as thiophanate-methyl for washing or spraying, then rinse 2-3 times with clear water.

    (4) Sowing: First fill the cells with substrate, try to fill each cell evenly, and press gently so that the middle of the substrate is slightly lower than the surroundings. The substrate should not be filled too full; it should be slightly lower than the height of the cell so that the outline of each cell is clearly visible. The day before sowing, wet the substrate to the point of just being thoroughly watered, that is, water seeps out from the bottom of the cells. When wetting, use automatic intermittent spraying or manual repeated spraying so that water slowly penetrates the substrate. Then carefully place the seeds into the cells, 1 seed per cell, and the seed must fall in the exact center of the cell. The seeds are light-loving, so no soil covering is needed after sowing. Outdoor sowing is often carried out in March-April, while greenhouse sowing is mostly carried out in spring, summer and autumn.

    (5) Watering: After sowing, spray water promptly until water seeps out from the bottom of the plug tray. In the early stage after sowing, soil moisture can be somewhat higher to ensure the seeds absorb water and swell; later, water should not be excessive, and moist soil is sufficient.

    (6) Germination promotion: After the plug tray is moved into the greenhouse for germination promotion, the greenhouse should be properly shaded, and the interior should be kept in a state of high temperature and high humidity. Under conditions of 21°C-24°C, germination occurs in 10-14 days; when the young shoots emerge, they can be moved out of the greenhouse.

    (7) Transplanting: When the seedlings grow to the 2-4 leaf stage, they need to be transplanted once. When transplanting, dig up the seedlings with roots and transplant them into shallow pots, with a density such that the leaves do not touch each other. When the seedlings grow to 6-8 leaves, transplant them again into small pots with a diameter of 10 cm, and retain 2-4 leaves for pinching. In July, when the seedlings are larger, change pots once more, and add a small amount of soybean cake as base fertilizer at the bottom of the pot.

    Plug cutting seedling raising method

    (1) Cuttings: Choose tender branches that are free of pests and diseases, moderately mature and vigorous. At 1-0.5 cm above the leaf bud, with the cut sloping toward the bud, use a sharp knife (or scissors) to cut a branch segment containing 2 or more axillary buds and about 5-7 cm long as the cutting.

    (2) Plug tray: A plug tray 54 cm long, 28 cm wide and 5 cm high, with cell diameter 3 cm or 2 cm and depth 5 cm, can be selected.

    (3) Substrate: Choose a loose and airy substrate, such as peat and perlite (3:1), leaf mold and sawdust (1:1), or peat and garden soil (1:1).

    (4) Cutting: Greenhouse plug cutting can be carried out from March to October, and in open fields mostly from April to September. The cutting density should be such that leaves do not cover each other and do not affect photosynthesis; the cutting depth is 2 cm, and it should not be too deep, so as not to affect rooting. After cutting, place the plug tray under a shade net with 70% shading, at a temperature of 25°C-32°C, in a small environment with a gentle breeze.

    (5) Watering: After cutting, determine the watering time and frequency according to weather conditions. On sunny days, spray water onto the substrate surface every 2 hours; on cloudy or rainy days, spray less or not at all, keeping air humidity at about 90%, and be careful that the substrate does not become waterlogged. About 10 days after cutting, new roots grow; gradually reduce the frequency of spraying, and after half a month transplant or plant out and enter normal management.

    Cultivation management

    Water management. Coleus leaves are large and thin, and if the soil is too dry the leaf color tends to fade, so during the growth period attention should be paid to watering and spraying the leaf surface; especially in the high-temperature period in summer, watering and leaf-surface spraying should be combined to increase air humidity. However, the potting soil must not be too wet, otherwise the plant is prone to leggy growth, resulting in overly long internodes and affecting plant shape. Long-term waterlogging can also easily cause root rot and leaf drop. In winter, watering should be controlled, with the temperature maintained at 15°C, ensuring a suitable balance of dry and wet.

    Fertilizer management. Coleus likes fertilizer; after each pinching, apply once cake fertilizer water or human and animal manure. During the growth period, apply 1-2 times of dilute phosphorus and potassium fertilizer, which can promote short internodes, dense branches, hard stems and bright leaf color. Absolutely avoid applying excessive nitrogen fertilizer, otherwise the leaves tend to become dull.

    Light management. Coleus is a light-loving plant, and under full sun the leaf color is more vivid, so generally no shading is used; however, in summer high temperatures, direct sunlight should be avoided. High temperature and strong light will destroy pigments, cause chlorophyll to increase, and make the plant's colors less distinct or even greenish, affecting ornamental value. Therefore, in summer high temperatures appropriate shading should be provided, while in other seasons shading must not be used, because dim light makes the leaf color grayish and dark.

    Temperature management. Coleus is not strongly cold-tolerant, and the suitable growth temperature is 20°C-25°C. In winter growth is slow, and the overwintering temperature requirement is above 15°C; below 10°C the leaves turn yellow and fall off, and growth stops. If the winter temperature remains below 5°C for a long time, the aboveground stems and leaves will become water-soaked, and in severe cases the plant will die.

    Pruning and shaping. If you want to cultivate a plant with a full shape, then pinch to promote side branch growth. If you want to cultivate a tree-like plant shape, then there is no need to pinch. After inflorescences appear, if seeds are not being collected, remove them promptly to avoid consuming nutrients and affecting plant shape. For mother plants kept for seed, reduce the number of pinchings so that they complete flowering and fruiting before winter begins.

Coleus Coleus illustrated guide: how to grow coleus / how to propagate coleus