Propagating coleus is one of the easiest plants for newer gardeners to propagate. Although Coleus is grown mainly as an annual plant for use in containers and gardens in the summer, it can be overwintered as a houseplant and easily multiplied for planting outdoors the following summer. Cuttings and seeds are the most common methods of propagating Coleus and can be done without the need to buy specialist equipment.
Methods To Propagate Coleus
Soft stem cuttings are the easiest and quickest method to multiply your stock of Coleus. Take cuttings during the growing season once the plants have reached a mature size and have multiple branches. Only cuttings that do not have flower buds will successfully grow roots so make sure to nip out and deadhead your Coleus thoroughly before taking cuttings.
Growing Coleus from seed will take more time but is not any more difficult than growing tomatoes or peppers for the kitchen garden. Roughly 8-12 weeks before your last average spring frost is the perfect time to start Coleus seeds in a bright location that maintains a day and night temperature of 68-70F. (20- 21C). Transplant seedlings into individual pots or large multi-packs once the first set of true leaves appears.
Coleus show their color patterns with the first set of true leaves although the dicotyledons (first set of leaves at germination) are always solid green. Plants will be ready to harden off and plant outdoors once the nighttime temperatures are above 50F (10C).
What You Need To Propagate Coleus
For cuttings: Cuttings can be planted directly into a well-draining potting medium such as 100% perlite or all-purpose potting mix and perlite in a ratio of 1:1. Cuttings also take quite well in a vase of water. Use any smaller vase or jar that allows the stem to reach the bottom while holding the top growth well above the top of the water. Roots of the coleus will grow quickly without the use of rooting hormones.
Small plastic pots are ideal and will help keep the rooting medium moist longer than a terracotta pot. Pots that are square in shape are the best as they allow for 4 stars to be placed near the edge in the corners. Keep pots to under 4 inches in diameter as softwood cuttings do not need much rooting medium and are more likely to rot in a larger pot that retains moisture for a long period.
For seeds: Grow lights and a small heat mat are great for starting Coleus seeds and are easily found at most garden centers and home stores. A window sill with bright sun exposure and a warm room are just as good for starting seeds as long as the pots are rotated regularly to prevent the plants from stretching toward the light. Keep the seeds in a humid environment until they start to show signs of germination.
Reusable items like a roasting pan with a plastic cover make a great “greenhouse “ for starting seeds and will need to be opened once the seeds germinate so that air can circulate well around the seedling to prevent possible diseases like damping off. Coleus seeds require light to germinate and should just be pressed into the seed starting mix, not fully covered. Expect the seedlings to start showing around 10-14 days.
Best Time To Propagate Coleus
For cuttings: Softwood cuttings can be taken from Coleus throughout the summer months. Only take shoots without flower buds or blooming flowers. The cuttings can be overwintered as houseplants and then replanted outdoors the following summer. Plants that are dying back for the fall may not have stems that are healthy enough to start roots. Make sure to get any cuttings well before the chance of fall frost and seasonal dieback.
For seeds: The seed of Coleus is very tiny but easy to collect toad the end of the summer. Do not deadhead plants that you wish to save seed from. Allow the seed to develop until the flower stem is dried t ensure that the seed ripens properly. It is helpful to place a small brown paper lunch back over developing seed heads to ensure that no seed is lost. Secure the bag with twine or a zip tie making sure to not damage the flower stems.
Keep in mind that many Coleus are hybrids and hybrid plants by nature rarely come true to the parents when grown from seed. The only way to ensure genetically identical plants is to take cuttings. Store any saved seed in a cool, dark spot preferably in a paper envelope to allow the seeds to breathe. Even properly stored seeds have a finite life span. Coleus seed survives for 2-3 years.
Steps To Propagating Coleus From Cuttings
Step 1 - Take cuttings from side shoots that have not developed flower buds or bloomed and are free of pests or diseases.
Step 2 - The cutting should be 4-6 inches long and include at least 2 sets of leaves. The roots will start from these join points. Remove all side leaves with a sharp knife, except for the top couple.
Step 3 - If using water, place the cuttings in a narrow neck vase filled with water and small enough for the stem to rest on the bottom of the glass.
Step 4 - If using a potting medium, fill up a 4-inch or less plastic pot with perlite or perlite and potting mix combination that has been premoistened. Lightly pack the potting mix to firm it.
Step 5 - Take one of the cuttings and poke a small hole with a pencil, chopstick, or your finger to help ease the stem into the potting medium without causing any damage to the stem. Gently tap the pot at the bottom to settle the potting mix in around the cutting.
Step 6 - Water the pot from the bottom so as not to disturb the cutting.
Step 7 - Place a plastic bag over the top of the pot so that the cutting has plenty of room to stand up straight. This will help keep humidity around the cutting until the roots emerge.
Step 8 - Place both types of cuttings in a warm draft-free location that has filtered indirect light
Caring For Young Coleus Cuttings
Do not let the potting medium dry out before roots emerge from the cutting. Once a new leaf or two forms from the top of the cutting that is the signal that roots have formed. Remove the “greenhouse” baggie and place the cutting in a brighter location. Water regularly so that the starting medium is consistently moist but not waterlogged.
Once significant new growth forms the new plant can be up-potted to its own container. Use an all-purpose potting mix for houseplants and containers that have good drainage. Fertilize very lightly with a diluted liquid feed at ¼ the recommended strength once a month before moving your new plant outdoors for the summer.
Sources:
“How to Grow Coleus from Cuttings”, Elizabeth C. Miller Library, University of Washington. www.depts.washington.edu/hortlib
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Author Robbin Small - Published 12-27-2024 |