Coleus

Coleus have been something of the star of this summer’s garden.

Maybe I’ve just been oblivious to the charms of the coleus. Over the years, I’ve seen the occasional coleus here or there, perched upon a shelf amidst a collection of houseplants, or placed as a potted accent along a front walk. This summer however, I’ve seen multiple elaborate coleus displays.

At the recent Buffalo Garden Walk, one homeowner had transformed their driveway into an outdoor living space by placing multiple potted plants, including coleus in 4 foot high clusters that formed the backdrop for walkways and seating areas. (I wish I took more pictures!)

Alone, the colour and patterning of a single coleus plant’s leaves are eye catching. What makes coleus really shine is when drastically different varieties are placed within close proximity to each other. Even with the drastic contrasts in colour between individual plants, their similar tonalities unify the arrangement and create something really striking.

Patience is a virtue they say, but why wait until next spring to start adding a pop of colour to your home! They’re easy to grow and it’s a delight to see the brilliant neon colours emerge.

Growing Coleus from Seed

Timing:
If you’re looking to place your coleus outside, start your seeds indoors 8 to 12 weeks before the last expected spring frost. Otherwise, start your seeds anytime.

Soil Prep:
Fill a seed tray with a lightweight, pre-moistened seed-starting mix.

Sowing:
Press the tiny seeds gently onto the soil surface. Do not cover them, as they require direct light to germinate.

Moisture:
Mist the tray lightly with water. Cover it with a clear plastic dome or wrap to lock in humidity. Keep the soil slightly moist, but not too damp or the roots may rot.

Light:
Move the sprouts to a bright windowsill or put them under grow lights for 12 to 16 hours daily. The colors of the plants vary greatly depending on how much light they receive. Leaves developed during the winter may be paler in colour than those produced in the summer.

Warmth:
Place the tray in a warm spot between 70°F and 75°F (21°C to 24°C).

Sprouting Time:
Seeds will sprout in 7 to 14 days. Remove the plastic cover immediately when green specks appear. The initial leaves will be green, but the following set of leaves should give you a hint of the colouration to come.

Transplanting:
Move young plants to individual pots when they grow 3 to 4 true leaves and are sturdy enough to handle safely.

Adult Plant Care

Light:
Bright, indirect light near an east or west facing window is ideal. Too much direct sun can scorch the leaves, while too little light causes the colors to fade and the plant to become leggy.

Temperature:
Keep temperatures between 60°F and 75°F (15°C to 24°C). Protect the plant from cold window drafts and heating vents.

Watering:
Water thoroughly whenever the top inch of soil feels dry. Never let the soil dry out completely, or the leaves will quickly wilt.

Humidity:
Coleus loves moisture. Group plants together, use a humid i fier. Many people place their plants on a tray filled with pebbles and water to boost humidity but it really only has limited impact on the area around the plant.

Fertilizer: To maximize the vibrant foliage of your coleus, use a balanced or high-nitrogen fertilizer while keeping phosphorus levels low. (We use Sea Magic.) Coleus are largely grown for their colourful leaves and not their flowers. High phosphorus can trigger premature flowering and yellowing, making the plant look leggy and spent. For house plants, apply a water-soluble liquid fertilizer diluted to half-strength. Stop feeding entirely during winter dormancy.

Rotate the pot:
Turn the plant a quarter-turn every week to ensure even light exposure and balanced growth.

Pinch the tips:
Routinely pinch off the growing tips to prevent the plant from becoming tall and spindly. While most coleus plants need to be trimmed in order to develop a pleasant shape, the Kong variety generally prefers to be left alone.

Flowering:
To help maintain the plants colour and shape, remove any flower buds that begin to form.

Outdoors:
If you place your coleus plants outdoors, they will need to be moved to a protected area when there is a chance of frost. It is not recommended to bring the plants back indoors as they generally don’t transition well and as insects may have made homes in the plants soil. An alternative is to take a few cuttings from your outdoor plant and root them in a small container of soil indoors.