The soil should not remain wet all the time, but long dry spells will slow the plants’ growth, and the leaves will start to turn brown around the edges. Black mold growing on top of leaves. If you are growing your plants in containers, this fertilizer can be applied every two to three weeks. Coleus > Leaves > Discolored leaves. Another option is to spray the plants with an insecticide. Aphids are another problem when it comes to the coleus plant. Over time, the plants can look like palm trees as the plant produces new foliage at the top but there are no lower leaves. It only grows up to 18” (45 cm) tall and is perfect for creating colored garden borders, decorate container gardens, or grow in pots indoors. This causes the yellowing and wilting. 1 of 4. Mulch will help the soil retain moisture longer, but don't use cedar mulch, which can be toxic to coleus. CAUSE: Aphids are tiny pests that can be red, green, black, brown or white. You can find Alaska fish fertilizer available at Home Depot. And while there are many reasons for plain old brown spots, when those spots look like little brown bull’s-eyes, the answer my friends is fairly simple, organism-wise that is. A stem borer would cause wilting. In mid-summer, feel free to trim back the coleus leaves to promote stronger growth. It is probably a caterpillar. Coleus plants grow best in soil that is consistently moist but not soggy. As well, pinch back the growing tips of the leaves every few weeks. Coleus that have wilted will usually respond quickly when watered, but coleus that have been repeatedly allowed to wilt will quickly show signs of wear and tear that make them less attractive: crispy edges, dry brown spots on the leaves, bleaching, and dull color. You can treat these insects by spraying them with water and then wiping off the plant. Mulch is recommended for Coleus grown in the ground in hot areas. Generally speaking, coleus is a full shade plant—while recent cultivars have made it more tolerant of sunlight, it still does not like direct, sustained sunlight and needs either shade or partial shade in order to thrive. Leafminer damage looks like brown or white squiggly lines on the leaf. I don't know about Australia but leafminer is not a known pest of coleus around here. Spider Mites. This makes the coleus grow out to the sides of the main stems, for a bushier, more shrublike plant. If you notice the colors of your coleus plant look washed-out and dull, that's a good indicator that it might be getting too much sun. This cultivar grows well in partial shade and is sun-tolerant. This is a 5-1-1 (NPK) fertilizer which will not cause the brown spots on the foliage typical of a coleus that has been overfed. Mealybugs, aphids, thrips, and scale are the other common culprits. The brown or blighted areas on diseased foliage have an irregular shape and can cause the leaf to twist and drop. From indoor and outdoor gardeners alike, one of the most common gardening questions is, “Why do my plants have spotted and brown leaves?”. Other sap-sucking pests can cause brown spots on houseplant leaves. Downy Mildew Plasmopara lamii. They cluster on the underside of leaves and suck the sap from them. This is my first coleus plant.. and I thought it was doing great until I found out one of its leaves look wilted and dying.. it is very limp.. however the other leaves look okay it does not need to be watered which I know because i can feel the soil is moist. Sometimes the caterpillar take on the color of the leaves they are eating and it makes them that much harder to see. All these bugs feed by sucking the sap from the leaves and stems of your houseplants, damaging a small area around where they feed, causing brown or yellow spots on the leaves. The Spruce / Kara Riley Light . The sporangia on the underside of the coleus leaves may be abundant or few in number. SYMPTOMS: Leaves develop yellow spots, then wilt. Large purple leaves with lime-green edgings make this coleus an eye-catcher in your garden. This will help direct growth toward the leaves.