Coleus (Solenostemon) care

One of the most colorful and vibrant annual flowers is the Coleus, also known as Solenostemon or Painted Needle. It is easy to plant and care for. In summer, it will have the most vibrant colors in a sunny spot, but it also grows well in partial shade. It can be planted in pots, balcony boxes, or directly in the garden. It looks best when planted in groups, so it's worth planting several together. Propagation is possible by seeds and cuttings.

The original habitat of the Coleus flower is Africa and Asia, but it also thrives well in our region. Several species have been present in Europe since the 1860s, yet it has not received significant attention locally. The coleus is an annual flower that grows up to 3 - 5 feet (1 - 1.5 meters) tall, and its leaves display a variety of colorful patterns.

The varieties of Coleus were discovered in the 19th century by Karl Ludwig von Blume when he traveled to Java, Indonesia. At that time, it received the Latin name Coleus blumei, but many people still simply refer to it as Coleus. Over time, more and more varieties were developed and patented by horticulturists.

As a result, in the late 20th century, the plant was renamed, and the Latin name Coleus blumei is no longer used. Instead, the various varieties are now called Solenostemon scutellarioides and Plectranthus scutellarioides. In our region, it is also known as painted nettle or flame nettle.

The varieties of Coleus differ not only in the color of their leaves but increasingly in the shape of their leaves as well. Their colors can range from pale yellow to pinkish, brownish, and even dark purple, which is almost black.

Coleus Care

Coleus care is simple; it prefers moist but well-draining, nutrient-rich soil. It can be planted in both sun and partial shade. In winter, it can be kept indoors, and after the last frost in spring, it can be moved outside. The easiest method of propagation is to root cuttings in water in spring.

During summer, it is recommended to prune the growing tips continuously to achieve a dense, bushy, colorful plant. To maintain the vibrant colors of the leaves, remove dried and shaded leaves regularly.

Coleus cannot withstand frost, so in colder regions, it is only grown as an annual in the garden. As a houseplant, it is a perennial flower, but the right conditions for overwintering must be provided.

Light Requirements for Coleus

In the garden during summer, Coleus prefers a bright but partially shaded spot, as too much and intense direct sunlight can damage and scorch its leaves. Ideally, it should receive 2-4 hours of direct sunlight in the morning and evening, but remain in partial shade during the hotter midday hours, receiving only diffused light.

As a houseplant, Coleus also needs light. If the windows do not receive strong direct sunlight during the midday hours, it can be placed in almost any window. However, if strong sunlight does come through, it is better to place it in a north or east-facing window.

Observe the plant to see how it responds to the light, and adjust its position to a shadier or brighter spot as needed.

Temperature Requirements for Coleus

Coleus loves warmth as it originates from tropical regions. The ideal temperature range in summer is 70 - 84 °F (21 - 29 °C).

It can tolerate slightly higher temperatures for short periods, but prolonged exposure to extreme heat can stress the plant, causing leaf burn or wilting. During the hottest hours, consider moving it to a shadier spot or providing some shade. In winter, the optimal temperature is around 50 - 59 °F (10 - 15 °C).

Watering needs for Coleus

In summer, keep the soil moist but not waterlogged. Water when the top 1 - 2 inches (2 - 3 cm) of soil feel dry. Water thoroughly and allow the excess to drain out from the bottom of the pot. Do not leave the pot standing in water.

The watering frequency of the Coleus plant depends on various factors. In a hot, dry environment, more frequent watering is necessary, while in cooler, more humid conditions, watering can be less frequent.

Planting Coleus

For planting Coleus, choose well-draining soil. The soil quality can be improved by adding compost or manure to increase nutrient content.

Whether planting in the garden or a pot, dig a hole slightly larger than the root ball. Ensure that the hole is deep enough for the roots to fit comfortably.

Place the plant in the hole so that the top of the root ball is level with the surface of the soil. Carefully fill in the hole with soil, pressing it down firmly around the plant to eliminate air pockets.

After planting, water the soil thoroughly to help it settle.

When planting in the garden, apply a layer of mulch around the base of the plant after watering to retain moisture. This is particularly important in very hot areas.

Wintering and Winter Care for Coleus

If you want to keep your Coleus for the next year, overwinter it in a frost-free location. A cool but bright hallway is a suitable spot. In a warm room, it may become leggy and lose its shape, especially if it receives insufficient light. Therefore, try to provide as much light as possible for coleus in winter as well.

Only water it sparingly when the leaves begin to droop. By spring, if it becomes leggy, prune it back and after the last frost, it can go back to the terrace, balcony, or flowerbed.

According to some opinions, even if the plant survives overwintering, it often becomes leggy and sparse, so it may be better to propagate new plants by rooting cuttings rather than keeping the old plant.

During overwintering, pests such as aphids, whiteflies, and spider mites may appear.

Propagating Coleus

Propagating Coleus by Cuttings

Expanding a Coleus collection is easy. The simplest method of Coleus propagation is by cuttings. Cut 4 - 6 inch (10 - 15 cm) long stems from the mother plant, remove the lower leaves, and place them in water.

Coleus roots very easily; within a few days, roots will appear. Once roots have formed, they can be planted in pots. Additionally, if a stem accidentally breaks off, it can also be used for propagation.

If the water quality is not adequate, rooting may be slow, or tiny black spots may appear on the stems. In this case, it is recommended to add a small amount of liquid fertilizer to the water (according to the dilution ratio indicated on the bottle). This will promote rooting.

Propagating Coleus from Seeds

Coleus can also be propagated from seeds, which germinate easily and well. For germination, a temperature of 59 - 64 °F (15 - 18 °C) is required. In the garden, sow the seeds at the end of February; in pots, coleus seeds can be sown almost any time. Within approximately two weeks after sowing, the first small leaves will appear.

If Coleus is intended as a garden plant, start sowing seeds about 10 weeks before the last frost (around March). The seeds are very small. Scatter them evenly over moist soil, then cover them lightly. Cover the pot with a glass plate to maintain humidity.

Place in a warm, bright location. When the first three pairs of leaves have developed, it is advisable to pinch back the plant to encourage a bushier growth. Once the seedlings reach about 2 inches (5 cm) in height, they can be separated to prevent overcrowding. Move them outdoors only after the risk of frost has passed, typically in the second half of May.

Training Coleus as a Tree

To train Coleus as a tree, start with a cutting and root it. Once it has developed strong roots, plant it and tie it to a stake for support.

Remove the lower leaves and ensure the growing tip is not damaged. Regularly remove side shoots to maintain a single, straight stem. Continue training the plant to develop a long "trunk."

Once the desired height is reached, pinch off the growing tip. This will encourage the plant to branch out and form a fuller crown. Continue to remove unwanted side shoots, allowing growth only in the crown area.

To achieve a larger foliage crown, pinch back shoots in the crown area regularly. If necessary, replace the stake with a longer one.

The stem is still fragile and can break easily, so handle with care. Strong winds or rough handling can damage it, so ensure the pot is stable and adequately sized. Regularly check the ties to prevent stem breakage.

Pinch off flower buds regularly to encourage the plant to focus on leaf production and develop more vibrant foliage.

Coleus Diseases, Pests, and Causes of Decline

Coleus Diseases

• Powdery Mildew: A fungal disease that creates a white, powdery coating on the leaves, causing them to yellow and wilt.

  Appears under conditions of high humidity. Ensure adequate air circulation and avoid wetting the leaves during watering.

• Leaf Spot: A fungal or bacterial disease that causes dark, water-soaked spots on the leaves.

  Remove affected leaves and avoid wetting the foliage during watering. Good ventilation is also crucial.

• Stem Rot: Caused by several types of fungi, infected stems become soft, waterlogged, and eventually collapse.

  Overwatering and poorly draining soil contribute to stem rot.

• Fusarium Wilt: A fungal disease affecting many plants, caused by various Fusarium fungi. It attacks the plant’s vascular system, disrupting water and nutrient uptake. Common symptoms include wilting, yellowing or browning of leaves, and stunted growth.

  The fungus can remain in the soil, making it challenging to eradicate. Prevention is key: avoid overwatering, keep leaves dry, and reduce humidity.

Environmental Factors and Improper Care of Coleus

• During summer, intense sunlight can scorch the leaves; in such cases, move the plant to a shaded area or provide shade protection.
• In winter, if it is too warm and the plant receives insufficient light, it may become leggy. Move it to a brighter, cooler location.

Also known as: coleus, flame nettle, painted nettle

Is Coleus Toxic?

Coleus is not toxic to humans. However, it can be toxic to pets if ingested. Symptoms in pets may include vomiting, diarrhea, and excessive drooling.