How to Sow and Plant

Thunbergia may be grown from seed sown early indoors and transplanted outside after frost, or sown directly in the garden

Sowing Seed Indoors:

• Sow thunbergia indoors 6-8 weeks before the last frost
• Sow seeds evenly and thinly and cover with ¼ inch of seed starting formula
• Firm lightly and keep evenly moist
• Seedlings emerge in 7-10 days
• As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
• Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
• If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 2 pairs of true leaves before transplanting to the garden so they have enough room to develop strong roots
• Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Transplanting in the Garden:

• Plant seedlings in the garden after all danger of frost has passed.
• Select a location in full sun in soil that drains well.
• Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
• Most plants respond well to soils amended with organic matter. Compost is a wonderful form of organic matter with a good balance of nutrients and an ideal pH level, it can be added to your planting area at any time. If compost is not available, top dress the soil after planting with 1-2 inches of organic mulch, which will begin to breakdown into compost. After the growing season, a soil test will indicate what soil amendments are needed for the following season.
• Dig a hole for each plant large enough to amply accommodate the root ball.
• Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand leaving a slight depression around the plant to hold water.
• Water thoroughly, so that a puddle forms in the saucer you have created. This settles the plants in, drives out air pockets and results in good root-to-soil contact.

Sowing Directly in the Garden:

• Direct sow in full sun in well-drained soil after danger of frost.
• Prepare the soil by removing weeds and working organic matter into the top 6-8 inches of soil; then level and smooth.
• Most plants respond well to soils amended with organic matter. Compost is a wonderful form of organic matter with a good balance of nutrients and an ideal pH level, it can be added to your planting area at any time. If compost is not available, top dress the soil after planting with 1-2 inches of organic mulch, which will begin to breakdown into compost. After the growing season, a soil test will indicate what soil amendments are needed for the following season.
• Sow seeds 6 inches apart and cover with ¼ inch fine soil.
• Firm lightly and keep evenly moist.
• Seedlings will emerge in 7-10 days depending on soil and weather conditions.
• Thin to stand about 12 inches apart when seedlings are 1- 2 inches high.

How to Grow

• Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating.
• Mulches also help retain soil moisture and maintain even soil temperatures. For annuals an organic mulch of shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
• Plants need about 1 inch of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It's best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
• Until plants become established, some protection from extreme winds and direct, hot sunlight may be necessary. Good air movement is also important.
• After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
• Remove spent flower heads to keep plants flowering until fall.
• Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
• Remove plants after they are killed by frost in fall to avoid disease issues the following year.

Growing Tips

• Provide a trellis or other support and train the vine to climb as it grows.
• Thunbergia may also be grown as an annual ground cover.
• Pinch or cut back to control the vine’s growth.
• Most thunbergia plants can grow 5-6 feet in one season.
• Thunbergia is a perennial in milder areas.

Common Disease Problems

Alternaria Leaf Spot: Small, round reddish brown spots with white to grey centers form on the upper surface of the leaves and along the midrib. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.

Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.

Root Knot Nematodes: Microscopic worm-like pests that cause swellings (galls) to form on roots. Plants may wilt or appear stunted. This is a serious problem in many Southern states. Burpee Recommends: Do not plant into infested soil. Try planting ‘Nema-Gone’ marigolds around your plants.

Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Practice crop rotation and do not plant related crops in the same area for several years. Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.

Virus (Various causes): The most characteristic sign of virus is tight and dark green mottling of the leaves. Young leaves may be bunched. Young plants may have a yellowish tone and become stunted. Leaflets may point upward and have a grayish cast. Burpee Recommends: This disease is readily spread by handling. Destroy diseased plants and the plants on either side.

Common Pest and Cultural Problems

Scale: Small bugs look like brown, black, gray to white bumps on the stems of plants. Scale may not have any apparent legs and may not move. Scales have a sucking mouth part. Scale may produce honeydew so leaves and stems may be sticky. Scale can weaken the plant causing it to grow very slowly and may wilt at the middle of the day. Burpee Recommends: Completely spray the stems with Insecticidal soap. For a severe infestation contact your local County Extension Service for recommendation for your area.

Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.

Whitefly: These are small white flying insects that often rise up in a cloud when plants are disturbed or brushed against. Burpee Recommends: They are difficult to control without chemicals. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for pesticide recommendations.

FAQ

Can I grow thunbergia in a container? Yes, thunbergia is great for hanging baskets.

Is thunbergia a good pollinator plant? Yes, thunbergia attracts bees and birds.

Is thunbergia deer resistant? Thunbergia can be deer resistant but not reliably so.

Can I bring my thunbergia inside for the winter? Yes, thunbergia is an evergreen tender perennial that may be grown as a houseplant. You can also grow new plants from cuttings.