How to Grow Black Eyed Susan Seeds
Grow Guide #2473
Binomial name: Rudbeckia hirta
Life Cycle: Perennial
This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Black Eyed Susan (Rudbeckia hirta).
When to Sow Black eyed Susan Seeds
Use the table below to identify the best time of year to sow black eyed Susan seeds in your climate.
Black eyed Susan plants are perennial, meaning they live for several years. Choose a permanent position where plants can grow undisturbed by regular digging or other disturbance.
Black eyed Susan plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.
Black eyed Susan plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.
How to Sow Black eyed Susan Seeds
Black eyed Susan seeds do not require any treatment (eg soaking, stratification) before sowing.
Black eyed Susan seeds grow best when they are raised in trays or other containers and transplanted to the garden once established.
- Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
- Sow seeds 1mm deep.
- Keep soil moist but never wet or dry.
- Seeds should germinate in around 7-14 days at a soil temperature of 20-22°C.
- Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
- Plant out, spacing plants 30cm apart.
Optional: In cool climates black eyed Susan seeds can be sown indoors 6 weeks before the last expected frost. Grow them in a warm position with plenty of natural light.
How to Grow Black eyed Susan
Black eyed Susan plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.
If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-potassium fertiliser or one formulated for flowering plants can be beneficial:
- Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
- Apply liquid fertiliser at the recommended rate and frequency while plants are fruiting or flowering.
Black eyed Susan plants should flower in approximately 95-110 days.
Deadhead black eyed Susan flowers regularly during the growing season. Using sharp secateurs or snips cut fading or dead flowers off just above a set of leaves. Removing old flowers regularly will encourage plants to produce more flowers. Learn more about deadheading flowering plants here.
If growing black eyed Susan for cut flowers, use sharp snips or secateurs to cut the longest stems possible, removing the lower leaves and placing the stems immediately in a clean bucket of water. Learn more about cutting and conditioning homegrown flowers here.
Black eyed Susan plants may die back in cold weather. Cut plants back just above ground level in late autumn, or prune off dead foliage when new leaves emerge in spring.
Common Problems when Growing Black Eyed Susan
Like all plants, black eyed Susan is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing black eyed Susan plants:
- Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
- Downy mildew is a fungal disease that causes yellow to grey-brown patches on leaves, especially the undersides. Water plants at soil level (not on the leaves), remove and destroy affected leaves and do not overcrowd plants to ensure adequate air flow. If problems persist, spray with a homemade milk spray or fungicide.
- Slugs and snails are molluscs that feed on tender leaves and shoots, mostly at night, leaving slimy trails behind them. Control them by removing their hiding places, keeping free range poultry, collecting them by torchlight or by placing traps. Read more about slugs and snails here.