How to Grow Wallflower Seeds
Grow Guide #2334
Binomial name: Cheiranthus cheiri
Life Cycle: Biennial
This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Wallflowers (Cheiranthus cheiri).
When to Sow Wallflower Seeds
Use the table below to identify the best time of year to sow wallflower seeds in your climate.
Wallflower plants commonly self-seed in the garden. Self-seeding plants drop seeds onto the soil at the end of the season that may germinate and grow without help the following season. Choose a position where new plants will be welcome. If you do not want wallflowers to become established in your garden, deadhead plants before they can drop seed or grow them in containers.
Wallflower 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.
Wallflower 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.
Wallflower plants can be grown in containers. If possible choose a variety that’s recommended for container growing. Use a good quality potting mix and make sure your container is large enough for mature plants; a minimum of 10 litres is recommended for wallflowers. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.
How to Sow Wallflower Seeds
Wallflower seeds do not require any treatment (eg soaking, stratification) before sowing.
Wallflower 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 6mm deep.
- Keep soil moist but never wet or dry.
- Seeds should germinate in around 10-15 days at a soil temperature of 18-21°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.
How to Grow Wallflower
Wallflower 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.
Wallflower plants should flower in approximately 180 days.
Deadhead wallflower 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.
Common Problems when Growing Wallflowers
Like all plants, wallflower is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing wallflower plants:
- Bacterial leaf spot is a disease that causes irregularly shaped brown spots on all above-ground parts of a plant. The spots at first appear to be wet but become dry and scab-like over time. Leaves and flowers can fall prematurely. Water plants at soil level (not on the leaves), dispose of fallen leaves and fruit and practice crop rotation.
- 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.