How to Grow Ranunculus Seeds

Grow Guide #2935
Family: Ranunculaceae
Binomial name: Ranunculus asiaticus
Life Cycle: Perennial

This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Ranunculus (Ranunculus asiaticus).

When to Sow Ranunculus Seeds

Ranunculus is a cool season flower. Use the table below to identify the best time of year to sow ranunculus seeds in your climate. Ranunculus grown from seed require a long cool growing season.

  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Cool
Temperate
Sub-Tropical
Tropical
Arid

Preparation

Ranunculus 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.

Ranunculus 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.

Ranunculus 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 ranunculus. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.

How to Sow Ranunculus Seeds

Ranunculus seeds do not require any treatment (eg soaking, stratification) before sowing.

Ranunculus seeds grow best when they are raised in trays or other containers and transplanted to the garden once established.

  1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
  2. Sow seeds 2mm deep.
  3. Keep soil moist but never wet or dry.
  4. Seeds should germinate in around 10-15 days at a soil temperature of 18-20°C.
  5. Transplant seedlings to the garden once they have their first true leaves and are large enough to handle (usually 5-10cm tall).
  6. Plant out, spacing plants 20cm apart.

Tip: Protect seeds and seedlings from hot weather. Some gardeners find that placing the seed tray on a cool surface (eg a tiled or concrete floor) or waiting until later in autumn to sow seeds provides the best conditions for germination. 

How to Grow Ranunculus

Ranunculus plants need regular watering during the growing season. Do not let soil dry out; keep soil evenly moist but not waterlogged. 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.

Ranunculus plants should flower in approximately 120-180 days.

Deadhead ranunculus 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 ranunculus 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.

Ranunculus plants can be grown as annuals and discarded after flowering, or their corms can be lifted, stored and replanted in autumn. Plants grown from seed will form small corms in their first year.

Lift corms when the foliage turns yellow. To lift ranunculus corms, first cut the foliage off at ground level. Use a garden fork to lift corms from the soil, taking care not to damage them. Spread the corms on a wire rack in a cool, dry place for 10-14 days to dry them. Then store the corms in a net bag or in just-damp vermiculite until it is time to replant them in autumn.

Common Problems when Growing Ranunculus

Like all plants, ranunculus is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing ranunculus plants:

  • Aphids
    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
    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.
  • Powdery Mildew
    Powdery mildew is caused by fungal spores reproducing on the leaves of plants. First showing as white spots on leaves, affected areas can spread quickly to cover the entire leaf surface. While rarely fatal, powdery mildew can reduce yields. Water plants at soil level (not on leaves) to prevent spreading spores, allow good air flow between plants, remove affected leaves and if necessary spray with an appropriate fungicide or homemade spray. Read more here about powdery mildew here.
  • rotten corms
    Rotten corms are caused by pathogens entering corms after sitting in cold, wet soil or being temporarily waterlogged. Corms may show obvious signs of rot or have no roots or shoots. If soaking corms before planting, do not soak them for longer than recommended. Plant corms in free-draining soil, raised garden beds or containers. If growing corms as perennials, lift and store them over winter and replant in spring.
  • Slugs and Snails
    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.

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