How to Grow American Basket Flower Seeds

Grow Guide #2472
Family: Asteraceae
Binomial name: Centaurea americana
Life Cycle: Annual

This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for American basket flower (Centaurea americana).

When to Sow American basket flower Seeds

American basket flower can be grown year-round in most climates. Avoid planting in extremely hot or cold weather which can affect germination and growth. Use the table below to identify the best time of year to sow American basket flower in your climate.

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

Preparation

American basket flower plants are best grown in full sun. Choose a location that will receive at least 6 hours of full sun each day.

American basket flower 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 American basket flower to become established in your garden, deadhead plants before they can drop seed or grow them in containers.

American basket flower plants need a very well drained soil. In most cases there is no need to enrich soil with manure or other fertilisers. Prepare soil by weeding it thoroughly and digging it over to loosen it. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.

American basket flower 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 20 litres is recommended for American basket flower. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.

How to Sow American basket flower Seeds

American basket flower seeds do not require any treatment (eg soaking, stratification) before sowing.

American basket flower seeds can be sown directly into the garden OR seedlings can be raised in trays or other containers and transplanted to the garden once established.

Sow Direct

  1. Sow seeds directly in the garden 3mm deep and 20cm apart.
  2. Keep soil moist but never wet or dry.
  3. Seeds should germinate in around 14-21 days at a soil temperature of 15-20°C.
  4. Young seedlings will need protection from pests, pets and weather until they are established.

Raise Seedlings

  1. Fill trays, punnets or jiffy pots with a good quality seed-raising mix, or use soil starter pellets.
  2. Sow seeds 3mm deep.
  3. Keep soil moist but never wet or dry.
  4. Seeds should germinate in around 14-21 days at a soil temperature of 15-20°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: American basket flower seeds can also be sown in the less formal ‘scatter seed’ method. Simply roughen the soil, scatter seeds evenly over the surface, then smooth the soil over lightly to cover the seeds.

How to Grow American basket flower

American basket flower 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.

American basket flower plants will grow in nutrient-poor soils and do not need additional fertiliser during the growing season.

Optional: To give plants room to grow, thin seedlings when they are large enough to handle. Pull out any weak or small seedlings so plants are spaced about 20cm apart.

American basket flower plants may need to be supported as they grow. Depending on the expected size and height of the plant, use a stake, bamboo cane, trellis or string lines to support plants. Make sure you have the support in place when you sow seed or transplant seedlings to avoid disturbing the plant's roots later.

American basket flower plants should flower in approximately 120 days.

Deadhead American basket flower 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 American basket flower 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.

Common Problems when Growing American basket flower

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

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