Common Knapweed Seeds – Centaurea Nigra

Pair with common agrimony and field scabious to create a butterfly garden or introduce into naturalised planting schemes to increase biodiversity.

Tough and vigorous, common knapweed is pollinated by a wide range of insects including bees, flies, butterflies, and beetles, and the resulting seed heads attract goldfinches and other seed-feeding birds. A member of the daisy family, knapweed flowers are made up of many tiny flowers with ragged bracts, borne on stems to a metre high above clumps of long entire or partly lobed mid-green leaves.

If you’re considering adding common knapweed to your garden borders? Here are some things to note:

How many grams of common knapweed seeds should I buy?

Our 1g seed packets contain approximately 150 common knapweed seeds and are ideal for sowing in seedling trays or direct sowing into garden borders. For larger areas, we recommend sowing at a rate of 2g/sqm and increasing to 4g/sqm for densely populated growth.

What are common knapweed seeds?

Common knapweed seeds are the seeds of Centaurea nigra, a wildflower known for its vibrant purple-pink, thistle-like blooms. It’s also called black knapweed or hardheads and is a staple in most wildflower meadow mixtures.

How do I grow common knapweed seeds?

Sow the seeds in autumn or early spring. Scatter them on well-prepared soil, either in a seed tray or on the ground, lightly press them in, and water with collected rainwater.

What growing conditions does common knapweed prefer?

Common knapweed thrives in full sun but can tolerate partial shade. It grows in most soil types but is particularly good for heavy clay soils as its root structure enables it to tolerate very wet and very dry conditions.

Is common knapweed good for pollinators?

Yes! Common knapweed is a favourite of bees, butterflies, and other pollinators, providing a valuable nectar source throughout the summer.

What other garden plants are related to the common knapweed?

Common knapweed (Centaurea nigra) belongs to the Asteraceae family and the genus Centaurea. Many garden plants and wildflowers are related to common knapweed, sharing similar characteristics and appeal. Notable relatives include Mountain Bluet (Centaurea montana), cornflower (Centaurea cyanus), and coneflowers (Echinacea spp.).

When does common knapweed flower?

Common knapweed typically flowers from June to September.

How tall does common knapweed grow?

Common knapweed usually grows to a height of 30–75 cm (12–30 inches), making it suitable for both meadow planting and mixed perennial borders.

How do I care for common knapweed after planting?

Common knapweed is low-maintenance. Water during dry spells and deadhead spent flowers to encourage prolonged blooming or control self-seeding.

Can common knapweed be grown in containers?

While it’s more commonly grown in meadows or borders, common knapweed can grow in large containers with well-drained soil and plenty of sunlight.

Is common knapweed suitable for clay or poor soils?

Yes, common knapweed is very adaptable and can grow in clay, poor, or chalky soils, making it a great choice for challenging sites.

When should I sow common knapweed seeds?

The best time to sow common knapweed seeds is in autumn to allow natural cold stratification, but early spring sowing is also effective.

Is common knapweed safe for pets and livestock?

Yes, common knapweed is safe and non-toxic for pets and livestock, making it a good option for grazing pastures or dog-friendly gardens.

Can I integrate common knapweed into existing garden borders?

Yes! Common knapweed pairs beautifully with cottage garden favourites such as black-eyed susans, Siberian iris, and geraniums.