Common Knapweed - Kew Wildflower SeedsCentaurea nigra

Direct sow wildflower seeds outdoors where they are to grow in spring or autumn. Choose a position in full sun on well drained soil which has been raked to a fine tilth. Sow seeds thinly, and rake lightly to cover the seed, or sow in at a depth of 1.5cm (&frac116;”) in drills spaced 30cm (12”) apart. Water the ground regularly, especially during dry periods. Germination usually takes 14-21 days. As seedlings germinate, carefully thin out any that are too close together with a trowel and replant elsewhere.

Water knapweed plants regularly until fully established. Knapweed is drought tolerant once established and will happily tolerate almost any soil, except those that are excessively waterlogged.

This plant will self-seed freely. If seedlings are not wanted, deadhead stems of knapweed flowers as the blooms fade. In autumn, cut back old stems to just above ground level to make way for new growth in the spring.

Seeds and garden supplies will normally be delivered within the time period stated against each product as detailed above. Plants, bulbs, corms, tubers, shrubs, trees, potatoes, etc. are delivered at the appropriate time for planting or potting on. Delivery times will be stated on the product page above, or in your order acknowledgement page and email.

Orders for packets of seed incur a delivery charge of £2.99.

Orders which include any other products will incur a delivery charge of £6.99.

Where an order includes both packets of seeds and other products, a maximum delivery charge of £7.99 will apply - regardless of the number of items ordered.

Large items may incur a higher delivery charge - this will be displayed in your shopping basket.

Please see our Delivery page for further details, and more information on different charges that may apply to certain destinations.

For more information on how we send your plants please visit our Helpful Guide on plant sizes.

Thompson & Morgan strives to ensure that all its plants are delivered to you in the perfect condition for planting. While the majority of our nursery plants cope well with slight delays in intransit, sadly, the time it takes to deliver to certain locations in the UK means that we can't guarantee this for some of our smaller plug products and tender bedding and vegetable lines, which do not respond well to the extra journey time. So regretfully while we offer the majority of our live plant offering nationwide, we are unable to ship plugs, begging plants and tender vegetable plants to the following areas: HS, IV41-IV49, IV51, IV55-56, KW15-KW17, PA34, PA41-48, PA60-PA78, PA80, PH40-PH44, TR21-TR24, ZE1-ZE3