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Sowing & Growing: Overseeding Wildflowers into an Existing Grass Meadow

If an existing meadow starts to loose floral diversity, or new wildflower species need to be introduced, then it’s possible to overseed with wildflower seeds into an existing grass sward.

When to Sow: Wildflowers should be oversown into existing grassland when the sward growth is slowing down and least aggressive. Autumn is the best time to sow, with early spring being another sowing window.

Sowing Rate: Wildflower seeds are generally very small in size which means that plenty of seeds are provided per kg of seed mixture. A standard overseeding rate for wildflowers is 2 kgs per acre, however this can be raised or lowered to ensure the seed cost is economical.

Preparation: The site should be grazed or cut hard before vigorously harrowing the existing sward. Ideally excess vegetation needs to be removed before sowing in order to reduce competition, open up new space and loosen the soil for the new seeds. Several passes with a chain or tine harrow at slightly different angles may be necessary.

The aim is to create 40-50% bare soil by the end of the preparation. When sowing the new seeds be wary of sowing too deeply with aggressive agricultural drills. Broadcasting the seed with a spinner or by hand is a good way to establish the mixture, followed by an additional harrow.

After sowing, roll to consolidate the area, lock in moisture and create good seed to soil contact. Livestock can be left on the area for 3-4 days after sowing to further keep on top of the old sward (soil conditions allowing) but must be removed before the new seeds germinate.

Do not fertilise the area before or after sowing as wildflowers prefer low nutrient soils. Highly fertile sites will encourage lush grass growth, making it more difficult for wildflower seedlings to establish. Most traditional perennial wild flowers are slow to establish, often taking up to 12 months to fully get their roots down and starting to show signs of flowering in year 2.

Pioneer wildflower species are quicker to establish, these include Oxeye Daisy, Wild Carrot and Red Campion. These species can be a useful indicator as to the success of an over sowing project.

Remember that annual wildflower species such as cornflower, corncockle, corn marigold and field poppy ideally need to be sown into bare soil to get the best establishment, rather than into an existing grass sward.

Date Posted: 26th May 2023