3.2 Principles for Selecting Seed Mixes for Wildflower Strips

Lene Sigsgaard (University of Copenhagen and Norwegian University of Life Sciences), Thomas van Loo (Inagro), Regine Albers (Carl von Ossietzky University Oldenburg), John Holland (Game & Wildlife Conservation Trust)

Pollinators and pollination are under pressure, as pollinators lack food and habitat in the landscape. In many places the natural flowering vegetation is not enough to support pollinators. The EU considers that there is a pollination deficit.

By sowing wildflower strips pollen and nectar can be provided to insects. Perennial flower strips and flowering hedgerows also provide overwintering sites and year-round habitat so pollinator communities can build up. Hereby wildflower strips can be used to increase pollinators and insect biodiversity and the stronger pollinator community ensures that crops get a more reliable pollination service.

In order to establish a wildflower strip, we recommend considering the following principles for the selection of the right seed mix:

Native seeds

• Choose plants that are compatible with region, climate and soil type.

• Include native plants in the mix. Insects are evolutionarily adapted to the native plants of the region, for this reason native plants will have value beyond providing pollen and nectar food for the natural enemies and will also contribute to biodiversity and wildlife.

Attract the right audience

• Choose flowers with known value to beneficial insects:

- Leguminous plants (Fabaceae), such as clovers and vetches, are great for bees especially for honeybees and bumblebees, which can use their tongues to get to the nectar.

- Solitary bees and natural enemies of pests (predators, parasitoids) need open flowers, which have nectar accessible. Flower families include for example Asteraceae, Apiaceae, Rosaceae, Malvaceae or Geranium.

Perennials!

• Choose perennial mixes. A flower strip that remains in place for several years will build up a population of beneficials year by year and thus increase in value with time.

• Create a flower mix which provides food for different beneficial insects, which will be flowering from early spring to late autumn to support pollinators and natural enemies all season.

• Annual flower strips will provide food during spring-summer only. Annual strips can be relevant in annual crops and should then be connected with permanent habitats such as hedgerows providing nesting and overwintering sites.

• Including grasses in the mix can make a flower strip more robust to traffic. However, in North-Western European climate grasses can become too dominant. Select non-competitive and tussock forming grasses and include less than 15% by weight and certainly no more than 40%.

Sowing, cutting, mowing

• Perennial strips do not flower the year they are sown but will flower the following spring when sown in autumn. Autumn sowing works best in North-Western Europe as spring may be too dry.

• If a perennial mix is sown in spring up to 20% annuals can be added to have some flowers the first year after sowing. Possible annuals to use are a mix of cornflower, poppy and corncockles.

• Flower strips should be cut 1-3 times per year. Find more details about the management of flower strips in our guides here.

• Phased mowing of Lucerne. Lucerne is a flowering crop and by phased mowing flowers are secured pollinators. Such an approach can also be used for legume only seed mixes.

• More flowering crops in the landscape. Examples: field beans, read beans, chickpeas, cup plant

Care for your weeds

• Weeds are also a good source of floral food for solitary bees, hoverflies and natural enemies of pests. Some species also flower early (Dandelions) or late in the year (Dead nettles) and so can extend the time over which floral resources are available. Natural regeneration or cultivating the soil in early spring can encourage annual weeds whilst leaving scruffy areas allows both annuals and perennial weeds to survive.

Not all bloom at once

Lene Sigsgaard from the University of Copenhagen investigated perennial flower strips on demo sites in Denmark. While “these native, highly diverse, perennial flower strips do look more like green ‘vegetation strips’ as not all species bloom at once, interestingly we still see more pollinators in apple trees near flower strips than in apple trees near ‘grass strips’ even when grass strips have more flower heads per m2 [of dandelions and daisies] than flower strips.”