Recovering wildflower diversity

This is the 7th summer when we have been able to enjoy a display of native wildflowers in the areas that we manage. Apart from the Cornfield Annuals on the triangle and now along the path side at the Heritage Viewpoint with the white Mayweed, yellow Corn Marigold, blue Cornflower and red Poppy, we also have a steadily developing community of more permanent wildflowers on the slopes of the bank below Crow Wood. Seeds of quite a range of different species were sown there in the spring of 2014, supplemented by a few seeds and home grown plug plants from other wildflower sources across this part of Scotland. It has been fascinating over the years to see the species mix develop. We now have a good scattering of colourful perennials such as Yarrow, Lady’s Bedstraw, Red and White Campion, Black Knapweed, Field Scabious and Meadow Crane’s-bill to name but a few of the 50 or so separate perennials or biennials that have been recorded as growing there on different parts of the bank.

Many of these species have increased in abundance each year so the growing conditions in that area must be suitable for them to thrive. Meadow Crane’s-bill have been particularly successful to the left of the path before the steps in an area where a colony of Yellow Rattle was seen to be established by 2016. The question is: If they can grow so well there, with our minimal management of strimming but not scalping the vegetation in late autumn and raking to remove the cut material, why are they not more widespread along similar grassy banks alongside roads and footpaths?

There are now many more areas where grasses are not cut so regularly or as short by some local authorities as they were in the past. This should help wildflowers to develop as they will not be cut down before seeds are shed. It is true that there are now more flowers to be seen in these areas, but many of the key species now established on our wildflower bank are rarely amongst them. I had always assumed that if a particular wildflower was not present somewhere where other wildflowers were already growing, the conditions must not be suitable for that particular species. That changed for me when someone scattered Red Campion seeds in patches along a path which already had a range of different wildflowers, but no Red Campion. Each year after that the plants that developed from the seeds continued to thrive and expand along parts of the path. So, as we are seeing on Crow Wood bank, some wildflower species were perfectly able to grow where none had been seen growing before, at least in the recent past.

After the Second World War there was widespread use of selective weed-killers, especially in agriculture, but they were also used on roadside verges and amenity grass areas. These killed any broad-leaved plants, but left the grasses unharmed. It became much easier to grow grain crops or keep paths and amenity grass areas tidy. If applied over many years, any flowering plants growing from seeds in the seed bank would be killed as they developed each year and the supply of seeds in the soil bank, already diminished by regimes that cut them before seeding, would then steadily decrease to the point for some species, of complete exhaustion.

Now that use of selective weed-killers on some amenity grasslands has ceased, why are some of the attractive and important species now growing on the Crow Wood bank not spreading more widely in other areas where the few patches that may still exist there could supply new seeds? One answer probably relates to seed dispersal.

Everyone is familiar with the airborne dispersal of Dandelion and other light, parachute dispersed, seeds like those of the Cat’s ear in the photo, which leads to their wide distribution once selective weed killers cease to be used. The hooked seeds like Sticky Willie or Wood Avens that get stuck on clothing or the coats of passing mammals can also be spread more widely.

The problem may be that species with large and heavy seeds cannot easily spread widely from where they are growing. Red Campion seeds when ripe sit in an open capsule at the top of the flower stalk. Wind, or passing animals will shake them out, but they will not go very far so they will only be able to advance their distribution by a metre or so each year.

Both Black Knapweed and Field Scabious have lighter seeds, but with no obvious features to help dispersal save a few tufts of hairs. They will travel further than Red Campion when aided by a strong wind, but only by a few metres.

Meadow Crane’s-bill does have a method of scattering the seeds away from the parent plant. Four or five very heavy seeds develop from each flower and they are each attached to a long, tapered strip of plant material along a central column, fused together along their length to form a beak like structure. This gives them their common name of Crane’s-bill.

As the seeds mature the beak like structure starts to point upwards and darkens. These strips, each with a cup at the bottom holding the seed, are naturally curved when dry and tension builds up in this structure as they are held straight along the central column. When dry enough, and especially in warm sunshine, the junctions between the 5 strips give way along their length while remaining attached at the tip. The strips, released from the tension, rapidly curl up and as this comes to a halt at the tip of the “beak” the seeds are catapulted some distance away from the parent plant. Even with this ability to project the seeds well clear, dispersal is still not going to be more than a few meters in each generation.

So, for all of these, and other similar species, even though there are still patches on verges and field edges, they are not going to quickly spread back to everywhere where they may be well able to grow and they probably would have grown in the past.

The results of our seed sowing on both Crow Wood bank and the Heritage Viewpoint show that very diverse communities of plants, well adapted to our growing conditions, can be established with a targeted sowing of a good range of perennial wildflower seeds and a bit of patience. Granted they do not have the visual impact of an area of Cornfield Annuals, but as we have shown, you can have both, and while both have wildlife value as well, it is the perennial wildflowers that provide the maximum benefit to a greater diversity of pollinating and other insects and invertebrates. For example, both Knapweed and Field Scabious, at least the various plants growing on Crow Wood bank, have long flowering periods with flowers being seen from late June right through to early September. This makes them particularly valuable for late summer butterflies and bumblebees at the end of their colony season with newly produced bumblebee queens needing to stock up on energy reserves prior to their long winter hibernation.

The benefits of these and other wildflower species, which provide interest and colour for people going past, together with excellent value for many pollinating insects, could be established in other grass areas that are now being managed more sympathetically. If that is to be achieved however there will need to be some targeted seed sowing or planting of plug plants in the available areas. It is to be hoped that more groups will be encouraged by what we have achieved to follow our lead and restore wildflowers to many more grassland areas.