Wildlife Gardening in October

N.B. If your new to David’s monthly column then please be sure to read the ‘setting-the-scene’ opening piece first.

Controlling the Growth of Grasses

Yellow rattle

Yellow rattle, Rhinanthus minor, is a meadow plant that everyone should know. Not that it is overly showy, nor does it smell so delightful that your loved one will be hugely impressed by your presenting a mini bouquet, but it does wonderfully exciting biological miracles.

Rattle is a member of the ‘eyebright’ group of plants, and all are (I believe) partial parasites in that their roots connect to specific local plants and steal nutrients from their vascular systems for their own use. Other plants within that group include: Eyebright (Euphrasia nemorosa), Red bartsia (that is common especially in over-grazed meadows) and louseworts. Our own mini-meadow has eyebright and red bartsia present, but in low quantities.

You will already be aware of the broomrapes, which are 100% parasitic and lack all greenness; the eyebrights are closely related but do possess green leaves that can photosynthesise at least partially.

Yellow rattle appears well distributed in wild, alkaline grassy places but seldom reaches the density that we have in our garden meadow, where it has been enhanced from the extant level by added seed and active encouragement.

Our garden soil, whilst difficult for much of the year, is rich in plant nutrients and grasses can grow exuberantly. Such lush growth is excellent for harvest mouse homes, but does crowd out the more showy non-grass species in a garden setting. So, here at Forest Edge, we reduce the grass’s growth by restricting any input of nutrients and by using the rattle to divert sugars and proteins from the grasses to the semi-parasitic rattle. The result is a change in grass species in the sward and a dramatic reduction in grass vigour, such that the meadow does not ‘crash’ in windy or wet conditions and allows the dicotyledonous meadow flowers to dominate.

This grass-controlling plant is not totally 100% specific to grasses and we have found it attaching to bulbous buttercup and reducing its ability to flower. No sign of other significant problems have been noticed. Our wild orchids appear un-phased by living alongside such a ‘difficult a neighbour’ as rattle.

We have been removing, by cutting and composting, nutrients from the Summer Meadow now for twenty years yet there is still too much fertility to alone control grass growth. Without the aid of the rattle the meadow would look much less attractive and, additionally, would fail to support our rich variety of insect species that rely on the pollen and nectar from the insect-pollinated blooms.

Initially we spread the seeds of the annual rattle to new parts of the meadow, and that worked well enough in bulking up the plant. Eventually purchased seed was added.

Yellow rattle was so named because of, yes, its flower colour and because farmers knew it was time to cut the hay when the seeds within the rattle’s pods rattled i.e. were ripe. Seeds are dispersed near to the existing dying plant in July and remain near the soil surface until they germinate in early March. Our large tractor mower, with scarifier, leaves the bulk of the seed in place so can be used with confidence.

Rattle is good for bees, with its flowers proving popular venues for foraging during the May / June flowering period.

How to add rattle to your garden

Being a parasitic annual the plant is grown in situ from seed. There is no point in growing the seeds in seed trays for once the stored energy and nutrients are used up on growth the seedling will perish.

Seed is naturally shed in high summer, but can be hand sown anytime until late winter (possibly even later, but I’ve never tried!). Some authorities suggest that you need to rake the grassy surface of the soil and repeat this process after sowing … rubbish! Hand sow and the rain will wash the seed onto the surface, whilst the winter’s weather will incorporate it into the soil.

There is no reason to use the plant in areas that are regularly cut for the chopping will kill it. Growing plants will however take a light trimming in May if that suits your meadow regime, and will flower as usual (but possibly two weeks later than expected.).

Seed can be purchased from wild flower seed suppliers – look on the Internet.

Problems that you might encounter

I have not known any of our seed straying far, so fear not for the survival of your vegetables and oak trees. Ungerminated seeds do remain viable in the soil for three or more years, so small numbers of plants will appear even when you least expect them; other than that, no problems.

Alternative techniques to control grasses

High nitrate levels stimulate grass growth. This is why some people add a high nitrate content fertilizer to their lawn. These lawns should grow well and require frequent cutting. They will however lack the more showy grassland plants that then fail to effectively compete with the grasses.

Sub-soil is usually lacking in fertility as it contains less humus; humus holds nutrients. Hence if one turns over the soil, with the subsoil above the topsoil or the topsoil is totally removed to expose the sub-soil this reduces fertility and grasses are inhibited.

Ideally we should have, twenty years ago, scrapped off our meadow topsoil and saved us years of trying to reduce fertility with cutting. Be wiser than us … try this if your £ allows. We didn’t have any £, let alone some to spare for topsoil scraping!

Animal boxes and Cameras

Now is the time to think about enhancing your bird, bat and other wee-beastie boxes around the garden; you may also decide to clean out existing boxes – but I leave ours well alone for they may be used by over-wintering mice and insects. Some of my wooden boxes, with which I am most unhappy (see next month), need felt on the roof to limit their rapid decay rate.

Cameras for bird boxes are frequently advertised these days and may well meet you requirements, if so you’ll need to order one that matches the in-nest equipment. Night vision, infra-red, cameras are also available for inside owl boxes. But I really fancy a remote still camera … like the ones used recently to obtain the first images of the African Golden Cat.

Forest Edge

August and September have been good for weather down here, with just enough rain to keep most plants alive. The Summer Meadow has been just maintaining its modest flowering of marjoram, knapweed and scabious so there has been bee food. But numbers of bees are now on a rapid decline.

2009 has been ‘the year of the white butterflies’ and our crucifers have been covered in larvae. As the butterflies should survive the winter in pupa form we can hope for plenty again next year. A scattering of late season butterflies, such as red admiral, painted lady, peacock and small tortoiseshell, gives some hope for 2010 – but numbers have been more modest than many recent years.

Grey squirrels may still be absent from our bird feeders but they have eaten most of the huge walnut crop even before others dare consume it. Greys are tolerant of tannin so can eat early. The few remaining nuts are now the focus of attention of rooks that fly off with a pair stuffed into their beaks to open elsewhere.

David is an ex-lecturer in Environmental / Biological Sciences.
He has written for most of the UK gardening magazines, including the RHS.
Forest Edge’s garden has been widely covered in magazines and has been featured in a BBC’s Gardeners’ World special.
He also maintains a blog at https://nwhwildlife.org/