Biodiversity
Guidance on restoring and creating species-rich grassland
Introduction
This is a brief guide to grassland creation and restoration. Much detailed guidance has been already been written on both subjects and links are provided here to online sources of further information.
The need for habitat creation and restoration
Lowland unimproved grassland is recognised as an important and vulnerable habitat under the UK Biodiversity Action Plan. Habitat Action Plans for the five types of lowland grassland listed below include targets for their restoration and re-establishment in Scotland. For further information, see the link to the UKBAP website at the end of this note.
- Lowland meadows (LM)
- Upland hay meadows (UHM)
- Lowland dry acid grassland (LDAG)
- Lowland calcareous grassland (LCG)
- Purple moor-grass and rush pasture (PMRP)
Terminology
Grassland creation is the establishment of a new grassland sward on a site which was previously arable land (including short term grass leys). Also called re-creation, re-establishment and arable reversion.
Grassland restoration is the increase of species-richness in previously species-poor, improved or semi-improved grassland. Also called sward enhancement and diversification.
Options for grassland creation
Site selection
The ideal site will be adjacent to an unimproved habitat from which species
can migrate into the new habitat. However, since ideal sites are rare
the main criterion for selection should be low soil fertility. Avoid soils
with high levels of available phosphorus (P) since this allows aggressive
grasses to outcompete the sown wildlfower species and dominate the sward.
Grassland creation is more likely to be successful on land that has been
fully arable than where grass leys have been grown and competitive grasses
are present in the seedbank.
Natural regeneration
The seed of typical grassland species does not persist long in the seed
bank so natural regeneration will not result in a species-rich grassland
within the 10 year timescale of agri-environment schemes. It is only likely
to be appropriate for long term grassland creation schemes adjacent to
species-rich grassland which can act as a seed source.
Ground preparation
Create a stale seed bed by repeated cultivations, with herbicide treatment
as well if necessary. Alternatively, apply one or more applications of
herbicide to kill off the existing sward without disturbing the soil.
These treatments deplete the seed bank of annual arable weeds, such as
pineappleweed (Matricaria recutita), chickweed (Stellaria media) and annual
meadow-grass (Poa annua), by first encouraging their germination then
removing them. Annual arable weeds thrive in disturbed soils and will
dominate the sward and prevent establishment of the sown species if not
kept in check.
Create a fine, firm seedbed by harrowing and rolling.
Seed
Wildflower seed mixtures should contain only species that occur naturally
in the locality, and should exclude competitive species that are likely
to dominate at the expense of greater diversity. As a general rule, seed
used on a designated site should be of local origin. In the wider countryside,
Scottish origin seed is desirable but UK origin seed is acceptable.
New species will not easily invade unless they grow nearby and some of the sown species may fail to germinate so a wildflower seed mixture should include at least 20 species if it is to create a new species-rich grassland. The mixture should contain 15-20% grasses and 80-85% forbs by weight.
Nurse crops are not usually necessary but are worth considering for very exposed sites or where there is a risk of soil erosion.
Sowing
A sowing rate of 15 kg/ha will be sufficient where establishment conditions
are ideal (low fertility and few weeds), 20 kg/ha will be appropriate
in most circumstances and 30 kg/ha may be necessary in difficult situations.
Some seed companies recommend 50kg/ha but this is only necessary where
it is important to get immediate results.
Wildflower seed tends to be small so should be sown on or near the soil surface. The site should be rolled after sowing to ensure good contact between seed and soil. The seed must be thoroughly mixed before and during sowing to avoid separation; mixing the seed with an inert substance such as fine sand, barley meal or sawdust helps to ensure even distribution.
Sward management
Regular cutting may be necessary during the first year or two to control
annual arable weeds and to reduce competition from the more aggressive
species. It does not matter if the sown species do not flower during the
first summer. Normal grassland management should be possible from the
second or third year, by grazing alone, or hay cutting followed by aftermath
grazing, or by two cuts per annum where grazing is not possible. For further
information on long term management, see the link to the Lowland Grassland
Management Handbook at the end of this note.
Options for grassland restoration
Site selection
As with grassland creation, the ideal site will be adjacent to an unimproved
habitat from which species can migrate into the new habitat. More realistically,
an acceptable site will have low levels of available soil phosphorus (P)
and of competitive perennials that tend to dominate at the expense of
greater diversity, particularly Yorkshire fog (Holcus lanatus), white
clover (Trifolium repens) and creeping buttercup (Ranunculus repens).
Management
Improved management alone may be sufficient to restore a grassland where
some botanical interest remains. This involves the establishment of an
appropriate grazing or cutting regime (see the link to the Lowland Grassland
Management Handbook at the end of this note) and no applications of inorganic
fertiliser, slurry or pesticides. Scrub clearance may be necessary to
restore lost grassland (see the link to the Scrub Management Handbook).
Where there are few species typical of unimproved grassland still in the sward, seed can be introduced by oversowing the existing sward or by slot seeding.
Oversowing
Create a short sward by cutting or grazing, then create 40 to 50% bare
ground by cattle trampling or by light mechanical disturbance such as
raking, harrowing or scarifying. As with grassland creation, the seed
should be sown on or near the soil surface and the site should be rolled
after sowing. The sowing rates described for grassland creation can be
followed but reduced in proportion to the amount of bare ground created.
Slot seeding
A slot seeder, where available, can apply herbicide to remove the vegetation
from strips of sward while sowing seed into the strips at the same time.
The resulting stripes can be visible for years but the effect can be minimised
by sowing in a random pattern.
Seed mixtures
As for grassland creation above.
Plug plants
These are seedlings, grown in individual cells of compost, which can be
pricked out or transplanted without disturbing the roots. They are more
expensive than seed but a useful way of adding a few individuals of expensive
species, or species that do not germinate easily.
Other techniques
Nutrient reduction
High levels of available soil P are associated with low botanical diversity.
P will decline naturally over time but various methods of speeding the
decline have been tested. Topsoil stripping may be appropriate in landscaping
schemes but not on agricultural soils. Harvesting productive crops for
a year or so without adding fertilisers is a useful technique where time
allows. Deep cultivation can reduce P by mixing highly fertile upper layers
of soil with less fertile lower layers.
Yellow-rattle
Adding the hemiparasitic yellow-rattle (Rhinanthus minor) to a sward has
a similar effect to reducing soil fertility. It reduces the vigour and
therefore the dominance of competitive grasses. It is an annual so should
be sown into a short, open sward after the first year or two are past
and the annual weeds have been controlled.
The Scottish context
Wildflower seed
Most wildflower seed is grown in England. Off-the-shelf wildflower mixtures
from English companies are usually not suitable for use in Scotland because
they include species such as betony (Stachys officinalis) which do not
occur naturally throughout Scotland. Scottish suppliers sell suitable
mixtures and some English companies include ‘Scottish’ mixtures
in their ranges. A list of suppliers is included on the Flora Locale website;
see the link at the end of this note.
Timing of operations
Late summer to early autumn is normally the best time for sowing. However,
seed bed preparation must be carried out early enough to allow adequate
seedling growth before winter and this may not always be possible in Scotland,
in which case April to May is the next best option.
Spreading green hay
Hay spreading is a recommended technique for transferring seed from a
species-rich grassland to a newly-created or a species-poor grassland.
This can be cheaper than buying wildflower seed and can transfer species
which are not commercially available, such as sedges and woodrushes. However,
the site supplying the hay needs to be a species-rich meadow very near
to the site where it is to be spread. There are virtually no traditionally
managed hay meadows in Scotland outside the Highlands and Islands so this
technique will rarely be practicable. For further information on methodology,
see the link to RDS Technical Advice Note 28 below.
Sources of guidance and information
Defra
Defra have published a series of Rural Development Service Technical Advice
Notes on arable reversion and sward enhancement. They can be downloaded
from the Defra website at the links given below.
RDS Technical Advice Notes on Arable Reversion
1. Technical Advice Note 21. Arable reversion to species rich grassland: site selection and choice of methods2. Technical Advice Note 24. Arable reversion to species rich grassland: establishment of a sown sward
3. Technical Advice Note 25. Arable reversion to species rich grassland: early management of the new sward
RDS Technical Advice Notes on Sward Enhancement
1. Technical Advice Note 26. Sward enhancement: selection of suitable sites2. Technical Advice Note 27. Sward enhancement: choice of methods
3. RDS Technical Advice Note 28. Sward enhancement: diversifying grassland by spreading species rich green hay
4. RDS Technical Advice Note 29. Sward enhancement: diversifying grassland by oversowing and slot seeding
5. RDS Technical Advice Note 30. Sward enhancement: diversifying grassland using pot grown wildflowers or seedling plugs
Flora Locale
Flora Locale is a registered charity aiming to promote good practice in the
use and sourcing of wild flora. Advisory notes and much useful information
can be downloaded from the online library in
Flora Locale’s website
Flora Locale Advisory Notes on Grassland Creation and Restoration
- Bringing back the meadows: Managing recently created grasslands
- Bringing back the meadows: Enhancing the floral diversity of semi-improved grassland
- Bringing back the meadows: Sowing wild flora seed
- Bringing back the meadows: Creating wild flower meadows on improved agricultural grassland sites
- Bringing back the meadows: Spreading hay
- Restoring native grasslands using local origin seed: Collecting and using brush-harvested seed
- Using native flora for quarry restoration
FACT: Forum for
the Application of Conservation Techniques
Fact is a partnership of organisations which promotes practical solutions
to conservation land management problems.