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Seed collection methods from grassland

Methods of collecting wild seed from native grasslands

Flora locale  01/01/2003
 

Harvesting grassland flora

 

Timing seed collection

 
The summer-flowering species ripen between mid July and the end of August
 
Some late-flowering species ripen in September (e.g. Devil's-bit Scabious, Centaury, Wild Carrot, Blue Fleabane) and ripe seed can sometimes be obtained in October
 
Spring-flowering species ripen in early July (e.g. Sweet Vernal-grass, Meadow Buttercup, Yellow Rattle)
Seed ripening times depend on:
  • Site management (e.g. grazing, hay cutting)
  • Geographic location
  • Altitude.

Grassland "whole habitat" harvesting

 
Guaranteed Local origin
  • Offers the only really practical field-scale solution for obtaining seeds of known local origin
  • This approach is the only way to obtain the full range of native grasses that are associated with native grassland
  • This technique is invaluable for restoring or extending ecologically sensitive sites.

Efficiencies of scale
  • Enables large quantities of seed to be collected with minimal effort
  • One hectare of land harvested produces sufficient seed for an equivalent area (but seed can be spread more thinly if desired, especially if used to inoculate floristically-poor grassland).
Species diversity
  • The composition of harvested seed mixtures directly reflects that of the donor site
  • Many species are sampled including a number that are simply not available from usual commercial sources
  • The overall diversity of meadow harvested mixes is often much greater than can be obtained in proprietary seed mixes

However, the composition of seed collected (species by quantity and weight) will depend on what is ripe at the time of harvesting:

  • Late summer harvesting leads to higher proportions of grass seed in the mix and spring-flowering species may not be well-represented.
Timing
  • The seed-harvesting window is brief
  • Timing is site- and weather-dependent.
Post-harvesting and sowing
  • Harvested seed can be sown directly onto a prepared donor site (although the best time to sow seed is late August-end September)
  • More usually seed is stored for later use, as the optimum window for seeding does not often coincide with the harvest
  • When seed is harvested to reinstate vegetation following engineering works several years may separate harvest and sowing (viability can be maintained only if the seed is correctly stored).
Disadvantages
  • Can be uneconomic, difficult and sometimes impossible in years when hay fields are sodden by prolonged wet spells
  • Hay cutting or grazing must be delayed to allow seed to ripen
  • Only suitable on level accessible sites which have a relatively large area of floristically rich grassland.

English Nature's protocol for harvesting from grassland Sites of Special Scientific Interest

Either harvest seed from no more than 30% of the meadow in any one year, or  
  • harvest from any given meadow no more frequently than every 3rd year
  • Up to two seed harvests a few weeks apart may be taken from (the same parts of) the same fields as long as the locations are adequately marked
  • Where seed is harvested from a whole field or a block as opposed to in strips, an agreed proportion (usually 5% of the harvested seed) should be retained and broadcast back across the whole area. This should be after the hay crop has been cleared, or ideally a few weeks later after chain harrowing or a period of aftermath grazing
  • After seed harvesting, harvest the crop as hay (not silage) and ensure that it is turned across the whole area to spread the remaining seed
  • Use a modified brush harvester which operates a low vacuum to minimise the impact on invertebrate communities
  • Spread harvested seed on a sheet (half-an-hour is fine) in the meadow to allow migration of invertebrates back into the sward

(Protocol as @ January 2003)


Harvesting methods and equipment

 
For technical specifications see the Flora locale Technical Note: Equipment for harvesting grassland wild flora and heather.
 

Brush-harvesting

 
Advantages
  • The most effective and wildlife-friendly method for whole-field harvesting
  • Lightly brushes seed off, with minimal chaff and minimal wildlife "bycatch"
  • Takes only a proportion of seed ñ unripe seed won't be taken (plants such as Yellow Rattle will still seed sufficiently to maintain their populations)
  • Brush harvester is easily transported
  • Offset versions don't flatten the sward prior to harvesting
  • Hay can be cut afterwards.
Disadvantages
  • Won't take seed easily from some species (e.g. Scabious, Knapweeds)
  • You may have to follow-up with some manual collections.
  • Commercially available equipment *indicates machinery that can be trailed offset
  • *Emorsgate Brush Harvester (requires standard 40hp agricultural tractor with 3- point linkage and PTO) - for large areas of grassland
  • *Eyre seed harvester (trailed using standard tow bar/tow ball fixing)
  • Rekord Seed Harvester (for use with pedestrian tractor so suitable for smaller sites)
  • Turf-cleaning machines (e.g. Charterhouse Turf Tidy).

Combining - using a plot combine
  • Available mainly as second-hand machinery (otherwise not widely available)
  • Used by commercial nurserymen and research stations
  • May be available for hire
  • Less efficient than a good brush harvester for collecting species having light seeds (e.g. Yellow Oat-grass Trisetum flavescens, Yarrow Achillea millefolium)
  • More efficient at collecting seed from species holding seed tightly (e.g. Knapweeds) ñ that can be missed by a brush harvester
  • Can be calibrated for different seed types
  • Cuts grass for hay and removes seed at same time
  • Used for harvesting some commercially grown wild flower crops.
Green hay collection and use
  • Suitable for whole-field harvesting or for smaller sites
  • Timing is critical
  • Carry out when the maximum number of species have ripe seed, but not too late in the season
At the field-scale:
  • Mow or forage-harvest the sward
  • Loose bale it straight away or blow the cuttings direct into a trailer
  • Transport it directly to the receptor site
  • Spread the hay immediately to allow it to dry and the seed to drop out (bales can be rolled out)
  • Leave it for a minimum of one week in dry weather and three weeks in wet weather to allow seed to ripen and fall out
  • Grazing or using a swath turner followed by rolling can be useful to aid seed shedding and bedding in.
To avoid the need for green hay to be removed, it may also be useful to specify that it should be spread thinly at a recommended hay: visible ground ratio of 1:3 for enhancing an existing sward and 1:2 for arable sites.

Alternatively, hay can be spread thinly on bare ground sites and not removed, or can be chopped before spreading and left. 
Advantages
  • Suitable for receptor sites very close to the donor site
  • Farmers can collect their own seed, using standard agricultural equipment.
Disadvantages
  • Hay is bulky and costly transport - so this method is only suitable for sites close by
  • Timing is critical - hay must be collected and spread within a few hours to prevent seeds dropping out, rotting or being destroyed by heat.
  • A usable or saleable crop of hay is lost (on a productive hay meadow, this could be equivalent to losing between 20 and 70 hay bales).
For smaller sites, e.g. road verges:
  • The sward can be manually or mechanically cut
  • Rake grass immediately and put into a trailer
  • Spread it directly on to the receptor site.
Equipment for small sites
  • Agricultural machinery isn't necessary
  • Standard car with towbar and trailer
  • Petrol/2-stroke brush cutter or heavy duty mower
  • Scythes, reap hooks and yard broom
  • Hay forks (to strew hay from trailer)
  • Labour - could be a volunteer conservation task.
Portable leaf vacuums
  • Readily available
  • Reasonably cheap
  • Easily carried to inaccessible sites
  • Designed for collecting leaves from parks and gardens
  • Good for using on steep ground and land not accessible to brush harvesters or pedestrian mowers
  • Can be used to collect seed from individual species and small sites.
Tips
  • Buy heavy duty, good quality, petrol/2-stroke versions
  • Disable the internal leaf-shredder if present (usually a fan) to prevent damage to seed*.
  • *modifications should be undertaken by a person knowledgeable about the technical specifications of the equipment, are at user's risk and may invalidate the manufacturer's guarantee.
To reduce impact on invertebrates
  • Disable the leaf-shredder (see above)
  • Spread the seed on to a poly sheet laid out on site for at least half-an-hour immediately after collection (to enable invertebrates to crawl off or fly away).
Other pedestrian equipment
  • Commercial leaf vacuums ("billy goats")
  • Small brush harvesters (e.g. the Rekord harvester)

Hand-picking

 
An effective method for collecting seed from:
  • small sites or small populations (e.g. wild flowers on road verges)
  • species which are difficult to mechanically harvest (e.g. Field Scabious Knautia arvensis, Harebell Campanula rotundifolia, orchids).
Substantial quantities of seed can be collected with the help of properly supervised volunteers or the family.

Equipment for hand-picking
  • Waterproof felt pen - to write on collecting bags (species name, date, where collected)
  • Collecting bags (not poly bags, which will sweat and rot the seed), e.g.
  • Strong brown paper or woven polyproylene flour bags
  • Old envelopes
  • Home-made from muslin (cheap to buy, available from fabric shops)
  • Cutting and raking equipment can be useful, e.g. strong pair of kitchen scissors or pruners, reap hook or slasher, rake.
Tips
Wear strong garden gloves for collecting from prickly species (e.g. Viper's Bugloss Echium vulgare).

Keep both hands free by tying the collecting bag around your waist (remember string).

Beware hazardous plants, such as Wild Parsnip Pastinaca sativa , which produces phytotoxins that can cause painful blistering following skin contact and exposure to sunlight.

Methods of hand picking
 
These will depend on:
  • The density of the plants and ripe seed heads
  • The ripeness of the seed
  • The species.
Two basic methods are:
  • Stroking, rubbing or shaking seed heads so seed falls into collecting bag
  • Cutting or picking ripe seed pods or stems holding one or more seed-heads.
Where there is a high density of seedheads holding ripe seed:
  • cut off the ripe seed heads (e.g. using a strong pair of scissors, or reap hook)
  • rake up the cuttings (e.g. for low-growing plants such as Birdísfoot Trefoil, where growing densely on short turf) or
  • cut the stem and put it or allow it to fall into the bag.

Paying for seed

 
It is appropriate to offer to pay for seed in some cases, e.g. for meadow-harvesting a privately owned site or where the seed is to be used on a privately owned site.

Drying and cleaning seed
  • Uncleaned seed can be put down directly on to a receptor site without removing chaff if spread by hand.
  • Other seed should be dried, cleaned and removed from pods and capsules.
This will reduce losses from:
  • Plant disease (e.g. fungi, viruses)
  • Invertebrate predators.
Seed of some species, e.g. Common Knapweed Centaurea nigra and legumes are particularly prone to predation by weevils. (Eggs are laid in the flower heads, and the larvae and adults feed on the flowers and seeds.)

Seed to be drilled should always be dried and cleaned, or chaff will block the drill.
 

Drying the seed
  • Initially, empty the seed hopper on to a polythene sheet on site; rake and spread the seed as thinly as possible to dry in the air (by reducing the moisture content you will also make the seed lighter and easier to handle)
  • Back at base, spread the seed on a polythene sheet either in an airy barn, greenhouse, polytunnel or outside (cover or bring in during rain); Rake it over periodically, until dried.
Drying the Seed
 

Drying racks: Weald Meadows Initiative

Once seed has been harvested it is taken back to the farm and spread thinly on specially made drying racks. These are made of wooden frames covered with a fine polypropylene mesh. The construction allows for air to circulate between the stacks of seed, and the racks can be moved with a forklift.
 
Seed racks © High Weald AONB         Drying seed Racks © High Weald AONB
 
 

Manual seed cleaning

A variety of methods will be required to remove stems, petals and leafy material,
and to remove seed from husks and pods.Peter Greenhalf/CA
  • Sieving - use sieves of different sizes (1cm coarse sieve may be
    sufficient just to remove large chaff): some initial sieving can be done
    on site if there is sufficient labour
  • Blowing -drop chaff and seed in front of a fan (heavy seed will drop,
    chaff will blow away)
  • Shaking (or raking) - light chaff will come to the top, heavier seed
    will drop to bottom
  • Rubbing and squeezing (this may be useful if whole seedheads of
    knapweed or composites have been picked
    .
Manually cleaning the seed

Treading or light crushing can be used for legumes with hard-coated seeds and unexploded pods (for small quantities, the seed can be put into a poly bag and bashed with a rolling pin to break up the dried seed pods and free the seed).
 
Light mesh racks, standing proud of the ground, with a diameter of 1 centimeter can be used on site to reduce the quantity of stem and leaf matter when unloading the seed hopper and before spreading the seed to dry on polythene sheets.
 
Drying seed on site can be thwarted in wet weather. It will also be more difficult on small sites that are sheltered by large hedges or in wooded areas, where humidity remains high even in warm weather.
 

Manual seed-cleaning is time-consuming and not 100% effective. For large quantities of seed, mechanical methods will need to be used. 

 

Storing seed
  • Store clean, dry seed only
  • Put in sealed labelled jars, poly bags, sacks or dustbins
  • Keep in a cool, vermin-free, dry place
  • Most wild flower and grass seed can be stored and remain viable for many years
  • Seed requiring hardening must be chilled at 0 degrees C or less for a week or more prior to sowing
  • Some species requiring hardening will not germinate in spring unless sown the previous autumn, even if pre-chilled.
Useful links
  • The following links are designed for North American wild flowers, but some of the general principles will apply to
    harvesting wild flower seed in other countries.
    •  Collecting wild flower and prairie seed
    • Guidelines for seed collecting (Lady Bird Johnson Wildflower Centre)

  • This technical note is one of a series produced by Flora locale, in association with English Nature, to encourage good practice in the use and collection of native flora. It may be downloaded and distributed electronically or by simple photocopies but may not be published, placed on a website or sold for commercial gain. To seek permission to publish this note, or extracts from it (electronically or otherwise) please contact info@floralocale.org
     
    Information in this note is provided for guidance only and focuses on wild seed collection in the UK. Flora locale accepts no liability over its use or application by individuals, businesses or institutions. See also the Technical Notes: Equipment for harvesting wild flora and heather and Harvesting and using heather seed. Training courses are available to practitioners wishing to learn more about issues covered in this Technical Note. See the training section of the website. Special training and demonstration events can also be organised by request.

    © Flora locale and English Nature 2003. Photographs © as credits.

    Acknowledgements
    Flora locale is grateful for financial support received from the Esmee Fairbairn Foundation and Ernest Cook Charitable Trust, which funded the production of this Technical note.

    With thanks to Tony Robinson (English Nature), Penny Anderson, Richard Brown (Emorsgate Seeds), Dawn Brickwood (Weald Meadows Initiative) and all contributors to the Enact magazine features Options for seed harvesting techniques (published in Enact Winter 2001 and Spring 2002) and Diversity from Molinia moorlands (Enact, Winter 2002). Back issues of Enact can be obtained from British Wildlife Publishing, tel: 01256 760663, enquiries@britishwildlife.com).
     
    Enact has been superceded as the magazine Conservation Land Management, available on subscription from the same address.

    Additional information, either text or images, which will enhance the usefulness of this technical note would be appreciated. Please email Flora locale using the above address.
    Compiled by Sue Everett, Flora locale.

 


Page last modified on Sunday 03 of February, 2013 23:00:03 GMT