Botanic Gardens Trust, Sydney, Australia

Department of Environment, Climate Change and Water NSW

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Collecting and processing

Making a seed collection

All collections of seed are made with appropriate permissions and licences from landholders. Populations must be located and collections made when seeds are mature but before they are naturally dispersed, which for some species occurs during a very limited time frame. A proportion of seed is collected from as many individual plants as possible to obtain a representative sample of the population. 

In addition to collecting seed, herbarium vouchers (pressed specimens) are made for each collection, and stored at the National Herbarium of NSW. This is important for allowing accurate identification by taxonomists and means that any future plant name changes can be tracked and applied to the seed collection. Collection data are also recorded, including details of location, plant habit descriptions, associated vegetation, geology and other useful site observations. Fruits and seeds are routinely photographed in the field as well, which provides an additional information resource associated with the collection.

There are a number of different methods by which seeds are collected. Some examples of collecting are illustrated below.

Richard-Johnstone-recording
Richard Johnstone recording field data

Seed may be removed by hand, or by cutting short tips of branches off

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Richard Johnstone hand-collecting Zieria formosa

 

Tree seeds, such as eucalypts, may be reached using an extendable pole to cut branches off, so that fruits can then be stripped off the branches at ground level

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Richard Johnstone using pole to collect Eucalyptus michaeliana

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Andrew Orme removing fruits from Eucalyptus volcanica branches

A drop-sheet may be placed on the ground and the plant shaken, causing mature seed to fall onto the sheet

Richard-Johnstone using a drop sheet
Richard Johnstone using a dropsheet to collect Pultenaea villosa

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Richard gathering the collection of Pultenaea villosa from the dropsheet

Mesh bags are sometimes secured over seed heads, especially where individual seeds mature and disperse rapidly. The bags are retrieved after a number of days or weeks, and the naturally dispersed seeds will have been caught in the bag.

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Amelia Martyn collecting bagged seed from Zieria arborescens

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Contents of bag collected from Zieria arborescens

 

Processing a seed collection

Seeds come in such a variety of shapes and sizes that every collection must be assessed individually to determine the best method of cleaning. The aim of cleaning a collection is to remove debris, insects and non-viable seeds to obtain a high quality seed collection for long term storage.

Some seeds will be released (dehisce) naturally as fruits dry, but others may require physical methods to open fruits. For example, Banksia requires heat (eg. fire) to release their seeds, so cones are put over a flame to open the follicles. Collections are cleaned using a variety of techniques including crushing, rubbing, sieving with a range of size gradations, and aspirating. We use a ‘zig-zag aspirator’ to separate material based on weight, allowing removal of light debris from heavier seed.

An example of processing a collection of Pomaderris is outlined below.
Pomaderris-lanigera-in-situ
1. Fruits of Pomaderris lanigera in situ		 Pomaderris-in-bag
2. Braches are removed and dried in a specially designed Drying Room - NB: each collection is labelled to keep track of it throughout the process		 Pomaderris-crushing
3. Fruits are stripped from branches and crushed using a rubber bung and rubber mat, allowing pressure whilst not damaging seed
Pomaderris-in-sieve
4. Collection is sieved to remove coarse material (mostly sticks and leaves).

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4a. Coarse debris following sieving.


 

Leah-Seed-using-zigzag-aspirator
5. Remaining material is aspirated in stages to remove more debris. Heavier material falls down zigzags on the left hand side, while lighter material is lifted off and collected on the right hand side.
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5a. Fine debris from first aspirating.		 Pomaderris-mixed-seed
6. The now almost-clean Pomaderris collection is ground further with rubber bung to release remaining seeds from surrounding cases.		 Pomaderris-clean-seed
7. The collection is aspirated again to obtain pure seed.
Pomaderris-in-jar
8. Cleaning is complete and the collection is ready for storage and testing.		 Leah-Seed-filing-seed-collection
9. The collection is vacuum sealed and stored at a low temperature in the fridge or freezer to slow the metabolic activity in the seed and hence prolong the life expectancy		  
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