|How to Collect|
Before you collect
With so many organizations and individuals involved in the seed-collection process, it is crucial that we do not duplicate efforts or overlook opportunities. If you are interested in making ash seed collections in your region and you have not collected ash seeds for the National Plant Germplasm System before, please communicate with Jeff Carstens via email Jeffrey.Carstens@ars.usda.gov or phone (515-294-3454) to confirm that the area targeted for sampling has not already been sampled nor has already been targeted for collection.
Mature Fraxinus pennsylvanica seed
(Green ash seed)
An initial summer reconnaissance to identify ash populations that meet the key points noted in "Guidelines for collecting seeds" is often extremely helpful. Summer visits are good times to locate the best areas of seed production, confirm site ownership and access, and make herbarium vouchers.
If you are planning to collect in (or you live in) an area that is within a Federal or State ash quarantine zone (see http://www.emeraldashborer.info/files/MultiState_EABpos.pdf for current map of quarantined and regulated zones), it is important that these quarantines not be violated. Ash seed samples and herbarium vouchers may be considered regulated articles and should not be transported out of quarantine zones without appropriate permits. A PPQ 540 or other permits may be required. Please contact your APHIS State Plant Health Director for more details. A contact list is available at http://www.aphis.usda.gov/services/report_pest_disease/report_pest_disease.shtml
How to collect
After suitable populations with good seed production have been identified and "georeferenced" (with a GPS unit or fine-scale maps) during reconnaissance, seeds can be collected. Harvesting time generally occurs in the fall (depending on location timing will vary), though blue ash can mature its seeds earlier in the summer and some green ash populations can retain seeds well into winter. During late summer and autumn, seeds start to ripen by displaying a gradual change in coloration from green to yellow and then to tan or brown. The first seeds to fall from the trees are typically of poor condition.
Samples of cut ash seed.
Empty/non-viable seed on left; viable on right.
Ash seed weevil. Lignyodes spp. Dejean;
Host: green ash Fraxinus pennsylvanica Marsh.
Image source: James Solomon, USDA Forest Service, Bugwood.org
Initially, time should be taken to estimate seed quality for each parent tree. Carefully examine a small, representative sample of seeds by simply cutting them in half. Visual observations should reveal a whitish endosperm that completely fills the seed pericarp. A photograph of an empty/non-viable seed and a viable seed is displayed at right (top). Seed quality can also be reduced by ash seed weevils (Lignyodes sp. — right, bottom), which destroy the endosperm.
At each collection site, a minimum of 1,000 seeds should be collected from each mother tree, but a larger amount (3,000-5,000 sd) is recommended to increase the likelihood of long-term success. The table below lists the average 100-seed weights, average 3,000-seed weights, and the average volume (in liters; 1 liter = 1.06 quarts). The ranges of weights and volumes are fairly large (range of volumes shown in parentheses), so keep this in mind when estimating the actual weight or volume needed for your collections.
The rough percentage of good seeds determined during collection by inspection will help you decide if collection is warranted or how much additional seed should be collected in order to reach the targeted quantity of live seed. Sample equally (relatively the same number of good seeds per mother tree) throughout the extent of the population. It is very important that seeds from each mother tree be kept separate.
If there are 5 to 15 (ideally 25) mother trees bearing a sufficient quantity of high-quality seeds within your collection site, then proceed to harvest seeds from each mother tree separately, either by hand from low branches or by cutting down seed-bearing branches. Pruning small branches (< 1/2 inch in diameter; i.e. < 12 mm dia.) with a pole saw can result in quickly obtaining a large amount of seed. Please note that seeds may disperse readily if a branch falls to the ground abruptly. Alternatively, depending on the seed-shattering characteristics of the parent tree, tarps can also be spread on the ground in order to catch seeds released from the tree by shaking the limbs or striking them with a pole. Large quantities of relatively clean seed can be gathered quickly in this manner. Do not collect seeds that have already fallen to the ground.
Fruiting trees may also be spotted more easily and from greater distances following leaf fall, but the ability to harvest large quantities of seeds at such a late stage can potentially decrease drastically. In addition, leaf samples may not be available for species identification during collection, but twig and seed characteristics along with bark patterns should facilitate identification.
The US Forest Service recently published a guide for ash seed collection with many useful hints to increase your overall success. See Methods for Collecting Ash Seeds to order a printed copy or download a PDF file.
Samples should be collected and stored in brown paper bags where they can dry upon collection. If seeds are wet, they should be air dried for at least 24 hours. Keep the seed collections in a cool (65-70 °F, 18-21 °C), dry (RH < 60%) place during the collection trip and prior to shipping. Do not freeze seeds. Do not allow collections to overheat, and do not leave them in a vehicle in full sun. Maintain ventilation around the collections at all times and try to park the collecting vehicle in the shade, or, at the very least, try to shade the windshield. Exposure to such sustained high temperatures can badly damage the seeds.
Clearly label all seed bags with a permanent black marker on the outside of the bag, along with a label containing the same information inside the bag. Seeds should be separated by mother tree and identified by marking each seed bag with an unambiguous numbering system, along with the proposed name of the species collected, the collection site name, and the collection date. If additional bags are needed to contain a large number of seeds taken from the same tree, simply indicate it is bag 1 of 2 or 3 of 4, etc. Seed bags should be folded and stapled.
Data collection forms should be completed for all seed collections. If an herbarium voucher was taken prior to collection, please include the voucher collection number that is associated with the sample being collected, along with associated information about any materials collected from these trees for DNA sampling.
When georeferencing ash populations, we prefer that you use a GPS unit and record your data in decimal degrees to at least 4 decimal places. Also, please set your unit to use the NAD83 datum. If you determined the coordinates retroactively, by using USGS topographic maps or online sources, please make sure that you note your source.