A Seed Zone Summit was hosted by the University of Kentucky at their Good Barn facility in Lexington May 9-10 2018 to allow for exchange of information and ideas about this project.  Over 30 people attended from across the eastern US representing states, industry, NGOs, and the US Forest Service’s three deputy areas. Our facilitator from the USDA Forest Service Enterprise Team, Clay Coleman, conducted a survey of attendees.

The program at the Seed Zone Summit encompassed four main topic areas:

  1. defining the importance of tracking seed origin
  2. assigning factors to use in delineating seed zones
  3. distinguishing taxa that would most likely fit this framework
  4. addressing challenges and next steps.

We invited speakers to lead off each topic area and followed each topic with 1-2 hours of small group discussions followed by a larger synthesis of ideas with the entire group.

Action Items from the Summit

We did not attain a formal consensus on any topic, but instead noted action items in which attendees were in general agreement.  Four key topics related to seed zone development are listed below.

1. Use of Plant Hardiness Zones as a Base Layer.

We agreed that some metric of minimum temperature is necessary as a layer in a seed zone map.  We discussed the use of different minimum temperature standards (minimum temperature of the coldest month, for example), but we were in agreement that the benefits of using an established standard (such as the USDA Plant Hardiness zones) would improve implementation of seed zones.

2. Incorporate a Precipitation Variable

We agreed that some metric of precipitation is probably necessary as a layer, but we made no final decision on the variable to use.  The Provisional Seed Zones rely on aridity, which works well for distinguishing dry areas in the western US, but doesn’t discriminate the regions well in the east. At the end of the summit, we did not make a decision on which precipitation variable to try. Instead, the core organizing committee was tasked with reviewing different precipitation layers to determine which, if any, should be incorporated in the seed zones.

3. Incorporate Ecological Provinces

Ecological province emerged as a potential layer in a seed zone map because the provinces separated areas that appear to have some genetic basis. Provinces also capture elevation and soil gradients which could make sense for some plants/trees, and provided east-west breaking points that made sense to the attendees in the room.  This layer would be fitted and evaluated by the core committee.

4. Incorporate County Lines

We had interesting discussions around the diversity of cultural practices in the seed industry:  sometimes, seed collectors are happy to provide specific geographic information about the seed origin, but in other instances the collector prefers to not reveal their sources. Even in the latter case, seed collectors are usually willing to provide the county where the seed originated, which seems a reasonable accommodation for plant and tree seed. Counties in the eastern US are relatively small, and could serve as a minimum descriptor of seed origin. Still, commercial seed producers and nurseries need a standard to bulk seedlots across counties for batch processing. A seed zone map that contains a county-layer as well as the larger seed zone in which that county belongs will provide collectors and nurseries flexibility to bulk plant material by county or seed zone.