Chestnut Pollination Season

by Bill Adamsen

Achieving the goals set out in our regional adaptation program require finding native American chestnuts and capturing their genes. We do this by finding American chestnut that can be …

a) validated as being pure American chestnut
b) cooperate by flowering
c) are accessible trees with accessible (bucket truck, ladder) flowers
d) cooperate by being compatible with our advanced breeding pollen
f) have the vitality to survive till harvest with the number of nuts outlined as required

Even with this daunting list of requirements we have slowly yet surely been inching towards our goals as outlined in our strategic plan for capturing genes. Spring of each year becomes a challenging time when new tree sightings are investigated and we attempt new and creative ways to find native American chestnut. We've determined that this is our single most important activity as an organization, and certainly most challenging. It is the bottleneck for developing blight resistant American chestnut with the local Connecticut genes we seek to provide the genetic diversity outlined in the regional adaptability program by TACF.

Fortunately, American chestnut trees do not flower at the same time across the Connecticut range. We suspect there are a variety of influences, including temperature, elevation, exposure or aspect, sunny days, perhaps genetics, as well as other reasons. The fact that flowering time is staggered over a one to two week period gives us the ability to work effectively with the bucket trucks donated by Bartlett Tree Experts.

Pollination timing[click for larger image]
Graph showing optimum pollination timing in CT
graph courtesy of Bill Adamsen

The above graph shows estimated timing for pre-pollination bagging, and then pollination along a hypothetical normalized curve (too few data points to be scientifically valid). The graph was created with data points collected in prior years. Prior year data may not relate to the timing of flowering in the current year.

[download graph as pdf file for printing – 6kb – opens in new page]

The following were historical notes made by Gayle Kida about previous year pollinations. Like financial returns, previous year results may bear little resemblance to what we experience this year. But it should provide some sense of urgency to those thinking the pollinations are a ways off. Once the opportunity to pre-bag is past, there are no assurances that open pollination has been prevented. Flowering trees are often in their last years of life. The mere fact that they're flowing is indicative of having a fair number of years of exposure to the blight. We have found through experience that a year of heavy flowering … pollinated or not … is often the last until the tree regrows from its root system. That can mean the next chance to capture the genes of that tree, if it happens at all, will be five to ten years down the road.


  • CAES Wisniewski bagged 6/16, pollinated 6/27 and 6/30
  • CAES Roxbury bagged 6/19-6/21, pollinated 7/5


  • Woodbridge Gregg bagged 6/21, pollinated 7/3
  • Manchester Marriott (shopping center – heat island?) bagged 6/21 pollinated 7/5
  • Burlington Miller Rd (high elevation) bagged 6/21, pollinated 7/5
    Canaan (far north but not high elevation) bagged 6/22 pollinated 7/6


  • Tolland Congregational Church (somewhat high elevation) bagged 7/3, pollinated 7/13
  • Stafford CCC (high elevation, north) bagged 7/3, pollinated 7/13
  • Old Lyme and Salem bagged 6/26-6/29, pollinated 7/9 thru 7/11
  • Salem 2008 bagged 6/28-6/29, pollinated 7/9. Same tree 2006 bagged 6/25 and 7/1; pollinated 7/9 and 7/12.
  • Litchfield Town Farm Rd bagged 6/27, pollinated 7/11 – pollination date would have been better around 7/9

The take-away is that the pollination season is here. If you have a tree you wanted to pollinate, please be sure your validation samples are on their way to Kendra .. or are already there! You should be monitoring the flowers frequently and coordinating with Gayle to make sure we have bucket trucks and permissions lined up.

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Bill Adamsen

Bill Adamsen

Bill Adamsen is a member of the CT Chapter of The American Chestnut Foundation (TACF) Board of Directors. He served as Chapter President for eight years.

Bill Adamsen

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