There are times when it is either impractical to pollinate a specific tree (poor access for instance), or when it is unclear that a tree being pollinated will produce the number of nuts required for a full line, and it is questionable the tree will survive another season to complete the line. In these situations it is sometimes worthwhile considering collecting pollen for use in pollinating the female flowers on the tree that would normally be providing the pollen. If the latter scenario, it makes sense to coordinate with the bagging or pollination process since the pollen is likely to be viable at the time of pollination, and the resources (bucket truck) are likely to be in the area performing the pollination.

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There are some fundamental challenges for the CT Chapter of TACF in using pollen to pollinate the advanced breeding female flowers. Typically the advanced breeding trees are located in Meadowview, Virginia, and are receptive a week or more before the pollen is available in CT. Subsequently, the processed pollen must be frozen for use the following year. Another significant challenge is finding the resource (person) to travel to Meadowview to perform the pollinations, and of course coordinating with Meadowview to ensure the tree is available for pollination. These are simply logistical considerations that require management.

The following was provided by Dr. Martin Cipollini from Berry College, Georgia. The southern chapters perform pollen processing frequently. They take pollen from wild trees in the south and transport it to Meadowview to pollinate advanced bred trees. They have the significant advantage that the advancement of their pollen coincides with, or even precedes the flowering time at Meadowview.

Overview:

Use Fresh Catkins or Use Dried Pollen

• Collect branches with catkins
• Keep fresh until ready to strip from branch
• Strip catkins and leave on table to dry overnight at air temperature
• Strip catkins of pollen
• Collect pollen in prescription bottles

Label bottles!!

• Tree from which it came and date of collection
• Use a permanent marker. Place masking tape on vial and write it on the masking tape.

Make sure your hands and all of the materials you use are sterilized with rubbing alcohol or hard liquor while drying pollen

Step by step process

• Collect catkins from desired tree – take a whole branch and place the branch in a jug/5-gallon bucket filled with water until you are ready to collect the pollen. Cover the branch and catkins with a paper bag. Don’t leave them too long in the jug – just overnight if possible.
• Very gently remove paper bag from flowers and flowers from jug.
• Separate the anthers from the catkins. You can do this by shaking the catkins, stroking the catkins with your fingers, or, and this is a great method, using a frying pan splatter screen. The latter method is faster, yields more anthers, and cuts down on the amount of debris in the sample. Place several individual catkins on top of the splatter screen and hold the screen over a piece of glass. Shake the screen horizontally causing the catkins to roll and drop their anthers. You can roll the catkins gently with your hands across the screen as well (don’t roll hard enough to rub off the hair like filaments onto the plate as well).
• Pick out the obvious trash and bugs with clean tweezers. Scrape the pollen into a pile with a single-edge razor blade (Gem). Use alcohol and kleenex to remove oil from the razor blade before use. You can separate most of the remaining fluff, trash, and bugs from the pollen and anthers by scraping off the top of the pile of pollen and "marching" it away from the rest of the pile. Then scrape what is left on the marching trail back into the main pile of pollen. Repeat as necessary. Bugs frequently will crawl out of the pile if you disturb it with the razor blade.
• Scrape the pollen pile into a labeled vial. Cap the vial with a labeled lid which has a 0.25-inch diameter hole in top and place in dessicator, over fresh silica gel or calcium chloride. Use a paper punch or similar tool to make the hole in the lid. The dessicator can be a plastic peanut butter jar. Desiccate the pollen for at least 4 hours, more if there is a lot of pollen; not more than 24 hours. Do not store fresh (undesiccated) pollen in high humidity or at room temperature any longer than absolutely necessary.
• Wrap a small amount of dessicant securely in dessicated paper and place in vial; make sure there's no dessicant on the outside of the paper. Recap vial with a lid with no holes. Tape the lid to vial to make sure the lid won't come off in shipping! After this the pollen can be safely mailed to other pollinators. Pollen should be refrigerated if it is to be used in the next week or so; frozen at 0°F if it is to be saved for next year. Do not freeze fresh pollen.

Freezing Pollen

This description of freezing pollen was provided by William White, the TACF Southern Regional Science Coordinator and former Lab Scientist at TACF Meadowview. William has years of experience successfully freezing pollen for use the subsequent year.

The protocol for freezing pollen is very simple. Just process the pollen as described by the instructions and make sure it is as dry as possible. I assume you are wanting to use the pollen next year I would recommend freezing right after decanting process. Germination rates are much lower after a pollen has been to the field and germination rates will be lower after freezing but will still be viable. You will expect to get a lower nut yield from pollen that has been frozen.

Pollen Testing

The following is from Dr. Fred Hebard TACF Staff Pathologist

Pollen testing - It does you no good to pollinate your tree with dead pollen. It is best to test pollen if possible. It may be advisable to test it every day or so during the pollination season. Chestnut pollen is easily germinated if floated on drops of 1% table sugar (or glucose) in non-chlorinated water, and held at 85°-90° F for one hour. Examine under a microscope at 30-100x magnification. Good pollen should show 15-60% of the grains with tubes (as long as the grains) growing out of them.

Illustrative Photographs

Dr. Paul Sisco took a series of photographs of pollen processing and those photos are available here or by simply clicking on the following links.

Glass Plate
Sterilizing the Glass Plate
Catkin Bag
Stripping Catkins
Collecting Anthers
Anthers onto Bag
Pill Vial
Anthers into Vial
Flaming Sifter
Pollen Sifting
Sifted Anthers
Label Tape
Dessicant Capsule
Labeled Vial
Paint Can
Drying Compound
Pollen Vials in Can