|
In the mountains from Georgia to Maine, you should start looking
at your trees twice weekly in the beginning of June, so you can
judge which trees will be flowering in the current year and when
you will need to begin pollinating. At lower elevations in the
south, it can be as early as the beginning of May. In many areas
of the country, American chestnut trees begin blooming between
June 15 and June 28. Chinese chestnut trees tend to begin blooming
about a week earlier.
- Records - Write down everything you do; how, when and
where. Any nuts you make might be unidentifiable and worthless,
otherwise.
- Species Identification - Check the species identification
of your trees; there have been plenty of long-standing misidentifications.
We will be glad to determine what species of chestnut you have;
send leaves and twigs of your trees to the ACF Wagner Research
Farm, 14005 Glenbrook Ave., Meadowview, VA 24361. In winter,
you can send old fallen leaves from around the base of your
tree.
Female Tree Operations
1. Bagging- Chestnut flowers to be pollinated will have to be
"bagged" to exclude random airborne pollen from fertilizing or
blocking them.
Use bag #421, a corn-shoot bag, from Lawson Bags, P.O. Box 8577,
Northfield, IL 60093, (800) 451-1495 or (847) 446-8812. (The minimum
order is 3000 bags, costing about $120; if you're only doing a
few, write the Meadowview Farms at the above address and we will
send you a few). Order these before you start! You can carry supplies
up the ladder in your pockets, in a folded pollination bag attached
to your pants with paper clips, or in a carpenter's apron.
In general, you can expect to harvest one nut for each bag placed
over several female flowers. Bag female flowers when they have
exerted their styles 2-4 mm. The styles are white or yellow, whereas
the remainder of the female flower is green. In this manual, we
also call female flowers burs, which is what they develop into
as they mature. It is safe to bag for only 5 days after style
emergence. Another good rule of thumb, which applies in most years,
is to begin bagging when green catkins on 50% of the flowering
branches begin to exert stamens and turn white or creamy yellow.
See Figures 1 and 2.
a) Remove all male catkins and leaves
and the male part of the bisexual catkins, using scissors or hand
pruning shears.
b) Puff up the bag, place over shoot,
twist on base and secure with a jumbo paper clip or a twist'em.
Try to place the bag so it does not touch the female flowers:
leave an inch of free space at the tip. Otherwise make the bag
extend down shoot as far as possible.
Figure 1.
A single flowering branch of chestnut, prior to emergence
of styles and anthers. Flowers not ready to bag.
Figure 2.
Chestnut flowers 3-5 days after first emergence of anthers. Ready
to bag.
c) When a ladder is in place,
branches may be pulled over to the ladder with a pole pruner and
tied off to the ladder to increase the number of flowers bagged
without moving the ladder. Make a loop in one end of a small rope
and either tie off the pole pruner or else the branch itself.
It can be helpful to have two ropes, one to secure a thicker part
of the branch and the second to tie off branch tips above the
thick part.
d) Leave a few branches unbagged
so you can judge when the tree is ready to be pollinated. Don't
use your worst branches for this!
2. Pollinating- In general, pollinate 12 days after
bagging. The female flowers are receptive when the styles turn
yellow and spread out across the top of the flower. At that time,
the base of the styles can often be seen protruding from the nascent
bur. Peak receptivity generally occurs when all the male catkins
are in bloom but before anthers emerge from the bisexual catkins.
The 12-day rule is a reliable guide to the best time for pollinating.
See Figure 3.
Figure 3.
A single flowering chestnut branch with male flowers in full bloom.
Time to pollinate.
a) Remove bag, pollinate (see below), and resecure
bag with a new paper clip or twist'em.
b) Save every tenth bag as
an unpollinated control; do not remove the bag. Mark unpollinated
bags with a metal or plastic tag twisted on above the paper clip.
You can write on the tag to indicate the male and female parents
of the real crosses. Do not save your worst bagged flowers for
unpollinated controls. It is important to do these checks. Despite
careful attention and experience from more than ten-thousand crosses,
I almost always have a few trees with nuts in the check bags.
It is important to know who the father of a cross is; that's why
you do all these manipulations! The check bags tell you whether
or not your cross is what you hope it is.
c) Branches or trees should
be labeled with information about what pollen or treatment was
applied. Label the branches or trees as you go, not later! Plastic
or aluminum tags can be used. Use a black Sharpie to write on
plastic tags. Both tend to disappear over the summer- wind, birds,
and curious people take them off. Write a description of what
branch was pollinated with what or make a map of separate trees
in your notes.
d) Bags may be left on till
harvest. In weevil-infested orchards, this reduces weevil damage
so that nuts needn't be hot-water treated nor trees sprayed. It
also can save some nuts in burs which open before you harvest.
Pollinating with Fresh Catkins
You can carry catkins up the tree in a cup or tin can in a
carpenter's apron, or in a folded corn-shoot bag tied to your
belt or pants with paper clips. Use a clean bag or can for each
type of pollen. Rub one catkin over all the styles of each female
flower 4-5 times. Use a new catkin when all the anthers have been
removed; every 5-10 female flowers at most. Use the whitest catkins
available. This is the easiest and possibly the best method of
pollinating.
If fresh catkins are in short supply, tap a previously
bagged catkin on a microscope slide and proceed as indicated in
the next section, "Pollinating with Dried Pollen." Catkins can
be tapped repeatedly on slides over a series of days. See more
below under "Male Tree Operations, From trees with few branches
and catkins"
Pollinating with Dried Pollen
Place a small sample of pollen in a 1-inch-diameter vial. Don't
carry your entire supply of pollen up the tree! Clean a microscope
slide with alcohol (Vodka or 70% Pure Grain) and dry thoroughly
with kleenex. Cover the mouth of the vial with the slide. Holding
vial and slide tightly together, turn the vial upside down, and
shake pollen onto the slide. Turn the vial right side up, shake
all the pollen you can off the slide and back into the vial. A
film of pollen will remain on the slide, which is now "loaded".
Re-cap the vial. Gently rub slide on tip of style (Figure 4).
You might want to mark the loaded side of the slide with a grease
pencil or crayon. Make sure style tip leaves streaks in the pollen.
Reload slide every 5-10 flowers. Use a clean slide every 50-60
flowers. Keep your pollen cool in the shade.
Figure 4.
Female chestnut flowers showing the style and stigma. Apply pollen
to the tip of the style, where the stigma is located.
Male Tree Operations
1. Male Flower Collection - Collect flowers
optimally when they are creamy white-yellow, before they have
started to turn tan or brown. If you are going to be collecting
in the morning and expect dew, cover the flowering shoots with
brown paper grocery bags at dusk the previous night so the flowers
will be dry when you pick them.
a) From large trees.
Cut flowering branches about 2 feet long and place in a 1-gallon,
very clean plastic milk jug with a 3-inch-diameter hole cut in
the top. Prune leaves and twigs off the base of branches which
go inside the jug. Fill the jug three-fourths full with cool (not
ice cold) tap water, so all branch bottoms are well immersed.
Label the jug with a black Sharpie . Cover flowers and branches
with a large paper grocery bag and place milk jug in a 5-gallon
plastic bucket, to prevent tipping over and spilling. Label the
bag and bucket. Keep the bucket of flowers cool, out of direct
sunlight. Try to keep them away from wind and excessive vibration.
Flowers will keep 3 to 7 days, longer if refrigerated. Catkins
may be obtained directly from the cuttings. Remove the grocery
bag gently.
b) From trees with few
branches and catkins. If there are only one or two catkins
on your tree, you may want to visit it early every morning while
it is flowering and pick off exerted stamens, placing them in
a vial. Then proceed as indicated under step e) in the next section.
This is a tedious method. If there are 10 to 20 catkins on the
tree, and you have a receptive tree nearby, simply put the catkins
in a tin can or corn-shoot bag and pollinate the receptive tree
with them. It is be best to collect the catkins early on a still
morning, but after dew has dried off (or to have covered them
the previous evening as discussed above). Collected catkins should
be stored in a sealed bag or can to prevent dessication: fold
over the top of a corn-shoot bag and secure with a paper clip
or put plastic film wrap over a tin can. Catkins will keep 1-2
days, longer if refrigerated. If you want to collect and store
pollen from 10 to 20 catkins on a tree, repeatedly tap each catkin
onto a small sheet of glass very early on still mornings. Then
proceed as indicated under step c) in the next section.
2. Pollen Collection & Preservation
a) Very gently remove paper
bag from flowers and flowers from jug.
b) Wrap wet base of branches
with several dry paper towels to avoid water drops on glass. Vigorously
shake the bundle of branches over a 2 to 3-foot square or rectangular
piece of glass. It is best also to unfold a few brown paper grocery
bags and place them under and around the glass to catch pollen
that falls around the glass. This process can be repeated over
a number of days, 2-3 times a day. If the flowers are in a cool,
still room, it is not necessary to replace the paper bag. They
can be stored on top of their piece of glass and will drop anthers
on it.
c) 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.
d) If possible use a separate
sheet of glass for each type of pollen collected, or else, between
pollen types, clean and dry it thoroughly as you would a drinking
glass, using plenty of dish detergent. Rinse very well. Keep branches
with different pollen types as widely separated as possible, especially
when the paper bags are not in place. Do not mix the jug, bucket,
paper bag, razor blade, and paper towel between types of pollen.
Clean the tweezers thoroughly with alcohol (Vodka or 70% Pure
Grain) and dry thoroughly between types of pollen.
e) 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.
f) 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.
3. 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.
Harvesting
Harvest the nuts when the burs begin to open. This
is around the last week in September, first week in October in
the mountains from Georgia north to Maine. In the Piedmont of
the Carolinas, Georgia, Alabama, Mississippi and Tennessee, it
can be as early as mid August. If possible, check your trees at
least weekly two weeks before the local harvest date. The main
reason for this is to check for squirrel predation. If squirrels
are clipping off the burs and eating through them, place a "peace
offering" of several pounds of chestnuts under the tree. This
will have to be repeated up to thrice weekly. Frequently, Chinese
and Japanese chestnut come in early enough to yield a supply of
nuts for the "peace offering." Squirrels do not attack chestnuts
in the bur every year, only when there is a high squirrel population
and a poor acorn crop. Shooting, trapping and poisoning have proven
ineffective in controlling squirrel predation.
a) Use heavy leather or rubber
gloves. If the burs still penetrate the gloves, put two pairs
on. Some of us put rubber gloves on underneath leather gloves.
b) Wrap a good-quality (Hefty,
etc.) black plastic garbage bag around your belt and secure it
with a paper clip or twist'em shoved through the bag and around
your belt. Keep a white plastic kitchen trashcan bag in your black
plastic garbage bag and put all the unpollinated controls in that.
Carry several spare bags in a pocket. If the burs can be grabbed
so that the nuts will not fall out, rip them off and put them
in the garbage bag. Take the pollination bags and ties off the
tree so it will not be unsightly and so you can count the number
of bags. Place them in the garbage bag too. If the burs have opened
too far or some nuts have fallen into the pollination bag, cut
or break off the whole branch while holding the nuts, or else
bend it into the garbage bag to save the nuts. Put all the burs
in the bag too so you can count them. Try to avoid cutting off
too many branches to get the burs, for this removes many of next
year's flower buds.
c) Put the metal tags with
which you labeled the branch or tree into the white trash bag
so you can identify the contents of both bags. The tag will be
less likely to fall out of a hole in the bag if it's inside the
white bag which is inside the black bag. Tie both bags securely
shut.
d) When you get home, remove
the burs from the plastic bag, count them and record the count
for that cross. Also count the number of pollination bags and
record that count. Put the unopened burs and the free nuts in
a large or small paper grocery bag, depending on the number of
burs. Also put the label in the paper bag, and write the cross
identification on the paper bag. Keep the controls separate in
the white garbage bag with tag inside. Record their bag and bur
counts also.
e) If you have a walk-in cooler,
put the bags of unopened burs in there to wait for them to open.
Otherwise put the bags in a room out of sunlight and reach from
mice! Every two to three days, go through the bags removing nuts
from opened burs, but do not remove nuts which are still sticking
to an opened bur. After a week to ten days, remove all the nuts
from all the burs, whether opened or not, sticking or not.
f) Immediately count and store
the nuts in moist, but not wet, peat moss (2-3 cups water per
gallon of dried milled peat moss) in a plastic bag into which
you have placed numerous holes with a tooth pick or paper clip.
Make sure each nut is surrounded by peat moss and not touching
other nuts or the side of the bag. Put the label in the plastic
bag and also write the cross id and the number of nuts in the
bag on the outside with a black Sharpie . Refrigerate the nuts
at 34 F until planting or shipping time.
Field Equipment Checklist
Some useful items in the field- If you are 30 miles
from home base and have to go back for something you forgot, you
have lost a good part of the day. Use the checklist every day,
and change it as needed.
Pollination-
ladder
pole pruner
small rope
keys
maps, compass
money
phone numbers
Foundation brochures- to introduce yourself
hat
raincoat
binoculars- for seeing flowers in the crown of the tree, examining
crown for blight
field notebooks
spare pens, pencils, black Sharpie marking pens
knife
insect repellent
sun screen
toilet paper
drinking water
lunch
carpenter's apron
pollen
fresh pollen application equipment - tin cans or pollination
bags
dried pollen application equipment - microscope, slides,
vials, alcohol, kleenex, grease pencil
pollen collection equipment - milk jugs, 5-gal buckets,
water, large paper bags, glass plates, tweezers, razor blades,
alcohol kleenex, vials & lids, hole punch, scotch tape, labels,
dessicator, pollination bags (corn-shoot bags), thousands of jumbo
paper clips or twist'ems, metal branch tags, pruning shears, scissors
Harvest-
ladder
pole pruner
hand pruning shears
rope
thick leather and/or rubber gloves
field notebooks
good-quality garbage bags (black and white) label material- moisture
proof
keys
maps, compass
money
phone numbers
Foundation brochures
hat
raincoat
binoculars- for seeing the burs in the crown of the tree, examining
for blight
camera
spare pens, pencils
knife
insect repellent
sun screen
toilet paper
water
lunch
|