[NAFEX] Re: Pawpaw pollination

Gordon Nofs gc_nofs at hotmail.com
Sun Apr 6 12:20:45 EDT 2003


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Doing~ what comes unnaturally
How to hand-pollinate pawpaws
By Neal Peterson


Some people find that Pawpaw trees just don’t produce fruit. “Why?” 
they ask. The answer usually is, “They need a pollinator.” Sometimes 
this means they need a helping hand in their pollination. Literally. 
Hand-pollination. The question then be-comes, “How do you do it if 
you’ve never done it? When is the pollen ripe? When is a flower in the 
female stage and most receptive? How do you do the act itself — transfer 
the pollen to its appointed spot?” It’s all very easy, but — like 
human sex — it ~ isn’t necessarily obvious how to do It.’he first 
time. Here are some simple pointers to guide you if you aspire to pollinate 
pawpaws by hand.
Pawpaw blossoms begin life as females and later become males. They are 
designed this way to discourage
self-pollination. In the female stage the petals are held rather tightly 
together, forcing the small flies and beetles that visit the flowers, 
searching for nectar, to brush past the stigmas where the pollen they carry 
on their backs can be deposited. In this stage, the petals will have turned 
color, from green to maroon (although some green may still show) but the 
anthers will be tightly pressed together as a solid green ball, and the 
stigmas will appear green and shiny.
In the later male stage, the petals darken more, the fetid flower odor 
intensifies, the ball of anthers loosens (no longer solid) and the anthers 
turn from green to brown, shedding the yellow dust-like pollen. In this 
stage, the petals flare back, allowing the visiting insects to brush easily 
past the anthers, thereby collecting pollen on their backs.
The first trick for the hand pollinator is collecting the pollen. There are 
many ways to do this, but my own
Preference is to use large empty gelatin capsules (size XXX) that you may 
buy at health food stores. I open
the capsule and use one end as a cup to scrap the ripe-with-pollen anthers, 
causing them to fall into the capsule. I then close the capsule and label 
the contents with an indelible pen. These capsules, being made of gelatin, 
absorb moisture, promote the anthers to release their pollen, which then 
adheres to the sides of the capsule. I then use a very small camel’s hair 
brush to collect the pollen from the sides of the capsule, and apply the 
pollen to the stigmas of the female flower. For the sake of thoroughness, 
and to learn the results of my efforts, I also tag the flowers I have 
pollinated.  The final pointer has to do with picking the right time of day 
and the right type of day for pollinating. I find that I get the best 
results on a perfect spring day, when the sun is bright, the air is warm, 
the breezes gentle or not at all. I don’t do it in early morning or late 
in the day. When in doubt about how to do it, think like a flower, think 
like a beetle.

**************************************************************************************
My Botanical Rendezvous

By Colleen Anderson
I’m an infamously bad gardener, but six years ago I planted a Pawpaw seed 
in my yard, and it grew. I nursed the little sprout along and, about the 
second year, transplanted it to the sunny side of Arlington Court, where I 
live. It thrived. Last year, the first blossoms appeared — only four of 
them, but there was no denying it — my tree was at least a teenager.  This 
year, it’s an adult. The tree is tall and straight, and the lovely, 
blood-brown, bell-shaped flowers are everywhere — there must be two 
hundred. My tree could be fruitful — but, like people, paw-paws need 
intimate company in order to reproduce — and there isn’t another Pawpaw 
within shouting distance.
So I have been assisting nature. My tree’s mate came from a fine stand of 
pawpaws in Kentucky. I carried the precious pollen back in small capsules. 
On a beautiful, warm day last week — the perfect sort of day for romance 
—1 had a go at hand pollinating. It didn’t take long, and it wasn’t 
very exciting — dipping a small brush into the pollen capsules and 
delivering it to the waiting blossoms — but still, I tried to

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accomplish it without attracting attention. Plants may not care about who 
watches their sexual encounters, but I couldn’t get over the feeling that 
there was something illicit about this endeavor.
Nevertheless, word got around. By that evening, my neighbors were teasing me 
about my midaftemoon botanical rendezvous. All over the block, they’re 
calling me “Madame Pawpaw.”
I feel more like a grandmother-in-waiting. I’m looking forward to the 
story this summer will tell.  Will my lovely young tree be compatible with 
her Kentucky gentleman? Will the blossoms swell into clusters of fruit? Will 
we have Arlington Court paw-paws this fall? Stay tuned. With luck, I’ll be 
making a birth announcement.
This essay was originally broadcast as a commentary on West Virginia Public 
Radio in April 1996. The
harvest was bountiful.
**********************************************************************************
Pawpaws in the Garden
SITE, SOILS, AND HABITAT. Although the Pawpaw is capable of fruiting in the 
shade, optimum yields are obtained in open exposure, with some protection 
from wind (on account of the large leaves). Germinating seedlings, however, 
will not survive under those conditions because they are extremely sensitive 
to full sunlight, which can kill them. Shading for the first year, and 
sometimes the second, is normally required, and it is for this reason that 
pawpaws are almost always found in nature as an understory tree. The soil 
should be slightly acid (pH 5.5-7), deep, fertile, and well-drained. Good 
drainage is essential to success. Pawpaws will not thrive in heavy soil or 
water-logged soil. In habit it is a small tree, seldom taller than 25 feet. 
Grown in full sun, the Pawpaw tree develops a narrowly pyramidal shape with 
dense, drooping foliage down to the ground level. In the shade it has a more 
open branching habit with few lower limbs and horizontally held leaves.
PROPAGATION BY GERMINATION. Pawpaw seed is slow to germinate but not 
difficult if certain procedures are followed. Do not allow the seed to dry 
for long periods (ie., months) because this can destroy the immature, 
dormant embryo. To break dormancy, the seed must receive a period of 
stratification (exposure to cold temperatures) for 90-120 days. this may be 
accomplished by sowing the seed late in the fall and letting it overwinter; 
the seed will germinate the following year in late July to late August. 
Another way is to stratify the seed in the refrigerator (32-40F/0-5C). In 
this case the seed should be stored in a plastic ziplock bag with a little 
moist sphagnum moss to keep the seed moist and suppress fungal/bacterial 
growth. After stratification the seed should be sown in a well-aerated soil 
mix, pH 5.5-7, with an optimum temperature of 75-85F (25-30C). The root will 
normally emerge from the seed coat on the 18th day, develop into a taproot 
about 10 inches deep, and then send up a shoot on day number 64. Germination 
is hypogeal: the shoot emerges without any cotyledons. For the first two 
years growth is slow as the root system establishes itself, but thereafter 
it accelerates. Fruitbearing normally begins when the sapling reaches 6 
feet, which usually requires six to eight years.
PROPAGATION BY VEGETATIVE MEANS. Pawpaw clones are easily propagated by a 
number of grafting and budding techniques, such as whip-and-tongue, cleft, 
bark inlay, and chip budding. The only method that does not produce good 
results is T-budding. Shoot cuttings have proved virtually impossible to 
root, while root cuttings are usually successful. Although it is common for 
a Pawpaw to sucker from the roots, and would therefore seem a natural way to 
propagate a clone through transplanting root suckers, in practice this is 
extremely difficult. Pawpaws are ordinarily quite difficult to transplant. 
They have fleshy, brittle roots with very few fine hairs. Experimentation 
has shown that, to be successful, transplantation should be done in the 
spring at the time that new growth commences, or soon after. (This is 
basically the same as for magnolia.) If many roots are lost, it may be 
desirable to prune the top to bring it into balance with the remaining 
roots.
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POLLINATION, NATURAL AND ARTIFICIAL.
Pollination is the major limitation to Pawpaw fruit set.  The flowers are 
protogynous, meaning that the stigma (the female receptive organ) ripens 
before the pollen, and is no longer receptive when the pollen is shed. Thus 
the flower is designed not to be self-pollinated. In addition, Pawpaw trees 
are self-incompatible, requiring pollen from a genetically different tree in 
order to be fertilized.  Finally, the natural pollinators of the 
Pawpaw—various species of flies and beetles—are not efficient or 
dependable. Although it requires a little extra labor, hand pollination can 
be well worth the effort and can be done as follows: Using a small, flexible 
artist’s brush, transfer a quantity of fresh pollen from the anthers of 
the flower of one clone to the ripe stigma of the flower of another clone. 
Pollen is ripe when the little ball of anthers is brown in color, loose and 
friable; pollen grains appear as yellow dust on the brush hairs. The stigma 
is ripe when the tips of the pistils are green and glossy, and the anther 
ball is still hard and green. Do not overburden the tree with fruit, as this 
will stress the tree, resulting in smaller than normal fruit, and may cause 
limbs to break under excessive weight.
PESTS. In its native habitat the Pawpaw has few pests of any importance. The 
worst pest is Talponia plummeriana, the Pawpaw peduncle borer, a small moth 
larva (about 5 mm long) that burrows in the fleshy tissues of the flower, 
causing the flower to wither and drop. In some years this borer is capable 
of destroying the majority of blossoms.  Another pest is Eurytides 
marcellus, whose larvae feed exclusively on young Pawpaw foliage, but never 
in great numbers. The adult butterfly is of such great beauty that this 
should be thought more a blessing than a curse.  Sometimes the fruit surface 
may be covered with patches that are hard and black; this is a fungus 
infection, but it seldom has any effect on flavor or edibility. Deer will 
not eat the leaves, twigs, or fruit. Outside its native region, the Pawpaw 
is sometimes reported to be plagued by pests, but this may be because of 
poor health resulting from improper soils and an unsuitable climate.
The Pawpaw Foundation, August 1990

Bees show no interest in Pawpaw flowers. The task of pollination is left to 
unenthustic species of flies and beetles. A better solution for the home 
gardener is to hand pollinate. Using a small soft artist’s brush to 
transfer pollen to the Stigma (Female part of the blossom)  Pollen is ripe 
for gathering when the ball of anthers is brownish in color loose and 
friable. (Male part of blossom, up to top inside flower above the female 
part)  Pollen grains should appear as small beige colored particles on the 
brush hairs. The stigma (female part) is receptive when the tips of the 
pistils are green, glossy, and sticky,  and the anther (male part) is firm 
and greenish to light yellow in color.
    So the female part is ready when the male part is not in the same 
blossom.

Gordon C. Nofs
6422 E. Pierson Rd.
Flint, Michigan  48506-2258

gc_nofs at hotmail.com

Gordon C. Nofs
Flint, MI.



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