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  • From: "Gordon Nofs" <gc_nofs@hotmail.com>
  • To: nafex@lists.ibiblio.org
  • Subject: [NAFEX] Re: Pawpaw pollination
  • Date: Sun, 06 Apr 2003 12:20:45 -0400

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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.

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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.
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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@hotmail.com

Gordon C. Nofs
Flint, MI.



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