Some interesting facts about pollen, how much we need etc.

[Rob]

This season I have researched caprifig pollen here, and there are a lot of interesting details that we need to understand, to get the best use of the often, seemingly small amount that is available to us. This can be a very complex subject, and a very interesting one, but if we can all work together, I think it can become much clearer given time.

SOME FACTS.
Firstly, just 1 fig wasp , as tiny as it is, can pollinate a fig well, and as we see here, they passively carry up to 3200 pollen grains each.(Some wasps actively collect pollen, and put it into tiny pockets on their body, our wasp ...Blastophaga psenes, does not, she collects pollen just by brushing past the pollen on the male flowers)

Screenshot 2026-01-04 at 20-39-19 Some pollinators are more equal than others Factors influencing pollen loads and seed set capacity of two actively and passively pollinating fig wasps - Kjellberg2014pollenload.pdf.png

We also see here that caprifigs can produce up to 46 MILLION pollen grains, and that means that pollen from 1 good caprifig can pollinate in excess of14,000 figs!
What we generally see, when we shake pollen from a caprifig is pinhead sized 'clumps' of pollen, not pollen grains, pollen grains are so small that they float in the air, and we cannot see them, they are about 12microns in size. They do vary a little but only by a couple of microns. Below is pollen I obtained from 1 caprifig, as pictured, and these are clumps of pollen from the anthers of male flowers, containing up to about 1500 pollen grains. NOTE... Only one pollen grain is needed on the tip of the female style to pollinate each flower.

Flour BL Dec 2025vs.jpg

Male flowers where I am have from 4-5 anthers (branches)/flower, giving about 7,000 pollen grains/flower, just as this table mentions..but they do vary a lot.

Pollen Grains per flower.png

Another important point with collecting pollen from caprifigs, is to carefully slit the fig, only a few mm in, from eye to stalk all around, and then break it open, this way, the juices from the fig will not contaminate the pollen, and as we know fig juice is very sticky, this can bind the clumps of pollen together, not releasing the grains well, when we but them into the sugar/water solution, to pollinate figs.

Once you have shaken the pollen from the caprifig, this is all you should see, clean pollen.

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If you leave the fig to try out too long, or the fig is totally cut through as we normally do with female figs, many of the male flowers are also cut apart, and you are left with this contaminated mess of pollen and parts of flowers. All of these flower parts can contaminate your fresh pollen, unless they are removed before adding the water.

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OK, now that we have clean pollen, this will very easily mix into the sugar/water solution, and just a very small amount will pollinate hundreds of figs, how much, is something that cannot be weighed, I tried even with scales that weigh down to 0.001gram and it does not register. The interesting part about this is that AI tells us that 0.5g of pollen/100ml of solution is correct, 0.5g of pollen is far from correct, as below.

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I have weighed pollen from hundreds of good caprifigs here, and that amount was nearing the most I was able to extract from 1 whole caprifig, close to the 46 million grain amount, it is a lot of pollen, as we can see here, and I zeroed the scales out after I added the paper tray.

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I bought some 5ml graduated glass tubes with screw tops, and tested various amounts of pollen/5ml of liquid, and then viewed one drop on a microscope slide with graduated squares, again, this was most interesting. The correct amount seems to be very small, on the counting slide, the correct amount of pollen looked like this, and in the 5ml liquid, it looked like the second picture, just a little cloudy, yet you can clearly see through it.

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Honestly, if the solution looks anything like this,below, it can be diluted many times, and it will go a great deal further, and pollinate all figs just fine.

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I have used several different sized syringes, and for me only pollinating 20 or so figs at a time, the small 5ml syringe is ideal, and just a 19gauge needle works a treat. I use a very thin spring steel wire down inside of the needle and insert all of it, before attaching the syringe, then withdraw the wire, insert the syringe, and push the plunger slowly. The idea of shaking the syringe often to keep the pollen suspended is generally unnecessary, since the pollen grains are mostly separated, and not in clumps. The reason for the wire, is to prevent the needle from clogging as we try to insert it, as the eye of the fig is closed, and is does save a lot of time unclogging needles, as we go from fig to fig.

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I collected pollen from many trees here and this is what it all looked like, some were totally full, 7ml, others only had a very small amount, 0.1ml.

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Pollen can be posted all over the globe, as I have already done, and it does not seem to be an issue with anyone, but it needs to be clean, and well sealed. I put it into aluminium foil folded packets, and vacuum seal it with desiccant, then into plastic pouches like below, and it fits well into an envelope. It is sent as a letter, as it is thin, and weighs very little.

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All figs need to be at the best receptive size to achieve the best results, and it can depend on the fig type, but generally somewhere between 15-25mm in diameter is good. the figs need to have a cavity (photo below), and I find that at this size, the needle is mostly able to be inserted with very little effort, the thin wire is able to be removed easily, and everything went well. If it seems too difficult, it's best to leave that fig, it could be too early or late to pollinate it. When figs are receptive the styles are very clean and white looking, once the styles turn darker, it is too late to pollinate. The pollen needs to grow as the fig grows.

No cavity Cavity VDB 5th Mar 2026.vs.JPG

When figs are receptive to pollination, they emit VOC's (volatile organic compounds), these attract wasps, and it seems that we can also smell this, although some figs are harder for us to notice. A lovely French researcher, Magali Proffit, together with Finn Kjellberg, studied a number of trees in France, noting the size of figs when they are receptive to pollen, and there will be a paper available soon for us to read. I believe that this will be the very first study done, and we may learn a lot from it.

One other piece of interesting information to add here, is this, telling us about how stigmas should look when they are receptive, and when past receptive.

Screenshot 2025-12-07 at 11-25-16 Biological studies on figs caprifigs and caprification - Figs Caprifigs and Caprification.pdf.png

Pollen sends out tubes like worms growing from it. Below is a video here on pollen growth, this is pollen from a flower, but it shows the growth well. I am hoping to do my own video on this soon, and when it is done I will replace this one with mine.

https://1drv.ms/v/c/ddf3dc321579369e/IQ ... 4?e=OgfiuS

[Rob]

For interest I did some further pollen testing here yesterday, using the amount mentioned by AI....0-5 grams of pollen per 100ml of liquid, and to be honest, it was as expected.

I used the same proportions, but with just 5ml of liquid, and this is how much pollen I needed. A Massive amount below.

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This pollen was 6 months old, not viable, and although it was kept in a screw top container, it was slightly clumpy, meaning it was damp, so I allowed for the extra weight, as I only needed 0.025g. Mixing this amount of pollen into the 5ml of liquid, I got this very cloudy looking mix below.

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I placed the smallest of drops onto my counting chamber 3mm x 3mm x 0.1mm and counted a few of the 16x16 squares you see below. This gave an average of about 60 grains/ counting square, giving a total for the 3mmx3mm area of approximately 15,000 pollen grains.

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I have not done any testing on an average volume inside a receptive fig, but at the very least, I would say it would be 20x more than on my small counting area, giving about 300,000 pollen grains/fig injected.
The wasps carry about 3,000 pollen grains, and one wasp can certainly pollinate a fig, so as expected, 0.5 grams/100ml, is a massive overkill. The black looking clumps of pollen are only showing, as I did not let the pollen stand long enough before viewing it. Normally I would have left the solution for a few minutes, and the clumps would have broken down to single grains for pollinating.

[Rob]

Continuing on from this above, I thought it would be worth diluting this mixture to see if I could come up with a reliable mix ratio.

I made sure the original mix was well mixed, I put 3 drops from it into a 5ml graduated glass vial, and filled it to the 5ml point with water. After mixing that well, I put a very small drop on the glass counting chamber under the microscope, and counted the pollen grains. Below is what I saw.

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This averaged out to be about 6 grains/square, making a total of about 1500 for the drop, so I was thinking I needed to test how many drops would a small fig be capable of holding. In other words, how much liquid can we insert into each small fig. I have a palmata tree with many small figs on it, so I collected 2, both about 20mm in dia, cut them in half and placed them on a flat surface. I filled my graduated dropper with water, and managed to put 2 drops in each fig half cavity, a total of 4 drops/fig. Of course, not a figs will have the same cavity size, but it gives us a good idea of what is possibly 'normal'. Then it seemed like a good idea to test the dropper, to see how much 4 drops really was...0.12ml. 4 drops in each small fig is basically equal to 2 wasps pollinating every fig. Below are the 2 of the small halves I placed drops into.

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This is a close up of one of the halves to show detail.

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Below are the items I used for this, but not the microscope. Te glass vial on the far left was the diluted pollen mix, showing almost totally clear liquid, and to the right of that, the original mix, looking totally flooded with pollen grains. To the far right of that, there is the graduated dropper I used.

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Of course, everyone can use whatever ratios of pollen they wish to, but it does give an idea of what will work, and for those with limited amounts of pollen available to them, it can certainly change the amount of figs they can pollinate.

Next season, I will be sending out pollen in different weights, with minimum fluid ratios, so users have an idea how far the pollen can go, or in other words, how many figs they can safely pollinate.

[Figgywiggy]

Very interesting Rob! Some great tips there. I am taking note in particular of not cutting the figs all the way through but slitting the outside and breaking open to avoid contamination.