We wrote a blog post on this topic a while back, but with four more years of pollinating experience we have learned a few more things, so this page will incorporate parts of the blog post with updates. Before we start, it is worth saying that this is not too hard. It sounds really complicated, but once you try it it is not too hard. Also, you can get a way with a lot of mistakes and still get pollinated figs. In this article we look at it from the point of view of trying to get seeds from pollinated figs, but the same process works just to get tastier caprified figs.
First you need a male fig. In order to have a chance of getting parthenocarpic, i.e. common, figs you need to start with a persistent male capri-fig. Even with a persistent male capri-fig you only have a 25% chance of getting a common female fig, but without a persistent male the chance is zero. If you live outside of an area with fig wasps then persistent male figs are also the only ones that will produce pollen.
The method of hand pollination came from the ‘Materials and Methods’ section of this paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5126050/ which is also similar to the method covered in this video: https://www.youtube.com/watch?v=XNNtWwaFYCU
Regarding timing, the male capri figs are similar to the breba crop on female fig trees developing the previous season and ripening in early to mid-summer (July and August in New Jersey). Harvest pollen from the male figs when they are ripe. Ripe male figs are similar to ripe female figs, they will start to droop and don’t leak much sap when picked. Pollen can be stored in a refrigerator after harvesting, so harvest the male figs and pollen when the male figs are ripe.
Ripe male figs will look similar to the ripe Saleeb figs above. You will get more pollen out of the figs if you leave them to dry for a day after cutting them. Once the figs have dried knock the pollen onto a clean surface. We use black paper since it makes the pollen easy to see and can be used to transfer the pollen around. You can also throw out the paper after each use to help avoid cross-contamination of pollen types. If you are trying to create controlled crosses, i.e. a known male parent, it is important to clean your work area thoroughly between each pollen type.
After harvesting the pollen it is very helpful to sift out the flower parts that inevitably end up in the pollen. The flower parts will make the pollination using a syringe more difficult and storing pollen with the flower parts seems to make the pollen spoil fairly quickly from our experience. We use an 80 mesh sift putting the pollen in the top of the syringe and tapping it on the paper till most of it has passed through. The clean pollen can be used right away or stored in a refrigerator. We use small vials to store ours. Note that the picture below was from before we learned that not sifting the pollen led to it clumping and spoiling in storage.
So far the steps are pretty straight forward, the first challenge is when to use the pollen. Generally speaking the main crop is ready to be pollinated around the time the male figs ripen, this is how it works in nature with the wasp of course. However, not every variety or every fig on a variety is ready at the same time. The best answer is probably to store some of your pollen and do several pollination sessions in July and early August. When you get to injecting figs you will be able to tell which figs have some hollow space in them. In our experience these seem to have the most viable seeds once ripe. Once you are ready to pollinate figs it is time to mix the pollen into a solution to inject into the female figs.
Mixing pollen with water is the next challenge. Pollen doesn’t want to mix with water. Mixing some sugar into the water is helpful, we use around 2%, though the exact amount doesn’t seem critical. Regular table sugar is also fine. We use distilled water most of the time, but have used tap water and can’t see any difference in the results. If you have limited pollen though it doesn’t hurt to use the distilled water.
The specific steps we use is to pour about 50 ml of water into a beaker and then add the sugar. We use an inexpensive beaker stirrer like this one. This stirrer is a magnetic based and white ‘pill’ that goes in the beaker. Turning on the base rotates the pill and stirs the water. It is effective and easy.
Once the sugar is mixed into the water we add pollen a bit at a time while the stirrer is stirring on a low speed. A solution that is cloudy with pollen seems to be plenty to pollinate figs, so we add pollen until the water looks cloudy. Allow it to continue to stir for a few minutes.
Next we use syringes to draw out pollen and water solution. These type of 18 gauge syringes seem to work well.
Drawing out water and spraying back in to wash the pollen off the sides of the beaker can be helpful. Also drawing water from near the surface (where a lot of the pollen stays no matter how much you mix it) is also helpful in getting pollen into the solution where you need it.
The labels in the picture above are how we mark which varieties of male pollen we are using to pollinate which figs. To make sure we don’t mix up varieties we also only pollinate with one type of male pollen per branch on a female tree.
Next up, pollinating some figs. The most successful figs seem to be the ones that have some room in them to inject the solution too. If it is too much of a struggle, it probably means that fig, and maybe that variety, needs another week or so.
Note that the syringe does get clogged with pieces of the fig sometimes when injecting. This can be minimized by picking varieties that are ready, but sometimes it is necessary to bring the syringe back to the beaker of solution and clear it into the beaker (otherwise you just squirt the pollen mixed all out in our experience). You can also use an empty syringe to poke each fig first to create a hole before using the syringe with the solution.
All that is left to do is wait. Inevitably some of the figs will get eaten by critters before you get to them, so do more than you plan to need. If you have the pollen it is really not hard, so we tend to pollinate hundreds over a few weeks each summer. We have very few fruit that spoil after being injected. It does happen, but for us squirrels get a lot more than we lose to spoiling.
Seeds!
Fruit will ripen as early as late August and as late as October in New Jersey. Harvest the fruit at the normal time. If you are making controlled crosses it is again important to process one male/female type at a time. If multiple figs of the same male and female parent ripen at the same time you can do more than one fig at a time, but keep different crosses separated and clean your workspace between types to avoid mixing up seeds.
The process we use to go from ripe fig to seeds is based on the fermentation process used for tomato and other seeds. There are many good articles and videos available on the fermentation process for tomato seeds if you are looking for more information. The process of fermentation helps to separate the viable seeds from the non-viable seeds and other material and helps break down barriers on seeds that prevent early germination. The steps we used were:
1.) Scrape the seeds and other goop out of a single fig into a Mason jar, discarding the skin and any parts not containing seeds. Fill the jar about 1/2 to 3/4 full of tap water, rinsing as many seeds as possible into the jar. Cover the jar with Mason jar lid and a paper towel to keep bugs out, but allow it to breath.
2.) Allow the jar to sit for 3-7 days.
3.) After 3-7 days the viable seeds should be on the very bottom of the jar. If there are no seeds on the bottom then the pollination was not successful. In order to separate out the goop from the viable seeds decant the mix until only the seeds remain. Do this by pouring off and discarding the goop, adding more clean tap water and waiting for seeds to settle, pouring off top part again, and repeat. Repeat this till the water is mostly clear. Once the water is clear, pour the water and seeds through a strainer.
4.) Allow the seeds to dry for about a day. Placing a paper towel under the strainer can help to wick some of the water away.
Seeds can be stored in a refrigerator for at least a year. We use small paper envelopes to store ours in. Once it is time to plant the seeds we recommend soaking the seeds in hydrogen peroxide (the 3% type from the pharmacy). This seems to speed up germination by about a week and slow germination is the primary source of problems for us, e.g. mold growth or soil drying out too soon.