Pollen and all its implications

As I sit quietly waiting for all of the moisture to eventually leave my body via my poor, sore, sneezy nose and leaky, watery eyes, my thoughts are drawn to pollen. Pollen is such a critical part of the natural and horticultural world. Without it, and its distribution via various means, we wouldn’t have any of the delicious and beautiful and useful plants and their products that we enjoy. We wouldn’t have yummy fruits, healthy seeds and grains, and we wouldn’t have the genetic crossing that brings variety and improvement in plants. So much of the natural world is linked in some way to pollen and its spread, either as a beneficiary of the results of the process of fertilization, or through a role in distributing the tiny pollen grains.

What is Pollen?

Pollen is the tiny structure or unit produced by plants that carries the male genetic material. It is a microscopic mass that can be many shapes and sizes, with different textures, appendages, and features that assist in its dispersal and function. Pollen often appears a dust or powder, but that is actually many, many pollen grains piled up together. Not surprisingly, pollen is produced in vast quantities and at different times of year, there can be quite a lot of it in the atmosphere. All of it has it in for me.

Pollen grains consist of a number of different cells, including a reproductive cell (containing the material for fertilization), as well as a number of other cells that protect the reproductive material and allow it to be introduced to the female parts when they come in close proximity.

Depending on the plant species, pollen is spread and transported by a range of different means, including wind, water, insects, birds, animals, humans, etc. It moves from the male structures to connect with the female structures, at which point fertilization can occur.

Pollination?

Pollination is the act of transferring pollen from the male plant parts to the female plant parts, leading to fertilization and seed formation. Sometimes this occurs within the same “perfect” flower, whereas other times there are separate male and female flowers (or plants, in some cases).

For some plants, pollen just has to float over to land on the exposed female plant parts. This is the case with things like conifers. In other plants, the pollen grain must land on a connected part of the female reproductive system, and then grow downwards to connect the male reproductive material to the female. This is the case in flowering plants.

Pollinators vs Pollinizers (Is there a difference?)

Up until now, this whole process has been pretty simple and straightforward. Pollen is produced and then transferred through the process of pollination. But sometimes we mix up the terminology when talking about pollination, specifically relating to the various players involved in the process.

A pollinator is any organism (or theoretically, a mechanism such as wind or water) that assists in the delivery of pollen to flowers (a.k.a. pollination). The most commonly recognized pollinators are bees, flies, wasps, moths, and butterflies. Bats and birds are also active pollinators, depending on their habits. The movement of and physical contact with animals can also disperse and spread pollen between plants and flowers. The activity of humans, as well as the movement or influence of wind, water, or gravity also play a role.

A pollinizer is a plant that supplies pollen to another plant. This applies to those plants that have both male and female parts, as well as plants that are male only.

Compatibility

Flowering (and fruiting) plants can differ in what their pollen requirements are. Some plants (the nice, easy ones) are referred to as “self-compatible”, which means that they can be pollinated by their own pollen. As a result, you don’t need to have more than one plant to get a good fruit set. Even though self-compatible species produce all the pollen they need on the same plant, they will typically need pollinators to move the pollen around between male and female parts, as their pollen is heavy and can’t be moved by wind.

Another group of plants are a bit more complicated, requiring pollen from another plant (often another variety). These types of plants are referred as to as “self-incompatible”. In cases such as this, you will need to plant 2 or 3 different plants of different varieties, to ensure that you get suitable pollen for pollination. The varieties will need to flower at the same time, otherwise they are not compatible, which is affected by genetics, as well as by location (sunny versus shady).

Some plants produce what are referred to as “perfect flowers”, which is where they have both male and female parts within the same flower. Other plants produce “imperfect flowers”, which means that they have male flowers and female flowers, either on the same plant (in different places) or on different plants entirely. Plants that have male and female flowers on the same plant are referred to as monoecious. Crops that have separate male and female plants (and flowers) are referred to as dioecious. Both of these types of plants require cross-pollination (usually with insects).

Thankfully, most of the common fruit crops that we grow are perfect, or have been bred to have perfect flowers, for the most part. It is similar to what occurs in vegetables, although hybridized varieties are perhaps more common in vegetables, where the sex of the flowers is more controlled.

Most of the common berries that we grow are self-compatible. This includes things like raspberries, saskatoon berries, strawberries, and sour cherries.

Some fruiting plants are self-compatible or self-fruitful or may be self-incompatible, depending on the variety. These include fruit like blueberries, currants, and highbush cranberry.

Self-incompatible fruit species include things like apples, crabapples, apricots, chokecherries, haskap/blue honeysuckle, plums, pears, pin cherries, and sand cherries. Some plants like arctic kiwi and sea buckthorn have male and female plants. Some of these plants are self-fruitful but will be much more productive with cross-pollination occurring.

Since most vegetables are not grown to the point of setting seed, pollination is largely irrelevant. However, if you are collecting seed, pollination is important and consideration should be given to whether a vegetable is a hybrid or an open-pollinated variety, as this will affect the likelihood of success. And, of course, the fruiting vegetables (tomatoes, peppers, eggplants, cucumbers, pumpkins, squash, and melons) all rely heavily on pollination.

Conclusion

Overall, pollination is not something to take for granted. Ensuring that the plants we grow can properly produce their fruit through complete pollination will ensure that we get good harvests each year. For some crops, that takes some planning and some extra effort. This might mean you arrange for pollinators to be placed in easy proximity to your crops. It might also mean that you are careful in your plant selection, to ensure that you get the right balance of pollinizers in your planting.

For now, I’ll chose to appreciate the pretty flowers and the positive benefits of pollen, even though it conspires to kill me every year.

Compatibility and Maximizing Productivity

(Original fruit base chart adapted from “Growing Fruit in Northern Gardens” – Williams & Bors)