What Does Open-Pollinated Mean?

Open-Pollinated, Cross-Pollinated, and Hybrids—A Pollination Primer

Zucchini plant with bumblebee

coramueller / Getty Images

If you have browsed a seed catalog, chances are you have come across the term open-pollinated. While it is mostly used in the context of vegetables and fruits, it is also relevant if you like to collect seeds from your ornamental plants for propagation. Whether you collect seeds from annuals or perennials, knowing what to expect from open-pollinated varieties is important to make sure that all your efforts saving seeds and growing new plants yield the expected results.

What Is Open-Pollinated?

Open-pollinated refers both to the way pollination occurs, and to the true breeding ability of the plant. Open pollination occurs in an uncontrolled manner by insects, birds, bats, wind, rain, humans touching the plant or brushing against it. Seeds from that plant result in a new plant that is true to the parent, which differentiates open-pollinated varieties from hybrids (crossbred-varieties).

Bee collecting pollen from a sunflower
Bee collecting pollen from a sunflower

JLGutierrez / Getty Images

How Pollination Works

Pollination is the transfer of pollen in flowers from the anther (the part of the male reproductive organ, the stamen, where pollen is produced) to the stigma (the part of the female reproductive organ, the pistil, that receives the pollen) to produce offspring. The male and female reproductive organs can be either in the same flower (perfect or complete flowers) or a plant has both male and female flowers.

Plants reproduce by making seeds which contain the genetic information for a new plant. Pollination can only take place between flowers of the same plant species.

For pollination to happen, the pollen needs to be moved by vectors. These can be either inanimate forces (wind and water) or animals and insects that act as pollinators (birds, insects, butterflies, bats. Pollinators visit the flowers to feed on pollen or nectar and as they move from flower to flower, the pollen grains that attach themselves to their bodies get transferred from the anther of one flower to the stigma of another flower and fertilizes the flower so it can grow seeds and fruit. Pollination is an unintended and beneficial side effect of animals and insects foraging for food. 

Seed packages

Peter Dazeley / Getty Images

Benefits of Open Pollination

There are several benefits to open pollination. The most obvious one for home gardeners is that you can save the seeds from your plants and won’t have to buy seeds every year. By collecting the seeds from your best plants, you can literally maintain your very own cream of the crop that adapts better to your particular growing conditions and microclimate year after year. Properly stored, the seeds might even be viable for more than a year depending on the type of seed. 

The advantage of saving your own open-pollinated seed goes beyond economical savings. Open-pollinated vegetable varieties usually have more flavor than hybrids, which are often bred for high yield, storage ability, uniformity, and disease-resistance, and not always for taste.

Because plant breeding is a lengthy and costly process, when you browse seed catalogs, you will find a much bigger variety of open-pollinated seeds than hybrids.

By favoring open-pollinated plants over hybrids, you also help preserving the genetic biodiversity of garden vegetables. Since the 1900s, farmers have grown more and more genetically uniform high-yielding crop varieties, which resulted in more than three quarters of the genetic diversity of agricultural crops being lost.

Open Pollination vs. Cross Pollination

One of the drawbacks of open-pollinated varieties is that because they can potentially pollinate with any plants of the same species, cross pollination may occur. Some vegetables are more prone to cross pollination than others, depending on their flower structure and way of pollination. Corn, for example, is wind-pollinated and easily cross pollinates. Zucchini, winter, and summer squash are notorious cross pollinators, resulting in odd, unappealing pumpcchini when zucchini and pumpkins cross pollinate.

If varieties are likely to cross pollinate, the information on the seed package often includes recommendations for the minimum planting distance between them to prevent cross pollination. 

Open Pollination vs. Controlled Pollination

Open pollination is uncontrolled in the sense that any flowers from the same plant species can pollinate each other. In controlled pollination, on the other hand, humans keep the breeding partners in check to make sure that only plants with known traits are pollinating each other.

In hybrid pollination, which is a type of controlled pollination, two different varieties of the same species are bred together. The seeds from the resulting hybrid plant will not produce a plant that is true to the parent.

Not all open pollination is necessarily uncontrolled pollination. The hand pollination of crops such as squash that is done to ensure good pollination, prevent cross pollination, and for other reasons, is a type of controlled pollination but the variety that is being pollinated is still an open-pollinated variety. 

Cherokee Purple heirloom tomato
Cherokee Purple heirloom tomato

Barbara Rich / Getty Images

Open-Pollinated vs. Heirloom Varieties

Although often used as synonyms, open-pollinated and heirloom varieties are not the same. All heirloom varieties are open-pollinated but open-pollinated varieties are only referred to as heirlooms when they have been handed down over generations. While there is no official age threshold for the definition of heirloom, open-pollinated varieties that have been around for more than 50 years and have remained unaltered are considered heirloom varieties.

While there is no official age threshold for the definition of heirloom, open-pollinated varieties that have been around for more than 50 years and have remained unaltered are considered heirloom varieties.

Article Sources
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  1. What Is Happening to Agrobiodiversity? Food and Agriculture Organization of the United Nations.