What Is Self-Pollination Versus Cross-Pollination?
As an Amazon Associate we earn from qualifying purchases.
What is self-pollination versus cross-pollination? The difference is where the pollen comes from. In self-pollination, pollen reaches the stigma of the same flower or the same plant, and in cross-pollination it arrives from a different plant or variety. A Penn State Extension page puts the distinction simply: “When the pollen transfer happens within the same flower, it is called ‘self-pollination.’ When it occurs between different flowers, it is ‘cross-pollination.'” This article explains the terms, the boundaries that the three sources draw around them, and why the difference matters for fruit set.
Quick answer
- Self-pollination moves pollen within the same flower, between flowers on one plant, or to a flower on another plant of the same variety, depending on the source.
- Cross-pollination moves pollen from one plant to a genetically different plant or variety.
- Some plants set fruit from their own pollen, and others cannot, which is the difference between self-fruitful and self-unfruitful plants.
- Cross-pollination is described as producing more genetic diversity in plant populations.
Pollination comes first
Both terms describe a type of pollination, so the general process comes first. The Penn State page defines it as “the transfer of pollen from the anthers of a flower to the stigma of the same flower or another flower.” The Iowa State University page uses similar wording: “Pollination is the transfer of pollen from the anther to the stigma inside the flower.” The Purdue publication describes it as “the transfer of male pollen grains by some means from stamens to pistils.”
After the pollen lands, fertilization follows. The Penn State page describes the sequence: “The pollen tube elongates from the pollen grain into the style and down to the ovules, resulting in fertilization and seed set.” Self-pollination and cross-pollination both end in this same step; they differ in which pollen is delivered to the stigma.
What self-pollination means
The three sources draw the boundary of self-pollination in slightly different places, which is worth noticing. The Penn State page uses the narrowest version, describing self-pollination as pollen transfer “within the same flower.” The Purdue publication is broader: “Self-pollination occurs when pollen is transferred within the same flower or between different flowers on the same plant or cultivar.” The Iowa State page is broader still, stating that self-pollination “occurs when the pollen is transferred from the anther to the stigma on the same flower, from another flower on the same plant, or from a flower on another plant of the same variety.”
The practical point is that the Iowa State definition counts pollen moved between two plants of the same variety as self-pollination, so the definition depends on which boundary a source uses.
What cross-pollination means
Cross-pollination has a clearer definition across the sources. The Iowa State page states that “Cross-pollination is the transfer of pollen from one plant to the flower of a genetically different plant or variety.” The Purdue publication gives a fruit-based version: “Cross-pollinated flowers must receive pollen from a different plant or cultivar of the same plant-type for fruit to set.” The key word in both is different: the pollen has to come from a plant that is not genetically identical.
The Penn State page links this to a biological benefit. It states that “Cross-pollination is preferable to self-pollination because it produces more genetic diversity in plant populations.” The page presents this as a general principle, and it does not say that self-pollinated plants fail to produce seed.
Self-fruitful and self-unfruitful plants
Whether a plant needs cross-pollination to set fruit is a separate question from how pollen moves. The Iowa State page explains that “Self-pollinated plants are said to be self-fruitful” and that some plants “require cross-pollination for fruit set.” It also states that “Many plants cannot produce fruit from their own pollen and are considered self-unfruitful.”
The Iowa State page gives an apple example in the same vein: “Most apple varieties will set a small crop with their own pollen.” The same page notes that “many self-fruitful plants will set fruit better when cross-pollinated.” The Iowa State page recommends for maximum production that a grower “plant at least two different varieties with overlapping bloom periods to ensure cross-pollination and fruit set.”
The Purdue publication lists examples on each side. It says that “Tomatoes, peppers, and strawberries are examples of self-pollinating plants,” and that “Examples of cross-pollinated plants are sweet cherries, most apples, and most plums.” It also explains the apple case directly: “For example, most apple flowers need to receive pollen from another apple tree and/or different cultivar for fruit to develop.”
Who moves the pollen
Self-pollination does not always mean the pollen moves without help. The Iowa State page notes that “The transfer of pollen from flower to flower in a self-fruitful tree also often relies on bees and other pollinators.” It adds that “For self-unfruitful plants, the transfer of pollen by an insect pollinator is essential.”
The Penn State page describes the general range of carriers. It says that “insects do most of the work of moving pollen,” and that “Bees are the most important movers of pollen, assisted by flies, beetles, wasps, butterflies, and moths.” Pollen can also travel without insects. The Penn State page explains that “Some plants have very lightweight, smooth pollen that is easily blown by the wind from one plant to another,” while “Many other plants, however, have heavy, sticky pollen that must be physically picked up from one plant and moved to a different plant.”
The Iowa State page adds that “This is especially true for fruit trees, although wind or other factors can also aid cross-pollination in some other plant species.” The two claims together show that the carrier matters most for cross-pollination and for plants that are self-unfruitful.
What can block fruit set
The Purdue publication lists conditions that reduce pollination even when a plant is capable of it. It states that “However, weather, lack of bee activity, and an absence of an appropriate pollen source can inhibit fruit formation.” The Iowa State page also recommends planting varieties “with overlapping bloom periods,” which places bloom timing among the factors that affect cross-pollination.
How to apply this in a garden
For a gardener, the first question is whether a crop is self-fruitful or self-unfruitful. The Purdue publication names tomatoes, peppers and strawberries as self-pollinating, and it names sweet cherries, most apples and most plums as cross-pollinated. For hand-pollination of cucurbits, see how to hand pollinate squash and zucchini. For a tomato-specific growing guide, see how to grow cherry tomatoes in raised beds.
How we chose these sources
The three sources were selected because they are university extension pages and publications from different states, which lets the definitions be compared. The Penn State page is titled Pollination and Pollinators. The Iowa State University page is titled Pollination Requirements for Tree and Small Fruits. The Purdue publication is titled HO-173: A Guide to Flowering and Why Plants Fail to Bloom. All three returned HTTP 200 when requested directly with curl on 2026-10-27, and each quotation was copied from the fetched text.
What we could not verify
The sources differ in how they draw the boundary of self-pollination, and this article reports those differences rather than choosing one. The Iowa State and Purdue pages focus on tree and small fruit crops, so their examples do not cover every vegetable or flower.
What the sources do not say
- They do not describe the pollination needs of squash or cucumbers.
- They do not list which specific varieties in a home garden will cross-pollinate with each other.
- They do not give a minimum distance between plants for cross-pollination.
Frequently asked questions
Is self-pollination the same as self-fruitful?
Not exactly. The Iowa State page explains that “Self-pollinated plants are said to be self-fruitful,” which describes plants that can set fruit from their own pollen. Pollination describes how the pollen moves, while fruitfulness describes whether the plant sets fruit as a result.
Why is cross-pollination described as beneficial?
The Penn State page states that “Cross-pollination is preferable to self-pollination because it produces more genetic diversity in plant populations.”
Do all plants need insects to pollinate?
No. The Penn State page explains that some pollen is “easily blown by the wind from one plant to another,” and the Iowa State page notes that wind “can also aid cross-pollination in some other plant species.”
Which common plants are self-pollinating?
The Purdue publication states that “Tomatoes, peppers, and strawberries are examples of self-pollinating plants.”
Why does an apple tree sometimes need another variety?
The Purdue publication explains that “most apple flowers need to receive pollen from another apple tree and/or different cultivar for fruit to develop.”
