american hazelnut pollination - Ask Extension
Hello, I saw your video of the roadside American hazelnut. The extension agent did not discuss pollination. I've read two things: 1.) self-pollinatin...
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american hazelnut pollination #799178
Asked July 02, 2022, 7:57 PM EDT
Hello, I saw your video of the roadside American hazelnut. The extension agent did not discuss pollination. I've read two things: 1.) self-pollinating so you need only one; 2.) you need two, a different cultivar for cross pollination. Which is true?
Howard County Maryland
Expert Response
Hi-
You should purchase and plant at least two different and compatible cultivars to ensure cross-pollination. Nurseries selling hazelnut should be able to guide your decisions on cultivar selection.
Here are some resources with more detailed information:
https://njaes.rutgers.edu/e368/
https://extension.usu.edu/yardandgarden/research/hazelnuts-in-the-home-orchard
Jon
You should purchase and plant at least two different and compatible cultivars to ensure cross-pollination. Nurseries selling hazelnut should be able to guide your decisions on cultivar selection.
Here are some resources with more detailed information:
https://njaes.rutgers.edu/e368/
https://extension.usu.edu/yardandgarden/research/hazelnuts-in-the-home-orchard
Jon
Hi Jon, thanks for your response. I've read the two resources but still a bit confusing... questions in red
The New Jersey site says: Hazelnuts are monecious (separate male and female flowers on the same plant) and wind pollinated. They are also self-incompatible, meaning the pollen from one plant cannot fertilize the female flowers on that same plant, including its own clones. Incompatibility is of the sporophytic type and controlled by S-alleles (also called incompatibility alleles) expressed in the pollen and the female flowers. The S-allele(s) expressed in the pollen of one tree must be different from the S-alleles expressed by the female flowers of the other tree to produce nuts. Thus, at least two hazelnut trees with different S-alleles are required for nut production.
I understand 'clones' means the suckers that come up, right -- and that won't work? So, for clarification, does this mean I can get another American hazelnut, but it has to be a different cultivar?
But, the Utah state reference says:
| American hazelnut (Corylus americana) | Nut production is best when cross pollination occurs with another variety of the same species (see Tables 1 and 2) or with other seed grown plants of the same species. From Table 1: Other seed grown American hazelnut plants. Purchase 2- 3 plants for sufficient pollination. What are "seed grown plants of the same species"? |
Plants grown from seed will have different genetic makeups between individuals, just like people (who aren't identical twins) -- the combination of genes from the "mother" and "father" plants will create unique seedlings. This genetic difference allows them to be compatible pollinators for each other -- the plant will "recognize" the pollen arriving on its female flowers as coming from another plant, so fertilization will occur. Pollen from its own flowers is rejected because the pollen grains contain the same genes, so no fertilization occurs and no seeds produced. Genetic diversity is ideal for giving plant populations better resilience and more evolutionary flexibility as their environment changes, which is why a number of plants are self-incompatible, or will produce the most seed or the heaviest crop of fruits/nuts when cross-pollinated.
Cultivar is shorthand for "cultivated variety," and a variety is simply a variation in a plant that differs from others in the wild population in a way that humans find important. Any number of attributes can define a variety, such as flower color, fruit flavor, or the mature size of the plant (dwarf versus not, for instance). The majority of plants sold at nurseries, whether decorative or edible, are cultivars, so they have traits that are consistent and known. In comparison, seed-grown plants, having genes unique to each individual, can express different and potentially undesirable traits. When the specifics of a plant's traits aren't critical, or when diversity is desired (such as with plantings to restore native habitat), plants for sale may be grown from seed instead of cloned.
Plant cultivars are almost always clones, meaning that all individual plants of one cultivar are genetically identical (clones of each other). Cloning is how cultivars are propagated because this is the only way to preserve the unique genetics of that individual -- desirable traits like flavor, ripening time, inherent disease resistance, hardiness, etc. -- as known features instead of pot-luck, as they would be with seedlings. If a plant is not grafted by a nursery onto different roots, suckers are part of the same plant, but would become clones when cut off and grown with their own roots as separate plants. (Suckers are new stems arising from a root system instead of branch growth. Suckers on grafted plants are not the same cultivar as the canopy growth, so would not be clones of the branches.)
The Rutgers discussion of alleles might be more technical than it needs to be, but essentially they're explaining the mechanism that makes the pollen from one flower genetically incompatible with the receptacle in another on the same plant. What Utah State is saying is that your pairing for pollination can include any combination of the following, because their genes will differ enough to be compatible: two different cultivars; one cultivar and one seed-grown plant; or two seed-grown plants. They're also making sure readers understand that the pollinator needs to be the same species (American Hazelnut in this case) and not a different kind of hazelnut or a different tree species entirely.
The final complication, which Jon alludes to when he mentioned compatible cultivars, is that Hazelnut blooms can open at different times over the course of its multi-week blooming window. Some cultivars bloom earlier in that window of time than others, so to make sure you're not having pollen blow around and then disappear before the female flowers are receptive, you pick two cultivars that bloom around the same time -- both early or both late, say. This nuance occurs with other fruit trees as well, like apples. They're often referred-to as "early-season blooming" or "late-season blooming"; whatever the exact term, it indicates what a good pollination partner will be if specific charts of compatible cultivars isn't available.
Abnormal weather that changes pollen release timing will also affect the female flowers, so the two should still say fairly in-sync for good cropping. Wind-pollinated plants like hazelnut don't rely on bees being able to fly for pollination, but if the weather is wet during the bloom window, that can still hamper pollination for that year, so the crop might be more paltry. All you can do is plant the appropriate pairing (or more than two cultivars if you wish) and hope for the best.
Apologies if you were already aware of most of the above, but we thought the explanation might help clarify why cultivars dominate the market and what purpose they serve with regards to plant genetics and producing crops.
Miri
Cultivar is shorthand for "cultivated variety," and a variety is simply a variation in a plant that differs from others in the wild population in a way that humans find important. Any number of attributes can define a variety, such as flower color, fruit flavor, or the mature size of the plant (dwarf versus not, for instance). The majority of plants sold at nurseries, whether decorative or edible, are cultivars, so they have traits that are consistent and known. In comparison, seed-grown plants, having genes unique to each individual, can express different and potentially undesirable traits. When the specifics of a plant's traits aren't critical, or when diversity is desired (such as with plantings to restore native habitat), plants for sale may be grown from seed instead of cloned.
Plant cultivars are almost always clones, meaning that all individual plants of one cultivar are genetically identical (clones of each other). Cloning is how cultivars are propagated because this is the only way to preserve the unique genetics of that individual -- desirable traits like flavor, ripening time, inherent disease resistance, hardiness, etc. -- as known features instead of pot-luck, as they would be with seedlings. If a plant is not grafted by a nursery onto different roots, suckers are part of the same plant, but would become clones when cut off and grown with their own roots as separate plants. (Suckers are new stems arising from a root system instead of branch growth. Suckers on grafted plants are not the same cultivar as the canopy growth, so would not be clones of the branches.)
The Rutgers discussion of alleles might be more technical than it needs to be, but essentially they're explaining the mechanism that makes the pollen from one flower genetically incompatible with the receptacle in another on the same plant. What Utah State is saying is that your pairing for pollination can include any combination of the following, because their genes will differ enough to be compatible: two different cultivars; one cultivar and one seed-grown plant; or two seed-grown plants. They're also making sure readers understand that the pollinator needs to be the same species (American Hazelnut in this case) and not a different kind of hazelnut or a different tree species entirely.
The final complication, which Jon alludes to when he mentioned compatible cultivars, is that Hazelnut blooms can open at different times over the course of its multi-week blooming window. Some cultivars bloom earlier in that window of time than others, so to make sure you're not having pollen blow around and then disappear before the female flowers are receptive, you pick two cultivars that bloom around the same time -- both early or both late, say. This nuance occurs with other fruit trees as well, like apples. They're often referred-to as "early-season blooming" or "late-season blooming"; whatever the exact term, it indicates what a good pollination partner will be if specific charts of compatible cultivars isn't available.
Abnormal weather that changes pollen release timing will also affect the female flowers, so the two should still say fairly in-sync for good cropping. Wind-pollinated plants like hazelnut don't rely on bees being able to fly for pollination, but if the weather is wet during the bloom window, that can still hamper pollination for that year, so the crop might be more paltry. All you can do is plant the appropriate pairing (or more than two cultivars if you wish) and hope for the best.
Apologies if you were already aware of most of the above, but we thought the explanation might help clarify why cultivars dominate the market and what purpose they serve with regards to plant genetics and producing crops.
Miri
Wow, loving this conversation and my deeper understanding. Still not sure about two different cultivars of Am Hazelnut, because you said cultivars are almost always clones....and you can't use clones for pollination but you give as an option for pollination two different cultivars, a cultivar and seed produced, or two seed produced plants. What am I missing or not understanding?
One cultivar is all the same clone, so (to make up names) the cultivar 'Bounty' is genetically different from every other cultivar, but every plant named 'Bounty' is a clone of the other. So, 'Bounty' can pollinate with 'Tasty' but not with another 'Bounty' plant.
Miri
Miri
Got it!!!! Thanks
You're welcome.
