Cross-pollination can absolutely negatively impact the desired traits of specific lavender cultivars, but this impact is not on the existing plant itself, but on the seeds it produces and, consequently, on the next generation of plants grown from those seeds.
Here's a breakdown of how this happens:
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Cultivars are Genetically Stable (Clones):
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A "cultivar" (cultivated variety) like 'Munstead' or 'Grosso' is a specific selection of a plant that has unique, desirable traits (e.g., specific flower color, compact growth, high essential oil quality, certain scent profile).
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To ensure these traits are consistently reproduced, cultivars are almost always propagated vegetatively (e.g., from cuttings). A plant grown from a cutting is a genetic clone of the parent, meaning it is genetically identical and will exhibit all the same desired characteristics. This is how the genetic stability of a cultivar is maintained.
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Cross-Pollination and Genetic Mixing in Seeds:
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When a bee carries pollen from a different lavender plant (a different variety or even a compatible species) to your cultivar's flower, and fertilization occurs, the resulting seed will be a hybrid. It will contain a mix of genetic material from your cultivar and the pollen donor.
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The genetic traits of the cultivar (e.g., the precise balance of chemical compounds that give its unique scent, its specific shade of purple, its plant size) are encoded in its DNA. When cross-pollination happens, this specific genetic code is mixed with another.
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Loss of Desired Traits in Offspring:
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If you plant these cross-pollinated seeds, the resulting new lavender plants will not be true to the parent cultivar. They will be genetically different, and their traits will be unpredictable.
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Impact on Scent/Essential Oil Profile: This is a major concern for commercial growers and anyone who values the specific aroma of a cultivar. For example:
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If a high-quality Lavandula angustifolia (English Lavender) cultivar known for its sweet, low-camphor essential oil (e.g., 'Maillette') is cross-pollinated by Lavandula latifolia (Spike Lavender) or a Lavandin, the seeds it produces will likely grow into plants that yield essential oil with a higher camphor content and a less desirable aroma profile for fine perfumery or aromatherapy. Even within L. angustifolia, cross-pollination between different cultivars can subtly alter the balance of key compounds like linalool and linalyl acetate.
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Studies have shown that while pollination generally increases essential oil yield, it can lead to changes in the chemical profile, such as lower relative amounts of linalool and higher linalyl acetate in L. angustifolia (though these are still desirable compounds, a precise balance is often sought).
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Impact on Visual Traits: The offspring might have a different flower color, a less compact growth habit, or vary in size compared to the parent cultivar.
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Impact on Hardiness/Vigor: While sometimes hybrids exhibit "hybrid vigor," they can also inherit less desirable traits or be less adapted to specific conditions than a carefully selected cultivar.
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Conclusion:
Cross-pollination does not affect the physical plant currently in your garden. Its flowers and scent will remain consistent. However, cross-pollination is a significant concern if you intend to collect seeds from your lavender plants and expect them to grow into new plants that are identical to the parent cultivar. Because cross-pollination introduces genetic variability, it effectively "dilutes" or removes the specific, desired traits of that particular cultivar in the next generation grown from seed.
This is why the vast majority of lavender used in commercial production and sold in nurseries for specific varietal characteristics is propagated clonally through cuttings, completely bypassing the unpredictable genetic roulette of seed propagation.
Lavender Farm in Door County Wisconsin. You can buy lavender products online at islandlavender.com
