What is the role of nativars (cultivars of native plants) in pollinator habitat creation?
Like most plants, Missouri native plants have been subjected to selection for specific features that make them more desirable to humans such as bigger flowers, longer bloom time, compact growth, showy colors, pest resistance, etc. It is obvious to see how plants that are pest resistant would be undesirable to insects but other changes to the true native can also be undesirable and it is hard to tell exactly what type of manipulation is acceptable since the insects don’t talk, they just slowly disappear. Since most of us are making these gardens to save the pollinators it is counter productive to plant a cultivar that does not provide optimum nutrition for the insect.
Buying plants at a garden center it is often difficult to avoid the nativars and many gardeners unknowingly buy them. Look for clear labeling that does not have any extra words after the genus and species. While we are talking about garden centers, I can not stress enough, the importance of avoiding plants treated with neonicotinoids. Neonics are a poison incorporated into the plant tissue that can kill large amounts of insects visiting the flower. Always check that your plant is neonicotinoids free and ask your garden center to stop selling treated plants.
The usefulness of a nativar depends on which structure of plant is manipulated. In general changes to plant structure are easier on pollinators then changes to flower structure. There is a cultivar of echinacea where the bloom has been manipulated to be only petals with no nectar production, obviously not great from the pollinators point of view. Hydrangea is another flower that has been changed to have more showy flowers with less nectar and pollen. There are also changes that we can not see that insects may be missing like loss of UV markings as nectar guides and changes in scent. When bloom time is changed it may no longer be in sync with pollinators. Some insects are very dependent on their host plant and an interruption in any stage of their life cycle means collapse of the species.
Many nativars suffer from inbreeding and reduced genetic diversity as they have been selected for a specific trait. Nativars cross pollinating with true natives could lead to the diluting and contaminating of the true native gene pool. Gardens that feature nativars and natives can produce seeds that are not true natives and should not be released back into the wild. When collecting seeds in a backyard garden the chance of genetic contamination is high so these seeds should not be used for reestablishing natural populations.
So much is still unknown about what exactly insects need from plants to be successful. More research needs to be done on nativars and their ability to provide for pollinators. Several institutions are working on this question now as insect populations collapse around the globe. I once had a tour of Mt Cuba center to see their trails of performance of natives and nativars. For more information on Mt. Cuba’s trials check out https://mtcubacenter.org/research/trial-garden/
There is good news, we can help with the research. Scientists are asking for native plant gardeners to submit observation of pollinators on natives and nativars as part of project budburst. So far project budburst data for the Midwest plants indicate that mean pollinator visits per minute are higher for true native plants than for their cultivars, however, they also see considerable variation among cultivars. Join in this citizen science project at https://budburst.org/projects/nativars#where
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