How To Evaluate Cultivars For Pollinator Performance

Cultivars. Always a controversial topic when it comes up in some Facebook Group or Reddit forum dedicated to native plants. Many of us spend time trying to persuade people to purchase and grow native plants, but sometimes it can backfire when your aunt comes home with a cultivar that has a double-flower structure that can’t even be pollinated! This is a real problem, because the tag on that plant probably claimed it was native!

But, nonetheless there are some cultivars that are perfectly ok for pollinators. And this article is going to help you tell the difference. I’m going to show you several methods where you can actually find information whether the plant should be beneficial to pollinators, at least as good as the straight native, or at a minimum, less risky.

Ultimately our approach to gardening with cultivars should be like the Hippocratic Oath, but with our ecosystem in mind and our plant selections: First, Do No Harm.

I’ve written about cultivars versus natives in the past, and summarized how pretty much all research shows that natives are always better than cultivars. But in those rare circumstances where someone just really wants one for aesthetics or can’t locate the straight species, we should try to help them out by pointing them to the information they need to understand whether or not that plant is helpful.

Now I would love it if everyone began saving flower seeds and winter sowing their plants! It would save them money, give them a better appreciation of nature, and help spread local eco-type natives, which would unquestionably help their ecosystems. But the fact is – most homeowners are not going to do this and would rather purchase plants from stores. And while many are not concerned about the cultivar vs native question, for those that are, we need to help them.

Why we need to understand the difference

So, why do we even bother considering this question if most research asserts that straight natives are nearly always the best choice for pollinators? Well, while native plant nurseries are growing in popularity, the biggest sellers of plants in America are still those big-box stores like Lowes, Home Depot, and Walmart. And they generally focus on what will sell as opposed to what is best for the environment. Unfortunately, what sells is often crazy cultivars that don’t necessarily resemble the straight species, but they still label them as ‘natives’.

Cultivars aren’t going away, but will increase

There are many reasons one may be tempted to buy a cultivar. One reason would be that you just fell in love with the looks – I mean, they are most often bred for that reason, right? Or what if you can’t find a straight native species in your area, and they only carry a variety of some sort? Will that particular type benefit the environment? Or could it even be toxic? These questions matter for several reasons. Most of us have limited space to work with, and can’t add natives endlessly. It is important for us to love our gardens (as we will take better care of them), so need to be pleased with the looks.

But, let’s dive into the details. What steps can we take to determine if a cultivar is as good or better as a straight native? I’m going to show you several methods to do so.

How to evaluate cultivars for pollinator preference

Ultimately, there are a few characteristics to check to see if a cultivar is as good as a native.

• Are the number of pollinator visits the same as the straight species? This would be a measure of attractiveness to the flower.
• Will the pollinator lay it’s eggs on the leaves? Dr. Tallamy has found that when leaf color changes, it may make pollinators less likely to lay eggs on it by either making it harder to find, or having lower nutritional value.

Method 1 – check for test garden research

There are several organizations that spend a significant amount of time evaluating native plants and their varieties or cultivars. The Mount Cuba Center in Delaware does exhaustive test gardens where they compare the performance of different cultivars and varieties against each other for various characteristics, including pollinator visits. These multi-year trials evaluate various plant characteristics and often include performance for pollinator visits as well as hosting.

Even if the particular cultivar you are interested in wasn’t contained in the Mt. Cuba study, you can often pick up patterns within them. For example, their huge Echinacea study found that in general, ‘double-bloom’ cultivars of Echinacea were the worst performing of all Echinacea cultivars in regards to pollinator visits.

Another excellent source is Dr. Annie White’s 2016 thesis. It’s several hundred pages long, but you can search for the genus of the plant you are interested to see if it was covered. As she compared common cultivars and their native counterparts, there is a good chance she covered that parent species.

Method 2 – check the patent

Most of the cultivars available for purchase are protected by a patent. Yes, you read that right, you can patent a plant! And in these patents they must describe what is special, novel, or unique about this particular plant (so that no other nurseries can breed it).

So, go get the patent (it’s public) and look for the special characteristics. You should avoid cultivars that change the color of the leaves or bloom. As well as any change to the shape or size of flowers. But cultivars that are selected specifically for overall plant size, fruit production, or growing condition tolerance are probably less risky.

How to find the patent

You may be wondering where you can actually locate the patent. Well, I will show you. (you can click on the images to enlarge)

Method 3 – Look for peer reviewed studies

Searching Google Scholar for articles containing the cultivar’s patented or trademarked name can sometimes yield studies that examined various aspects of the plant in question. But even if this doesn’t turn up any results, you can search the parent species + “pollinator” and “cultivar”, “hybrid”, or “variety”. This can yield studies that examine hybrid pollinator performance against straight species. And you can investigate if these different characteristics are similar to the cultivar you are interested in.

Now, we aren’t all scientists, but just reading the abstract will contain the main points of the study. They will relay what they studied, how they studied it, and what conclusions they could draw. And if they weren’t studying the particular cultivar you are interested in, it still can be insightful. For instance if they found that modification of the color made it harder for bees to locate the plant, then you should consider avoiding that cultivar. Another reason is that if the bloom time is effected, as in blooming earlier or later you may also interfere with pollinator visits.

Conclusion

While using straight native species is pretty much always the best option for pollinators, cultivars are here to stay. That being said, we cannot make blanket statements about whether all cultivars are ‘good’ or ‘bad’. Nature is a complex system, as are the modifications to specific plants we make. And the best situation is if a specific cultivar has been evaluated in a research trial, which would allow us to make a sound judgement as to it’s suitability for pollinators. But in the absence of that, at least we can try to only choose a cultivar that doesn’t modify floral structure, color, or size.

Find more gardening tips here….especially for natives