Keystone Plants

“Learn how to see. Realize that everything connects
to everything else.” Leonardo da Vinci”
— Leonardo da Vinci

Five percent of native plants are Keystone plants. This 5% supports 70-75% of our wildlife and holds our food chain together. Let’s get into some detail!

If you spend time outside or have paid attention to ongoing nature research, you know there is a notable decline in insect and bird populations on Earth. Climate change, habitat destruction, and pesticide use are reasons for this decline. Another significant factor, though less frequently highlighted, is the loss of native plants. We generally label it as loss of bodiversity, but it is much more of an issue. Many insects rely on Native Plants they evolved with and without them they are not able to live.

We have all been busy gardening with plants that did not evolve locally and have little value to our ecosystem and food chain. That means our native insects do not have their host plants. Our food web is broken! In the past several decades there has been a focus on reversing honeybee decline. At long last, there has been more interest in the decline of native bee decline, because it has become clear that their pollination is essential to feeding the world. And yet, the overall loss of insects is more complicated.

It starts with how our food chain has evolved and how it works when it is healthy. The foundation of our ecosystems are the plants and the insects that evolved with those plants. Insects are integral to our food web and gardens, since they are predators, decomposers and parasites, all tied to the plants we grow.

Let’s focus on two components: Firstly, Lepidoptera, which are the butterflies and moths. The caterpillars that emerge from the eggs they lay are needed by birds to raise their young, because they are rich in protein and antioxidants. It takes an estimated 6,000 caterpillars to raise one clutch of 6-8 baby Chickadees. Every kind of Butterfly relies on a specific host plant to lay their eggs on. If that plant isn’t available, you won’t see that kind of butterfly.

Monarchs are an example of a butterfly that has specific host plants in the Milkweed genera.

Secondly, we all know the importance of bees and pollination. Did you know that 25% of our native bees are Specialist Bees. This means that they evolved over time with a certain plant(s) and now rely on the pollen that plant species or genera produces to raise their broods. The plant, as well, may have evolved to totally depend on that pollinator insect as well.

Take the Cucurbita family of plants (squashes, pumpkins and gourds), for example, that rely on Peponapis and Xenoglossa Squash bees for pollination. Generalist bees such as Honey Bees and Bumblebees are not effective Cucurbita pollinators because they are not equipped to handle the pollen, which is large, sticky and spiky. So next time you enjoy a meal of cucurbitas, you have these squash bees to be thankful for.

Also, in many cases the specialist bee will emerge in spring, at the same time that their host plant produces its pollen.

Some specialist bees have evolved with one plant species or genera, while others evolved along with multiple plant families.

It is clear we all need to plant Natives to help the birds and specialist bees! But which Native Plants would be best at preserving our food chain? Fortunately, experts have been working on this issue for years.

Doug Tallamy, an entomologist and author, has extensively researched this issue in two of his books, Bringing Nature Home and Nature’s Best Hope (sources below). His research assistant Kimberley Shropshire was able to put together data from the last hundred years she collected from different sources (books, papers, records). The result was surprising. They found that just 5% of our Native plants end up supporting 70-75% of wildlife! All native plants are helpful but this 5% is Key to a healthy food chain. They support the most Butterflies and Moths as Host Plants and Specialist Bees. These plants are named Keystone after the key stones that hold arches together and upright. The database that Shropshire developed is divided into regions and is accessible by zipcode. Check it out at National Wildlife Federation!

Top Keystone Plants for Michigan & the Eastern Regions

Trees & Shrubs

Quercus, Oak Trees – Support 436 of caterpillar species

Prunus, Plum and Chokecherry – Support 340 caterpillar species

Salix, Prairie Willow & Pussy Willow - Support 289 caterpillar species and 14 Specialist Bees

Betula, River & Sweet Birch - Support 284 caterpillar species

Populus, Cottonwood -  Support 249 caterpillar species

Acer, Box Elder, Maples - Support 238 caterpillar species

This does not mean that you will get the number of caterpillar species noted for each tree/shrub. But it does signify the potential. these keystone plants have to attract numbers of insect species.

Trees have the biggest impact.

Lets look next at the Keystone Perennials!

Perennial Keystone Plants

Solidago, Goldenrods, #1 Perennial Keystone, supports 104 caterpillar species and 42 Specialist Bees

Symphyotrichum, Asters supports - supports 100 of caterpillar species and 33 Specialist Bees

Helianthus, Sunflowers – supports 66 of caterpillar species and 50 Specialist Bees

Rudbeckias support 20 caterpillar species and 29 Specialist Bees

Other Keystone Perennials include - Coreopsis, Veronia, Cup Plants, Echinacea, Helenium (Sneezeweed), Ratibida and Heliopsis (False Sunflower), Cornus (Dogwood)

These are perennials that we stock in our Native Plant Nursery. They are fairly common and are important nectar sources for bees.

What can we do to help the insects?

As Doug writes in his books, there is no easy solution. Even if all the powers to be got together and agreed, there is not enough available land available to make a difference. Food production claims a huge portion and then we have vast parking lots, lawns and golf courses. However, if each of us planted natives in our own yards it could make a huge difference.

Ask yourself, do you really need the azaleas, hostas, primroses, and other nonnative plants that blooms for a short time, but provide no food for insects, or would it be wise to incorporate some keystone plants into your landscapes that provide food for a variety of insects?

Hop on over to our Native Plant webstore and explore!