Before You Cut Down Those Perennials

Barbara Mrgich
Adams County Master Gardener

If you left your native perennials stand for the winter so the birds could eat the seeds, good for you! Now you are ready to clean up that garden to greet the new gardening season. But before you do any cutting, please read this.

We all know that pollinators are very important to our existence in this world. Pollinators provide a service to the vast majority of our food plants which makes it possible for them to produce a product. There are many kinds of pollinators, but bees rule the pollinator world. They are far better equipped to collect, store, and spread pollen because of their physical and behavioral traits.

It is a known fact that bee numbers are declining rapidly mostly because of lack of suitable habitat needed for their survival. Bees can’t survive in concrete and turf grass. That leaves us home gardeners with the task of providing them with suitable habitat.

Did you know that many of our native bee’s nest in the hollow stems of native plants? For many years, agriculture has relied heavily on the imported honey bees to pollinate their crops. It is only recently that the agricultural world is realizing the true value of long-overlooked native bees. In fact, latest research tells us that the native bee is actually the more efficient pollinator.

There are hundreds of different species of native bees that all look and behave differently. Some pollinate early spring crops, while others are more active during the summer and fall. Most are not "social" bees, like the honey bees who live in hives. Most native bees, with the exception of bumble bees, are "solitary". They go about their business all alone raising their young, and pollinating the flowers. Since they do not have a hive or "home" to protect, they do not tend to be aggressive in the least. Only female bees of all species are capable of stinging, and they rarely do. If I am working in my garden, and the plant where I am working is covered with bees, a gentle wave of my hand is enough to move them over to a different plant.

Native bees have basically two methods of protecting their eggs. Some dig tunnels or holes in bare soil to deposit their eggs, and some lay their eggs in the hollow stems of native plants. You may wonder why it has to be native plants. Some favorite garden plants such as Daylilies have hollow stems, but wild bees don’t usually choose daylilies as a safe harbor for their eggs. Why?

The reason is because native bees and native plants have evolved and interacted together for thousands of years. The newcomer, Daylily, has only been around in this country for two hundred-fifty years. The bees don’t recognize it yet.

If you have started buying native plants recently, you may notice that when you snip off a stem, that stem is usually hollow. If it’s not hollow, it probably has a soft pithy center that is easy for a bee to bite through. This is where many species of native bees go to lay their eggs, but bees cannot nest in growing plants. They also can’t get into those hollow stems while the flower, or seed head, is still on the plant. So, it becomes a dilemma for the prudent gardener. Should I leave the seed head for the birds, or cut the top off for the bee? Well, you can do both!

My personal solution has been to cut the seed heads, leaving about 18 inches of the hollow stubs stand. Then I pick up my "bouquet" of cut seed heads and place them in an urn or outdoor pot where the birds can just as easily get to them. (This also prevents the seed heads from flopping over each other in the garden and helps satisfy my "neatness" urge.)

The female bee will lay eggs in those hollow stems, either in the fall, or the following spring. She will seal each egg with a provision of pollen for the baby to eat until it is ready to emerge which probably won’t happen until the following year.

Now, when you cut down your native perennials this spring, be very mindful of whether those stems are hollow. If they are, cut them to about 18" tall, and leave the stubs stand. The new growth will soon come on the plant covering those stubs, and you really won’t notice they are there. The problem I have noticed in my garden, is that those dead stubs holding bee larva will eventually fall over causing an unsightly mess. Again, the neatness thing!

My solution is to carefully collect these dead, flopping stems, and take them behind a row of thick evergreens that grow along one end of my house. I gently lay them back there where they can lie unnoticed and undisturbed for as long as those babies need. While there, they are acting as mulch to suppress any weeds that might want to pop up in that area.

My conclusion about all this is that once we have the research and the facts at hand, a little common sense will provide us with solutions making it possible for us to create beneficial habitat for surrounding wildlife.

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