Save the Stems

Today’s Backyard Nature: bee butts. These are the back ends of little bees: native, solitary bees who make a nest *inside* last year’s flower stems.
Each bee is one female making one nest: laying one egg at a time in its own little chamber and with its own cake of pollen as baby food.

This is my proof that “Save the Stems” works.

[TLDR summary of this post: “Save the Stems” makes bees! Do it!]*

“STEM Education“

Years ago, I stopped tidying flower beds in fall, and left the old flower stems for the birds. Most of Nashville’s winter birds eat seeds, and I loved seeing finches glean seed-heads; and watching juncos and sparrows scratch underneath like little chickens. Come spring, I chopped the stalks down to the ground, and threw them on the Brushpile-for-Habitat.

And then I learned about “Save the Stems” for bees.
Now, there is no chopping to the ground. Ever. 

Stems are Habitat

About 30% of our native bee species nest in cavities. Some use cracks in concrete, mortar, wood, window casings, etc., but many target the stems of last year’s flowers.

Here’s the infographic I like to show people:

These bee experts advise cutting stems in spring, but only the TOPS!
Why?
Trimming to varying heights of 8 to 24 inches…
-opens the top of a stem for a bee to find,
-makes a stem less likely to topple,
-looks better for humans who prefer order to chaos,
-hides old stems among emerging new ones,
-gives humans a low, convenient view to the Wonders Within!

Which stems? Which bees?

My bee butts are in Goldenrod and Rudbeckia fulgida (the gold Blackeyed Susan), but there are many native plants perfect for bee nurseries, and I’ll be watching these, too. Good candidates are plants with naturally hollow stems or stems full of spongy pith. “Spongy pith” is fun to say and fun to play with, which you already know if you’ve poked a fingernail inside an old stalk of Frostflower or Cup-plant. The softer the pith, the easier for a bee to excavate.
I’ve put a list of likely plants in the Resources below.
Which bees? Good question…

Questions:

How does the bee dig? How deep does she go?
And then what? Does she turn around and peer out at the world like the Spring Beauty bee (link)?
Or does she plug the hole to protect it from weather and predators?
Is her body the plug?
Or does she leave and die?
Or does she leave and, job done, live in carefree retirement?
Or does she guard the nest till the kids emerge?

I wonder about the life cycle here in Nashville. Some sources says adult females overwinter in stems, and then in spring renovate their refuge into a nursery.
But when does the mating happen? And when—exactly—do the eggs hatch, pupate, become adults, emerge?

I’d know more if I knew the species of my bees, but I can’t ID based solely on butt.
My guess is Ceratina, a genus of small Carpenter bees. Not the big Eastern Carpenter bees people try to kill, but the tiny ones people rarely notice.

Ceratina strenua and C. calcarata are in Tennessee, so maybe mine are one of these?

I’ll find out eventually, but for now, it really doesn’t matter.

What matters is that there are bees in the stems,
and the bees are making more bees.

***

How to see Bee Butts:

Would you like to see bee butts? Sawdust is a clue. Sawdust near wood might mean the Big Carpenter bees, but sawdust nowhere near wood might mean the small carpenters. On a day with no wind, the shavings will linger at the stem, or get caught in wide leaves below.
If you still have old stems, it’s not too late to check them for occupants, and if there aren’t any, cut them 8 to 24 inches tall, and keep checking.

Why these Bees matter:

They matter because they’ve been here longer than we have, and deserve to thrive in their own native habitat. Yes, they pollinate, but they are more than “just” pollinators. They matter as every plant and animal in native habitat matters. We need every single one.

Here in the Southeast, we have about 700 species of native bees, and about 30 percent of these make homes in cavities, like these stem-nesters. The other 70 percent make homes in the ground. And the vast majority of all these bees are solitary.

But every single one of these species is harmed by our mosquito contract, our lawncare pesticides, herbicides, fertilizers, weed ‘n’ feed applications, automatic irrigation systems, and weekly mow ‘n’ blows.

So, let’s save money, time, pollution, and our part of the planet by only mowing *at most* every other week on a high blade, with zero leafblowers, zero applications.
Our lawns can be habitat!

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Resources:

–Printable brochure of how/why to save stems for bees (from Xerces Society) (link)

–Bee Nesting Resources from Xerces Society (link)

–List of plants with likely stems for bees (NC Extension article by Debbis Roos, link)

–“Leave the Leaves: these invertebrates depend on it” from Xerces Society (link)

–Lawn as habitat: see my post on “Wildlife-Friendly Lawncare“

–No yard? Save the stems in (native) container gardening, too (link to HomeGrownNationalPark)

* TLDR = too long, didn’t read.