Some leaves I’m not leaving. And I’m confused about leaving the stems

Some leaves I’m not leaving. And I’m confused about leaving the stems

We know a lot more these days about how our gardens can support (or harm) wildlife and, like no doubt many of you, I’m leaving as many leaves in place as possible.  So my garden beds are leafy and will stay that way until spring.

But I’m here to confess – there WERE some leaves that I removed.  Don’t judge me yet!

On Sidewalks, Etc.

Surely no one would argues with the much older, tried-and-true two-word meme: “Safety First!” It’s what comes to my mind when I see the sidewalks in my neighborhood looking like this….for months. Imagine this with snow or ice on it.

On Lawns

I don’t have a lawn myself (anymore), but if I had one, what would I do about leaves on it?

Here’s a lawn near me in its unmown, unblown condition this week. I’ve read that lawns can survive a certain amount of leaf cover all winter, but how much – certainly not this much, right?

Here’s an answer from the University of  Minnesota:

The most important point with fall cleanup is that the tree leaves are not covering a significant portion of the turfgrass canopy. 10-20% coverage of your lawn might be okay, but I certainly would make sure the leaves aren’t covering any more than that. Excessive leaf matter on your lawn going into winter is bad for several reasons. First, it will smother the grass and if not removed very soon in the spring it will inhibit growth. Second, it can promote the snow mold diseases. And finally, turf damage from critters (voles, mice) can be more extensive in the spring.

I heard more on the subject from GardenRanter Emeritus Thomas Christopher’s interview with Connecticut designer Kathleen Connolly on this episode of his Growing Greener podcast. She offers three options for leaves on lawns:

  • Good to do: Run a mulching mower over the lawn a couple of times, and leave the chopped-up leaves there. She says as long as the chopped-up leaves aren’t more one-half inch high, they don’t harm the lawn and they provide all 19 essential nutrients that turfgrass needs.
  • Better to do: Rake the leaves and compost them for your garden.
  • Best to do (“for wildlife”):  Nothing. Leave the leaves whole on the lawn. It’ll take a while for the leaves to decompose, of course. She mentions that oak leaves take as long as two years to do decompose.

Connolly adds that if you have enough space, you could employ all three of these strategies on your property. 

When I had a lawn I raked and composted the leaves on it but boy, it was a lot of work to turn the compost pile enough to see progress.  So I switched to mowing over them and leaving them there to improve the soil and the turfgrass, too.

On Sun- and Dry-Loving Plants

So what about plants that naturally grow nowhere near deciduous trees but are well-adapted instead to sunny, dry locations? I have a couple of them – groundcover sedums (a succulent), like the S. takesimense above, and lamb’s ear, which is native to the rocky hills of Turkey, Armenia, and Iran.  So I uncover just those two plants to keep them dry and happy over the winter.

Certain Leaves, like Magnolias

A final caveat about leaving the leaves: not all leaves are created equal in their ability to decompose over the winter, and magnolias are the example usually given.

What about Leaving the Stems?

Here in my front garden, there are leaves among the stems of Joe Pye Weed and wood aster, which I leave standing to create habitat for stem-nesting bees.

In the same podcast, Connolly went on to address leaving perennial stems standing for wildlife, and the details surprised me. For example, it’s not until the second year of standing that young bees emerge from hibernation inside the stem.

And when she’s asked, as she is frequently, “When can I cut them down?,” her answer is to wait until May, then cutting the stems to varying heights between 6 and 24 inches.

Other sources agree with her recommendation as to height. The NWF says to “cut the stems down to 10 or 12 inches, and native bees will nest inside.” Benjamin Vogt says in “early to mid spring, you should leave 12-18 inches of stem when cutting back the garden — you will soon see swarms of bees coming to lay eggs in hollow stems or to excavate pith before egg laying begins. After a few weeks the ‘ugly’ dead stems will soon be covered by new green growth as insects keep doing their thing.”

The Nebraska Extension expands on the advice, without specifying when in spring to do the cutting:

Cut Down Stems – Part Way
Many gardeners know leaving dead plant stalks standing over winter is a good practice. Hollow stems are used by some insects as overwintering sites, such as mason bees.

The stems many also provide some support for your perennials next summer, helping those that tend to flop down stand a little taller. Your plant’s new growth will quickly cover and hide these old stems from view. This infographic (below) from The Ohio State University gives a good overview of how to maintain garden perennials while maintaining good bee habitat.

Once you’ve cut your perennial stems back to staggered height, consider cutting the old stem tops into smaller pieces (about 4-6 inches) and allow them to lay on the ground, utilizing them as leaf litter. They contribute organic matter to the garden as they decay and any remaining seeds in the old flower heads may start new plants.

If the garden doesn’t look neat enough when you’re done, lightly top dress with mulch. This will hold any leaves or debris in place, reducing the potential of it blowing out of your beds. Just don’t put it on too thickly if you’re trying to maximize habitat for ground-nesting bees.

When you’re done, you’ll have neat looking gardens ready for next spring’s growth, a little food for wildlife and great habitat for bees, pollinators and other beneficial insects.

I can’t resist correcting the top entry – “intact” is one word.

So When Can We Do the Gardening?

Here’s my dilemma, which many of you may relate to. I’ve always removed stems, leaves and weeds in the early spring before my beds are full of newly emerging perennials and spring-blooming bulbs. That way I’ve avoided stepping on the new growth when I’m doing spring clean-up.  Which raises the questions:

  • If I cut back the stems in early spring to the recommended heights, does it still help? (Sources above recommend “spring,” “early to mid-spring,” or waiting until May.)
  • What would perennial beds look like over the following season if fallen leaves weren’t removed at all but simply left in place to decompose slowly, potentially over two seasons?
  • Is there any impact on the growth or performance of perennials to have their stems left in place year after year?

We’re talking about changing our gardening practices to better support wildlife, and I’ve happily joined the movement!  But to turn urgings from entomologists into changes we gardeners can implement, we need input from eco-minded horticulturists and gardeners.  Gardeners are pragmatists, of necessity.

The devil is in the details.

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