Pollinator garden spring clean-up

Okay, now that spring has arrived, you can finally clean up the garden — sort of.

In the past, I used to remove all the leaves, cut back perennial stems to the ground, and put it all into leaf bags destined for the curb. Then, I would spread mulch to make it look tidy. It turns out that this typical approach to spring garden cleaning is bad for pollinators and birds. It’s also a lot of unnecessary work.

Now, I continue to leave the leaves in the garden, cut stems to 15 inches from the ground, and chop up the rest and to decompose over the summer. I no longer need to buy and spread mulch because the plant material I left in the garden becomes the mulch. Here’s more detail on how I clean up my gardens in spring…

ASAP

As soon as I can work outside, I do remove the leaves and I cut down stems only at the edges of garden beds that can be viewed from the sidewalk, and from paths. I clear as far as I can reach without stepping into the garden to avoid compacting the soil. I don’t want neighbours to think I’m neglecting our yard, especially since I didn’t tidy up in the fall like they did. I also move or remove the leaves to reveal emerging Crocuses and Bloodroot shoots.

Periodically throughout April, I poke around in sunny areas to see if plants are starting to come up. The Oak leaves that blow into the front garden in the fall form thick mats. If plants are coming up, I remove some of the Oak leaves. The Maple, Basswood, and Birch leaves in the backyard are much lighter and break down quickly, so they don’t threaten to smother plants like Oak leaves.

Using the wheelbarrow, I move the leaves and old plant material to the backyard. I toss it around shrubs in the hedgerow or in the compost pile. I no longer put anything into leaf bags, another way I now save money and labour.

Wait for warmer weather

According to Savvy Gardening’s Spring garden clean up done RIGHT, we should wait until the daytime temperature warms to a consistent 10°C (or 50°F). (I assume this means daytime high temperatures.) Insects that have been overwintering in the garden will have had a chance to wake up and leave their winter sheltering spots. The Xerces Society provides additional guidance for figuring out when its safe to start in their article Don’t Spring into Garden Cleanup Too Soon!

Stems left standing for the winter. We’ve seen Juncos, and the occasional Goldfinch and Chickadee, eating from the seed heads. (November 18, 2019)

Who’s still taking shelter in the garden?

I was surprised to discover that while some butterflies migrate, others overwinter here. The North American Butterfly Association’s Questions and Answers page describes the butterflies that do migrate, like Monarchs and Painted Ladies. However, other butterflies and moths overwinter here in one of their life stages, such as in a chrysalis camouflaged on a branch, or as an adult tucked under leaves, bark or rocks. Adult Mourning Cloaks, Question Marks Commas, and Compton’s Tortoiseshells will take shelter in your winter pollinator garden, and emerge early in spring. They drink sap if there are no flowers blooming yet. Then, if the weather cools again, they seek cover under leaves to wait some more.

I spotted this Mourning Cloak butterfly basking in the garden in early April. It may have spent the winter in my garden sheltered in the leaf litter or brush pile. (April 6, 2020)

The Wild Pollinator Partners blog post Another good reason to hold back “cleaning up” the garden, describes recent research showing that after queen bumblebees emerge from underground in spring, they hang out in leaf litter while they slowly wake up. If we clean up leaves too soon, we risk raking and bagging queen bumblebees.

Leave the leaves

Continue to leave the leaves on the ground (that you already left in place in fall and winter) instead of stuffing them into leaf bags; they will decompose to become a free mulch substitute. For a tidier look, remove leaves near garden edges and start a leaf mulch pile elsewhere in your yard. You could also focus on leaving leaves just in shady areas where you’re trying to mimic humus-rich, woodland conditions.

Leave stems 15-inches above ground

Typically, when we clean up our gardens, perennials are cut back to ground level. Instead, cut pithy or hollow plant stems to 15 inches, so they can be used as cavity nests by solitary bees, like Mason Bees and Small Carpenter Bees. Some stems that are used for nests include Joe Pye Weed, Cup Plant, sunflowers, goldenrods, coneflowers, Swamp Milkweed, bee balms, raspberries, elderberries, roses, and sumac. In my garden, I have seen Small Carpenter bees use stems of Anise Hyssop, Ironweed, and Purple Coneflowers.

New plant growth will soon cover the awkward stems that remain.

If you look closely, you can see the Small Carpenter Bee sticking out of this Ironweed stem. Several Small Carpenter Bee queens dug nests in these plant stems, and were flying back and forth with pollen to provision them.

Chop and drop

I now also use the chop-and-drop method, that I learned from permaculture vegetable gardeners, to deal with lengthy debris. Once I cut off last year’s growth, I chop it up and leave it right in the garden. I used to put it all into leaf bags to be picked up for the city’s composting program. If there’s too much material for my liking, or if the stems are too hard to cut, I simply add them to my own compost pile or brush pile.