Ouch!
I cursed as something in the handful of weeds pierced my hand. With the coming
of the frost, it was time to clean out my garden. In this corner, a small patch
of parsley had gotten overgrown by the gracefully arching seed heads of a
grass. My flesh had found the spiny, well-armed basal leaves of a thistle in
the bunch, too. The deep green leaves spread out in a perfect circle, at least
a foot in diameter. Spines adorned the jagged leaf margins menacingly. This
year it didn’t produce a flower stalk. Next year it won’t either—because with a
quick pry of the pitchfork I dislodged the offensive weed, roots and all.
As I
continued to load up the wheelbarrow for a trip to the compost pile, I waded
into the overgrown garden border to remove a couple of bushy, second-year thistle
plants, too. (I donned gloves for this task.) A closer look revealed spiny
wings of leaf material along the stems – a sure sign of a non-native thistle,
probably bull thistle. Although many of the seeds had already drifted into my
green beans, I figured I could keep at least a few more seeds out of the
garden.
Each
summer I struggle with time management – as soon as I start harvesting, I stop
weeding! If I was really responsible (a.k.a. not busy), I’d have taken care of
all the late summer weeds before they went to seed. But, when life gets busy
and I have to choose, I pick beans.
In
some ways, I’m also choosing to share my garden with wildlife. As long as
thistles don’t take over an area from native plants or interfere with grazing,
they can benefit a surprising number of species. At least twenty-three species
of insects feed on thistle foliage. Countless other insects (and hummingbirds)
feed on the nectar and pollen. Even more spiders, birds, reptiles, amphibians
and mammals eat the critters that feed on the thistles.
Of
course, native thistles will host the most diversity of life. Most need high
quality prairie remnants to thrive. Bull thistle may not be ideal, but at least
it is a biennial and dies after producing seed in its second year. It can be a
problem in disturbed areas, but generally won’t take over quality habitat. Canada
thistle (actually from Europe) forms perennial colonies that are much tougher
to eradicate.
I
suppose one reason I didn’t bother to pull the thistles earlier in the summer –
when they still sported fuzzy, fuchsia flower heads – has to do with some
childhood nostalgia. As a native Iowan, I have a special place in my heart for goldfinches
(they are our state bird). For as long as I can remember, I’ve been taught that
goldfinches have a special relationship with thistles; first by my parents, and
then by poet Mary Oliver:
“the finches/wait for midsummer,/for the
long days,/for the brass heat,/
for the seeds to begin to form in the
hardening thistles…”
–
from “Goldfinches” in New and Selected Poems by Mary Oliver.
I
first learned that American goldfinches nest later in the summer from this very
poem. While the little yellow birds use the soft fibers of thistledown to line
their nests, in truth, it is the energy-packed thistle seeds they are waiting for.
If
you feed birds, you know how much goldfinches love thistle seeds. The seeds in
your feeder aren’t even true thistles. They are seeds from the unrelated
African nijer thistle. In the wild, many relatives of thistles in the Aster or
Composite family are favored food sources for goldfinches, and most of them are
late-summer bloomers. Thistle is one of the most common, as well as Joe-Pye
weed, and sunflowers. Dandelions are an early-blooming exception, and
goldfinches may feed heavily on spring dandelion seeds in addition to the seeds
you put out.
As seed-eating
specialists, finches are among the most strictly vegetarian birds of the world.
While many small birds eat seeds, most of them also feed insects to their
young. Finches feed their chicks exclusively on regurgitated seeds! This has an
unexpected advantage: when brown-headed cowbirds try to mooch (they are nest
parasites who don’t build their own nests, and instead lay their eggs in the
nests of other birds), the invading young die after three days on this diet.
With
such a strong reliance on thistles for their nesting success, goldfinches need
to make sure that their timing is perfect. One researcher found that male
goldfinches exposed to both warm temperatures (a July-like 82 degrees F) and
blooming thistles will rev up their testosterone production. It is pretty
incredible that they respond to the flowers as a precursor to seed production,
and not just the seeds themselves.
As
year-round residents, goldfinches don’t need to hurry up and prepare for
migrating thousands of miles. Instead, they can patiently make use of an
abundant late-summer food source. As I hauled the loaded wheelbarrow toward the
compost pile – a crown of thorny thistles perched on top – a flock of goldfinches
sang me cheerfully along.
 |
| A goldfinch gathers thistledown for its nest. Photo by Larry Stone |
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