Black Swallowtail caterpillar
Decades of vegetable gardening in the Piedmont of North Carolina have taught me the value of post-growing-season clean-up. Our warm and muggy climate offers many opportunities for harmful insects and diseases to make themselves at home. And in the last decade, I’ve noticed that climate change has made our winters much less reliably cold. Prolonged cold spells, say, two weeks when the highs never top 45 degrees Farenheit, and nightly lows lingering in the teens and twenties just don’t seem to happen anymore.
Without those long cold spells to kill overwintering insects and diseases, my best weapon against them is garden clean-up. So as soon as I can manage after our first killing freeze, I remove every speck of dead vegetable plant and annual flowers and herbs from the vegetable garden area. I am not sufficiently dedicated in my composting techniques to be certain it gets hot enough to kill loitering diseases on my dead veggie leaves, so I bag them up and take them to the dump. It’s the only way I can be sure the bad guys don’t gain an easy foothold in my garden.
I’ve found that it’s best to do this as soon as possible, so that any evils lurking among browned tomato vines and limp cucumber leaves are removed before they multiply. It’s hard on my aging hands and back to laboriously cut off every strip of tomato tie attached to the trellis. And my nose inevitably gets sneezy as dried bits of vegetable matter released from yanked stems float on the breezes and all over me. But the effort is worth a few aches. I’ve seen what happens when I wait until spring to remove the remains of the previous year’s garden. Disease and bug problems are always much worse.
Here’s a shot of a piece of the garden with its cleaned trellises:
Fewer places left for pest diseases and insects to hide
The white flowers are the Sweet-Alyssums-that-would-not-die. That’s what I’m calling these “annuals” that I grew from seed last spring. Pollinators are enjoying them on warm days. The deep green plants are crimson clover, which I sowed about six weeks ago. They serve as a winter cover crop on my beds.
In addition to fall clean-up, I also rotate crops to reduce pest problems. You should never grow members of the same plant family in the same spot two years in succession because it allows disease and insect pests of those families to prosper at the expense of your crops. The Solanaceae family is the trickiest. That includes peppers, tomatoes, eggplants, and potatoes; they all share genes and pests. Likewise, you must be mindful not to plant cucumbers, melons, gourds, and pumpkins in the same area two years in a row, since they all belong to the Cucurbitaceae family. Ditto for beans and peas (Leguminosae).
I’ve been working for the last couple of weeks to cut, pull, and bag all the dead vegetable matter and their ties. Wonder Spouse helped me with the taller parts of the trellises that I can’t reach — thanks, Big Guy. Yesterday while I was finishing up, I found the caterpillar in the above photo dining on one of my Bronze Fennels. I had noticed that my fennels were looking chewed on, but I hadn’t spotted the culprit until yesterday.
I confess I was surprised to find a Black Swallowtail caterpillar still alive and eating my plants. But I was also delighted; I plant Bronze Fennel in my garden specifically for these caterpillars. Black Swallowtail larvae dine on members of the carrot family, including Queen Anne’s Lace, parsley, carrots, dill, and fennel. They also like the herb rue. During the growing season when I find one of these caterpillars chewing on a dill or parsley plant, I relocate them to the fennel. This way I can maintain plenty of my favorite herbs and also get to enjoy the beauty of the butterflies when these caterpillars metamorphose.
My favorite caterpillar reference (Caterpillars of Eastern North America by David L. Wagner) says that Black Swallowtails are increasingly rare in the northeastern part of the US, because fields and agricultural lands have largely been replaced by concrete and forest. Members of the carrot plant family don’t generally grow in such places, so there are no food plants for this butterfly.
I’m happy to report that this species is a common visitor of flowers in my summer gardens, and I’m happy to ensure their food supply by offering up Bronze Fennels for their consumption. I suspect the caterpillar in the above photo is about to morph into its chrysalis form for overwintering. I found one of its siblings already metamorphosed, tucked against a rusty trellis stake nearby here:
Black Swallowtail chrysalis
Sweet dreams, garden friends. May your winter musings make next year’s growing season the most richly vibrant one yet.
Piedmont Gardener 