Summer begins

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Male ruby throated hummingbird (Archilochus colubris) at one of our feeders

Last Monday was Memorial Day, the traditional start of the summer holiday season in the U.S.  In my garden, summer begins when the fireflies appear, and the baby hummingbirds fledge.  We spotted the first fireflies a couple of weeks ago, but this week the population increased dramatically.  When the sun goes down, the garden is filled with slowly flashing yellow lights as the little beetles fly up from the grass and flowerbeds.

During the day, the action is a lot more frenetic.  Since early April, a few adult hummingbirds have been visiting our two feeders, which I refilled once a week or so.  But suddenly there are dozens of hummers jockeying for position, and we go through a liter of sugar solution a day.  Their harsh chattering and the sound of buzzing wings fills the air as they dogfight over the lawn and chase each other away from the feeder or favorite flowers.  Occasionally several will settle down to drink peacefully at the same feeder (four on the small, six on the large), but it never lasts long.  Another soon shows up and starts a chain reaction fight in which the tiny birds orbit the feeder like fighter ships in a Star Wars movie.   I have counted ten or more at a single feeder, and the other is just as busy.

Ruby throated hummingbirds

On dry, sunny roadside banks and meadows, patches of bright orange show that the blooming season of native butterfly weed (Asclepias tuberosa) has started, and as Spigelia marilandica finishes flowering, A. tuberosa takes over as my favorite flower in the garden.

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Asclepias tuberosa. The best specimen in the garden is a volunteer seedling that sprouted in the gravel path beside the mint patch.

This is one of the best insect plants that you can grow in North Carolina.  Like all milkweeds, it is a food plant for the caterpillars of the monarch butterfly (Danaus plexippus).  Monarchs are becoming very scarce, sadly, and in ten years gardening at this location, we have only had caterpillars one year.  But A. tuberosa flowers provide food for bees and other butterfly species, and those are not in short supply:

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Carpenter bee (Xylocopa sp.) visiting A. tuberosa flowers
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Pipevine swallowtail butterflies (Battus philenor) on A. tuberosa

When the plants are finished flowering, they attract beautifully colored milkweed bugs (Oncopeltus fasciatus) that feed on the developing seeds.  But no matter; enough seed survives to float away on tufts of fluff, so that more plants appear every year.

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Oncopeltus fasciatus nymphs on A. tuberosa follicles.

Once planted, A. tuberosa can be tricky to transplant, because its tuberous roots grow deep and break easily.  If you plant a couple of potted seedlings, they’ll cross-pollinate and give you plenty of seed that you can spread around.  It seems to take about two years for seedlings to reach blooming size, and a couple more to grow a really nice clump.

Much less colorful but still elegantly beautiful, Yucca filamentosa is also blooming now.  I planted it on the dry mound around our wellhead, along with the prickly pears and a few other xerophytic plants.

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Yucca filamentosa

It was supposed to be the variegated clone, ‘Color Guard,’ but it seems to be some sort of unstable mutant.  New growths come out variegated, but over the course of the year, they darken until they are indistinguishable from a wild type plant.

On the other side of the house, Hydrangea quercifolia, oakleaf hydrangea is also blooming white.

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Hydrangea quercifolia

This is a southern species, with a native range centered on Alabama.  It is a much more reliable bloomer than the Japanese Hydrangea macrophylla, because the new growth is less susceptible to damage by late freezes.

Some cultivated clones have inflorescences made up entirely of large sterile flowers, equivalent to mophead forms of the more familiar H. macrophylla.  However, I prefer the look of wild type plants, equivalent to a lacecap H. macrophylla, with a few sterile flowers surrounding clusters of tiny fertile flowers that attract many bees.

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The H. quercifolia flowers are looking their best this week, and they’ll continue to look good until the Japanese beetles, the scourge of summer, arrive to devour them.  That could happen any day.  I saw a few beetles this week, munching on banana leaves, but most will emerge over the next couple of weeks.  If I can keep the beetles from doing too much damage to the hydrangea, its inflorescences will slowly turn pink and will be attractive until well into autumn.  Eventually they’ll dry out and turn brown, but they’ll remain on the plant and, together with the peeling bark, provide winter interest.

Alien sea creatures?

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A tentacled horror from beyond space and time
Aristolochia fimbriata flower
Aristolochia fimbriata flower

The flowers of the white-veined pipevine, Aristolochia fimbriata, resemble some strange sea creature with an array of tentacles surrounding a rugose head and dark maw.  The “mouth” won’t consume anything larger than the small flies that it attracts as pollinators, but the flowers aren’t the only thing about this plant that is vaguely Lovecraftian.  A. fimbriata is also a host plant for the sinister, spiky caterpillars of the Pipevine swallowtail butterfly (Battus philenor).

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Pipevine swallowtail caterpillar

It has been suggested [1] that pipevine swallowtail caterpillars mimic tropical Onychophorans (velvet worms), and the two horns do give it vague resemblance.  I’m not sure the theory makes sense, though.  The caterpillars’ diet of toxic Aristolochia leaves probably makes them less palatable than the velvet worms they are supposedly mimicking for protection, and some other caterpillars that feed on toxic plants (e.g. Monarch and Gulf Fritillary larvae) also have spikes or tendrils as part of their warning to predators.

The heart shaped leaves that the caterpillars feed on are as beautiful as the flowers are weird:

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Variegated foliage of Aristolochia fimbriata

Many Aristolochia species are large, climbing vines, but the stems of A. fimbriata stay small, no more than a foot or two long, and instead of twining, they creep along the ground around other garden plants.  This is a plant that plays well with others.

Seed production is quite prolific in my garden, and in some flowerbeds the plants have started to form a very pretty summer ground-cover.  Nevertheless, A. fimbriata doesn’t seem to be an invasive species; the seedlings surround the original mother plants and haven’t spread to other parts of the garden.  And in any case, biological control comes on blue and black swallow-tailed wings.

A. fimbriata is a subtropical species native to southern Brazil, Bolivia, Paraguay, Uruguay, and Argentina.  Its foliage turns to mush at the first frost, but the tuberous roots are completely hardy here in the piedmont.  Seed also overwinters in the mulch of my flowerbeds and sprouts in the spring.

The butterflies arrived early this year, and the first crop of caterpillars have reduced many plants to stubs.  Now, there are chrysalids scattered around the garden.  When ready to metamorphose, the caterpillars will travel a considerable distance to find a good spot:

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Pipevine swallowtail chrysalis on a thornless blackberry, about fifteen feet away from the nearest A. fimbriata plants.

The butterflies will probably emerge and lay the next generation of eggs  just about the time the foliage starts to look good again, but hosting such beautiful insects in the garden is well worth a little leaf damage.

Notes

[1] “It has been suggested”–The passive voice here is a weaselly way of indicating that I have read this in various places but haven’t been able to track down the original source.

Flowers that fly

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A tiger swallowtail butterfly (Papilio glaucus) visits wild columbine (Aquilegia canadensis). It’s too early for mantises, so I suspect a bird or lizard took the chunk out of its wing.

It has been chilly for the last couple of nights, but I think we have dodged the possibility of a late frost.  There should be lots of flowers for the nectar sippers this year.  The first ruby throated hummingbirds (Archilochus colubris) have arrived in the garden, just in time for the peak of wild columbine blooming, and tiger swallowtail butterflies are chasing each other through the trees.  Pipevine swallowtails (Battus philenor) have been checking out the newly emerging leaves of the white-veined pipevines (Aristolochia fimbriata), but if they are wise they’ll wait a few weeks before laying eggs.  Being patient will guarantee that there’s plenty of delicious, poisonous foliage for their caterpillars.

It feels as though we have passed a dividing line in the last few days, transitioning from tentative early spring to SPRING!  In the woods and along the roads, the native dogwoods are wrapping up their annual show.

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A dogwood tree (Cornus florida) in our woods earlier this week. Trees that grow naturally in the forest have a much more open appearance than those cultivated in full sun.

The predominant colors of spring are becoming much more saturated and vibrant as the azaleas take over.  For a couple of weeks, piedmont gardens will be almost garish, and then we’ll have a green interlude until the summer perennials begin their show.

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Florida flame azalea (Rhododendron austrinum) is native to the Florida panhandle and southern Alabama and Georgia, but it is perfectly hardy in the North Carolina piedmont.