Loving monarchs to death

The lead story in today’s Science Times concerns a new threat to monarchs: too much love. It seems that people in northern areas are planting milkweed for monarchs, which is great, but some are planting tropical milkweed species instead of our native temperate zone species. Finding milkweed at the wrong time of year, the monarchs breed out of season, leading to reproductive failure and high rates of disease. Nature is complicated.

If you plant milkweed for monarchs, stick to native species, such as orange butterflyweed (Asclepias tuberosa), which blooms in June, is very tolerant of dry sites, and is shown here with bergamot (Monarda fistulosa)

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or red milkweed (A. incarnata), which blooms June-July and is taller and more moisture tolerant

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or common milkweed (A. syriaca), which has large, leathery leaves and can still be found growing wild in our area.

Photo by Rachel Vannette

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6/27/14: In the garden this week

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The garden is becoming colorful! In this picture you see yellow sundrops (Oenothera fruticosa), which has been in bloom for a couple of weeks, and pink beebalm (Monarda fistulosa), and orange butterflyweed (Asclepias tuberosa), which have just begun to bloom–a bit late this year. The very tall plant on the left is sweet joe pye weed (Eupatorium purpureum), which will be in bloom very soon. Usually my garden turns pink around June 10, when the beebalm, queen of the prairie, coneflower (Echinacea purpurea), and red milkweed (Asclepias incarnata) all come into bloom together. Everything is still a bit late this year.

keep newly installed perennials and woody plants well-watered throughout the growing season. The recommended amount is 1 inch per week during dry spells. The storm on Wednesday night brought between 1 and 2 inches of rain to my garden, so there should be no need to water this week. Established plants should not need supplemental water.

do not do any pruning except removal of dead or diseased material while woody plants are in active growth. They are using all their energy to accomplish the vital tasks of blooming and setting fruit. They have no energy to spare for making scar tissue. The next window of pruning time will come in midsummer.

– for better bloom next year, remove the flowers of spring-blooming shrubs such as lilacs and mountain laurel after they finish blooming. The exception, of course, is fruit-bearing shrubs such as native dogwoods and viburnums.

monitor the vegetable garden for pests and diseases and take action immediately. In particular, remove plants affected by borers and wilt, and hand-pick to keep pest populations low.

water tomatoes deeply (up to 2” per week) until fruit begins to ripen, then cut back to 1” per week. Remember to take rainfall amounts into account when determining how much to water. Water in the morning, and water deeply. Continue to stake and tie tomato plants and to remove suckers.

– pick peas while young; cut down basil plants to  make pesto before plants begin to flower, remove early spring greens and lettuce when they bolt. Most vegetables taste better young.

– perennials should need no care except pinching to promote bushy plants and keep plants short when necessary

— lawns should not need watering this week because we’ve had ample rain, and they need no fertilizer until early fall, if then. Mow with a mulching mower and leave the clippings on the grass. Remember that the more you water, the more you have to mow.

Here’s the red or swamp milkweed (Asclepias incarnata) in full bloom yesterday:

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Missing monarchs

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Today’s NY Times Sunday Review section carried an eye-opening article about the migration of monarch butterflies–or rather, the fact that the migration has almost collapsed. See also this previous post about the details of the migration to understand why it really is a problem if pesticides and genetically modified crops result in the disappearance of milkweed.

Add milkweed to the list of plants you plan to order next spring. The picture above shows a closeup of the flowers of orange butterflyweed, Asclepias tuberosa. It’s a drought-tolerant species that needs full sun, grows 2-3 feet tall, and blooms in June and July. And, of course, attracts butterflies by the score. Another lovely and easy-to-grow species is swamp or red milkweed, Asclepias incarnata. It likes moist soil (although it does just fine in my dry, sandy soil) and full sun, grows up to 4 feet tall, and produces lovely pink flowers, also in early summer. Pink or orange–take your pick.

More about milkweed

In a previous post, I described two lovely species of milkweed (Asclepias) that I grow and explained the relationship between milkweed and monarch butterflies. But the ecology of milkweed is much more complicated than the simple equation of milkweed = monarchs. Lots of other critters are dependent on milkweed as well. There are milkweed bugs, milkweed beetles, and milkweed aphids, to name just a few, and all feed on milkweed and nothing but milkweed. All these critters can safely consume the cardiac glycosides in all parts of the milkweed plant. All have bright orange coloration so that their predators are warned away.

I’ve seen very few monarchs this season. Usually many arrive to lay eggs on the milkweed leave in July; this year I saw only one. Loss of wintering habitat in Mexico may be the problem. So may a dramatic increase in pesticide use.

As soon as i started growing milkweed, the milkweed bugs arrived. They perch on the seedpods as they form and destroy the developing seeds inside. Here’s one on a butterflyweed (A. syriaca) pod:

Milkweed bug feeding on seedpod of butterflyweed (A. syriaca).

As you see, there’s a low level of infestation this year. Some years all the pods on all the plants are completely covered with bugs. The seeds inside the pods never develop. But then guess what happens? The plants hold some pods in a kind of suspended state–the pods remain tiny. As soon as the bugs complete their life cycle and die off, the plants then grow and develop those seed pods. Pretty amazing, isn’t it? It happened just last year, when the infestation was particularly bad. I think my plants are enjoying a low point in the milkweed bug population cycle this year–generally a population will reach a high point, crash, and the gradually recover.

Milkweed pods, as you can see, have an unusual (and very graceful, I think) shape. When the seeds are ripe, the pod turns brown and splits open bottom to top, and the seeds gradually waft out on the breeze, each one propelled by a tiny parachute of milkweed down. Here’s one of the first red milkweed (A. tuberosa) pods to open this year:

Asclepias incarnata pod opening.

The seeds leave the pod one by one, slowly and gracefully drifting away. This undoubtedly increases the probability that they will land away from the parent plant. Plants have all kinds of strategies for spreading their seeds, but this is one of the loveliest I know.

Summertime (I)

The garden in mid-July.

We’re approaching the height of summer, and the garden is blooming almost aggressively. Tomatoes are ripening–finally–and the weather is hot. (My apologies to the great Ira Gershwin.) The picture above features Rudbeckia subtomentosa, sweet black-eyed Susan, which I really must cut back severely next spring; Vernonia fasciculata, ironweed (purple); and some perennial sunflowers not yet in bloom (Helanthus mollis, downy sunflower). Today I saw goldfinches for the first time this season. These late breeders arrive when the prairie plants are ready to set seed, and they feed the seeds to their babies. They’ll be with us for the rest of the summer, hanging upside down on seedheads and providing great entertainment.

American plums--beginning to ripen.

The fruits on my native plum trees (Prunus americana) are finally ripening–notice the first hints of yellow. They first turn yellow, then red, and finally purple. As with most wild fruits, they ripen one-by-one, and we’ll almost never see a ripe one. The plum crop is heavy this year, but the birds get up earlier than I do.

Grey dogwood berries almost ripe.

Another plant that ripens its fruit one by one is grey dogwood (Cornus racemosa). This shrub is beautiful in all seasons, but I particularly love those red stems that signal to the birds that the fruits are almost ripe. The berries turn white when they’re ready to eat; as with the plums, we almost never see a ripe one.

Unripe pods of swamp milkweed.

Almost hidden among the Rudbeckias are the unripe seedpods of swamp milkweed (Asclepias  incarnata). When the seeds are mature, in another month or so, the pods will dry up and split open, and the seeds will drift away, each attached to a tiny parachute of milkweed down.

Elderberries ready to ripen.

This year also promises to be a bountiful one for elderberries (Sambucus canadensis). Notice that the stems are turning purple–the fruit will ripen soon. This is another favorite of the birds, and there will be great exultation among the catbirds when the fruit are ripe. I can usually manage to pick some of these, however,–perhaps to put in the Aronia jam I hope to make later in the season.

I have not seen any monarchs this year, and this is the time they usually migrate through. I am seeing a great abundance of fireflies, however, and I think of the presence of these delightful insects as a sign of a relatively healthy environment. Do you see lots of fireflies on your property? If you do, good for you. If you don’t, you might want to think about trying to manage your yard in a more sustainable way.

How about growing this: Milkweeds

Orange butterflyweed (Asclepias tuberosa)

“Milkweed”  (the name refers to the milky sap that is produced when the stems are broken) is the common name for over thirty species of perennials, all members of the genus Asclepias, that are native to North America. Thirteen are native to northern New Jersey. Only one species, common milkweed, with huge clusters of mauve flowers, still seems to grow wild in our area, although it’s now pretty hard to find. Milkweed is one of those plants, like elderberries and serviceberries and asters, that should be everywhere, because it’s that crucial a part of our ecosystem. Sadly, many of these crucial plants have been crowded out by development and alien invasive plants, so the birds and butterflies that once depended on them have disappeared as well.

I grow two milkweed species, swamp milkweed, A. incarnata, and butterfly weed, A. tuberosa (shown above). All milkweeds have the unique flower structure you see in the photo, with clusters of small flowers whose parts are arranged in tiers of five; but very few plants have flowers with this wonderful intense natural orange color. Butterfly weed grows two to three feet tall and likes dry soil. It has brilliant orange flowers and blooms nonstop from the end of May throughout the summer. Swamp or red milkweed is about four feet tall, and as its name implies, it likes wet soil (although it is an adaptable plant that does fine in my dry, sandy soil). It has huge, deep-pink flower clusters and blooms in June.  All milkweeds are magnets for butterflies and other pollinators and incredibly easy to care for—plant them in a sunny place and stand back. All produce seedpods that are a source of fascination to children. I can’t imagine why everyone doesn’t grow milkweed.

Most people know there’s a connection between milkweed and monarch butterflies, but there are a lot of misconceptions out there. The real story is quite complex, as is true of most things in nature. Monarchs, those gorgeous, large, black-and-orange butterflies that flutter lazily over the summer garden, are long-distance migrators. However, it’s not individual butterflies that migrate from Mexico to Canada and back again each season; it’s three or four different generations of individuals. After wintering in Mexico and south Texas (where their habitat is rapidly shrinking), the butterflies begin migrating north, some going up the west coast of the United States, some taking a Great Plains route, and some traveling along the eastern seaboard. Along the way, the first generation will mate, lay eggs, and die. The eggs that live become the second generation, and they continue on northwards.

I often see monarchs laying eggs in July in my garden, and sources differ on whether this is the second generation or the third of the year. Those eggs hatch into caterpillars with distinctive black and yellow stripes, and this is where the milkweed comes in. Monarch caterpillars eat milkweed and only milkweed. A female butterfly must find milkweed plants on which to lay her eggs. When she does, she perches on a leaf, curves her body under, and deposits her tiny eggs, one by one, on the undersides of the leaves. After laying eggs, she dies. If she doesn’t find milkweed—because someone mowed it down or used herbicides to kill it—she leaves behind no progeny to continue the journey north.

Suppose she manages to find a stand of milkweed—one that hasn’t been mowed down or sprayed with herbicides or pesticides (most pesticides kill all insects, including butterflies, ladybugs, lacewings, fireflies, and honeybees). She lays her eggs, and soon afterwards the tiny striped caterpillars hatch. They grow larger over several weeks, steadily eating the milkweed leaves. Then they pupate, or form pale green cocoons, or chrysalises; about two weeks later, adult butterflies emerge. The cycle continues as these adults fly north. In late summer, a final generation makes the long flight back to the southern wintering grounds. I often see monarchs nectaring on my New England asters in the fall. How do they manage to fly thousands of miles and find that place where their ancestors wintered in the past? It’s quite amazing.

But the milkweed is amazing as well. Notice that it’s the monarch caterpillars that exclusively depend on milkweed. Many insects sip milkweed nectar, and adult monarchs sip nectar from many different flowers—asters and liatris are favorites—but the caterpillars can eat only milkweed leaves. This is true of many butterfly species—the caterpillars can feed only on a single genus or species of plants, often, unsurprisingly, plants that are native, that used to be common, and that we consider to be weeds. Fritillaries need violets, skippers need grasses, red admirals need nettles. The list goes on and on.

The reason for this specialization is simple. Plants are the basis of the food chain, so animals eat them. To protect themselves, plants have evolved a variety of mechanisms, such as thorns, tough stems, hairy leaves, and chemical defenses. In response, specific animals have evolved the ability to withstand specific types of plant-produced poisons. That allows them to specialize in that one food source that other species ignore. Monarch caterpillars have evolved the ability to tolerate the deadly cardiac glycosides that milkweed plants produce. Female monarchs will lay their eggs only on milkweed plants. No milkweed, no monarchs.

Other animals have evolved the same strategy as well: small and large milkweed bugs, milkweed beetles, and milkweed aphids all feed exclusively on different parts of milkweed plants. All have bright orange or red markings, just like adult monarchs—small milkweed bugs are particularly handsome, with vivid orange X’s crisscrossing their black backs. Why the distinctive markings? All these creatures eat those deadly cardiac glycosides, and as a result, they themselves are rendered poisonous to other creatures that might prey on them. And there’s no point in developing a chemical defense unless your predators can recognize it, is there? A young bird that eats a monarch will taste something awful and get sick; if it survives, it will remember those orange markings and never eat another monarch.

The next time you see a monarch, observe its slow, smooth flight pattern. Other butterflies typically fly quickly and erratically to foil predators. Monarchs can take their time, because they have few predators. And guess what? Other butterflies have evolved to mimic the monarchs: they have look just monarchs to fool their predators.

Here’s a picture of swamp milkweed, which is just coming into bloom in my garden while butterfly weed is in full bloom:

Swamp milkweed (Asclepias incarnata)

Plan to get yourself some monarch magnets next summer.

6/21/13: In the garden this week

Beebalm (Monarda fistulosa) began to bloom this week.

Happy summer! Or if, like me, you belong to the minority of people who dislike hot weather, I wish you a cool summer.

My perennials gardens turn pink in late June. Beebalm (Monarda fistulosa, shown above), swamp milkweed (Asclepias incarnata), and queen of the prairie (Filipendula rubra) turn the garden various shades of pink, from cotton candy to subtle mauve. They are enlivened by the brilliant orange of butterflyweed (A. tuberosa) and the subtle whites of wild quinine (Parthenium integrifolium) and Culver’s root (Vernoniscastrum virginicum). And within the next week, the first of the rudbeckias, orange coneflower (R. fulgida) will begin to bloom, and it won’t stop until September.

It’s time to shift from spring to summer mode in the garden. Spring is the time to do–to move, to dig, to plant, to weed–but summer is the time to enjoy the fruits of all that labor. There’s much less to do. It’s time to stop transplanting and start making plans for next year:

– keep the grass long (3″ or more) to reduce mowing times. There is no need to fertilize or water. As the weather heats up, the grass wants to go dormant, so let it.

— start to collect perennial seeds: columbine, heuchera, and other spring bloomers are ripening seeds, even as they continue to bloom

– if you have not already done so, pull out early spring greens, such as arugula, spinach,  and lettuce; pull out pea plants after they finish producing; compost all these plants unless they are diseased

– continue to plant beans, kale, chard, and other members of the brassica clan if you have room; harvest peas, young squash, and beans before they get large and tough

– continue to stake tomato plants firmly and remove all suckers

– monitor the vegetable garden carefully for pests and diseases

Enjoy the first weekend of summer.