In the eyes of butterflies, not all flowers are created equal.
“Butterflies don’t see things the way we do,” explained Ellen Zagory, public horticulture director for the UC Davis Arboretum. “Insects mostly see ultraviolet; the colors they see we don’t normally see. Flowers look very different under ultraviolet.”
Keep that in mind when picking out posies to lure swallowtails and skippers.
At the arboretum, Zagory and other butterfly lovers have learned which plants are possible butterfly magnets. Several of those favorites will be available during the fall plant sale Saturday, Oct. 1, at the Arboretum Teaching Nursery.
Butterfly gardens have become increasingly popular as more gardeners create habitat for these beneficial insects and other wildlife, Zagory noted. Another benefit for a water-wise landscape, many of the plants that attract butterflies also are drought tolerant.
“I have a lot of butterflies in my own garden,” she said. “I also have a lot of flowers in bloom. It’s an interesting experiment to see what they actually visit.”
Her conclusion? “They really really like the asters! They can’t get enough asters,” she said. “In particular, they like the Monch aster. It’s a lovely little lavender aster that comes into bloom in spring and stays in bloom a really long time. They go for lantana; it’s so full of nectar. They also love goldenrod and anything in the mint family. They like lavender and sedum. And in the shade, they’re going for the dwarf plumbago.”
It’s not the color so much as the shape of those flowers that attracts butterflies, which also pollinate the flowers as they hunt for food.
“Butterflies need a landing platform,” Zagory said. “That’s why they like daisies and daisy-shaped flowers; those flowers are flat and they can land on them. Hummingbirds can hover while they drink, but not butterflies.”
Butterflies sip nectar “and not all plants have nectar,” she added. “Their caterpillars eat leaves. That’s why some plants are butterfly nectar plants and others are butterfly host plants; the hosts are where they lay eggs.”
Some species are very specific about which plants they prefer. For example, the pipevine swallowtail makes its home only in the California pipevine. Monarchs must have milkweed. The gulf fritillary gravitates to passionvine. Hairstreaks go crazy for buckwheats.
Common landscape trees such as sycamore, ash, willow, plum, cottonwood and liquidambar are popular host plants for the Western tiger swallowtail.
“That’s why that butterfly is so common in city parks and older neighborhoods,” she said.
Hungry caterpillars can do a lot of damage to foliage, but those voracious eaters turn into magical butterflies.
“Caterpillars are important,” Zagory said. “About 96 percent of songbirds – the birds we love – feed caterpillars to their young. It’s a really important source of protein and fat for baby birds. That made me look at cabbage white caterpillars in a whole new way.”