Caterpillar Food Plant: Gardening with Milkweeds

Monarchs and Milkweeds
The following article originally appeared in Butterfly Gardener, a NABA publication for members.
NABA member Lenora Larson has graciously allowed us to reprint it here.

Caterpillar Food Plant:
Gardening with Milkweeds
By Lenora Larson

All nature-lovers celebrate the spectacular Monarch fall migration. However, most are unaware of the equally impressive spring migration. Generation by generation, each newly-emerged adult continues the northward journey until they reach Winnipeg, Canada in mid-August. The diminishing sun signals the turn-around, back to their wintering site near Mexico City. Obviously, if Monarchs can’t find sufficient spring and summer milkweeds to feed the caterpillars, there will be no southward fall migration.

The Garden Design for Milkweeds

Swamp Milkweed - Asclpeias incarnataMost public gardens now feature an area designated as the “Butterfly Garden.” Unfortunately, this rarely meets the needs of the public or the butterflies. The public wants to see beautiful gardens. They stroll through the majestic Formal Gardens. They smile in the diminutive Fairy Garden. They saunter through the charming Cottage Garden and gaze in awe at the sweeping English and American Landscape Gardens. Then they reach “The Butterfly Garden”, that pitiful patch of scraggly weeds, devoid of design style and beauty. No wonder it is so difficult to convince gardeners to plant for butterflies!

Philosophically, entomologically, horticulturally and esthetically, the ideal “Butterfly Garden” is not a separate entity. The nectar and caterpillar plants should be incorporated into the entire garden, placed in conformity to the overall design. Butterflies can not read and do not limit themselves to that little patch. Mother Nature intermingles her caterpillar foods among all the other plants. And the fiercely territorial butterflies should not be forced to compete for egg-laying plants in a small area–especially Monarchs whose caterpillars promptly eliminate all competition by eating their siblings’ eggs. Milkweeds should be artfully placed to showcase their beauty and disguise their straggles—just as we do for all our other garden perennials. Plant labels shaped like caterpillars will educate the public and delight the children.

Choosing your Milkweeds

Tropical Milkweed - Asclepias curassavicaI boldly insist that every garden should include milkweeds to replace the wild milkweeds being lost to urbanization and herbicides. Monarch Watch™ estimates that 2.2 million acres of wildlife habitat are lost to development every year.) Fortunately, many milkweeds are supremely garden-worthy. The unique horned flowers are massed in umbels for abrilliant show, ranging from white, pink or purple to red, orange and yellow. Plant growth may be a ground cover to 5 foot perennial to sprawling vine.

Natives are always the preferred choice and there are 108 native species! One caveat: avoid planting the common milkweed,Asclepias syriaca. Yes, the pink flowers are beautiful and fragrant, but the plant is coarse-looking and aggressively spreads by rhizome and seed. Its thuggish habits have created the negative perceptions of the milkweed family.

The other challenge: most milkweeds are not commercially available and collecting from the wild is not only illegal, it’s futile since their taproots thwart transplantation. Fortunately, many nurseries offer the flamboyant orange Butterfly Milkweed, Asclepias tuberosa, and new cultivars of yellow and red are also available. The pink flowering Swamp Milkweed, Asclepias incarnata, is another attractive native and I adore the Green Antelopehorn Milkweed, Asclepias viridis, which is available via the Internet. Huge cream and purple flowers dominate this diminutive 8” plant, perfect for edgings.

Antelopehorn Milkweed - Asclepias viridisThe most readily available and showy milkweed is also the Monarch caterpillar’s favorite: Asclepias curassavica. Typical of successful ubiquitous plants, it has many names: Mexican Butterfly Weed, Blood-flower, Silky Red Milkweed, Tropical Milkweed, Scarlet Milkweed, etc. Incredibly flexible in its soil, moisture and sunlight requirements, this South American native has naturalized throughout the southern states and is grown as an annual in the north. About 50% of my plants survive my zone 6 winter; self-seeding makes up for the deaths. Blood-flower’s slim profile intermingles beautifully with other plants and conforms to any design style that can handle a punch of brilliant color for the entire growing season.

Tropical Milkweed also adapts to containers. I’ve seen it growing in large urns on balconies in Florida, patio pots in Texas and large planters in public gardens throughout the Midwest. Ease of propagation contributes to its success with self-seeding and starts from cuttings. Pots of Tropical Milkweed can even be brought indoors to over-winter! Native plant Absolutists should be reassured knowing that Tropical Milkweed was probably the original Monarch caterpillar food plant. The Monarch is a tropical butterfly with many tropical relatives. It is unique in evolving to include the annual migration to North America in its lifestyle.Butterfly milkweed - Asclepias tuberosa

Milkweed Pests

Milkweeds are poisonous, but three other insects find them delicious. How should we deal with this challenge since insecticides are not an option? The best approach is tolerance, made easier by the beauty of each competitor. The Milkweed bugs are brilliant red nymphs and striking black and orange adults. The aphids are clear golden orbs and the Milkweed Tussock Moth caterpillars are just darling! If you can’t stand it, hand-picking is the ration

Preserving the Fall migration

Butterfly plants should be integrated into the rest of your garden following the maxim ” right plant, right place.” And Tropical Milkweed can be so right! Together, we gardeners can help the Monarchs without sacrificing garden beauty.