Why We No Longer Carry Non-Native Tropical Milkweed

The red and yellow blooms of tropical milkweed are ubiquitous in North Florida butterfly gardens. This non-native milkweed has exploded in popularity as demand for milkweed grows to support declining monarch butterfly populations.  This tropical species, native to Mexico, is very easy to propagate. Growers are able to quickly produce plant material of this species to meet the milkweed demand. It’s also very showy, blooming prolifically all season and regrowing quickly after being decimated by hungry caterpillars. But unlike our native milkweed species, the lush green foliage of tropical milkweed will stay up all winter if not killed back by frost – and that is a problem.

Tropical milkweed has been an invasive species in Central and South Florida for a while now.  The fast growth and prolific re-seeding of this species has remained unchecked by warm winters, resulting in large monocultures of tropical milkweed in natural areas. This replaces native plants and disrupts native ecosystems. But it’s not just the invasive quality of the plant that is damaging.

A protozoan parasite that evolved with monarch butterflies, Ophryocystis elektroscirrha (OE) lives on infected monarchs and is deposited on the plants they land on; especially when the butterflies deposit eggs on the plants. The resulting caterpillars hatch and ingest the OE when they begin eating the plant, and the parasite is able to replicate inside them. Those caterpillars will grow into butterflies infected with an increased load of OE.

Many species across the animal kingdom have evolved with their own particular parasites – humans included. Those parasites are often not too harmful unless they receive some sort of increase in advantage; a weakened immune system or way to accumulate in numbers on its host. Monarchs evolved with OE and are able to prosper while still carrying some of the parasite, but high OE levels in adult monarchs can cause them to fail to emerge from their pupal stage because they are too weak and unable to fully expand their wings. Monarchs with even mild OE infections can appear normal (though are usually a little smaller) but they don’t live as long, cannot fly as well, and are not able to migrate successfully.

In contrast to this tropical species, our native milkweeds naturally senesce in the fall and stay leafless and dormant through the winter. This effectively cleans the plant of the parasite. When the leaves die back, the parasite dies along with them so that when the butterflies return each spring and summer, they feed on fresh, parasite-free foliage. Whereas tropical milkweed, remaining evergreen throughout the winter, allows OE levels to accumulate on the plant. The following generations of monarch caterpillars that feed on those plants can be exposed to dangerous levels of OE.

As our winters have become increasingly warmer in North Florida, we are noticing the invasive potential of tropical milkweed is growing. Warmer winters also mean tropical milkweed is less likely to be killed by frost and more likely to accumulate OE on its leaves. Tropical milkweed can also interfere with monarch migration and reproduction. In northern areas it grows later in the season than native species, and just the presence of tropical milkweed may confuse monarchs into breeding at a time when they should be migrating. There is evidence that suggests the chemical composition of tropical milkweed may trigger this disruption of the innate migration cycle of the monarchs that interact with it – they are fooled into thinking they are in the safe wintering grounds of Mexico. 

With this mounting evidence of the detrimental effects of tropical milkweed, we have decided to only sell native species of milkweed. Unfortunately our growers are still working hard to build supplies of stock to meet demand. Though supplies are limited of native species, we have decided it is better to be without milkweed at some points than to sell a tropical milkweed plant. While it may feed your caterpillars in the short term, it is harmful to the species as a whole in the long term.

Florida has 21 species of native Asclepias, but many are difficult and slow to grow and only a few are well suited for home gardeners. We will continue to work with our growers to provide an increasing variety of native species, but we have found the following species to be the easiest and fastest growing to provide leaf matter for caterpillars:

PINK SWAMP MILKWEED

Asclepias incarnata

A pink-blooming native milkweed that gets big! It grows 4-6ft tall, providing the most amount of caterpillar food (of the native milkweeds) for monarch and queen butterflies. The plants regenerate leaf matter quickly during the growing season and have a short season of bloom in late summer - providing nectar-rich blooms for adult butterflies and other pollinators. They grow best in full sun with moist to wet soils, rich in organic matter. I have found this species to be adaptable in my yard in part sun with average moisture and clay soil amended with compost.

WHITE SWAMP MILKWEED

Asclepias perennis

This free-flowering native milkweed usually only grows 12-24inches tall, continually sending up stalks topped with white blooms that often have a pink blush. They grow best in full sun with moist to wet soils - even growing directly in water! I've found them to be adaptable to quite a bit of shade and also average moisture and clay soils. The leaves provide substantial larval food for monarch and queen butterflies, and the constant flowers attract lots of adult butterflies as well as many other pollinators.

BUTTERFLYWEED

Asclepias tuberosa

One of the most common and noticeable native milkweed species, the clusters of bright orange blooms are often seen on roadsides and grow as far north as Canada. Like many plants with such a large native range, it is important to find plants that are grown from seed sources in your region - this is called an "eco-type". Our plants are North Florida eco-types, so they are well adapted to our hot and humid climate and our soils. Butterflyweed in N. FL tends to be lower growing than it's northern relatives - only 1-2ft tall. It prefers full to part sun and average to dry soils - it can be quite drought tolerant once it has an established root system. I've found these plants to be pretty tough and low-maintenance, and adaptable to sandy or light clay soils. They usually bloom in spring, and then will often rebloom later in the summer.

Airplants

Airplants are the common name of a variety of epiphytic species within the Tillandsia genus. Tillandsias are members of the pineapple family, also known as the bromeliad family. Airplants get their common name from their epiphytic habit – they grow on trees without soil. They receive all their water and nutrients through fuzzy gray scales on their leaves called trichomes. In nature, nutrients are provided by decaying organic matter like leaves or insects. The visible, wire-like roots are only used for anchoring themselves to the limbs and trunks of trees.

Florida has several native species of Tillandsia, which includes Spanish moss, but most of the commercially sold plants are native to Central & South America. They come in a wide variety of shapes and sizes. Tillandsia likes bright light, but not direct sunlight which can burn their leaves. A bright window in the house or a shaded patio are ideal spots for your plants. If temperatures drop below 45, be sure to bring your Tillandsia indoors, as they dislike cold weather and will die if exposed to frost.

To water, soak the plant once or twice a week, or use a spray/mist bottle to thoroughly wet it. Watering with rainwater or filtered water is best. After watering, shake out the excess so that no standing water remains in the center. Let plants dry in a well-ventilated place so they don't remain wet. Water more frequently in air conditioning, and hot weather, and less frequently in cool, cloudy weather. Also, when "planting" them, avoid tucking them into moss that stays damp, which may cause them to rot.

You can fertilize airplants once a month with a diluted water-soluble orchid or tillandsia fertilizer, following package instructions for dilution. We recommend diluted fish & seaweed emulsion, which can be applied with the misting or dunking methods. Not properly diluting your fertilizer, or fertilizing too often can kill your plant. If your plant is very dry, soak it first, then fertilize it the next day.

Garden to Table: Baked Okra

Before you know it your okra plants will be popping off with plenty of pods - they need to be harvested before they get too woody and inedible, which happens quickly. They also don't last for more than 4-7 days once harvested. 

This is an easy-to-make, quick way to enjoy and make use of all your tasty, homegrown okra. The crunchy and salty flavor might fool your kids into eating some veggies too. Feel free to add or subtract the quantities of salt and spices according to your taste, or experiment with new ones!

HOW TO MAKE BAKED OKRA: 

1. Preheat the oven to 450F degrees.

2. Rinse the okra, and dry with a paper towel. Trim away the stem ends, and then cut it into 1/2 to 3/4-inch pieces. Spread the okra on a sheet pan in a single layer. Drizzle with olive oil, paprika, salt, and a pinch of cayenne pepper. Stir.

3. Bake the okra for about 15 minutes. The okra should be lightly browned and tender, with a nice seared aroma. Serve immediately.