honey

Invasive honey plants: are they good for bees?

It’s not surprising that beekeepers are often in favor of invasive plants that “normal people” find objectionable. After all, honey bees are themselves invasive. Once they landed in North America via the Jamestown colonies, honey bees lost no time distributing themselves across the continent. They engulfed the wildlands in a fashion that defines invasive. They thrive not only where you put them but everywhere else, reseeding themselves wherever they felt at home.

This article first appeared in American Bee Journal, Volume 161 No. 6, June 2021, pp. 643-646.

Some of the contemporary articles explaining why we should preserve invasive plants for honey bees are downright embarrassing. A few authors openly state we must allow the destruction of natural environments and the loss of biodiversity so beekeepers can prosper. They present this philosophy as “being for your own good.” After all, where would you be without honey bees to pollinate your fruits and vegetables?

I have no objection to honey bees, just as I have no objections to other livestock, but there is an appropriate place for everything. We don’t seed the wildlands or destroy native environments so growers of pigs and cows and chickens can prosper, so why should we do it for beekeepers?

The real problem with native species

Beekeepers sometimes miss the point about invasive weeds and the problems they cause. The issues are subtle and can be difficult to understand, especially since bountiful crops of starthistle or Japanese knotweed honey are easy to understand. In many cases, invasive weeds make the year’s profit, the only thing keeping a beekeeper in the black. But are weeds that displace hundreds of native species the best thing for bee health? I think not.

The ultimate problem — and one that affects both native bees and honey bees — is that invasive plants create monocultures. The word monoculture simply implies that one crop (or one weed) grows over a wide area to the exclusion of all else. For bees, the monoculture is a one-trick pony, blooming all at once with a single amino acid profile in the pollen.

To illustrate, let’s go back in time and visualize what might have grown in a place when it was wild. In most undisturbed areas, whether they be prairie, grassland, forest, or even desert, you have many species of flowering plants. Each of those species — and there may be hundreds in a small area — bloom at a different time, and the pollen of each has a unique array of nutrients.

For bees, this means that something is always in bloom. One species follows another, sometimes covering season after season, so there is always something to eat. And those foods — in this case, pollen — are each slightly different, which gives a bee the wide range of nutrients it needs to thrive.

The spice of life

When you think of a human diet, you know we must eat a variety of foods to stay healthy. In fact, we’re taught to eat multiple sources of vitamins, minerals, carbohydrates, protein, and fats. It’s difficult to be healthy if we eat just one thing at a time. Carrots, oats, and salmon are all rumored to be good for us, but if we ate just carrots for six weeks, only oats for six weeks, and salmon for six more, chances are we wouldn’t feel great by the end of eighteen weeks.

A limited diet can be harmful because no single food has all the nutrients we need. In a natural environment, we would eat whatever we killed or caught or dug from the ground, things like berries, leaves, tubers, bugs, and fish. Our foraging diet might not have the bounty found on a super combination pizza, but it would definitely have variety.

Honey bees also need variety. Very few plants produce pollen with all the amino acids honey bees need to thrive. In an environment with many flowers going in and out of bloom during the season, this is no problem because what one plant lacks, another plant supplies. So just like the variety in our chef salad or chicken stew, the bees get a cornucopia of nutrients from a panoply of sources.

One and done

However, the model of variety goes to pot when an invasive species takes over. Invasives displace so many plants that it becomes difficult for bees to eat a balanced diet. Instead of getting a large variety of pollen types overlapping over many weeks, bees get heaps of one pollen type followed by nothing. This is an impossible situation for wild bees that can’t fly very far, but it’s even difficult for honey bees.

For example, if nurse bees lack the building blocks for brood food, the entire colony may suffer. Poor diet is one reason almond pollination can be stressful for our colonies. Almond pollen isn’t especially nutritious and there’s very little other forage available at the same time — only a sea of almond trees, one row after the next. It’s nuts.

Similarly, when we encourage the growth of invasive weeds in our beekeeping environment, we may increase our honey harvest but decrease honey bee health. Certainly we are harming wild bee species — those with short foraging ranges and no beekeeper supplements — and we are damaging other pollinators such as butterflies, moths, hummingbirds, and flies.

Without the plants that sustain them, many organisms disappear, causing entire ecosystems to collapse. Insects and spiders along with the birds that prey on them may disappear in addition to the soil organisms that decompose them. Take away one flowering plant and an entire network of life can collapse along with it. The amount of damage multiplies with each additional loss until the ecological upset is unfathomable.

I’m not saying invasive weeds are the fault of beekeepers, and I’m not saying I haven’t benefited from invasive weeds myself. But I draw the line when I hear of beekeepers collecting and saving invasive seeds, replanting weeds where governments are spending hundreds of thousands of taxpayer dollars to control their spread. Not only is it unethical, it’s also short-sighted. Those who seed invasives are not doing themselves, their bees, or our environment any favors.

An invasive honey crop near you

Unfortunately, honey bees often do well on invasive species, many of which have multiple advantages over native ones. With few natural enemies to weaken the invasives, they often thrive under conditions where the native plants fail — and the honey bees are quick to notice.

So what are these crops that beekeepers find so appealing? Honey-producing invasives span the continent, displacing old-time varietal honey with the flavor du jour. There’s something for everyone, so the list below is just a sampling.

Chinese tallow

The Chinese tallow tree, Triadica sebifera, is systematically swallowing the American southeast. Also known as the candleberry tree, chicken tree, or popcorn tree, the Chinese tallow is now considered an invasive species in most areas in which it grows. The Mississippi Fish and Wildlife Foundation calls it “one of the ten worst invasive weeds” in the state, and it’s officially noxious in Florida, Louisiana, and Texas, too. The tree has become particularly problematic in eastern Texas where it grows in stifling regiments.

A member of the Euphorbiaceae family, it grows 30 to 50 feet tall, prefers full sun, and thrives in USDA hardiness zones 8-10 where it can flower as early as February. Historical rumor says a botanist friend of Benjamin Franklin introduced the plant, a native of eastern Asia, in 1772.

The sap and leaves are poisonous, causing skin irritations. In its homeland, the waxy coating of the seeds — which is not poisonous — was used for making soap and candles. The tree is deciduous and in autumn the leaves turn striking shades of tangerine, crimson, and plum.

In spite of its negative attributes, the Chinese tallow produces large quantities of high-quality honey in many areas of the south. Colonies can produce up to 200 pounds of light brown honey with a herbal aroma and pleasant, spicy flavor. Beekeepers often move their hives into tallow tree areas in order to harvest the bountiful crops or to build colonies for pollination services. On the other hand, Chinese tallow readily out-competes traditional bee forage such as buttonbush, eastern redbud, and red maple — a sad loss of biodiversity.

The Chinese tallow tree has beautiful fall colors and is a prolific honey producer. Photo by Larry Allain, USGS.
The Chinese tallow tree has beautiful fall colors and is a prolific honey producer. Photo by Larry Allain, USGS.

Japanese knotweed

We all know that Japanese knotweed is an invasive species, prone to tearing up your driveway, cracking your foundation, and choking rivers and streams. But what’s the best thing about knotweed? That’s easy. It’s in bloom when nothing else is, at the very moment when no other plant is even thinking about it.

Japanese knotweed, Reynoutria japonica, is an herbaceous perennial in the knotweed family, Polygonaceae. Many people think it is a type of bamboo because of its hollow stems and raised stem nodes, but it has no relation to true bamboo, which is actually a grass.

The World Conservation Union lists Japanese knotweed among the top 100 worst invasive plants. But if you can look past that detail, it is actually a pretty plant with large spade-shaped leaves and showy cream-colored flowers. The plants may grow 5-8 feet tall in a dense bush-like display.

During late summer, you can hear these bushes before you see them. They vibrate with pollinators, especially honey bees. Many beekeepers harvest the monofloral honey from enormous stands found locally. And if you don’t harvest, knotweed makes a great late-summer boost to a colony’s winter pantry.

The honey is dark and flavorful, and many people compare it to a mild form of buckwheat honey. Personally, I don’t notice a resemblance, but it’s tasty and definitely worth a try. You can often find it sold as “bamboo honey,” especially on the east coast. The sample I purchased crystallized quickly at a rate similar to the bramble honeys.

Japanese knotweed makes great honey but is extremely destructive to wetlands, salmon streams, and even buildings. Wikipedia public domain photo.
Japanese knotweed makes great honey but is extremely destructive to wetlands, salmon streams, and even buildings. Wikipedia public domain photo.

Bristly oxtongue

Bristly Oxtongue, Helminthotheca echioides, is especially plentiful along the California coast, but it also likes the northeastern US and southern Canada. An import from the Mediterranean area, the plant has a yellow dandelion-like flower and a taproot that extends into the abyss.

Gardeners absolutely abhor this plant and its taproot, but beekeepers find it useful, especially because the early blossoms open before many other flowers, feeding the bees in the early weeks of the year. In addition, the sparkling amber honey is a good seller, having a pleasant floral aroma and fresh taste.

Himalayan blackberry

Here in the coastal Pacific Northwest, Himalayan blackberry (Rubus bifrons) grows in dense thickets, blanketing the earth, climbing trees, and swallowing fences and outbuildings. Our area is famous for berries, but without vigilance, the Himalayan blackberry will devour native trailing blackberries, dewberries, thimbleberries, salmonberries, and black caps, crippling them with sun-blocking leaves and nutrient-stealing roots. Local blackberry snobs (yes, they exist) won’t eat them, although the more philosophical types like me turn them into pies, jams, and ice cream.

Himalayan blackberries are the big cash crop for most beekeepers in this area. The honey is tasty and plentiful, and the early summer pollen and nectar stash can keep colonies fed all during the summer dearth. The flowers also attract native species. Bumble bees, halictids, Andrena, and Osmia all converge on the pink-tinted blossoms, collecting pollen and drinking the sweet nectar.

Invasive honey: Honey bees and many native bees love Himalayan blackberry flowers. Photo by Rusty Burlew.
Honey bees and many native bees love Himalayan blackberry flowers. Photo by Rusty Burlew.

The knapweeds

Knapweeds are everywhere and most yield delicious honey. Dozens of species dot the map, but I’ve singled out the two I most often encounter, yellow starthistle and spotted knapweed.

Yellow starthistle, Centaurea solstitialis, is native to the Mediterranean area. We now find it throughout California, where it’s also known as yellow cockspur or St. Barnaby’s thistle. The plant invades dry rangeland where it easily out-competes native grasses and wildflowers. Since it blooms July through September, it is a favorite of honey bees and their keepers.

Yellow starthistle is dangerous to livestock because the ring of spines at the base of the flowerhead can injure grazing animals. The sunny blooms produce sparkling greenish-yellow honey with an assertive, but clover-like taste. The honey is much in demand at farmer’s markets and roadside stands where it sells at premium prices.

Yellow starthistle is dangerous to livestock because of the ring of spines around the flower head. USDA-ARS photo.
Yellow starthistle is dangerous to livestock because of the ring of spines around the flower head. USDA-ARS photo.

Spotted knapweed, Centaurea stoebe, has spread across the continent in aggressive stands that degrade meadows, pastures, and wildlife habitat. It also invades floodplains, vacant lots, roadsides, railroads, and forest clearings.

Like the other knapweeds, the plant is a perennial with a deep, wide taproot. It has a pink or purple flower that blooms about five feet above the ground at a time when little else is in bloom. It produces sought-after honey with a fruity flavor and a buttery mouthfeel.

A leafcutting bee (Megachilesp.) enjoys some spotted knapweed in central Oregon. Photo by Rusty Burlew.
A leafcutting bee (Megachile sp.) enjoys some spotted knapweed in central Oregon. Photo by Rusty Burlew.

Kudzu

I’m including kudzu, Pueraria montana, on this list because I get more inquiries about purple honey than any other type. People want to know where they can buy it and will pay just about anything for it. Part of the intrigue comes from the novel “The Secret Life of Bees” by Sue Monk Kidd. The characters in the book claim the color comes from elderberry juice, but beekeepers say the honey appears before the elderberries do.

I side with the folks who say that purple honey comes from the flowers of the kudzu vine. Kudzu and purple honey (sometimes described as blue) share a geographical distribution in the southeast. Also, beekeepers say purple honey tastes like grape jam and smells like grape soda — descriptions that are often applied to kudzu flowers as well.

Kudzu is not a favorite of honey bees, but in dry years — especially during a summer dearth — honey bees will forage on it to a limited extent. This comports with the fact that purple honey is most often collected in years of drought and never in large quantities. Several years ago I was given a small jar of this reddish-blue delicacy. The flavor was definitely grapey and a bit startling, pleasant and intriguing.

Although the jury is still out on the source of purple honey, the damage to the environment from the kudzu vine is undisputed. It’s certainly not worth the off-chance of harvesting a few cells of grape-scented honey from one of your hives, no matter the revenue.

Kudzu can cover anything, including these trees in Atlanta. Wikimedia photo by Scott Ehardt.
Kudzu can cover anything, including these trees in Atlanta. Wikimedia photo by Scott Ehardt.
The flowers of kudzu are purple with a grape-like fragrance. USDA-ARS photo by Peggy Greb.
The flowers of kudzu are purple with a grape-like fragrance. USDA-ARS photo by Peggy Greb.

Tree-of-heaven/spotted lanternfly

In an interesting twist of fate, the invasive spotted lanternfly, Lycorma delicatula, is supplying some beekeepers with so-called lanternfly honey, popular with consumers because of its novelty. Some northeastern beekeepers report selling out of the darkly viscous, mysteriously flavored product in a matter of hours.

The spotted lanternfly is actually an invasive leafhopper that is doing millions of dollars of crop damage in about ten states in the northeast. The epicenter is Berks County, Pennsylvania, but the spread has been quick and unrelenting since the lanternfly was first discovered in 2014. County quarantines have done little to slow the spread, and the list of infected areas is expanding.

The nymph stage of the spotted lanternfly feeds on its favored host plant, Ailanthus altissima, the invasive tree-of-heaven. The nymphs gorge on the tree, leaving patches of honeydew on the trunk and branches that drip into the understory. This sugary substance, a spotted lanternfly excretion, is extremely attractive to bees, wasps, flies or anything else looking for a sweet treat. Honey bees collect it like nectar and store it like honey.

While governments are spending millions to eradicate the spotted lanternfly, some beekeepers eyeing the potential profits are protecting their personal populations of both the tree and the leafhopper. Other beekeepers, distraught over finding dark, heavily flavored honey in their supers, worry that leafhopper dew-doo will taint the light, ethereal honey crop they depend on.

In any case, the spotted lanternfly has an unfettered appetite for North American crop plants and has already damaged upwards of 70 different plants in the northeast. And since the host tree-of-heaven has already invaded 44 states, the spotted lanternfly may just be warming up.

The favored host of the invasive spotted lanternfly is the invasive tree-of-heaven. Pixabay photo
The favored host of the invasive spotted lanternfly is the invasive tree-of-heaven. Pixabay photo
An adult spotted lanternfly and colorful nymphs explore a tree limb. USDA-ARS photo by Steve Ausmus.
An adult spotted lanternfly and colorful nymphs explore a tree limb. USDA-ARS photo by Steve Ausmus.

Control the Spread

Responsible beekeepers should enjoy their invasive honey by harvesting it, selling it, or feeding it to bees. But I hope beekeepers will refrain from seeding or spreading any invasive species. Even if we can’t halt the spread of invasives, we can stop short of promoting that spread and making the problems even worse. Humans and pollinators of all sorts — including your honey bees — will benefit from greater biodiversity.

Rusty Burlew
Honey Bee Suite

A flashlight shows off the color of this purple honey, compliments of Flying Pig Apiary. Photo by Rusty Burlew.
A flashlight shows off the color of this purple honey, compliments of Flying Pig Apiary. Photo by Rusty Burlew.

5 Comments

  • Rusty, you won’t necessarily remember, but a while back I posted about how prolific a “re-seeder” our California figwort was here in Olympia, WA. You indicated you weren’t sure it reseeding and YUP you were right! It is a mega rhizome mess and spread so much this year that even the entire section dedicated to goldenrod, sweet white clover, buckwheat, and several filbert trees that is never irrigated was completely over-run. The other plants struggled with our bone dry summer, but not these beasts. Last weekend figured oh what the heck, I’ll just pull some out. Wrong! Took mega shoveling up root clumps and runners, and no doubt it will be back soon enough. I’m gonna label it a non-native invasive! Don’t even dare put it in the compost pile.

  • “We don’t seed the wildlands or destroy native environments so growers of pigs and cows and chickens can prosper, so why should we do it for beekeepers?”

    I think that the history of North America and the westward expansion of settlement by Europeans is all about destroying native environments for growers of pigs, cows, chickens, and sheep!

    But I completely agree with you that invasive plants are terrible in all the ways you mentioned, reducing biodiversity and smothering native habitats. I can’t control where the bees & pollinators forage (and they DO like Japanese knotweed!) but I would NEVER plant or encourage the growth of invasives. Thanks for making a good point.

  • Thank you, Rusty, for timely information and reason to stop before we purchase another plant from who knows where that’s not native. Also, ones that are GMO insect resistant. We have a lot of invasive stuff here in Florida as well that keeps bees and natives alive year-round and we pay billions a year to get rid of them without much gain. Thank you for bringing this to the light.

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