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How Invasive Plants Threaten Bees

Many blooming plants have a beautiful relationship with honey bees and other insects. The bees provide pollination while plants lure them in with food. But not every flowering plant is a welcome member of the environment. When a new type of plant is introduced into an area it may become invasive. Yet, there are some invasive plants that bees love in spite of their bad reputation.

Purple loosestrife an invasive plant attractive to bees growing in a meadow image.

Why Invasive Plants May Be Bad for Bees

An invasive species (be it plant or animal etc.) adapts very easily to a new area. It is not native to the region in question. But, capable of rapid reproduction, it causes harm to native plants and animals, property or the economy.

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Some plants considered invasive are not only attractive to bees but major food sources. Beekeepers actually harvest large honey crops from some of these species. Their business model depends on the nectar source.

So they may be a little aggressive -if the plants are feeding bees what is the problem? As usual, the answer is not a simple one.

Though beneficial as a food source, many invasive plants actually create bad living conditions for bees.

  • create monocultures
  • smother out native plants that may bloom longer

How can a plant that provides pounds of nectar be a bad thing for a honey bee colony? When introduced into a new area, invasives often out-compete native plants. They are capable of taking over the area.

This creates monocultures. A large area of one nectar source blooming all at one time does provide abundant food. However, the bees suffer nutritionally due to only receiving one food profile.

Nectar and pollen from different sources have unique amino acids and nutritional substances. Eating only 1 type of food is not good for us or honey bees.

Also, if the invasive plant is more attractive to pollinators, native plants may suffer. They may not be pollinated well. As they fail to produce seed, native plants with a longer bloom period may disappear from the local landscape.

This creates an environment that provides large honey harvests but unhealthy bee colonies. Is the short-term gain worth the long-term loss? The scope of the problem depends on who you ask.

Weeds and Bees

It has been often said that one man’s weed is another man’s bee plant. (That goes for us lady beekeepers too!).

In fact, many weeds are beneficial to bees and I often encourage beekeepers to let them grow for a few weeks. Trimming the lawn can wait a bit longer in most cases.

Dandelions, goldenrod and even clover are beneficial when other food sources are lacking. Even though they are weeds, they are not necessarily aggressive growers.

And, even in the world of invasive plants, some are a bigger problem than others. The region in which you live plays a role in whether a particular plant is a nuisance or a serious big green problem.

Common Invasive Plants

In no particular order, let’s look at some of the most notable problem plants. They are considered aggressive or invasive in many regions even though some are beneficial to bees.

Privet in bloom on streambank near farm image.

Chinese Privet (Ligustrum sinense) is a popular shrub that has many different varieties. It is also one of the worse invasive shrubs in the eastern US. Forming dense thickets, it displaces many native species.

Bees love privet in my area and produce a light colored honey. Some varieties of privet produce honey with a detectable scent and taste that not all honey consumers enjoy. Yet, the bees don’t seem to mind and enjoy the bountiful food source.

Fall leaves and white seed pods of invasive popcorn tree chinese tallow image.

Chinese Tallow (Triadica sebifera) is a fast growing tree native to Asia. It has become widespread through parts of the southeastern US. Chinese Tallow trees produce small flowers in Spring.

They are commonly called “popcorn trees”. This is due to the resulting seed pods that remain attached to the limbs into Winter. The tree is considered by many to be one of the most aggressive weeds in the US.

Attempts to eradicate Chinese Tallow in some South states has been met with considerable angst from beekeepers. Chinese Tallow provides valuable forage for honey bees and other pollinators.

White blooms of japanese knotweed plant image.

Japanese Knotweed (Reynoutria japonica) is an herbaceous perennial. Similar in appearance to bamboo, it is actually a member of the grass family. In some regions, it is in bloom when no other plants are and provides needed food for bees.

The World Conservation Union includes Japanese Knotweed on its top 100 worst invasive plants. It can grow 5-8 feet tall and forms a dense bush with pretty cream-colored flowers.

Kudzu (Pueraria montana var. lobata) is native to China, Japan and the Pacific Islands. This plant needs no introduction to those of us living in the Southern region of the US. An aggressive grower that seems to actually run across the ground during the warm Summer months.

It is responsible for killing many native trees and shrubs as it climbs and blocks the sunlight. Did you know that Kudzu blooms? It does and honey bees will harvest the nectar-though the blooms are not highly attractive to my bees.

I have tasted Kudzu honey and it has a slight grape flavor. But seriously, who wants more kudzu in their area? I would think that no one who is familiar with this plant would knowingly bring it home.

Wild growing mimosa trees image.

Mimosa (Silk Tree) Albizia julibrissin: Native to China, the Mimosa tree is a beautiful ornamental tree. The fern-like foliage, showy flowers and sweet fragrance has made it a landscaping favorite.

However, it is a messy tree dropping flowers and seeds and is prone to broken branches. And, yes it is invasive. Having escaped cultivation, you can find Mimosa growing wild across the landscape.

In the wild, this tree develops dense foliage and shades out many native grasses and shrubs. Mimosa blooms can benefit honey bees and other insect pollinators by providing nectar.

Mimosa honey is creamy and sweet with a distinct smell and aftertaste. But, this tree is not a major source of nectar in most regions. For most, the problems outweigh the benefits of growing this tree.

Purple Loosestrife (Lythrum salicaria): This plant is native to Europe and parts of Asia. It was brought to American for ornamental and medicinal uses in the 1800’s.

A wetland plant, it is an aggressive grower in most states and propagates by underground stems and seed. One plant can produce 2 million seeds in a season.

This beautiful plant with purple spikes of flowers is very attractive to bees. The nectar results in a dark honey that can be sold or left to feed the bees.

Some states are using imported European Beetles and other methods to attempt control of Purple Loosestrife.

Multiflora Rose (Rosa multiflora) is a shrub type plant that is native to China, Japan and Korea. It was originally used by the US horticultural industry as root stock for rose breeding programs.

It was also used by the USDA for erosion control and natural barriers (living fence) for livestock.

The mid-Summer flowers are visited by honey bees and other pollinators providing some food. Personally, I do not have any problem with this shrub.

However, left to its own devices I understand how the thorny limbs could create an issue. If you have Multiflora Rose in your area, try to keep it trimmed and under control.

Pink flowers of invasive saltcedar Tamarisk trees image.

Tamarisk Trees (Tamarix ramosissima ) Also called “Saltcedar” is referred to by some as the “Monster of the Southwest”. These trees are very invasive in areas of central Arizona. They suck up large amounts of water from the desert landscape.

They also spread rapidly and are hard to eradicate – taking up space where useful foraging grasses could grow.

The feathery pink flowers of the Tamarisk attract numerous bees, dragonflies and hummingbirds. They provide large amounts of forage at a times of nectar dearth or drought.

Water Hyacinth (Eichhornia crassipes): This beautiful water plant is native to South America and was introduced into the United States as an ornamental.

It grows quickly and clogs waterways crowding out native plants. Here in SC, it has such a bad reputation – it is illegal to purchase.

Water bodies of the lower regions become covered with a thick mat during Summer. However, in northern areas of the state, Water Hyacinth dies out during the cold Winter. Bees are attracted to its purple bloom.

Beekeeper Response to Planting for Bees

We can all recognize the benefits and problems caused by some of these aggressive growers. And, not all beekeepers will be on board with efforts to completely eliminate plants that they feel are beneficial.

In some regions, the nectar from an invasive plant makes the difference between profit and loss for the year. I can understand the dilemma facing these beekeepers. However, will the health of the bees and other pollinating insects suffer later?

Remember, there are many who consider the honey bee to be an invasive species. They are not native to the US either.

No matter your opinion on what to do. It is the good environmental citizen that gives serious thought to plant choice – beekeeper or not. As you choose trees for bees or shrubs for the landscape, do you homework before planting.

Try to avoid seeds or transplants that will cause harm to your local ecosystem. A plant that is invasive in one area may not be in your climate.

Often, there are other choices – perhaps native plants to use instead. My goal is not to promote any one point of view.

Merely to say that as beekeepers and homeowners, when you are choosing plants – make the very best choices possible. We want a healthy environment for all.

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