Non-native, Invasive Honeysuckles: ‘Tis the Season!
Robin Schachat
Early in the spring it is a great pleasure to go for a walk and see the lovely fresh green of early emerging foliage on trees and shrubs – “spring green” is a happy phrase almost whenever you hear it, signaling renewal, regrowth, the onset of longer and sunnier days. Unfortunately, locally one of the earliest of these pretty sights is the soft green leaf of a bush honeysuckle.
Honeysuckles are members of the genus Lonicera. None of the bush species of Lonicera is native to Ohio. All of them are aggressive, fast-growing, and invasive to almost any ecoregion not only in our own state but throughout the Midwest, New England, the mid-Atlantic states, and eastern southern Canada. If, like me, you are unlucky enough to have a neighbor who loves them, you will find yourself removing them from your own garden by the multiple dozens every year.
Why? What makes them so bad? First of all, as I already mentioned, they leaf out very early. They also hold onto their relatively thick foliage quite late into the fall. This means that they are in active growth for a longer season than most native understory plants, and they block sunlight to plants trying to grow beneath their cover. Further, their root systems are thick and extensive (although shallow), also outcompeting most other plants for ground water and the nutrients carried by it. To top it off, there is some evidence that they are allelopathic: that is, their roots release chemicals that deter the growth of other plants within their range. In short, they outcompete native plants for light, water, nutrition, and space. They spread like the dickens, and can form large, impenetrable thickets within only a few years. (photo #1)
Loniceras spread through three common means. First, even though they are listed on many states’ lists of Noxious or Invasive Plants, you can find honeysuckle bushes for sale at many garden centers. If you are tempted to buy one, ask if the plants for sale are natives. If they are native shrub “honeysuckles”, they will belong to the genus Diervilla, and should be clearly marked that way. (photo #2) The native true honeysuckle in Ohio, Lonicera sempervirens, is a vine. (photo #3) And the state of Ohio does not allow sale of any bush Lonicera species…but you will find them for sale here anyway. It’s illegal to buy them, by the way, or to plant them. So don’t.
The second common means of spread is by root expansion. They spread; it’s that simple. And if you dig up a bush honeysuckle and leave any roots in place, it might regrow from those bits of root, too.
Finally, it’s the birds and the deer. The nonnative, invasive honeysuckles fruit with bright, jelly-like red berries in late summer through fall. (photo #4) These berries are delightful in appearance but are lacking any major nutritional value for our birds. Nonetheless, they are so attractive that the birds eat them anyway, instead of healthy berries from the native plants with which our birds have co-evolved. The berries pass through the guts of the birds, in so doing scarifying the included seeds and encasing them in “birdie fertilizer”. These drop to the ground and, not surprisingly, set to work growing. Our white tail deer, like the birds, go for these berries and spread seed, too.
So…how can you tell if you have these plants in your garden already? There are four varieties that have taken hold in our ecoregion. We shall examine each one.
Lonicera maackii, Amur Honeysuckle, grows to a maximum width of 10’ – 15’ and height of up to 20’, in an attractive, fountain form. Its stems are woody and brown, exfoliating in strips when relatively young, with mature bark of fissured light brownish gray. (photo #5) Its blooms emerge bright white, in pairs, in April and May, maturing to golden yellow once they have been pollinated. (photo #6) As with all honeysuckles, they are pleasantly fragrant. Berries are ¼” long, red, sometimes orangey, and very juicy in appearance. They are also poisonous to humans: watch children near these, and all, honeysuckle berries! The leaves are soft to the touch, grass green, ovate to 3” long, and held opposite each other on the twigs. This plant will grow in any condition from dry soil to damp, clay soil to sandy, full sun to full shade. It is native to China, Korea, and Japan – in the last of which, ironically, it is critically endangered!
Lonicera morrowii, Morrow’s honeysuckle, is a smaller shrub, growing to about 8’ in height and 10’ width. Foliage is similar to that of Lonicera maackii, but is colored a soft gray/green and is slightly downy on the reverse. Bloom is creamy white in color, maturing to yellow, in May and June. (photo #7) Growth habit is fuller, but very similar to L. maackii. Fruit is alike, and appeals to birds, deer, and small mammals. This species is not endangered in Japan, and originates from the same areas as the preceding plant.
Lonicera tatarica, Tatarian Honeysuckle, comes to us from Russia, other parts of China, and the Himalayas. Like the preceding two species, it grows magnificently healthfully, and rapidly here in NE Ohio, with an eventual height and spread of 8’ – 12’. Also like them, it can grow in almost any conditions, although this species eschews full shade. Leaves are a hint smaller, and bluish-green; otherwise similar. Bark is also exfoliating, but darker in maturity. The tubular flowers of this species are pink, varying from blush to almost red, appearing in pairs in May and June and maintaining their pink coloration. (photo #8) Fruit is the same as the prior species, and appeals to the same audience.
Lonicera x bella, Showy Honeysuckle, is a hybrid, as its botanical name shows. It is a cross between L. morrowii and L. tatarica. Although it has been suggested to have arisen in nature, since the source ecoregions of the two parent species are not the same that is highly unlikely. It has, however, crossed and backcrossed often enough in the wild once it got here to have produced a wide variety of appearances suggestive of either or both parents. It is often taller than either, growing to a height of 10’ or more. (photo #9) Almost always its bloom is rosy pink, maturing to golden yellow.(photo #10) Foliage may be downy, hairy, or smooth. This is the plant we see most often in the United States, an escapee from cultivated gardens. And this is what you are most likely to see for sale on line or (not legally) in garden centers.
Early spring is a terrific time to dig these plants out of your garden! Root spread is wide but shallow, and if you expose remaining tiny bits of root to dry sun they will be unlikely to regrow. Mark the spot where you have removed your bush honeysuckles, and if they do begin to regrow in the summer you can spot them easily and dig them out again. Don’t worry about confusing them with other plants; that soft, pretty foliage is a dead giveaway.
If your bush honeysuckles are too large to dig out easily, this year you will have two jobs. First, after they have bloomed (why not enjoy the spring color?), cut off any branches that bloomed before the berries form. Ta-Da! No berries will be eaten and spread by birds and animals! Mark the plant’s location so you know what to target later. In fall, prepare to poison. I generally do not truck with plant poisons in my garden, and I will not officially tell you to do the following, because it is using a chemical against its approved label directions. But you can learn online from many other sources that this is definitely the most effective way to do in invasive honeysuckles: Cut and Paint. This is most easily done by a team of two, because it involves quick sequential actions. Wear gloves, and do not attempt on a windy day. Saw off the trunks of the shrubs (they may be quite large) very few inches from the ground. As soon as the trunk is cut, paint the stub coming from the ground with concentrated glyphosate (commonly available as concentrated Round-Up). In fall sugars are flowing down from upper branches to the plant’s roots, and so will the poison. Be extra careful not to spill glyphosate on other plants or on the surrounding soil – it’s a poison, remember. You might want to paint with a disposable paintbrush, too. I am not a great believer in single use items, but there are times it makes sense.
These are the bad guys. Read the next article to consider some of the alternative lovely native shrubs you could plant in your garden!
