Which plants to avoid like the plague

It’s a nice spring afternoon, and you are so excited to start planting in the garden. You visit your local plant nursery and a gorgeous, healthy shrub catches your eye. When you check the tag, it says “Easy to grow!” and you notice that it’s cold hardy in your area. Perfect—add to cart, right? Not so fast!

Touted as an easy evergreen hedge, when Privet (Ligustrum) blooms it can be pure torture for allergy sufferers! Here is a list of better alternatives.

Lazaregagnidze, CC BY-SA 3.0, via Wikimedia Commons

Look, I am not trying to boss you around. I am not a huge fan of strict rules in the garden (or anywhere else in my life, for that matter). But I do have one cardinal rule. Before you buy ANY plant, thou shalt do a quick search to find out if it’s invasive or potentially problematic in your area. That’s it! Of course we should prioritize native plants. But if we are going to plant non-natives, we have a responsibility to do a little due diligence to avoid causing potentially devastating consequences in our ecosystems. This USDA website is a good resource, but a regular internet search for the plant name + “invasive” is also a good idea.

The signage, plant tags, and marketing information at garden centers can be confusing, and unfortunately some well-meaning employees don’t actually know what’s invasive and what’s not. The situation is made worse by some of us using the words “aggressive”, “invasive”, and “non-native” interchangeably. So for the purposes of this article (and all other Unruly Roots information), here are some definitions modified from the MO invasive plant council’s website:

Native plants originally occur within a region and are adapted to local climate and soils. They have co-evolved with native insects and wildlife and are critical to ecosystem functions. In America, this usually refers to plants present before widespread European colonization.

Non-native plants are those introduced (intentionally or accidentally) to a new place or habitat, usually resulting from human activities. Since they did not evolve locally over thousands of years, their presence can have negative impacts on endemic ecosystems. The words “exotic,” “alien,” and “introduced” are synonyms for “non-native.” Not all non-native plants are invasive.

Aggressive plants are species that, usually because of human-caused disturbances, spread rapidly and can outcompete other plant species. Aggressive plants can be native or non-native. Certain species may be aggressive in some situations or regions, but not others, so this term can be somewhat subjective.

Invasive plant species are aggressive AND non-native. They grow and reproduce rapidly, and their presence causes or is likely to cause economic or environmental harm.

Many gardeners are familiar with the frustration of english ivy. It was often planted to prevent erosion, but its roots are quite shallow so it’s not very good at it. If you go on a hike near Atlanta, you are sure to see both English Ivy and Privet spreading happily through our native forests.

So, now that we are all on the same page. Here are a few species that I urge you (beg you) to never plant, no matter how nice and non-threatening they might look in the nursery!

Any type of privet (Ligustrum) — They are extremely aggressive and are choking out our native plants across the US. They can sucker or spread by seed, with the help of birds or wind (Note: supposedly ‘Sunshine’ is sterile and won’t spread… but I’ve seen “Jurassic Park”). Their pollen is also particularly problematic for asthma and allergy sufferers. Some reports estimate that Asian Privets have taken over more than 14 times the acres of forestland that Kudzu has! Now I know you wouldn’t plant kudzu, so don’t plant privet. Please!

English Ivy (Hedera helix)— You probably already know about this one, but it can still be tempting to some who want a nice English cottage garden feel, or people want to cover a shady area quickly. It smothers native plants, climbs and kills trees, and is a great haven for rats and snakes. Oh and it will ruin your walls if you let it climb them. What’s not to dislike?

Barberry (Berberis vulgaris or thunbergii) — These rapidly spreading, spiny shrubs have aggressively infiltrated our native forests (mostly the northern US), can be hosts for diseases like black stem rust, and are even suspected to be related to rising tick populations and the spread of Lyme disease. Several other barberry species are native to North America, although they are not always easy to find in nurseries. Look for one specific to your ecoregion.

Bamboo (Phyllostachys, Pleioblastus, Pseudosasa, Bambusa) — Once you plant it, you will never get rid of it. At first it may seem well behaved, but after a few years it will start growing completely out of control. It’s important to note that bamboo essentially only spreads by underground rhizomes (or clumping), so if it is confined to a container you probably won’t have any issues.

Japanese Honeysuckle (Lonicera japonica or tatarica) — Does not play nicely with others, climbs all over everything, and will spread out of control. Plant a native honeysuckle (like ‘Major Wheeler’) instead.

Chinese or Japanese Wisteria (Wisteria sinensis or floribunda) — The bane of my existence! Can climb up to 80 feet, and its woody trunks can grow up to 15 inches in diameter. It will strangle all of your trees, spread by seed, and is guaranteed to grow a new plant at every little node that touches the earth. While the American Wisteria can also be quite vigorous, it’s much more well behaved, only grows to 20-30 feet, and it is likely to mature and bloom for you sooner than either of its exotic cousins.

Leatherleaf or Japanese Mahonia (Berberis japonica or bealei) — This spiny, strange-looking plant spreads aggressively through suckers. More problematically, birds love the fruit and propagate the plant far and wide by eating and dropping its berries. There is a lookalike that is native to the West Coast, as well as a few other native Mahonias all frequently (confusingly) called Oregon Grape.

Himalayan or Evergreen Blackberry (Rubus armeniacus or laciniatus) — They spread like crazy into impenetrable, thorny thickets. Just plant the native blackberries. I have a few thornless “Navajo” blackberries that have done well for me so far!

Nandina (Nandina domestica) — Supposedly some the newer dwarf cultivars like ‘Flirt’ and ‘Lemon-Lime’ are sterile and won’t spread. Typically, nandina is spread both by roots and by birds eating and spreading its bright red berries all over the place, which happen to show up when other food sources are scarce. If you really like seeing red berries around the holidays, consider a Winterberry, American Holly, Yaupon Holly, Possumhaw, or Flowering Dogwood.

Common periwinkle (Vinca minor) — It may look innocent, but this vine-like plant forms dense mats to choke out other plants along the forest floor. Plant Green and Gold for a nice shade-tolerant evergreen, flowering groundcover instead.

Carpet Bugle (Ajuga reptans) — Similar to periwinkle, it spreads through runners and outcompetes native plants, especially in shady areas.

Princess Tree / Empress Tree (Paulownia) — It can grow 15ft per year. Each tree is estimated to produce 20 MILLION seeds, which can travel long distances through wind and water. It’s reported to survive wildfire and even bulldozing! Just don’t do it. Do yourself a favor and remove it the moment you see this pop up in your yard.

Lantana (Lantana Camara) — I know! It’s pretty, easy to grow, and it attracts butterflies. The problem is it can grow a little too easily. While Lantana seems to cause the biggest issue in humid, tropical areas like neighboring Florida, it’s starting to become a problem in Georgia too. If you want a plant that actually helps butterflies, plant butterflyweed or another native milkweed, a native verbena, any coreopsis, anise hyssop, or echinacea instead to provide just as much beauty and much more wildlife value!

Butterfly bush (Buddleja davidii) — posing a problem mostly in the northwestern US, butterfly bush can spread quickly since one single flower can produce 40,000 seeds. Same alternatives to Lantana above for attracting butterflies and pollinators in a more beneficial way.

Chinese Wisteria is beautiful, but not worth the nightmare of keeping it in check. A nice American Wisteria (Wisteria flutescens) like ‘Amethyst Falls’ is much easier to manage and you can enjoy its abundant repeat blooms guilt-free!

Designing your landscape can be overwhelming, and the information overload on the internet there can be daunting, but unfortunately you are almost certainly going to deal with an invasive species in some form or another as you work in your garden. Some of us inherited invasives when we purchased our properties (I am battling most of the bad guys on this list myself!), and sadly people are still selling, purchasing, and planting these problematic plants every day, whether they realize it or not. If you need help navigating all of the confusing information out there, Unruly Roots can provide garden consulting services so you can plan, build, and maintain your dream landscape with confidence. We can help make the process of growing your garden fun, accessible, and rewarding! Learn more here. Good luck out there!