Monday, April 3, 2017

Gardener Beware: Invasive Plants, Part 2: Plants that should come with a Warning Label


Missed Part 1? Read it here.

One of the more popular things I have ever written (for another website as it were) was an article on invasive garden plants. It has been viewed almost 200,000 times. At the end of the article, I asked readers to share their experiences with aggressive plants. Readers left almost 500 comments! It seems that many people have had a plant that has run wild through their yard. Gardeners welcomed a chance to share their frustrations and struggles in the comment section of the article.

But as well as sharing their problems, a few readers took exception with one of the plants that I had deemed problematic: Lily-of-the-Valley.

"I would LOVE to have Lily-of-the-Valley take over my space. They have a sweet, delicate smell." wrote Lois Gibbs of Buzzards Bay, MA

Ah, Lily-of-the-Valley! Yes, the white bell-shaped flowers are cute and their fragrance is divine, but boy can it spread.  Here's Lily-of-the-Valley's secret underground weapon:


Just look at those roots! They run deep and shoot out in different directions (I actually missed some of the deepest part of the root when I dug this plant out). Unless you dig down deep and wide with your shovel, you are very likely to miss a segment of the plant's prolific root system. 

Just when you sit back and relax thinking the issue is dealt with, new Lily-of-the-Valley pops up to mock your efforts. 


Not only does Lily-of-the-Valley spread unseen under the ground, it developes little orange-colored berries that are filled with seed.


And while I am grumbling about issues with this plant, I'll also mention that Lily-of-the-Valley is very susceptible to fungal leaf spot in the late summer.

Some of my readers did not appreciate it when I expressed a need for caution when it came to planting aggressive plants:

"OK ladies...this article and all your comments were all very helpful...however...any "bloomin' idiot flowers" you'd like to get rid of just send them "crazy" growers to me!" Jan B. Crossville, TN

"I am glad you posted this, I need some aggressive plants up here..." Debby Boyle, Necedah, WI

"Funny. Everyone is trying to get rid of invasive plants and I am trying to find them. I am in Dallas, TX and it's so hot and dry...I need something for my pitiful yard..." SkyN, Texas

I will reply here as I did in the original article. Be careful what you wish for! With all due respect, what these people are really looking for is not an invasive plant, but one that will be successful in a challenging outdoor area. Yes, they may face some difficult growing conditions, but that isn't a good reason for resorting to a plant that is as problematic as it is pretty. It's so much better to take a step back and look for a plant that is appropriate to the site. 


I am not going so far as to say never plant Lily-of-the-Valley. Just do it cautiously knowing you are planting something that can really spread. Choose your spot carefully, so hopefully it can be contained. 

I found Lily-of-the-Valley growing in my garden when we moved in. Under a big maple at the back of the yard, it's limited to an island bed and hasn't been a problem... so far. In the shadow of the maple, it fights periwinkle and English Ivy for turf. In the front garden however, Lily-of-the-Valley is a real nuisance. I've tried to get rid of it, but man is it difficult!

 A shade gardener who is not afraid of Creeping Jenny.

Groundcovers

The majority of readers wanted to weigh-in on plants that were giving them grief. Groundcovers were high on the list of problem plants. Here's a list of the ones mentioned most frequently:

Creeping Jenny, Lysimachia nummularia
• Goutweed, Aegopodium podagraria 'variegatum'
Periwinkle, Vinca minor
False Lamium, Lamium galeobdolon 'Florentinum'
Bugleweed, Ajuga
Lily-of-the-Valley, Convallaria majalis
Winter Creeper, Euonymus fortunei
Chameleon Plant, Houttunynia cordata

"Chameleon Plant– beautiful, but it spreads like crazy and I can't get rid of it. It's those underground runners. NEVER, NEVER PLANT THIS." Diane D. Lawrenceville, GA

"Creeping Charlie is much worse than Creeping Jenny and I am not just saying that because I am a woman.", E. Simmons, Florence AZ

Suggestions and Alternatives

As I wrote in the previous post, gardeners can on occasion be too impatient when it comes to filling up their flowerbeds. Patience is a virtue, especially when it comes to gardening. It is better to look for plants that are"clump-forming" and fill a space with a larger number of plants clustered together.

Chinese Lanterns, Physalis alkekengi

Gooseneck Loosestrife, Lysimachia clethroides on the lower right.

Rose of Sharon (left) and Obedient Plant (right)

There were lots of other plants that were called out for not being well-behaved. Here are just a few that readers complained about:

Japanese Knotweed, Fallopia japonica
Anemone Canadensis
Chinese LanternsPhysalis alkekengi
Spiderwort, Tradescantia
Obedient Plant, Physostegia virginiana
Gooseneck Loosestrife, Lysimachia clethroides 
Bamboo, Bambusoideae (spreads underground)
St. John's Wort, Hypericum perforatum
Purple Heart, Wandering Jew Purpurea
Ribbon Grass, Phalaris arundinacea
Sundrops, Evening Primrose, Oenothera 
Mexican Evening Primrose, Oenothera speciosa
Snow-on-the-Mountain, Aegopodium podagraria
Rose of Sharon, Althea (a terrible self-seeder, but it has to be said that it is a good, late-summer shrub. Look for one of the varieties that are sterile, if you are concerned.)
Orange Daylilies, hermerocallis fulva (not the hybrid daylilies, but the kind you see growing in ditches and at the side of the road)

"I have Yarrow that has taken over my front lawn..." Kris Lee, Jackson, WY

Another problem is Purple Heart, Wandering Jew Purpurea. It came with the house when we bought it. It is everywhere. I have removed bags of it and every year it comes back. I have grown to detest it...", Burrgmb, Southlake Texas

"Tree of Heaven is the worst name for a pest that I can think of!", Kristen McCann, Fresno CA

"Snow-on-the-Mountain and Yucca are both my garden nemesis. Here in Michigan they grow like CRAZY! Catnip is another that I will always avoid." J Merillant, Michigan, MI

"Another aggressive plant is Mexican Morning Primrose. It is a really pretty pink groundcover. However it developes a very intricate, dense underground network of roots that are a real problem to eradicate..." Gerald K, Mather, CA

Suggestions and Alternatives

There are so many great perennials! There is no need to feel that you have to resort to an unstoppable plant just to find something that works. If you are stuck on what will grow in a difficult area, do some homework. Look for books on shade, clay soil, dry or otherwise inhospitable conditions. See if there is a garden tour or open gardens in your area and find inspiration there. 
There is a great plant for almost any situation– even the difficult ones!

I have Anemone Canadensis in an isolated bed, so for me it hasn't been a problem. Others really dislike its spreading ways. On the right is Snow-on-the-Mountain.

Wisteria (top), Trumpet Vine (lower left) and Virginia Creeper (lower right)

Vines and Climbers:

So many different types of vines have given gardeners concern. Trumpet Vine and Asian Wisteria were amongst the most-hated vines, but the others mentioned most frequently were:

Honeysuckle, Lonicera (native to Korea, China and Japan)
English Ivy, Hedera helix
Virginia Creeper, Parthenocissus quinquefolia

"Morning Glories* are a nightmare. One plant had taken over and I find myself constantly trying to pull them out as they reappear. Ugh...." Mary Kay@Studio23 Thirty

*Morning Glories are great self-seeders and can become a problem given the right conditions. If you have white flowers on Morning Glory-like foliage, you actually have Bindweed.

Suggestions and Alternatives

Most Clematis are a great choice for full sun (Sweet Autumn Clematis might be one of the exceptions). Climbing roses on a support are another choice for sun (or in some cases for part-shade. Rambling roses will often scramble up a tree for instance). 

If you want to grow Wisteria, I have heard that the North American native, Wisteria frutescens is a much better choice than Asian Wisteria. 

For shade you can always try a Climbing Hydrangea, Hydrangea petiolaris. It is a vine that is a little slow to get established, but isn't invasive to my knowledge. 

A large patch of Oregano in the left foreground and Chives on the right.

Herbs:

"Mint!!! I made the mistake of planting it in my flowerbeds, as they told me it was a natural ant repellent at the garden centre. Yeah right! Not only has it helped, it has taken over my bed..." Ldavis49, Knoxville, TN

• Mint, Mentha
• Oregano, Origanum vulgare
• Lemon Balm, Melissa officinalis
• Sweet Woodruff, Galium odoratum
• Chamomile, Matricaria maritima (great self-seeder)
• Feverfew, Tanacetum parthenium (great self-seeder)
• Chives, Allium schoenoprasum (great self-seeder)
• Thyme, Thymus (given ideal conditions)
• Tansy, Tanacetum vulgare
• Comfrey, Symphytum officinale
• Bee Balm, Monarda (makes some lists. I have it in my garden and find it is fairly easy to remove)
• Pennyroyal, Mentha pulegium (member of the mint family)

Suggestions and Alternatives

The solution for herbs that spread a little too vigorously is simple: plant them in a container. 

Cut chives back hard after they flower. You'll have fresh growth in a couple of weeks and will eliminate the possibility of unwanted seedlings.

Some gardeners, myself included, like herbs like Feverfew despite the fact that it reseeds itself a bit too readily. If you dislike prolific self-seeders, cut off the spent flowers before they set seed. Another way to limit the number of new seedlings is to remove most of the plants after they've finished flowering and leave only a few to reseed.

If you have any problems with plants, please share your experiences in the comment section of this post. Suggestions or alternatives to invasive plants are also most welcome!

Read Invasive Plants Part 1 and Part 3.

35 comments:

  1. I heartily agree with you on the invasives. The lady I bought my home from seemed to have grown EVERY SINGLE ONE. I'm sure it's because they are so easy to grow. But---getting rid of them---a nightmare. Dig dig dig dig. Then dig some more.
    I won't use chemicals so that was my only alternative. Keep spreading the word. Repeat often. These plants are a nightmare not only to the gardener, but they often take over the natural areas. Bad Bad NEWS!

    ReplyDelete
    Replies
    1. I feel for you Sue. It is hard to face a problem someone else made for you. I am with you on the chemicals. I prefer to dig,dig, dig as well.

      Delete
  2. I will be fighting to eradicate Chameleon weed as long as I live in this house! It's not even pretty anymore, as it's reverted to plain green leaves rather than the pink, white and green sold in garden centers.

    ReplyDelete
    Replies
    1. My sympathies! It seems to be a plant that so many struggle with.

      Delete
  3. I would not be without lily of the valley for their precious flowers. I have them in a strip on the north side of my house. If they escape the brick edging, I mow them off. I would never give them prime real estate, but it is an out of the way place where I can enjoy their wonderful, but fleeting flowers. I have some buttercups (look like tiny ranunculus) that have precious flowers with a long bloom period, but they spread pretty quickly. I have to be careful where I put them.
    My main nemesis is the little pansies that reseed everywhere! I am constantly weeding them out.
    And brome grass, which came in some manure from my son's ranch! Holy cow! That is the worst.

    ReplyDelete
    Replies
    1. Sounds like the Lily-of-the-Valley you have Karen is ideally situated in a spot where you can control it. I know the buttercups you are speaking of, but the botanical name escapes me just now. I've never grown them, but I've heard they spread. At least the pansies are easy to weed out and the flowers are cute. Good point to ring up about manure (and compost)! Weeds can hang on sometimes despite all that they go through. Some really aggressive things are almost best left out of the compost pile.

      Delete
  4. Another informative and interesting post! My mom had planted Lily of the Valley when I was a child growing up in the home where I still reside. After many years of it taking over everywhere, I finally eradicated it by pulling every last one out by the roots. It's pretty, but needs to be in the right place. Right now I am battling with wild chives. They are in my perennial border and have been a nuisance for years. I finally got a wonderful tool which looks like a long spade and digs them right out, and I am winning!

    ReplyDelete
  5. We have some lily in the valley in our shady back yard (like Sue the previous owners planted pretty much EVERY invasive on the list!), but for some reason it isn't spreading. In fact it seems to be shrinking in area...
    I'm looking forward to your next post though... the goutweed throughout my front and back yards is awful hard to get rid of!

    ReplyDelete
    Replies
    1. Curious that the Lily-of-the-valey in your yard hasn't spread and is actually shrinking in size. It seems to be a pretty adaptable plant. Hopefully I get the post on Goutweed done for nepotism week. It's another difficult plant to contend with.

      Delete
  6. OMG Chives!!! I have chives coming out my ears! Luckily the plants are easily pulled out but holy moly are they prolific :) Have a happy week!

    ReplyDelete
    Replies
    1. I had chives in the garden at the very back of the yard (it was a herb garden for the previous owners). The chives seedlings would pop up in the cracks between the paving stones of the pathway that divided the sections of the circular garden. In the cracks between stones, they were a nightmare to remove, so I have gotten rid of the old bunches of chives and plan to replace them with sterile 'Profusion' chives.

      Delete
  7. I see so many plants on your lists that I've done battle with.... right now it's Monarda. My old tidy clump failed to come back last year and I bought a new variety. By October I was pulling out clumps and thought I was safe. Over the winter it spread underground like.. well, like Monarda and now it's at least a foot out in all directions. I have to get it out before my husband sees it.... will I ever learn??!!

    ReplyDelete
    Replies
    1. You must have ideal conditions for Monarda. For me it wanders, but it doesn't go wild. Summers are dry here, so perhaps that's why. It will be a chore to remove it, but at least the roots aren't as deep as some of the other invasive plants. Good luck with getting rid of the problem.

      Delete
  8. Thank you, this is so useful! For all of you fighting invasives planted by previous home owners, I can understand where they were coming from. We moved into our current home last spring and it was months later that I fully understood the amount of shade and leaf fall to which our outdoor space is subject. I have gotten a lot of great ideas for shade plantings from this blog (so incredibly helpful!) but am still worried about being able to rake the tremendous amount of leaves that fall each day from the giant (city-owned) trees that border our property. The invasive plants that have been listed here are so tempting because they sound so sturdy. Any alternative suggestions from the group would be most appreciated. A bed full of just creeping jenny still sounds better than nothing!

    ReplyDelete
    Replies
    1. I am going to give you a design reason not to put in a groundcover like Creeping Jenny. If you are looking to make the garden feel full, a low ground-hugging plant will have minimal impact. The ground will have cover, but the space above will still feel empty.
      I don't have a lot to go on, but I imagine a shady yard bordered by a fence with trees on the other side of the fence. What I think you need to do is forget a low plant and make big, bold moves. Start with a few understory trees. This could be American Service Berry (shrub form), Dogwood and Star Magnolia. Then plant some shade-loving shrubs. I have no idea where you are or what the soil is like, but shrubs could be Yew, Boxwood, Ninebark, Viburnum, Azaleas and Rhododendrons (if the soil is on the acidic side). Next add some big scale hosta for impact. Fill in with ferns, hellebores, Bleeding Heart, Heuchera, Goat's Beard and smaller hosta.
      The leaves that fall on your property are honestly gold. Your soil is likely to be very rich if they have been falling for years. If you dislike the look of them, rake them up and shred them with a mover than has a collection bag attached. Uses the shredded leaves as mulch. It will keep down the weeds and your garden will love you for it!!
      I have been meaning to update my shade garden examples. Here are a few posts in case you missed them:
      Woodland Garden:
      http://threedogsinagarden.blogspot.ca/2015/05/a-natural-forest-garden-in-mississauga.html
      Great shade backyard:
      http://threedogsinagarden.blogspot.ca/2016/03/a-garden-in-sun-and-shade.html
      Note the impact of the larger shrubs and small understory trees in this garden:
      http://threedogsinagarden.blogspot.ca/2016/01/a-bird-friendly-shade-garden.html
      Great hosta garden:
      http://threedogsinagarden.blogspot.ca/2016/02/hostas-have-some-of-best-names.html
      Good hosta reference:
      http://threedogsinagarden.blogspot.ca/2016/05/collectable-hostas.html
      Hope that helps!

      Delete
    2. Thank you so much for your response! I really appreciate all the info and guidance. You are absolutely right, we have a side yard bordered by a fence with enormous trees on the outside. Once their leaves come in later this spring we will have just a small spot that gets about 45 minutes of direct sunlight a day; otherwise we are all shade, all the time. And we live in Chicago, so not that far off from Toronto weather. I will definitely take your mulching advice to heart and work that into my garden plan. Thanks again, I so appreciate your help!

      Delete
    3. Plants will have to struggle with that lack of sunlight, so offering them nutrient rich soil is key. All those falling leaves will help. One other thing to keep in mind. There is dry shade and moist shade. Both types favour different shade plants.It is a good idea to make note of how damp your soil is.

      Delete
  9. What a great post, Jennifer!
    As much as I love Lily of the Valley, I have just never found a way to contain it, and so I have to agree that it is quite invasive.
    As always, thank you so very much for all the information and beauty that you post here. It is very, very much appreciated.

    ReplyDelete
  10. Very useful post, Jennifer. I am looking for more perennials for my garden. I've attentively read your list of invasive plants, and can say that Lily-of-the-valley is n0ot very invasive here, in North, zone 4, because of frost and ice in winter. I have 4 plants that hardly survive every spring. Vinca minor was very invasive, it spread on the conifer bed, but in winter 2015-16 it completely dead covered with ice.
    Thanks for your advice!

    ReplyDelete
    Replies
    1. I guess things must be that little bit colder where you are Nadezda. Winter there seems o have its own way of dealing with aggressive plants.

      Delete
  11. 20 yrs ago I gladly took donations of lily of the valley, fern and pachysandra. OUCH! Spent last two summers digging them out of the large front beds (under mature oak trees.) NEVER AGAIN!

    ReplyDelete
    Replies
    1. This is the reason I wanted to do this post. There is nothing worse than discovering you have planted a problem!

      Delete
  12. I managed to avoid Goutweed and chameleon plant for twenty years in my old garden and it's all over my new one along with a weed that I think is nightshade (thorny, tap root, berries, nasty). I'm gearing up for an all out assault...

    ReplyDelete
    Replies
    1. It is hard to inherit a problem someone else made. I feel for you Sue!

      Delete
  13. I can see why some people might disagree on some of these choices; sometimes what is invasive in most gardens isn't in others. Many years ago, my friend shared some False Sunflower with me, warning me that it might take over as it had her garden. But I could never get it to grow for me:) Creeping Charlie has to be the worst invasive plant for me, and I didn't even plant it. Another I would add to the list is Rudbeckia Triloba. One volunteer plant appeared one year, probably courtesy of the birds, and I thought it was so pretty in the fall. Fast forward about three years, and now I have seedlings all over the place! Great article--you're doing a great service to gardeners everywhere, Jennifer. It's easier not to plant something in the first place if you've been warned than pulling out seedlings for years afterward.

    ReplyDelete
    Replies
    1. Thanks Rose. I learned these lessons by making mistakes myself. I had no idea Lily-of-the-Valley would be so problematic when we moved in. Now I know!

      Delete
    2. I totally agree, Creeping Charlie is evil. We have pets so no chemical weed killers are allowed. As a result I get to work every few days pulling up all of Charlie I can from one area, but I can never get it all. It is everywhere. I am beginning to think that Charlie likes me tugging at it. A patch I managed to clear out last year, thinking I won that battle, seems to have become a favourite spa for that devil. I have given up on the backyard lawn, between deep shade, thanks to the neighbours large cedar trees all around us, and Creeping Charlie it is hopeless. Any ideas about how to get rid of it will be very appreciated.
      I am in zone 5b

      Delete
  14. What a hot topic! My mistakes are: Acanthus m., Hops, Sweet woodruff, etc. I got rid of hops! But, the others.... ooops! Arum italicum and Acanthus are moved to the pots. Acanthus is very smart - it was sitting, as one nice plant, for many years before I started to dig and found the underground giant net of its roots!
    Thank you Jennifer! I agree with you that the area for growing such plants should be carefully chosen.

    ReplyDelete
    Replies
    1. I have heard that Acanthus can be a problem. Didn't know about the Arum italicum though. Thanks for the warning Tatyanna!

      Delete
  15. I never planted Lily of the Valley they invaded from my neighbors...but love seeing them since they were my maternal grandmothers flower...and oh the smell...and how well they dry. I have a huge wisteria and try creeping everywhere but I keep under control...A very invasive vine is Porcelain Berry vine, spreads like wildfire, ask me how I know.? Ripped out my rose of sharon and will never plant another one.. Yes Gooseneck Loosestrife is invasive but very easily controlled...I love the look o the flower. A native I found invasive to IL is Northern Sea Oats, which is a very big reseeded.. and three years later still trying to get it under control.

    ReplyDelete
  16. PS...i keep creeping Jenny in containers only...comes back every year and saves me money on trailers.

    ReplyDelete
    Replies
    1. I have used Creeping Jenny in containers too. As long as it doesn't reach the ground and take root, it is a great container plant.

      Delete
  17. Wow! I guess I got lucky. Last year I planted 20 bugleweed plants as ground cover in my true shade garden, among the host as that are doing well. I wasn't aware that it could be problematic. This year it has not made an appearance. I have spent a good bit of time trying to figure out what I did wrong, after learning here that it is best to avoid it, I am now rejoicing and praying it isn't one of those things that will show up later in the season.
    I must mention that I am so glad to have found this blog. I have a hunch that I will be learning a lot here.

    ReplyDelete
    Replies
    1. To be a real problem Bugleweed, Ajuga needs somewhat moist conditions. Perhaps your plants got too dry? If you have something that creates a barrier to contain its spread, Ajuga can work as a groundcover. The trick is making sure it doesn't escape and spread unchecked. An even better suggestion is to look for cultivars of Bugleweed that are less aggressive. Ajuga 'Chocolate Chip' is one example.

      Delete

I love to hear from you. Thanks for leaving a comment.