Some 150 years ago, when American horticulture was still in its infancy Asa Gray of the Arnold Arboretum made note of the similarities of American plants and those of Asia. He speculated that the glacial editing we had in North America and Europe wiped out many specie of plants. Those glaciers did not affect Asia as much. So many Chinese and Japanese plants are begging to be introduced into our American gardens.
Many are closely related to our own native American plants and are well adapted to our gardens. (Skunk cabbage story) :-)
In the last two decades S.Africa and Chile have become the new resource for plant introductions. We are fortunate that they adapt well to their new homes.. Some however, are invasive and are slowly overwhelming our own wonderful native plants
What we do in our own private gardens is one thing but if we live in the woods or are by riparian streams it is our obligation not to introduce things that can travel.
With good judgment and proper placement they can be a joy. My talk will be about bad judgment and improper placement as that is the type of guy I am.
With the cornucopia of plant material we are now introducing, some material is questionable and aside from the investment may well create future problems as we now discover that these "adventuresome" plants have become weeds requiring much labor or herbicides to remove from our landscape.
"Dan Hinkley of the Heron people often used adventurous” and other such descriptive's such as “likes to travel”. I don't know about you, but when I plop a plant into the ground, I expect it to stay put and not to stray. I could buy a dog or cat for that purpose. Look seriously at the ornamental merit of all your plants and avoid those that only create work opportunity for the gardener you hire.
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I will not dwell on particular plants but on the general reasons for my deletions. I will undoubtedly insult retail and wholesale nurseries that peddle these invasive plants, but I am sure I will insult some of you as well as some of my employers. . I just began a new job and saw Cape Fuchsia widely planted. It was my first negative comment on the garden. I still got the job.
More interestingly I had not mentioned one invasive weed, that being oxalis. I figured anyone dumb enough to buy that deserves what they get. HHMN, I am sounding like that elitist Ann Loveloy, and her talk down attitude to Neophyte gardeners. There are a great many want-to-be gardeners who get demoralized because they are sold the wrong plants, given wrong advice or are simply not steered in a good direction.
Why do nurseries get away with it? Don’t know, but if I went into an auto supply center and asked for oil and they gave me cheap paraffin: guess what – when the engine seized up I would be ticked off. I feel more people should feel equally protective about their own gardens, or to what they leave behind.
This is a gardening tale by a Nurseryman who is now eradicating many of the plants he once sold; it might even be termed as a mea culpa or a sermon. The Good, the Bad and Ugly of the plant world.” Yes, there are plants I have come to hate. Many are invasive, and often are poisonous plants as well. These plants should come with a warning label.
Consider this lecture as my own warning label. Or as a British man said:" Not all plants belong in the choir of your garden.")
A Sweet William wrote that there was no plant he could not like. It was but a challenge to get to know them better. —To grow closer to them. This not me. I find that there are some plants I really don’t like. Did you really intend to make your house into a Chia planter?
Some are based on a weed factor basis, either by stoleniforous adventuring or by spreading by seed. Some commentary is based on foliage impairment.
Houtyinia cordata (Korean Ivy) fits in both categories. :”Planting it in a moist border is like inviting the Hell’s Angels to a choir outing!”
As a nurseryman I will also mention the cost factors, both in future labor costs and in the need for chemical use to eradicate plants that ought not to have been planted. Most Nurseries label these plants as “fills in rapidly” or “easy spreader.” Beware of using such invasive plants They may be a quick or CHEAP fix, but your future gardener will have years of labor and work trying to get rid of them.
Please follow up with your own problem plants. Some of mine include.
Hellebore (aptly named), most Euphorbia, Alstroemaria (the species), Lady’s Mantle, Veronica. Goutweed, Bishops weed, some honeysuckles, bittersweet, a native Ginger (Asarum) and much more.
Trees/Shrubs-
Sumac, Daphne retusa, Stranvaesia davidiana Amur Maple, A. tataricum. Sub with a native Stewartia. Or Smoke tree. Why plant the invasive Norway Maple (Sycamore Maple when you have so many native alternatives Acer rubrum English Holly! WHY! Plant the Tan Oak or anything else. The common and invasive and brittle Popular – substitute Alder, Birch Even nice trees such as the Pyrus calleryana is invading much of our East coast all the way to Texas. Substitute Amelanchier. Serviceberry. The native birds will appreciate it.
Chionanthus would be an equally beautiful alternative. So would Halesia (Silverbell), Cladrastis kentuckea (Yellow wood.)
English Hawthorn (Crataegus monogyna) I would not even sub with the American native, because of its thorns, but , Viburnums, Chionanthus might do.,
Black Locust – Sub with Kentucky Coffeetree Gymocladus. Palo Verde, Chilopsis etc.
European Mt. Ash, aucuparia, why not the Native Sorbus americana every bit as attractive.
Shrubs
Berberis thunbergii (Japanese Barberry) and others. Why not fothergilla (witch alder), Itea Virginia allspice Diervilla lonicera (Native bush honeysuckle/ can spread by seed), Clethra (summersweet.
Buddleja Sub with the native Cephalanthus (Button Bush), Clethra, Ceanothus
Caragana (Siberian Pea Shrub), sub with Flowering Currant, Leucophyllum
Cotoneaster (has invaded the entire Pacific Northwest .. Sub with Toyan Heteromeles arbutifolia, the wonderful arctostaphylos (manzanita) family Coralberry (Symphoricarpus)
Cytisus (Scotch Broom) and even worse Gorst. Sub Myrica pensylvanica or Myrica californica. Bayberries. (MORE on this! As colorful the now native Tree Lupine, Lupinus arboreus. (More on this … Victoria sub-specie.) Can spread by seeds.
Harder to find is Waxflower, Cliffbush, Jamesia Americana or our Pacific native Indian Plum (Oemleria) also spreads by seed.
Eleagnus angustifolia (Russian Olive) and Eleagnus umbellata Sub with our native alternative being Silverberry Eleagnus commutata, Buffloberry (Sheperdia argenteao Again any of the Bayberry’s would be better. Styrax americanus (Snowbell tree)
The beautiful Euonymus alata (Winged Euonymus) provides little to wildlife, the native and more invasive (be careful Aronia melanocarpa provides incredible fruit for human use as well as for birdlife. The Highbush Blueberry (Vaccinium corymbosum) is not so. Both give great fall color. Try these instead. If you just want a tough shrub use the fragrant sumuc, Rhus aromatica . The native Callicarpa (Beauty Berry) is another good alternative to many of these problem shrubs.
Even the dwarf Euonymus fortunei can be an invasive shrub. Arctostaphylos, manzanita, is a much better alternative and provides food for wildlife. If you have moister soils try any of the native Vacciniums. Vaccinum ovatum (Evergreen Huckleberry) and or the groundcover dwarf Bilberry.
Privet, (Ligustrum) I just hate these plants. Viburnum prunifolium would be a much more attractive hedge alternative and does better here to begin with. Osmanthus would be another choice of mine. Again the Myrica family or Ceanothus
Lonicera tatarica (Tartarian honeysuckle and many others. Why not use our own native Lonicera’s Lindera benaoin, Spicebush might be another alternative and it does take deep shade. Lonicera involucrate (Twinberry is a tough plant for mass plantings, but does spread.
Roses, such as R. rugosa, multiflora, witchuriana, and our own native Woods Rose.can become a pest. Even my Rosa glauca will spread by seedlings. The others are more of a problem as they sucker so. The Nootka Rose (R. nootkaensis) is much better mannered.
Tamarix, can be very invasive and has caused problems in many regions. The dessert willow, Chilopsis or the hybrid children Chitalpas are good alternatives.
Apache Plume or Fallugia might be another Xeric alternative.
Invasive Vines (Bittersweet) Celastrus orbiculatus
English Ivy – Just avoid. For the latter, if used as a groundcover. Sub. Salal, or Gaulnettia, Vancouverii, Mahonia nervosa. (all spread )
All Lonicera vines are invasive, that is their nature, but why not stick with the native forms. L. Canadensis, L. sempervirens – Why bring in the Japanese Hoeneysuckle? Lonicera japonica.
Plants
Bishop Weed is on the top of my list. At least substitute it with the equally invasive but native Asarum canadense. In this case the non-native Asarum europeum would be the preferred plant. Much nicer foliage and less rampant.
If you need a more Xeric alternative. (California Fuchsia) Zuaschneria californica is a must have, so is Penstemon pinifolius.
Euphoria (spurges) I try to stay away from all of them. Some can become VERY invasive.
Iris pseudacacorus (Yellow flag) Iris versicolor is a much better sub. Be very careful about all pond plants. Your water feature can invest another persons just from the ducks and herons that visit and carry your plants to another pond.
(Giant Knotweed) Polygonum cuspidatum Simply horrific. Hard to eradicate and of no food value to livestock. Next to ivy, brooms this is the most danger to our forests and landscape. Goatsbeard (Aruncus dioicus ) is a practical alternative, the other native alternative being Ocean Spray , also invasive)
Vinca minor and especially major (Periwinkle) They are colonizing much of the east coast and has also invaded WA. Forests. I have also seen them climb up to three feet choking out small shrubs. The native Barren Strawberry or the native Beach strawberry at least won’t choke out your plants. Waldsteinia, and Frageria chiloensis.
Houtinyia cordata
Grasses and Bamboo Too many to get into. Just be very careful about introducing seed bearing grasses. Stipa and Eragrostis would be at the top of my concerns. Phalaris and Blood grass can also run out of control.
Last you get into bug or slug magnets. Pesticides are going to become more and more expensive, so Hosta and Bergenia come to mind.
Let me know some of your own dirty dozen! For a quick effect in your garden, choose plants the nursery ahs labeled “fills in rapidly” or “easy spreader.” Beware of using invasive plants for ground covers unless they’re contained by a barrier such as a sidewalk (though such a border won’t stop invasives that spread by seed). Mint is notorious for spreading mainly by roots. Put it in a large container, either on your patio or on pot feet—not on bare ground. Some notorious, but commonly sold, invasive groundcovers and vines include goutweed or bishops weed, oriental bittersweet, snow on the mountain, English ivy and Japanese honeysuckle.
One mitigation: Replace those plants preferably with native alternatives.
No sooner are you thrilled that a certain plant is thriving than it pops up unexpectedly where you didn’t plant it. Then, before long, it has aggressively spread its way through your garden.
Some reproduce themselves by seed and replant themselves thanks to ants, birds and breezes &slugs.
Others spread aggressively by stolons (stems that creep along the soil surface, taking root wherever. Eventually such stoloniferous plants like asters can choke out or smother their neighbors. Pulling or hoeing them can become a half-year job as stolons left in the ground just re-sprout. The upside to these lovely invaders is that they make good soil binders for slopes, and grow where nothing else will. A good example being two lovely native groundcovers that I once sold. Vancouverii. Unfortunately, they are so invasive that they will grow through dwarf. Azaleas, Mugho Pine and can hardly be pulled out.
Runaways to watch out for—Illegal immigrants.
Some plants, cannot be safely controlled. Introduced species once cherished as rare and special become demons of the woodlands or waterways. Scotch broom (Cytisus scoparius),and purple loosestrife (Lythrum salicaria and related species) are examples. Check out The Federal Noxious Weed Program: www.aphis.usda.gov/ppq/weeds.
Individual states have similar websites. What is noxious in one place may not be a threat elsewhere. Simple matter of weather. David Douglas introduced Salal to Britain, we in return were given Gorst. Plant fanatics are also responsible, finding the native vegetation boring we import non local wildflowers. Our Olympic National forests, now have over ninety introduced wildflowers that choke out what we once treasured. Opium poppies being one of them! Which brings me to a few favorites.
Seed-spreaders
Forget-me-nots (Myosotis). these demure little blue flowers refuse to be forgotten, persisting for years as they self-sow. Easy to pull where you don’t want them.
Oxalis (Bermuda Buttercup). Sold in Nurseries and on eBay.
Welsh Poppy. Glorious yellow that fits right in with the above. I have been fighting those for years.
The common Viola (Viola tricolor) or even worse Viola labradorica.This petite flowered member of the viola family so loved relentlessly reseeds
Jupiter’s beard (Centranthus rubra). Self-sows prolifically thanks to small dandelion-like seeds.
Fireweed though beautiful will waft for acres in the wind, spreading your garden addition to neighbors a mile away.
Helleborus niger (Not invasive) but its cousin H. orientalis can be! Same for most of the species. HYBRIDS usually are less of a problem.!
Helleborus. Not only do their roots suck the nutrition from anything else, unless dead headed their seedlings will overwhelm most gardens.
Linaria purpurea A popular perennial, spreads like crazy. It is on my to kill list wherever I see it.
Same for Lady’s Mantle, five years ago I killed the last plant in someone’s garden. Her seedlings are still coming up. A special thank you to Ann Lovejoy! :-
Asarum – Wild gingers especially the N. American variety can throw out thousands of seeds that ants will spread all over your garden.
Veronica spicata and some other species If you love their flowers you will soon be seeing more of them. All over your garden.
Stolon-spreaders
Most bamboos! Unless you like working with a pickax and pry bar, try not to put them in your garden unless in containers.
(Physostegia virginiana). an obiediant plant it is not. It needs to be root pruned and cut them back all the time. I personally would prefer to do other things in my garden.
Ground cover asters. Hardy, small-flowered types sold simply choke the soil with stolons and send up new shoots everywhere. Curb them with deep six inch plastic edging. Today I pulled out two wheel barrows of them. They are toast. I will spend the entire winter watching the bare soil for new surfacings. This plot will not be plantable until next summer.
(Duchesnea indica). A trailing ground cover with wiry stems that invest small shrubs or small trees.This can be a rampant invader both for the stolons and the berries.
Matilija poppy (Romneya coulteri). A glorious six-foot-tall, gray green stems produce yellow-centered white flowers that resemble fried eggs A good plant on hillsides, keep it on the dry side or contain it like you would bamboo. In an irrigated garden it can surface six feet away from the original planting.
(Oenothera speciosa and others).In a rich environment it can become a pest.
(Vinca major). And Ivies These popular ground covers that root wherever they touch the ground Supposedly a ground cover, I have seen Vinca major choke out choice plants by climbing three feet up their trunks. Ivy of course can make a Chia planter out of your house or garage. In trees they can grow some forty feet high with their vines actually sending root hairs into the bark of the tree.
Sweet woodruff (Galium odoratum). Don’t even get me going on this attractive ground cover. Given a moist garden it can be a major problem.
Gorgeous but heartbreaking. Your runaway plants.
Some are even edible, but even my choppers can’t keep up with runaway mint or Oregano’s. Add Lemon Balm, one garden I work in smells like I’m working in an Italian restaurant, so many herbal seedlings have spread all over.
Phygelia capenses -- African Cape Fuchsia
Physalis franchetti(Chinese lanterns) Nursery’s sell these suckers for 19.95 in five gallon cans never telling the consumer how invasive they can be Lily of the valley. Is another one, wonderful but can get so thick you can barely get a shovel into it.
Rosa witchuriana – A beautiful ground cover rose. But have you ever tried weeding it? Also when it finds vertical support, hint your shrubs – it will climb all over them making pruning an adventure in band-aids and peroxide.
Their could be additional sub-sections.
Poisonous plants that children could eat the fruit of.
Laburnums etc.
Your own Runaway Plants List (Please add your own)
Many of the sedums
Chives and many of the onions.
The milky sapped family of Euphorbia.
Bishops weed – anything but holy
Plant debris or the problem-- what to do with it?
Many places no longer allow you to burn, so one has no other alternative but to shred and compost or to take it to the dump or recycler. The latter costs five dollars here.
One place I work for accumulates about that load EVERY week. That is a couple of hundred dollars every year. That is just a normal garden.
However, gardens with Miscanthus and other large plants end up having to dispose of those leaves. One large Miscanthus floridilus would nearly fill my pickup. I shall bring a sample or photo
A special negative Darwinian award to those nurseries that still sell Gorse and invasive oxalis! Who doesn't want a thorny shrub, up 6 ft. tall, with inch-long spines in their garden? This Western European native was introduced as food plant for sheep and as a "living fence" The minor drawbacks are:
This plant forms dense, impenetrable thickets that allow nothing else to grow
Seeds can remain viable in the soil for more than 30 years
Deep roots help this plant survive fires, and fire helps the seeds sprout
Just the type of plant to survive the new global warming landscape. Egad!
One last issue. Disease prone plants, Why introduce plants that are anthracnose or verticilleum wilt susceptible. Not all Maples or say Dogwoods are the same in this.
The Coral Bark Acer japonicum is a good example of this. I cannot think of one tree that I have seen that is not diseased. Others are much more resistant even in the japonicum family. Buy those instead. Acer griseum and the Korean Maple are two other alternatives.
The same holds true for the small and attractive Redtwig Dogwoods. Not only does it sucker but is prone to bacterial diseases. This could spread to your Maples or other Dogwoods.
Last caution. Plant Hardiness! Why purchase plants that are marginally hardy.
Insert link to my hardiness and climate zone blogs.
Too many nurseries are selling non-hardy plants and telling customers. “Oh, its hardy!”
Not so. The box stores are even worse. Definitely selling non-hardy plants. Do your own research before you shell out the bucks. The tags do not always tell the truth. Bring The Ceanothus tag. Hardy to ( –30 F.)
I wish to end with a positive note with a poem by Leigh Mercier
To plant a tree is
an act of faith in the earth,
An act of hope for the future
An act of humanity towards
Coming generations
Who will enjoy its fruits
After we shall be gone :
That is the garden and world, I wish to leave behind, and this Thursday's child has a long way to go on that score.
Something to think about.
© 2009 Herb Senft
