I'll start by saying I live in the woods and would hate to introduce an invasive species here. I so wanted to plant the Berberis thunbergii ' Rose Glow' and 'Lime Glow' but am now having second thoughts. Does anyone know if these are sterile or what conditions will encourage their spread? Are 'Royal Burgundy' and 'Crimson Pygmy' as likely or unlikely to spread? Thanks.
They are not sterile. To the best of my knowledge, cultivars of both European and Japanese Barberry have not been proven to be safe and certainly not sterile. Many are found to revert back to type when they escape and this has been documented.
Several neighbors have planted Japanese Barberry around me when it became really popular a few years ago. For the first time last year I found them popping up everywhere. That took all of 3 years to make it over to my property. We're not talking one or two of them volunteering but quite a few. I didn't plant them. I am on 5 acres and we have quite a few forest preserves in the area so I suspect I'll be seeing many more of them. My neighbors are also on larger lots so something is out there pollinating them and something is out there spreading them to me. These plants are a lot like Multiflora Rosa and Bradford Pear cultivars when they revert back to type as every single Japanese Barberry I found here had thorns and was not a rosy red yet the neighbors all seem to have planted one of the red cultivars that are being released by the boatloads.
Regarding sterile, Barberry cultivars are going to be in the same league as Purple Loosestrife and Bradford Pear cultivars and here's a cut and paste regarding what I wrote about PL in another thread.
Quoting:To add insult to injury, the Green Industry began developing and marketing varieties of PL sold as “sterile” in the mid 1900’s and we stood in line to buy them. Often marketed as "Guaranteed sterile", highly fertile cultivars of PL were introduced to even more landscapes across the US. What we weren’t told was that while most cultivars were in fact self-sterile, they were anything but incapable of reproducing sexually with another self-sterile cultivar. Self-sterile meaning that one plant could not reproduce alone. Symantics. The big problem was that we weren’t told that “Guaranteed Sterile” cultivars could produce large quantities of extremely viable seed when functioning as either male or female parents in cross breeding with other cultivars and species of loosestrife. And, wasps were such effective pollinators that the cultivars didn’t even need to be in close proximity to each other to set seed.
Barberries' thorns were what turned me off to gardening at a young age. We had large ones at the front of our house that had to be trimmed twice a year. You're right about the nastiness of the thorns on the species. So far, though, of the ones I "fondled" at the nurseries, the thorns seem quite soft. Maybe I'm just a lot tougher?? :)
No Connie, Barberry is not a turn off to hungry deer. Deer will even eat Downy Hawthorn. You should see the thorns on those. I’m surprised they don’t penetrate through the roofs of their mouths when they’re browsing. Basically, we collectively are starving out the deer with repeated introductions of non native plants that out compete plants that are indigenous. Increasingly, deer are forced to consume species that are not traditionally a part of their diet to survive.
Aside from that, here’s why this forum was created-
Quoting: Here's a forum for thoughtful and respectful discussion of invasive plants (whether native or exotic/alien species); their effect on your garden and the environment, and a place to seek help with identifying and eradicating or controlling such plants.
I want to add that I just bought a "Lena's Broom" which is apparently NOT invasive. It has won awards, one from the Royal Hort. Society in England. It's beautiful--just the orange-red color I was looking for. Just thought people would like to know about this plant because from what I've read, most people hate Scottish Broom.
Hey Connie, Lena's Broom = Cytisus x dallimorei 'Lena'. C.x dallimorei is a hybrid of C. scoparius. There are over 100 cultivars out there of Scotch Broom. The 'Lena' cultivar is every bit as much of a cause for concern as the straight species and is anything but well behaved. To say that Scotch Broom is a prolific and tenacious seeder would be an understatement. A mature plant can produce in excess of 10,000 seed per year and 40% of that seed will germinate immediately. Add to this that the seeds are hard coated and are able to survive well in excess of 50 years. This species was introduced to the US in the late 1800's as an ornamental and was later used to stabilize and control erosion on road sides. Bad move on our behalf given we know so much more about this plant than we did 50 years ago. The seed from road side plantings is transferred to uninfested areas by runoff. Have you ever heard the term "hybrid vigor"?
Scotch Broom is an extremely harmful invasive here on the continent of North American regardless of how the Royal Horticultural Society rates it and regardless of how many awards it has won throughout Europe. Scotch Broom, also referred to as English Broom, is indigenous to southern Europe and northern Africa including all of the British Isles. In its native range, the plant is under control as a result of predation by a host of insects. Sadly, these insects are indigenous to Europe and Africa and are not present here on the continent of North America which gives Scotch Broom "diplomatic immunity". http://tncweeds.ucdavis.edu/esadocs/cytiscop.html
This plant repeatedly escapes cultivation. When it does, it forms dense monocultures that prohibit to exclusion the regeneration of native species that our North American wildlife depend upon for survival. Additionally, these dense monocultures promote invasion by other exotic invasive species. Many of the infested areas are grasslands. This is big trouble for species of North American fauna that depend upon those areas to graze. We are losing thousands and thousands of acres of prime grasslands and hillsides. Unfortunately, the impenetrable monocultures this species can form also pose a fire hazard to humans. This plant is a threat to our forestry industry in that seedlings out compete desirable species being planted in areas that were recently logged because they grow much faster than our native hardwoods and evergreens.
These cultivars that are repeatedly being introduced are adding to our existing problems. The cultivars are not sterile. The plant reproduces both vegetatively as well as by seed. Scotch Broom is a major problem child plant because gardeners view it as a desirable ornamental and some nurseries continue to introduce cultivars that many view as not being a threat. Basically, the plant is very popular and appears to rise in popularity with each and every new cultivar introduction.
Quoting:How do you get rid of it?
*Pull out the entire plant, including roots. When the soil is moist, small plants can be pulled easily by hand. Winter and spring are good seasons to do this in California.
*Larger plants must be removed with a tool such as a Weed Wrench (tm). Be sure to remove the entire plant. Broken stems re-sprout and are much harder to remove for the next person. Plants can be left where pulled.
*Well planned prescribed burns in fall can further reduce the broom in infested grasslands:
*Dense infestations of broom and infestations in the shade remain too moist to carry fire and will require pulling and some time to dry prior to a successful burn.
*A head fire is likely to only burn the tops off of the broom, and the broom will survive.
*A slow, hot, backing fire kills most of the broom. Some plants are consumed outright, and others are scalded around the root collar, later dying from the injury. Use of a backing fire reduces the need for laborious manual removal.
*Prescribed burns in grass consume some broom seeds and break the seed coats of others, allowing pathogens to enter and kill the seeds. Still other seeds may be stimulated to germinate so that plants can be pulled out. Over time, regular prescribed burning may be expected to help deplete the pool of long-lived buried broom seed in the grasslands of the Bald Hills.
*Other benefits of burning the park's native grasslands are 1) control of invading trees and 2) rejuvenation of grassland plants by comsuming dead thatch. The newly burned grasslands attract elk because of their greater forage value.
What can you do to help?
*Spread the word about how this plant alters the natural scene, displacing native vegetation and degrading habitat for wildlife.
*Discourage people from planting Scotch broom or allowing it to grow undisturbed wherever they live and work. Since broom will have produced many, long-lived seeds, well before it reaches its ultimate size, people may be unaware of its potential as a weed in cultivation.
Thanks for the copious note! I'll try to locate the article I found...and admittedly it was from a nursery...so they would have a vested interest in SELLING the plant so of course they would say that this particular cultivar is not invasive. I believe the site was one that Dave's garden links us to, so that should make my search easier.
The plant is still in the pot, so there's still time!!
If only we all had a dollar for every plant that the nursery industry sold claiming it was sterile hence not invasive only to turn around based on scientific research to say "oops". Nurseries do make mistakes and some are honest mistakes. I just wish I didn't have to get rid of so many of the honest mistakes around me that keep popping up everywhere making my life miserable. For the record, Scotch Broom was an honest mistake in the beginning. We really had no clue as to the invasiveness of this species. It was pretty so we planted it. It showed promise for being able to control erosion so we planted it. I know it doesn't make it any easier when one chooses to take time out of one's busy life to exchange a plant for a more appropriate plant or when one unwittingly plants one of these species and ends up dealing with thousands of seedlings cropping up in natural areas as well as in perfectly manicured landscapes in future years. Been there done that and still doing it to this day. Really sorry about the 'Lena' Connie. I saw photos of your property and it is absolutely breathtaking. That place has unparalleled potential that people only dream of being able to work with and you own it and it's all yours. The thought of thousands of 'Lena' seedlings ending up in all those terraces you have year after year after year sort of got to me. Probably because I know how disappointing and frustrating it has been for me in the past when I planted some species that I had no idea would end up being so much trouble. I'd much rather be planting than weeding.
Please, I beg of you, reconsider planting that Scotch Broom - I promise you, you will be kicking yourself unto the tenth generation.
"Lena" is just as invasive as the other kinds, which friends of ours discovered, when they had to pull twenty zillion seedlings of it from their perennial beds, after the guy across the street from them planted them all along his property as a blooming hedge!
Hey 2zeus, Connie_W wrote this, "The plant is still in the pot, so there's still time!!" as well as "and admittedly it was from a nursery...so they would have a vested interest in SELLING the plant so of course they would say that this particular cultivar is not invasive" which means to me that she hadn't planted it and wasn't going to plant it because she believes it might be invasive although the nursery that sold it to her advertised the plant as not being invasive because it was a cultivar. I had to read what she wrote a few times too just to make sure but that's how I interpreted what she typed. I could be all wrong and if I am I hope Connie_W comes along and corrects me but I get the distinct impression Connie took her 'Lena" back for a refund or exchange.
So Scotch Broom is a problem child up in British Columbia too?
Unbelievably invasive, any area not forest will be colonised with the stuff, and the seeds seem able to live through anything that might kill slightly less cast-iron species - our poor friends had been assured by their neighbour - "No, no, this is the good kind!" - but it was amazing, every ten days or so, all spring, summer and into the fall, there would be a brand new crop of seedlings popping up in their perennial beds - sort of science-fictionish, eh?
My friend said she'd once read that after a nuclear holocaust, all that would survive would be certain forms of lichen, and cockroaches, and she wished to amend that very short list to include Scotch Broom, since it seemed completely impervious to any kind of control measures, chemical or otherwise.
Merry Christmas, and may you never have it colonising your garden!