Shrubs

WorryFree Barberries … and Why They May Never Be Sold in Canada

For years now, I’ve been following the development of sterile barberries, that is, varieties of Japanese barberry (Berberis thunbergii) that produce no fertile seed. 

Why is this important? Because this popular shrub has escaped from culture in many parts of the Northeastern United States and become invasive, taking over vast tracts of fields and open forest where it forms much of the undergrowth. This is thanks to the seeds contained in its berries that are ingested by birds and spread everywhere in their droppings. 

Here, Japanese barberry has entirely taken over the forest floor, leaving little room for native plants. Photo: Leslie_J. Mehrhoff, University of Connecticut, Bugwood.org

I’ve actually visited such a forest in a nature reserve in New England and was amazed at how abundant Japanese barberry was. It was quite obvious that it was indeed taking over and likely replacing native plants, including food plants for many native animals.

The situation is so serious that Japanese barberries, although long a staple in landscaping, have been banned from sale in Massachusetts and other states are considering following suit.

Sterile Barberries to the Rescue

Crimson Cutie barberry. Photo: SynRG, LLC

Dr. Mark Brand of the University of Connecticut has been working on developing sterile barberries for over 15 years now. It’s just not a question of finding a sterile plant, but of testing it, not in only in a greenhouse, but in the field, for both ornamental value and total sterility. Any barberry worth releasing as sterile simply must neverproduce fertile seeds. 

Barberry fruits with fertile seeds (left) and aborted seeds (right). The latter are sterile and will produce no offspring. Photo: Dr. Mark Brand, Dept. of Plant Science and Landscape Architecture, University of Connecticut

But Dr. Brand has indeed found totally sterile clones; in fact, many of them. They produce berries just like any other barberry, but the seed inside aborts at an early stage and so can never germinate.

And the best are now being released in the WorryFree™ series. So far, the series is composed of Crimson Cutie™ (‘UCONNBTCP4N’), a dwarf mounding variety with deep purple leaves, already available in many areas, and Lemon Glow™ ‘UCONNBTB048’, likewise a dwarf mounding variety with brilliant chartreuse-yellow leaves, just coming out now. Others are under study.

WorryFree barberries can be used in the landscape without fear their seedlings will escape into the wild. They are such outstanding garden plants—attractive and easy to grow—that they have already been adopted by the Hand Picked For You Plants® plant certification program, designed to recommend only the very best garden plants to home gardeners. And even states have become involved: Crimson Cutie has been approved for sale in New York State by the Department of Environmental Conservation and other environmental associations are considering such an approval.

But Never in Canada

WorryFree Lemon Glow barberry. Photo: SynRG, LLC

It is, however, unlikely that WorryFree barberries will ever be commercially available in Canada. 

Wheat rust, carried by the common barberry (Berbris vulgaris), but not the Japanese barberry (Berbris thunbergii), is a serious disease of wheat. Photo: http://www.ars.usda.gov

That’s because, in 1966, Agriculture Canada banned the sale and distribution of barberries. This ban was due to a wheat disease, black stem wheat rust (Puccinia graminis), that was known to use certain barberries as an alternate host. In other words, the disease necessarily spends part of its life cycle on a barberry plant before moving to nearby fields of wheat. For that reason, all barberries were banned to protect Canada’s wheat crop.

In the years that followed the ban, it was discovered that not all barberries are hosts of wheat rust. In fact, the main culprit is the common barberry (B. vulgaris). The Japanese barberry (B. thunbergii) does not carry the disease. Bans on Japanese barberry were therefore lifted elsewhere in the world, but remain in effect in Canada.

However, after 35 years of pressure from plant nurseries, in 2001 Agriculture Canada finally relented and allowed the sale of 11 cultivars of Japanese barberry that were individually tested and found to be rust-free. They quickly became popular garden shrubs and indeed are already staples in Canadian landscaping.

Barberries ‘Helmond Pillar’ and Sunjoy Gold Pillar™ are not available in Canada and probably never will be. Photo: springmeadownursery.com

However, although new and interesting disease-free barberry cultivars (think of the beautiful pillar-shaped varieties ‘Helmond Pillar’, with purple leaves, and Sunjoy Gold Pillar™ (‘Maria’), with golden ones) have since been released, no other barberry has ever been approved for sale in Canada, nor, from what I hear, does Agriculture Canada ever intend to change things. Given the reluctance with which Agriculture Canada has responded in the past to matters concerning ornamental plants, obviously very much the least of its concerns, I don’t expect wider barberry approval will occur in Canada within my lifetime.

Admittedly, the problem may be less serious in Canada than in the United States, as, according to my personal observation, Japanese barberries simply don’t seem to self-sow in cold climates. Thus, although the adult shrubs may thrive in very cold conditions (up to zone 3), there appear to be few seedlings below zone 6 and certainly none in zone 4 where I live. Thus, many Canadian gardeners might not need to be too concerned for now (although with global warming looming…!). Still, southern British Columbia, southern Ontario and milder parts of Nova Scotia are prime candidates for Japanese barberry invasion and I know that the Ontario Invasive Plant Council is very concerned about the species.

So, as the rest of North America switches to sterile barberries for environmental reasons, stodgy old, misguided regulations will likely prevent Canada from following suit. 

Environmental damage due to government inaction? Gee whiz, there’s really nothing new under the sun!

Larry Hodgson is one of Canada’s best-known garden communicators. After studies at the University of Toronto and Laval University where he obtained his B.A. in modern languages in 1978, he succeeded in combining his language skills with his passion for gardening in a novel career as a garden writer and lecturer. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He is a regular contributor to and horticultural consultant for Fleurs, Plantes, Jardins garden magazine and has written for many other garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening, Rebecca’s Garden and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 50 other titles in English and French. He can be seen in Quebec on French-language television and was notably a regular collaborator for 7 years on the TV shows Fleurs et Jardins and Salut Bonjour Weekend. He is the President of the Garden Writers Association Foundation and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. An avid proponent of garden tourism, he has lead garden tours throughout Canada and to the gardens of over 30 countries over the last 30 years. He presently resides in Quebec City, Quebec.

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