Barberies
Many varieties of the over 100 species of Berberis have been grown in North America. Interspecific hybrids and hybrids with Mahonia occur naturally, or have been produced by plant breeders. Restrictions on the number of kinds that can be grown in North America have been legislated by governments in the U.S.A. and Canada. Many Berberis act as alternate hosts for the very destructive black stem rust of wheat - not that wheat is a major crop in Nfld.
We often forget that many organisms can be pathogenic on a wide range of species. West Nile virus is a good example. Spread by mosquitoes, in which it appears harmless, West Nile virus causes diseases that may be lethal in birds, horses and humans. Similarly in the fungal world many species, especially rusts, live on two widely different plant species. The common rust fungus found on chuckly pear berries spends part of its life on either common juniper (Jumperis communis) or J. horizontalis.
For ease of enforcement, blanket controls on movement of plants of specific species, or of soil, were often introduced by governments. We are familiar with restrictions prohibiting the movement of plants and soil out of this Province to the mainland to prevent the spread of two potato pests, potato wart disease fungus and potato cyst (golden) nematode.
These blanket restrictions have now been modified in the case of Berberis species and varieties so that movement of plants is now possible. Nurseries are now able to sell a much wider range of plants, many of which would be quite hardy in St. John's.
Varieties that have been shown to be rust resistant can now be imported into Canada and moved freely between Provinces.
Of particular interest to us would be the rust-resistant deciduous varieties of Japanese barberry (Berberis thunbergii)
Aurea Nana;
'Monlers' Golden Nugget;
'Rose Glow; ' 'Gentry' Royal Burgundy;
'Bailone' Ruby Carousel.
The bright green foliage variety Tara' Emerald can also be imported. Unfortunately, the purple variety, atropurpurea, used as a hedge in some older gardens, is not on the list.
Except for the following species, all other species of Berberis and Mahonia are prohibited from entry into Canada.
Berberis with yellow (gold) or red purple foliage, for example:
B. buxifolia; B. candidula; B. chenautii; B. darwinii;
B x gladwynensis; B. insignis; B. julianae; B. linearifolia;
B. lologenesis; B. replicata; B. sargentiana; B. stenophylla;
B. taliensis; B. verruculosa;
Mahonia
M. aquifolium; M. atropurpurea; M. ealei; M. compacta;
M. dietyota; M. fortunei;M. lomariifolia; M. nervosa;
M. pinnata; M. piperiana; M. pumilia; M. repens; M. japonica.
Mahonia x Berberis (Mahoberberis)
M. aquicandidula; M. aquisargentia and M. miethkeana
All these species are non deciduous. Interestingly, despite considerable acreages of wheat in European countries, including England, prohibitions on the growing of Berberis species are not in place-maybe black stem rust is not a major problem because of the climate or other factors.
Descriptions of species and varieties can be found in Wyman's Gardening Encyclopedia and the RHS A-Z Encyclopedia of Garden Plants.
Kenneth G. Proudfoot