(New links added to this post as of May 2020).

Alberta’s long-awaited reworking of the Weed Control Act came into effect on 16 June of this year, and while typical, the lack of fanfare and media coverage pretty much ensures that the average gardener has no clue idea that she may be harbouring newly-prohibited plants in her own yard.  Trouble is, most people think of “invasives” and “weeds” as the same thing, and while that is in part, accurate (in the sense that most weeds are invasive, meaning that they spread a trifle too vigorously), certain plants that are valued as ornamentals are also very invasive.   The Alberta Invasive Plant Council explains it very nicely:  “Invasive alien plants are species introduced deliberately or unintentionally outside of their natural habitats.  In this new environment, free from their natural ‘enemies,’ non-native plants have an advantage that allows them to out-compete native plants and agricultural crops for space, moisture and nutrients.”  The potential damage caused by invasives is actually even greater, as they threaten watersheds as well as the diversity of both (native) plant and animals species in wild ecosystems.   Thus, it is necessary to eradicate any weeds and ornamentals that pose certain danger, and the Act gives the government the legal teeth to do so.

There are now two different types of “noxious” weeds listed in the Act, “PROHIBITED NOXIOUS” and “NOXIOUS.”  (The former Act had three categories and was a tad more vague).  Prohibited plants are illegal and must be eradicated if present in gardens, on farmland, or in any landscape in Alberta.  You cannot purchase prohibited plants at garden centres and nurseries, and you must not obtain cuttings or plants or seeds from outside of the province (that means your friend in Nova Scotia can’t send them to you, and you’re not allowed to order them from a seed catalogue in Ontario, for example).  Before mass panic sets in, however, ensure that you’re aware of exactly which species are on the list – some of these plants have very popular cultivars that are readily available in garden centers, and these cultivars are NOT on the list.  (For instance, just because common barberry is on the list as prohibited, that doesn’t mean that Rose Glow Barberry, or Emerald Carousel Barberry, or Cherry Bomb Barberry are prohibited.  They’re not).  Obtain a copy of the 2010 Alberta Weed Control Act and study the botanical names (not the common names – they can be localized and misunderstood).   A partial list of prohibited noxious weeds includes:  St. John’s wort, Purple loosestrife, Tamarix, Common buckthorn, Garlic mustard, and most knapweeds and knotweeds.  (Whew!  Thank goodness that St. John’s wort I planted a few years back kicked the bucket after only one winter!  I had purchased it from a B.C. grower at a local garden centre, which will no longer be possible).

Noxious weeds are a different matter – they are not “prohibited,” so they’re presumably not considered as highly on the nasty scale as the aforementioned plants, but they should not be purchased or planted or transplanted from other sites, and existing plantings should be removed, if possible.   On the list:  the yellow clematis I so strongly defended all those years ago when a customer in the garden centre I was employed in declared it an abominable weed.  (She was apparently clairvoyant).  We were allowed to carry Clematis tangutica back then, however, and to be fair, the plant label was clear in its declaration of the plant’s aggression.  I still think it is absolutely gorgeous when in full bloom!  Also considered noxious:  Himalayan balsam (orchid), oxeye daisy, common baby’s breath, common tansy, creeping bellflower (how many of you are growing this one?  I bet it’s a fair number), dame’s rocket, and leafy spurge. Russian olive, Queen Anne’s lace, and Maltese cross (again, a very popular ornamental) are not on the list yet, but there is a good possibility future incarnations of the Act will include them.  As well, those wildflower mixes you buy in packets and large tubs and mats in the spring to “naturalize” the garden are highly suspect, as many of those so called “wild” flowers are seriously non-native, and may very well be noxious.  Instead of buying the mixes, buy separate packets containing clearly-indicated LEGAL and non-invasive species – you can always mix up the packets together before planting, if you prefer.  Another plant that is being considered for future inclusion on the noxious list is caragana (not the weeping or hybridized cultivars you can purchase in nurseries, but the common species) – this may impact Prairie gardeners, as caraganas are employed in huge numbers as shelterbelt plants.  It will be interesting to follow their status in years to come.

So, Albertans, roll up your sleeves and start weeding!  (And if you’re not from this province, seek out your own Act and do your part).

Links to:

The Alberta Weed Control Act

Alberta Invasive Species Council