Bluestem Nurseryhardy field grown plants

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Ornamental grasses at Bluestem Nursery


Hardiness Information

From our newsletters:

The Zone number indicates the coldest zone in which we believe the plant will survive. This is based on USDA specifications, our own and customer's experience with the plant and/or data regarding where the plant is native to. The lower the number, the colder the zone. So if a plant is hardy to Zone 3, it will grow in very cold climates!

If you are not sure of the zone that you are located in, please refer to the following:


Hardiness Zone Map - Canada - 2000 data
Note: you need to click on the Legend link on the left, or order to make sense of this. Easy to zoom in for the complicated Zone situation in BC


Hardiness Zone Map - USA

The zones actually blend into each other, and within each zone there are microclimates that can be colder or milder than the surrounding area. Use the map Zone information only as a guide.

Cold temperatures are only one of many factors that influence the hardiness of grasses. Other factors include:

  • how long the cold lasts - cell damage from freezing can repair, except when the cold is prolonged
  • the snow cover - snow is generally good for insulation, but if it is icy oxygen is prevented from reaching the soil
  • how moist the ground is - many grasses suffer more from too much winter moisture than from winter cold
  • summer temperatures - if there is plenty of heat the plant will store more sugars and therefore have a greater resistance to stress
  • wind
  • microclimates - low places are frost pockets, increasing the exposure to cold temperatures
  • freeze-thaw cycles - these can create the icy snow conditons, or can trick plants into breaking dormancy too early

With so many variables we think it is more useful to talk about our growing conditions (see the write-up with each individual plant). We can usually count on having Zone 4/5 winters for our hardy field grown plants, but with so many "record breakers" lately it is hard to know what to expect. One advantage is that grasses and willows tend to survive, when many other plants succumb.

Miscanthus purpurascens
Miscanthus purpurascens does
well in cold climates

That said, we would also like you to know that as a nursery we feel a need to be cautious in regards to the Zone listing. Through feedback from our customers we are aware that many grasses have survived and indeed thrived in climates much colder than we are listing. Here is an example:

"I've actually grown Chasmanthium latifolium successfully in two Winnipeg gardens, one north facing, the other south facing. It did better in my north-facing garden, I think because it was in a raised bed and had good drainage .... it has survived a very cold winter here - last year was the coldest winter in 80 years.... The two others I've used a lot are the blue fescue.... and Helictotrichon sempervirens, which is listed as zone five...."
E. Jones, Winnipeg, Manitoba, Canada, Zone 3

"Miscanthus purpurascens does fine here too, as does all Calamagrostis (Foerster and Overdam), ribbon grass and fescues."
Customer in Saskatoon. SK, Canada, Zone 2

You may be able to create microclimates that allow you to grow more than the zone listed or you may find that seemingly inexplicably, a plant has died when it should have been fine in your zone. The zones are a good starting point, but you still need to determine for yourself what will and won't work in your garden.

How to push the zones:

  • give adequate care during the growing season
    • water as required
  • protect for 3 to 4 seasons and the chances of the plant surviving without further protection are greatly increased
  • mulch heavily
    • be sure the plant is dry when mulch is applied, or it may rot
  • create a microclimate
    • plant near a brick or stone wall, particularly on the south side
    • avoid planting in low areas
    • screen from from wind
    • avoid planting where water collects in the winter
  • don't cut down in the fall

And most important - a healthy plant has a much better chance of surviving the winter than does a plant whose needs have been neglected.

  • give the plant the amount of water it requires during the spring, summer and fall.- don't let it get too dry and don't drown it
  • make sure it isn't crowded or shaded and therefore not receiving enough light

Any more suggestions? E-mail us!

The University of Minnesota did a winter hardiness study of ornamental grasses. The results are available online and in their wonderful book Ornamental Grasses for Cold Climates.