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Retail Newsletter from Bluestem Nursery

Nov 2003


So this would be a good time to discuss the winter care of ornamental grasses. I realize that it is rather late for some of you while for others you don't even have to worry about cold temperatures.

Ornamental Grasses in the Winter

Saccharum ravennae
Saccharum ravennae on a wet day in November

Jim suggests that the grass garden should not be "put to bed" (cut down and cleaned up) for the winter. To enjoy the 4-season interest that grasses can often supply, leave them standing. Depending on your climate some grasses will remain standing all winter. Wet snow is heavy and will cause some grasses to keel over.

Calamagrostis x acutiflora 'Karl Foerster' will remain green through the early frosts and the blossoms will remain upright until a heavy snowfall takes them down. If you want to cut any for dried arrangements be sure to get to them before that snowfall!

Miscanthus may remain upright all winter. Saccharum ravennae (we will be carrying it in the spring) is a very strong plant and is unlikely to be taken down by mere snow! Its 10-15' tall blossoms add wonderful interest to the winter garden.

Protecting Ornamental Grasses in the Winter

We sell grasses that are adapted to cold climates and should survive Zone 3 and 4 winters without any problem. However if your climate is severe and you want to ensure the survival of your grasses you may want to mulch some of them. Snow is an excellent mulch, but if you don't have it yet, then you need to use a substitute.

The very best is compost and/or shredded leaves (not from a Black Walnut tree). Both will feed the soil in the warm season and both are light and airy enough to allow oxygen to reach the soil. Neither will they become compacted, preventing oxygen from reaching the soil. Straw or hay is also very good. though there are seeds in hay.

Apply mulch to the moisture-loving grasses including sedges and rushes. For those of you who do not already know, sedges (Carex) and rushes (Juncus, Luzula) are not actually in the same family as grasses, though they are generally lumped under the term Ornamental Grasses.

One of the benefits of applying winter mulch is that the soil maintains a more constant temperature. The freezing at night and then thawing during the day can cause many small or shallow rooted plants to be heaved out of the soil. This leaves their root systems exposed and resulting in injury or death. Mulching reduces the chances of heaving.

Some of the smaller dryland grasses and the prairie grasses do not tolerate mulch close to their crowns. The constant moisture will cause rot. Dryland and prairie grasses include the Fescues, Koeleria, Andropogon, Panicum, Sorghastrum, Schizachyrium and Sporobolus.

When to Apply Mulch to Ornamental Grasses

Hmm, I see a nice cozy place to hunker down for the winter...

Mulches used to protect tender plants from the ravages of winter temperatures should be applied late in the fall after the ground has frozen but before the coldest temperatures arrive. Mice and other rodents are looking for a protected place to spend the winter. If you apply mulch before it freezes you have created a nice home for them! But if you wait to apply it you should prevent this problem as, hopefully, they will already have found some other place to nest. That said, we haven't found mice to be much of a problem for ornamental grasses.

Mulching too early will also contribute to the possibility of rot.

Hardiness of Grasses

From our website:

Cold temperatures are only one of may 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

If you would like to reprint any of this information, the answer is usually yes -- but please contact us first. We ask that you include a link to our website and mention the source of the information.

Lastly -

From a cynical gardener:

"Zone hardiness" -- The part of the country a plant is most likely to die in.


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