Living Roof Bench in Alberta, Canada

Carolyn Rallison (who also makes willow baskets, which are shown on our website) sent us this picture of her latest creation - a bench with a living roof. What a talented lady she is!!

I asked Carolyn if she had anything she would like to add:

"I built the bench of spruce limbs and poplar boards. The planting box is lined with pond liner, then a layer of coco mat for drainage. The soil is lean and sandy, as soil that is too rich makes lush and lanky growth. The whole structure is 7 feet tall, 6 feet wide, and 2 feet deep. Last summer was quite dry, so I had to keep it watered; but my intention is to have it "self-sufficient"."

"I first saw and read about green roofs on the internet, then bought a book to read about the subject. I know that there are sod roofs here in Alberta, but have never heard of one with perennials. So I really wanted to give one a try. I planted with assorted perennials and a few annuals for colour: Bearberry, blue flax, alpine poppies, Alpicola primulas, hens & chicks, alpine columbine, species tulips, squill, nemesia & dwarf phlox (annuals). "

"It is just coming through its first winter, so will soon see what has survived! If nothing else, I will just plant it to drought-tolerant annuals every year. I will report on survival rates of the different plants as soon as I know."

Carolyn Rallison
Last West Gardens
Bluffton, Alberta
Zone 3

Growing Grasses in Cold Climates

If you live in Zone 4 or colder, you would be wise to consider not just the hardiness of the grass, but also whether it can be expected to bloom in your short growing season.

Warm Season Grasses

Warm season grasses tend to have more spectacular blooms, but they also bloom late in the season. If you have a short growing season they may only be just starting to bloom when a hard frost hits. Miscanthus is finished once that happens. The blooms that have opened will remain, but the leaves turn beige and no more blooms are produced.

Here is a list of warm season grasses:

• Andropogon - Big bluestem
• Bouteloua - Blue gama
• Imperata - Japanese blood grass
• Miscanthus - Maiden grass
• Panicum - Switch grass
• Pennisetum - Fountain grass
• Saccharum - Hardy pampas grass
• Schizachyrium - Little bluestem
• Sorghastrum - Indian grass
• Sporobolus - Prairie dropseed and Alkali sacaton

In a climate where the soil does not warm up until mid May or later, there will not be any signs of life from warm season grasses before then. You will be emailing us and telling us your plant(s) have not survived the winter! But they are just waiting for the soil to warm up before they send any leaves up. They thrive in hot weather.

So the use of warm season grasses means that part of your garden will look very bare well into the spring. If you have a lot of garden space planted in warm season grasses, your garden will not show any greenery before late May or maybe even well into June. In a climate with a short growing season you may feel a little cheated. Pennisetum is especially suspenseful because it is the very last to grow, waiting until well into May or even June in a Zones 4 or 5.

Cool Season Grasses

The cool season grasses are much better suited to cold climate gardens. They are in a hurry to produce offspring, so they are up and growing and blooming as quickly as they can. They like the cool weather. So they bloom early, meaning that frost won't ruin the blossoms. Many have blossoms that hang around until winter.

Here is a list of cool season grasses:

• Achnatherum - Spear grass
• Alopecurus - Golden foxtail grass
• Arrhenatherum - Bulbous oat grass
• Calamagrostis - Feather reed grass
• Carex - technically not a grass, and many are evergreen
• Chasmanthium - Northern sea oats
• Deschampsia - Tufted hair grass
• Elymus - Wheat grass or Wild rye
• Festuca - Fescue
• Helictotrichon - Blue oat grass
• Juncus - technically not a grass, and may be evergreen
• Koeleria - Hair grass
• Luzula - technically not a grass, and will probably be evergreen
• Molinia - Moor grass
• Phalaris - Ribbon grass
• Poa - Blue meadow grass
• Sesleria - Moor grass
• Stipa - Feather grass (S. brachytricha, an exception, blooms in lt Aug or Sept)

Cool season grasses, for the most part, bloom in cool weather and shut down in the heat of summer. If they are not allowed to dry out too much they continue to look good, but they are usually done blooming. Seslerias heufleriana and caerulea bloom with the daffodils!

The four champion/pretty-well-fool-proof grasses in the cool season category are:

• Calamagrostis, particularly Karl Foerster, our top-selling grass
• Deschampsia - very hardy and Goldtau is absolutely lovely
• Festuca - many to choose from
• Helictotrichon - its evergreen in most climates, so that's a real bonus!

So in climates colder than Zone 3, we recommend only cool season grasses. In Zone 3 we suggest about 80% cool season and in Zone 4 about 60% cool season grasses.

On our website we state the blooming time for a grass. The earlier blooming warm season grasses are the ones to choose in a cool climate. For instance Panicum blooms early and is hardy, so it is a good choice.

Of course we understand a gardener's love of pushing the boundaries, so these are only suggestions. Even I do it. In my Zone 5 garden with early sunset of 5pm, I have a Pampas grass that I have nursed back from near death (because I transplanted it at the wrong time!). Last year it started to look happy, but didn't bloom. Maybe, just maybe it will this year....?