On a warm sunny evening at Wolf Creek campground, botanist and plant ecologist Chris Marion has assembled a wide sampling of local plants for the interested group who's turned up. The evening is part of the Wild Discoveries summer program sponsored by Yukon's Department of Renewable Resources to help people better understand the natural world around them.

"What I'd like to show you tonight is how to put a name on those plants yourself using a very simple tool called a key," says Marion. "I'm going to let you in on a secret; when you have a key, and you know how to use it, you can identify anything -- whether it's plants, birds, or butterflies."

She begins by explaining that botanists give Latin names to plants to avoid confusion, because the same plant can have different common names in different areas, or may share the same common name with an unrelated plant.

Those two-word Latin names classify a plant according to its genus (for example, Pinus or pine) and species (for example, contorta, which means twisted or contorted). Pinus contorta is the Latin name of the lodgepole pine -- the only pine found in the Yukon -- which has twisted or contorted needles. Pines, along with spruce and fir, belong to the pine family, or Pinaceae.

Plants are grouped together in families because of shared characteristics, explains Marion. The rose family, for example -- which includes the raspberry and cinquefoil -- has flower parts that come in fives, or multiples of fives. Members of the cabbage family, by contrast, have plant parts that come in fours.

That brings us back to the use of a key, essentially a series of choices between plant characteristics that helps narrow down its possible identification.

"Most keys work by starting at a very general level and giving you two choices," explains Marion, handing out a key to a sampling of western boreal plants that she has developed.

"For example, is it a tree, or not a tree? If it's a tree, then is it a tree with broad leaves or a tree with needles? If it has needles that occur singly rather than in clusters, then, according to our key, it's white spruce."

Now that we have our key we are invited to practise with the plants Marion has assembled. Are the leaves simple or compound (that is, made up of many smaller leaflets)? Are they alternate or opposite (facing each other)? Are they toothed, serrated, lobed, or entire?

Are the veins in the leaf parallel, pinnate (one main vein with smaller branches) or palmate (like the palm and fingers of the hand)? Does the fruit occur as a single berry or in a pod?

Later, in the evening sunshine, we climb up a steep south-facing slope to examine plants adapted to very dry hot conditions. For example, sage has tiny hairs all over its leaves that create a boundary layer, or a layer of air that never moves, which helps prevent water loss.

Another plant, the three-toothed saxifrage, has leathery leaves which lessen water loss, while its epidermis, or skin, closes its pores to keep the water in.

Marion crouches down to show us juniper, the subject of her master's thesis, which can come in female individuals -- indicated by the presence of berries -- or male ones. Juniper must mature for 20 or 30 years before it can produce berries, and its yearly growth is clearly visible from the colour and size of the fruit.

On the same dry sunny slope we also find the purple trumpet-shaped blossoms of beardtongue, yellow locoweed, showy Jacob's-ladder, northern bedstraw, and cut-leaf anemone.

There are two species of Jacob's-ladder in the Yukon -- showy and tall -- but it is the showy that is found on dry sandy slopes. The skunklike smell of the bruised leaves has given this plant another common name: skunk-weed.

Northern bedstraw, surprisingly, is a member of the coffee family, and its fruits can be roasted and used as a coffee substitute.

The ability to distinguish between plants requires a little practice and patience, and the assistance of a good guide to plants. An excellent book on Yukon plants, just out in a new expanded edition, is Plants of Northern British Columbia, edited by MacKinnon, Pojar, and Coupe.

The book is organized by plant family and includes a photograph of each plant, a detailed description, and specific information such as uses and the origin of the name. It also includes numerous keys -- to trees, willows, and clubmosses among others -- to help users distinguish between often confusingly alike plants.

"Keys are the trick. Keys are the way to go," says Marion.