Treeless landscapes characterize the northern part of the mainland and the entire Arctic Archipelago comprising nearly one-third of the total area. The severe climate with its long, excessively cold winter and its low rainfall have already been described. Another important factor is the perpetually frozen subsoil, above which the ground thaws out to a depth of 2 or 3 feet annually.
The word tundra is derived from the Finnish "tundren" meaning a treeless rolling plain. Treelessness was formerly thought to be due entirely to low temperatures but various investigators in recent years have indicated that lack of moisture is just as important. Some of the "barren ground" therefore may be regarded as Arctic steppe. Porsild states "So light indeed is the rainfall during the growing season that, were it not for the fact that the ground remains perpetually frozen a few inches below the surface thus preventing the surface water from penetrating to levels beyond the reach of the roots, most of the Arctic zone would be a lifeless desert." 1. On the other hand our climatic maps show that the extreme eastern part of the Arctic has an excess of moisture. It is evident then that there is no simple floral association that may be said to characterize the tundra. Rather it is a complex mosaic of associations.
The vegetation of drift covered plains consists of prairie and heath. In the Arctic prairies, grasses and sedges comprise the bulk of the cover forming a short dense sward. Arctic poppy, dandelion, Arctic wallflower and other flowering plants are found. Such meadows are very extensive in central Keewatin and along the Arctic coast. On the upland north of Great Bear Lake and in other places as well there are wide areas of Arctic heath. Here are found ground birch (Betula glandulosa), Labrador tea (Ledum decumbens), white heather (Cassiope tetragona), bilberry (Vaccinium uliginosum var. alpinum), Alpine cranberry (V. Vitis-Idaea), cotton grass (Eriophorum vaginatum), Arctic lupine (Lupinus nootkatensis), loco-weed (Oxytropis) and rhododendron (Rhododendron lapponicum).
The rocky areas have a much more scattered plant cover including rock lichen (Gyrophora), arctic ferns (Woodsia glabella, W. ilvensis and Dryopteris fragrans), saxifrages, crowberry (Empetrurn) and vetch (Astragalus alpinus). The outstanding characteristics of arctic plants are their low cushion-like growth forms and the amazing rapidity with which they go through the annual cycle of growth. The small purple flowered saxifrage (Saxifraga oppositifolia); the yellow whitlow grass (Draba alpina) and the yellow Iceland poppy are able to mature seed within a month of commencing growth. However, very few plants are annuals and most of them have some vegetative means of reproduction, such as overwintering buds, and are not totally dependent upon seed production.