East of the 100th meridian in the United States ninety per cent, of the cases of hay fever are caused by the common ragweed {Ambrosia elatior) while in the Rocky Mountain and Pacific states the sage brush {Artemisia) replaces the ragweed as the most common hay fever weed. The so-called "rose fever" from which many people suffer each year is not caused by roses at all but by pollen from several different grasses. There are a number of commonly planted ornamental plants which possess hay-fever producing characteristics, as follows:

1. The flowers must be wind pollinated.

2. The flowers must be very numerous.

3. The flowers are generally unscented and not conspicuously coloured.

Some plants, like the goldenrods (Solidago), when used in large quantities in a room may prove irritant, but the pollen is not wind borne and thus it is not a true hay-fever plant. Dandelions have been known to cause irritation when children press the flowers too closely to their nostrils; but the dandelion is not a true hay-fever plant. The list of plants given below has been divided into two parts: (a) those plants which are active hay-fever producers, and (b) those which are mild. None of these plants should be used about hospitals, nor where hay-fever sufferers are likely to come in contact with them.

a. Active:

Artemisia frigida Wormwood Sage

Aster ericoides White Heath Aster

Aster novae-angliae Hardy Garden Aster

Carya ovata Hickory

Centaurea cyanus Old-fashioned Cornflower

Chrysanthemum leucanthemum Ox-eye Daisy

Dianthus chinensis Chinese Pink

Miscanihus compactus Plume Grass

Eupatorium sessifolium Upland Grass

Helianthus angustifolius Hardy Sun-flower

Ipomoea purpurea Common Morning Glory

Iva ciliata

Marsh Elder Juglans nigra

Black Walnut

Juniperus virginiana Red Cedar

Poa annua

Annual Meadow Grass

Populus detoides Southern Cottonwood

Quercus nigra Water Oak

Solidago canadensis Goldenrod

Spiraea vanhouttei

Van Houtte's Bridal Wreath Vernonia noveboracencis

Ironweed b. Mild:

Acer rubrum

Red Maple Acer rubrum drummondi

Drummond's Maple

Lonicera flava

Yellow Honeysuckle Rhus typhina

Staghorn Sumac

Salix nigra Black Willow