The ability of some plants to resist drought lies not in their ability to extract more water than other plants from the same soil, as commonly supposed, but in their ability to send deep roots after water, or else to cut down the loss of moisture through their tops when soil moisture is scarce. All plants require about the same amount of available moisture in the soil around their roots, to keep them from wilting when growing in the same type of soil. But soil types vary in their ability to give up moisture, and the moisture content in a sandy soil can fall much lower than in a more retentive loam or clay soil before plants begin to wilt. This explains why plants adapted to drought conditions and growing in a sandy soil can survive a period of drought which will seriously injure other plants growing near by upon a clay loam soil actually containing more water.

All of the plants in the following list possess some characteristic which fits them for growing in dry places and should be chosen for planting in those dry spots upon embankments or on sandy soil where it is so hard to secure results with ordinary herbaceous perennials. While the plants included in this list are called drought-resisting plants they are not such plants as will withstand deliberate abuse through lack of cultivation or other normal care. The attempt to adapt plants of this kind to extreme soil conditions should not be made until a decision has been reached that no changes in soil conditions are practicable or justifiable.

Achillea filipendula

Oriental Yarrow Anchusa italica

Alkanet Anchusa mysotidiflora

Caucasian Alkanet

Arabis alpina Rock Cress

Arenaria montana

Sandwort Artemisia abrotanum

Southernwood Artemisia stelleriana

Beach Wormwood

Calandrinia umbellata Rock Purslane

Cerastium tomentosum Snow-in-Summer

Cheiranthus allioni

Hybrid Wallflower Dianthus deltoides

Maiden Pink Draba azoides

Aizoon-like Whitlow Grass

Echinops ritro Globe Thistle

Erigeron speciosus Oregon Fleabane

Eryngium amethystinum Amethyst Sea Holly

Euphorbia epithymoides

Yellow Wolf s-milk Glaucium flavum

Sea Poppy

Helianthemum (in variety) Frostweed

Liatris pycnostachya Blazing Star

Liatris scariosa

Large Button Snakeroot Linaria dalmatica

Dalmatian Toad-flax

Lupinus polyphyllus Perennial Lupin

Nepeta mussini Catmint

Oenothera fruticosa Sundrops

Oenothera speciosa

Missouri Evening Primrose

Papaver orientale Oriental Poppy

Platycodon grandiflorum Balloon Flower

Salvia azure a

Blue Salvia Salvia pratensis

Meadow Sage

Santolina chamaecyparisus Lavender Cotton

Sedum (in variety) Stonecrop

Sempervivum (in variety) Houseleeks

Stachys lanata

Wooly Woundwort Tunica saxifraga

Saxifrage-like Tunica

Verbascum olympicum Greek Mullein

Verbascum phoeniceum Purple Mullein

Verbascum phlomoides Clasping-leaved Mullein

Yucca (in variety) Adam's Needle