VARIOUS TYPES OF SOIL CONDITIONS 183 



c. Fines: 



Actinidia (in variety) Lonicera japonica halliana 

 Silver Vine Japanese Honeysuckle 



Akebia qutnata Wisteria sinensis 

 Five-leaved Akebia Chinese Wisteria 



D. Trees Tolerant of Alkali Soils. Trees which are used 

 in this type of soil should be extremely vigorous in their habit of growth. 

 There is no special reason which can be set forth, from a physiological 

 standpoint as a guide, for selecting types of trees for these conditions. 

 The best and safest guide is the experience of others. — ^ 



{Black Alkali Soils — Sodium Carbonate): 



Koelreuteria paniculata 

 Varnish Tree 



{White Alkali Soils.) 



Ailanthus altissima Populus fremonti 



Tree of Heaven Western Cottonwood 



Eleagnus angustifolia Prunus davidiana 



Russian Olive David's Flowering Peach 



Gleditsia triacanthos Quercus lobata 



Honey Locust^ojily fairly tolerant) California White Oak 



Halimodendron halodendron Robinia pseudacacia 



Salt Tree Black Locust 



Platanus orientalis Ulmus (in variety) 



Oriental Plane Elm (only fairly tolerant) 

 Note: All varieties of Prunus will thrive in alkali soils if grafted on Prunus davidiana. 



E. Drought-resisting Plants. 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^lay loam soil actually containing more water. 



