TREES 



.I/. I'm Azedaruch, var. itmbracHlifonnix, is found un- 

 satisfactory in the immediate vicinity of the coast; as a 

 sidewalk tree it is exceedingly untidy when losing its 

 leaves, and is also much subject to scale insects. 



Ai-ddd melanoxylon is generally debarred from the 

 Citrous belt, as a breeder of scale; when mature it is 

 said to suffer quickly from the effects of drought. In 

 the moister climate of the immediate vicinity of the 

 coast, near San Francisco, however, it proves entirely 

 satisfactory. 



Populus alba, Eobinia Pneudacacia and Ulmus 

 racemosa are exceedingly troublesome when used as 

 sidewalk trees on narrow streets; their surface roots 

 often break the cement 

 or asphalt sidewalks, 

 and the suckers come 

 up in the midst of 

 lawns several yards 

 away from the parent 

 tree. 



Ficus macrophylld 

 is another tree injuri- 

 ous to sidewalks. 



Eucalyptus Globu- 

 lus, and in fact almost 

 all species of the ge- 

 nus , are frequently 

 debarred by town ordi- 

 nance from growth 

 within 60 or even 70 

 feet of a sewer, on ac- 

 count of the remarka- 

 ble length and pene- 

 trating power of their 

 roots. 



Paiilownia imperi- 

 alis is sometimes ob- 

 jected to on account 

 of the somewhat un- 

 tidy appearance of the 

 persistent seed - pods, 

 which require no little 

 labor if all are to be 

 removed after flower- 

 ing. 



Grevillea robust a 

 has brittle wood and is 

 usually much broken in 

 heavy winds, but can 

 be used with satisfac- 

 tion if kept well cut 

 back. 



The species of Phoe- 

 nix and Jubffia should 

 be avoided on account 

 of their low, wide- 

 spreading habit, ex- 

 cept for avenues and 

 boulevards where there 

 is no sidewalk or where 

 there is from 20 to 80 

 feet space between 

 sidewalk and drive- 

 way. 



Ailanthus glandu- 

 losa has a bad reputa- 

 tion on account of its 



disagreeable odor, but as this is only found in the stami- 

 nate trees, it can be avoided by planting the pistillate 

 (fruit-bearing) trees only. 



8. Trees for Alkali Soils. There are many places in 

 those parts of the state that enjoy a high temperature 

 and low rainfall, where the percentage of alkali salts in 

 the soil is too great for the cultivation of most of our 

 ornamental trees, and where it is very important that 

 some shade-producing species be grown. 



A. Tolerant of strong "black" alkali (Sodium car- 

 bonate). 



The most alkali-tolerant tree of those yet tested is 

 Kwlreuteria paniculata, a small species 15 to 30 feet 

 high, with feathery, pinnate leaves and ornamental 

 yellow blossoms. 



TRKKS 



1847 



. Tolerant of medium alknli (<!,,', fhj ",//' 



Acacia melanoxylon, 



Ailaiitus glandulosa, 



Alliizzia lophantha, 



Casuarina cQiiisi-tifolia, 



Eucalyptus amygdalina. 

 var. angustifolia (appa- 

 rently the least SCUM 

 tiveof theEucalyjii- 



Eaealypta* rostrat., 



Eucalyptus sideroxylon, 



var. rosea, 

 Phoenix dactylifera, 

 Platanus oriental is. 

 Populus Fremonti, 

 Quercus lobata. 

 Robinia Pseudacacia. 

 AAA. Only fairly tolerant. 



Acer macrophylhun. 

 Acer Negundo, var. Ca!i- 

 fornicum, 



Cinnamomum Camphora, 



Gleditschia triacanthos, 



Ulmus spp. 



Washingtonia fllifera. 

 AAAA. Tested and 

 found unsuitable. 

 Most of those trees 

 of the humid regions, 

 e. g. , the eastern states 

 and N. Europe, which 

 have been tried on al- 

 kali soils, have been 

 found to suffer and to 

 remain dwarf and 

 stunted. This is par- 

 ticularly true of Liri- 

 odendron Tulipifera, 

 Quercus pedunculata 

 and species of Tilia. 



Since writing the 

 above, the following 

 additional information 

 on the alkali tolerance 

 of ornamental trees 

 has been brought to 

 light through the in- 

 vestigations of Dr. R. 

 H. Loughridge of the 

 Agricultural Experi- 

 ment Station at Berke- 

 ley, and has courte- 

 ously been placed at 

 my disposal. 



Total amount of salts 

 actually found in the 

 upper four feet of soil 

 in which the following 

 trees were growing, ex- 

 pressed in tons per 

 acre : Tong ^ apre in 



depth of 4 feet. 



Kcelreuteria pani- 

 cnlata 32 



Plntanus orientalis 21% 



Kucalyptus amyg- 

 dalina 20 



Kucalyptus angus- 

 tifolia 20 



Wnshingtonia(spe- 

 cies not stated).. 7% 



Phoenix dactylifera 5 



Cinnam o m u in 



Camphora 3% 



Jos. BURTT DAVY. 



2566. One of the gum trees Eucalyptus rostrata. 

 Eleven years planted; 86 feet high. California. 



IV. TREES FOR 

 SOUTHERN CALI- 

 FORNIA. Street Trees: 



Sterculia diversifolia, Australian Bottle Tree; Acacia 

 Melanoxylon, Blackwood Acacia; Cinnamomum Cam- 

 phora, Camphor Tree; Sterculia acerifolia, Australian 

 Flame Tree ; Eucalyptus robusta, Swamp Mahogany 

 Gum; Grevillea robusta, Silk Oak; Acacia deaUxitn, 

 Black Wattle; J-acaranda oralifolia ; Liyustrum Ja- 

 ponicum, Japan Privet; Pinus radiata, Monterey Pine. 

 The above are the best ten trees for street purposes, 

 but among these might be placed Cordyline australis 

 and C. indivisa, and several kinds of palms. One de- 

 ciduous tree is much used^JfeJm Azfderach, vnr. um- 

 braculiformis, the Umbrella Tree. Though less known 

 or used, Eucalyptus calopJiylla is by far a better street 

 or sidewalk tree than E. robnxta. Very few conifers 

 other than those noted do well in this climate. Any ex- 

 tension of the above list must be made almost entirely 



