Page 6 



c. Fertility and maiuiring practises: 



d. Cultivation and cover crops. 



In a perfectly dormant tree, the order in 

 which different tree structures are killed, 

 depending upon the degree of cold and 

 other factors is as follows: 



1. A ring of wood next to the pith. 



2. The pith. (These two are mostly 

 found on twigs and small branches). 



3. The youngest layer of wood next the 

 cambium. 



4. The woody cylinder. (Injury to the 

 wood can be definitely detected by the dis- 

 coloration produced even by slight injury 

 that does not affect the vitality of the tree. 

 The degree of this discoloration can, in 

 most cases, be taken as an index of the 

 severity of the injury). 



5. The fleshy bark. (This is often 

 merely flecked or streaked, but in severe 

 cases the entire bark finally dies and turns 

 brown ) . 



6. The cambium. 



The degree of killing of fruit and leaf 

 buds depends upon the hardiness of the 

 buds and the species and variety of tree. 

 Fruit buds of most species, when fully dor-- 

 mant, are about as hardy as the woody 

 cylinder and generally die only when the 

 trees are quite badly blackened in the 

 wood. But in the case of the plum, for 

 instance, the fruit-buds may be killed by 

 winter cold while the wood shows no in- 

 jury. With the apple, on the other hand, 

 the wood is severely injured before the 

 buds are affected or the twigs are killed 

 back. 



' I ^HF cambium is one of the last struc- 

 -■- tures to die in severe freezing weather, 

 provided it is thoroughly dormant. But just 

 under the cambium is the newest formed 

 part of the wood, a ring of varying width. 

 This is much more easily killed, and, 

 showing as a black line in cross section, it 

 is frequently mistaken for the cambium. 

 However, when the least bit of growth has 

 taken place on the cambium, or if.it is not 

 thoroughly dormant, it is likely to be the 

 first thing killed. Likewise, in the case of 

 fruit-buds, if they are the least bit swelled 

 they are most susceptible to cold and very 

 easily killed. Fruit-buds are most sensitive 

 when swelled, but the cambium may be 

 killed or lifted from the wood either from 

 the fact that it has not ripened (in event of 

 fall freezing), or that it has swollen from 

 mild winter weather, or spring growth. If 

 the bark is lifted from the wood this does 

 not necessarily mean that the cambium has 

 been killed in all cases, though this may be 

 true. There is always a chance for the 

 cambium to be alive if the bark is alive. 

 After a few mild days this can readily be 

 determined by examination. But in your 

 examination make . perpendicular cuts 

 through the bark, not at right angles to the 

 direction of growth. A narrow strip of bark 

 with underlying wood attached, cut in the 

 direction of growth of the part examined 

 iffords ample opportunity for diagnosis and 



BETTER FRUIT 



leaves a wound that does not impair the 

 recovery of the tree if it has the least 

 chance. In case of lifted bark the cambium 

 frequently splits, part remaining attached 

 to the wood and part to the bark. In such 

 cases where the bark remains alive, wrap- 

 ping or bandaging the trees or nailing the 

 bark to the wood will be of considerable 

 benefit by holding it in place and allowing 

 it to become attached again. 



The daily minimum preceding the 

 coldest spell of two years ago varied from 

 32 degrees to 10 degrees above zero in 

 those sections west of the Cascades, but east 

 of the mountains zero temperatures were 



This seedling Franquette walnut tree at 

 McMinnville was saved by stump graft- 

 ing after being killed to snow-line. 



experienced before December 1, and up to 

 the time of the extreme drop. The drop 

 to this minimum was therefore more sudden 

 and generally greater in the west side 

 districts than in Eastern Washington. The 

 suddenness of the drop in itself probably 

 was of some moment in the production of 

 injury, since trees in a particular condition 

 of dormancy require particular temperature 

 to adversely affect them. 



It is quite easy to see why the trees in 

 the milder Coast climate were much more 

 severely affected than those growing east of 

 the mountains. In the latter case they had 

 become inured to greater extreme of tem- 

 perature since they were planted and they 

 were subjected to a gradually increasing 

 degree of cold and had a chance to develop 

 a gradually increasing degree of dormancy, 

 whereas, in the case of trees growing on 



December, 1021 



low bottom lands in the milder climate, 

 with its fall rains, the fact of their in- 

 complete dormancy is hardly open to 

 question. 



Growers stated that the trees dropped 

 their foliage much earlier than usual and 

 that, at the time of the freeze, were as dor- 

 mant as they ever get. But that the trees 

 were really dormant does not appear prob- 

 able, in view of the character of the injury 

 developed. The soil for the district is quite 

 uniform, a sandy loam, sandy subsoil. In 

 general clean intensive cultivation was prac- 

 tised. The topography of the land is very 

 level, hence the air drainage is poor. 



LET us consider some individual orchards 

 as I examined them in 1920 to illus- 

 trate the effects of the freeze and factors 

 influencing the treatment and recovery of 

 the trees: 



Italian prunes, 30 years old — When 

 visited in February no injury was found 

 below a point 10 inches from the ground, 

 but from this distance upward the bark was 

 discolored and rather dry and spongy, the 

 injury extending outward on the main 

 branches. The sapwood was not affected, 

 but the cambium was discolored and ap- 

 peared to be dead. The bark was frequently 

 loosening from the wood. One-year-old 

 wood was not affected and only about 25 

 per cent of the fruit-buds were killed. 

 Old devitalized fruit spurs, so com- 

 mon in the average mature Italian prune 

 tree of this region, the long slender spurs 

 that hang pendant, were frequently killed, 

 being frozen through at the base. In July, 

 when this orchard was again visited, many 

 dead and dying branches were found. A 

 part of it had been pruned during the 

 latter part of June, removing all branches 

 that looked "sick" at the time, but inside 

 of ten days other branches on these same 

 trees had reached the same condition. 

 Considerable barnyard manure had been 

 used on this orchard in recent years and the 

 injury was worse in the section that received 

 manure containing sawdust and shavings 

 as litter. This material would tend toward 

 an acid soil condition and it may be that 

 trees growing on such soil are less hardy, 

 but further study is needed to verify this 

 point. 



Cherries, 9-year-old Lamberts, Bings, 

 and Royal Anns — In February most of the 

 trees showed the bark loosening on the 

 south side above snow line and the cam- 

 bium region was discolored. Lambert fruit- 

 buds were dead, likewise most of the 

 Bings, but the Ro}al Anns appeared to be 

 more hady and only about 50 per cent 

 of the buds were dead. By July the bark 

 on the south side of the bodies had burst 

 and peeled back from the wood. On the 

 under side of this loose bark, however, had 

 formed a most remarkable callous growth, 

 often fully an inch thick. Had 

 this bark been nailed back in place it would 

 soon have become atatched again and the 

 (Continued on fage 18) 



