September 8, 1906 



horticulture: 



263 



^^Burning*' of Conifers and Ever- 

 greens 



The Inirning or drying up of leaves commonlj seen 

 on conifers and other evergreens in spring is the result 

 of winter or spring injury. Trees afEeeted in tliis man- 

 ner show the burning generally on one side, w-hieh coin- 

 cides with the direction of some prevailing wind or 

 storm. This is a sun scorch, similar to that prevailing 

 on other trees, and occurs at a time when the ground 

 is frozen and drying winds prevail. This is usually 

 brought about by a sudden rise of temperature m the 

 early spring when the plants are in frozen ground, at 

 which time transpiration is active. Under these con- 

 ditions root absorption is limited, whether the soil is 

 moist or dry, and burning results. 



An arbor vitse hedge, which has been under our ob- 

 servation for some years, located on high ground with 

 a severe exposure, becomes burned more or less every 

 year. Frequently the burning is on the southeast side 

 and occasionally on the southwest, but more often on 

 the northwest, which is the direction of the prevailing 

 winds. 



There is a considerable amount of burning to conifers 

 and rhododendrons in this State, and not infrequently 

 this is so bad tliat the specimens are ruined. Much of 

 this injury occurred during the wdnter of 1904-5, on 

 evergreens located on private estates and in nurRCries, 

 and included various species of abies, buxus, chamascy- 

 paris, juniperus, picea, pseudotsuga, taxus, thuya, 

 retinospora and tsuga. 



Our native conifers are seldom injured in this man- 

 ner except when transplanted in some uncongenial 

 place, or where the environment is more or less modi- 

 fied. Swamp cedar burns frequently when taken from 

 the swamp and grown in ordinary soil, and the arbor 

 vitse, sparingly found as a native in this State, fre- 

 quently burns when planted on high or more or less 

 dry land with severe exposure. This holds good also 

 for hemlocks, and to a certain extent for pinc^ and 

 junipers. 



One of the conditions whicli induce burning is heavy 

 mulching. When plants are heavily mulched during 

 the spring, the frost is retained in the ground for a 

 longer period than is good for the plants, A pile of 

 chestnut burrs four inches high and two feet in diam- 

 eter when left on a lawn prevented the frost from com- 

 ing out from the ground for three weeks longer than 

 where there were no leaves, and the frost woukI un- 

 doubtedly remain longer if the leaves had not been re- 

 moved. No doubt much of the sun scorch on rhododen- 

 drons and conifers could be obviated if the mulching 

 were raked away from the plants during the early 

 spring, so as to allow the frost to come out of the 

 ground. 



The dry winds of spring cause considerable damage 

 to trees, especially to newly transplanted hemlock.-, etc. 

 There are situations where it is almost impossible to 



get hemlocks establislied. Young, undeveloped maple 

 leaves are very susceptible to sun scorch, as the strong, 

 dry winds cause tlie edges of the leaves to wilt and ulti- 

 mately turn brown and fall otf, A few years ago rock 

 maples all over Massachusetts showed a sun scorch on 

 the northwest side of the tree. This followed a warm, 

 bright, sunshiny day in May when the winds were 

 blowing at the rate of over 70 miles an hour. The oc- 

 currence in this case of sun scorch on the northwest side 

 of the tree was quite unprecedented and formed a good 

 illustration of the effects of severe winds on one side 

 of the trees. Some maples are scorched badly every 

 year for some unknown reason, although such might 

 occur from some peculiarity in the inherent, absorptive 

 capacity of the roots, or even from some peculiarity in 

 the constituents of the soil where such trees are grow- 



ing. 



Amherst, Mass. 



"Y ~^ ^^<C<f>tA> 



Growth of Cambium Tissue 



it is the general opinion that the cambium tissue in 

 trees starts to grow in the early spring, when the sap 

 is running, and continues until the fall of the leaves in 

 autumn. It is only vaguely mentioned in many books 

 on forestry and similar subjects. 



The late Prof. Thomas Meehan had an idea that the 

 actual gro\rth of this tissue was confined to a certain 

 period, and desiring actual data had the writer experi- 

 ment one season. 



A silver maple, two and one-half feet in diameter, 

 was selected and a wire placed around the trunk, 

 after having removed all the loose bark to prevent un- 

 natural swelling by rains. The wire was tightly fas- 

 tened in such a manner that the least swelling would 

 cause it to feed out, and in this way a record could be 

 taken. 



Though placed around in early Maj', no swelling oc- 

 curred nntil the 28th, when a slight change was no- 

 ticeable. In the course of a few days it had moved a 

 quarter of an inch. This continued increasing a little 

 until about the middle of June. During the rest of 

 June it did increase, but continued to make a regular 

 swelling all the time. 



On July 6th the wire recorded a fraction over an 

 inch and three-quarters. This growth had all occurred 

 during about five to six weeks. From July 6th until 

 the end of the season no further increase occurred. 



This record, though proof in this particular case 

 may differ in other varieties and the time may also not 

 correspond in other sections. It proves one fact, how- 

 ever, and that is that only at certain periods does the 

 cambium tissue swell. 



