Page 14 



BETTER FRUIT 



April. ip20 



dissolve in water is but sliglitly afTccted 

 by the substances that are already in 

 solution. This allows the possibility 

 of a very concentrated solution, and 

 each of these substances has its influ- 

 ence in lowering the freezing point of 

 the water largely independent of the 

 others. For these reasons, rather a 

 low freezing point of a solution is pos- 

 sible. A very concentrated juice, there- 

 fore, in the buds would be expected to 

 freeze at a fairly low temperature. In 

 spite of this, however, the unusual hardi- 

 ness of some buds to freezing is really 

 surprising. The difference in sensitive- 

 ness to cold of different buds on the 

 same branch and of the same buds at 

 different stages of development may be 

 in part due to the difference in quality 

 and concentration of the cell sap. 



When li(iuids are cooled to their 

 freezing points, if there be none of the 

 solid material present, they rarely 

 freeze. They may be cooled further 

 several degrees and kept for days with- 

 out solidification taking place. The in- 

 troduction of as small an amount of the 

 solid as one-hundred-thousandth part 

 of a milligram is sufhcient to cause 

 freezing to commence. Enough solid 

 will now separate out to raise the 

 temperature of the whole to the melting 

 point. The temperature now remains 

 constant, and at the melting point until 

 all of the liquid has become solid, the 

 heat that is being lost by radiation be- 

 ing supplied by the heat that is always 

 evolved when liquids solidify. In su- 

 perfused liquids that have not been in- 

 occulated, crystalline nuceli make their 

 appearance spontaneously at different 

 points in the liquid and then begin to 

 grow. The chance of these nuclei ap- 

 pearing increases with the quantity of 

 liquid present and it has been found 

 experimentally that liquids may be 

 cooled far below their freezing points 

 and maintained at these low tempera- 

 tures for long times when they are kept 

 in capillary tubes. In these tubes the 

 rate at which these nuclei form and 

 grow is sufTiciently slow to be mea- 

 sured. The rate of growth is approxi- 

 mately proportional to the degree of 

 superfusion when that degree is not 

 very great and the number of nuclei 

 formed in a given volume in a given 

 time at first increases with the degree 

 of superfusion, but afterwards reaches 

 a maximum, and begins to diminish as 

 the liquid becomes highly superfused. 

 Liquids that have been very suddenly 

 cooled far below their freezing points 

 have been kept for months without 

 freezing. The juice of the buds is con- 

 fined in small capillary spaces and the 

 above mentioned phenomena will help 

 to explain in part the unusual hardiness 

 of the buds and the great difference in 

 hardiness of buds that appear to be 

 very similar because they may thus be 

 cooled below their freezing points and 

 warmed again without ice forming. 



A reading of the popular literature 

 on the subject is likely to cause one to 

 infer that buds have a certain freezing 

 temperature, and that when they 

 arrive at this temperature they all 

 freeze. This, of course, is wide of 

 the truth. There is a range of four 



or five degrees between the highest 

 temperature at which two or three per 

 cent of the buds are injured, and the 

 temperature at which all the buds are 

 killed. It should be remembered that 

 on the same branch are often found 

 buds that have swollen but slightly 

 when others arc in fuH bloom. A freeze 

 or two in the early spring will usually 

 do no harm; they simply serve to thin 

 the buds out, for it is generally known 

 that there are niany more buds on the 

 tree than actually mature info fruit. 

 The number that can be allowed to 

 freeze without heating the orchard will 

 naturally depend on how many there 

 happen to be on the tree at that particu- 

 lar time. It is very rare that a tree has 

 so few buds on it that it cannot lose 

 one-half of them and yet mature an 

 average crop in the fall. Where we 

 have endeavored to select a critical 

 temperature we have taken it as near 

 as possible to the point where not more 

 than 50 per cent of the buds will be 

 killed by experiencing the cold men- 

 tioned. 



Some of the more important conclu- 

 sTons which will be of interest to the 

 orchardist, arrived at by these experi- 

 ments are as follows: 



To kill plant tissue by freezing, either 

 the cell wall must be ruptured when 

 ice forms, or else after the ice forms, 

 it must thaw rapidly. An occasional 

 case of ice formation and slow thawing 

 without death resulting to the tissue 

 has been observed. 



Fruit buds will stand a lower temper- 

 ature by several degrees than the freez- 

 ing point of the expressed sap, and the 

 sap freezes at three or four degrees be- 

 low the freezing point of pure water. 



The literature on the subject might 

 lead one to infer that the buds have a 

 definite freezing point and that when 

 the orchard reaches this temperature, 

 practically all of the buds are frozen 

 and the crop for that year is to be a 

 failure. This is not the case. The or- 

 chard can usually stand two or three 

 freezes without losing more than half 

 of its buds, and this number is usually 

 sufTicient for a normal crop. 



It doesn't make any difference, in the 

 first two or three days, as to when the 

 injury to the buds by direct observa- 

 tion of them is determined. 



The further developed the buds are, 

 the more sensitive they are to frost. 



There is a range of at least five de- 



grees Fahrenheit between the tempera- 

 ture at which only about five per cent 

 of the buds are damaged and the tem- 

 perature that will kill all of them. 



In the case of Double Nattie cherries 

 when the fruit is setting, 29 degrees 

 Fahrenheit caused no damage and 24 

 degrees killed practically all of them. 



With Jonathan apple blossoms in full 

 bloom, 28.5 degrees Fahrenheit caused 

 no damage and 24 degrees killed about 

 half of them. 



Prune buds are slightly hardier than 

 those of the other kinds of fruit that we 

 tested. 



The temperatures which will kill 

 about fifty per cent of the buds of the 

 Elberta peach are as follows: When 

 they are slightly swollen, 14 degrees; 

 when well swollen, 18 degrees; when 

 they are showing pink 24 degrees; when 

 in full bloom 25 degrees; and when 

 the fruit is setting, 28 degrees Fahr- 

 enheit. 



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One of Hood River's show places for sale. Thirty-three acres, all under 

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