-4- 



is girdled entirely, anything beyond the girdle is incapable of regeneration. 

 The cambium layer is, of course, . s necessary in the growth of a root as in the 

 grovrth of a branch. Roots grow in diamettsr by laying down new wood just beneath 

 the c^cmbium l^yer. 



In the case of the top, replacoraent of branchos comes largely from pre- 

 existing growing points, or buds. These buds nay remain dormant for ye^^rs. In 

 thu c^Sto of roots, new portions of thu root system may arise from ali.iost anywhere 

 in ih^ older p-rts of the roots. V/e do not have to have tjiy definite buds. 

 Th^so "adventitious buds" are found almost anywhere in the root system. But 

 if vi/e cut off a root vdthin two or three feet of the trunk there is a tendency 

 for a number of new roots to start at thc^t point. Such roots ap^eu.r fibrous at 

 first as in the case of a root-pruned nursery tree, but it does not take very 

 long for some of these fibrous roots to turn into anchorage roots and thus pro- 

 vide a stabilizing influence for the tree. Roots may grow out for several feet 

 in a single season. 



The "food" required for root grovrth is not, of course, the fertilizer 

 you place on the soil. This fertilizer is nothing more than the nutrient ele- 

 ments which must be taken into the tree and assimilated, thus building up real 

 nutrients for the cells and for the energy necessary in the functioning of leaves. 

 we nevcr apply any plant food to the soil. Me merely apply the nutrient elements. 

 The bulk of the food is manufactured in the leaves. The root system cannot make 

 any growth unless it has this manufactured food material. This gives us an im- 

 portant lead in pruning. 



It has been demonstrated time and again that if we prune the tops of 

 trees very heavily we reduce the total weight of the tree as cOL.pared with a 

 similar tree which has been left unpruned. If a tree is heavily pruned, it 

 takes many weeks before the leaf area removed in pruning, is restored. Thus, 

 the tree must get along with less food, viftien we prune heavily we reduce the 

 vifeight of the root system much more than vi/e do the Vi/eight of the top. This is 

 due to the competition for food materials. Food manufactured in the leaves is 

 utilized largely in the vicinity where there is an active demand for it. If we 

 have an active shoot growth early in the spring the food manufactured by the 

 leaves is taken away from the roots and used in growing more shoots. Also, if 

 there is ^i crop of fruit, a good sh-^re of the food manufactured by the leaves 

 is used in fruit development. There is relatively little increase in the weight 

 of the root system early in the spring. Roots do not grow until most of the top 

 grovrth is completed. 



In mature trees most of the nev/ twigs, etc., have been laid down by the 

 first of June. After th^^t we get the bulk of the root activity. The recovery 

 of the root system of hurricane damaged trees is going to depend on getting a 

 good supply of food down to the root system as rapidly as possible. Competition 

 between top and root must be reduced. That means, first of all, that \<ie must 

 avoid over-stimulating the top. Vi/e must not use too much nitrogen. An abundance 

 of nitrogen early in the spring tends to utilize carbohydrate material in top 

 grovrth. Later in the season, of course, we ir.ay cash in on this larger leaf area. 

 But in our particular situation at the present time, if we force a lot of top 

 growth we are depriving the root system of food for a longer period. V;/e are 

 anxious to get food down to the roots just as soun as we can. We must therefore 

 avoid over stimulating the top and also avoid unusually heavy pruning. Heavy 

 pruning tends to remove a lot of leaf area which might be present as early as 



