Northern types root-grafted on northern stocks not having been tested, no definite information can be given, of course; but with all southern varieties winter-killing in the North, when root-grafted on either northern or southern stocks, and the Virginia variety winter-killing when root-grafted on southern or northern stocks, and the Indiana varieties winter-killing both in the North and in the South when root-grafted on southern stocks, it seems reasonable to presume that the northern varieties root-grafted on northern stocks will also winter-kill. The stocks of the root-grafted trees are seldom injured. They send up sprouts except in cases where the graft union is so far beneath the surface of the soil that after the grafted part is killed the stock is too deep to grow out.
Not a single tree out of a total of 40,000 seedlings in Virginia grown from northern nuts planted during a period of six years has ever been found affected by winter injury; practically all the trees out of 50,000 or more grown in the same locality from southern nuts, planted during the same years had their tops affected by winter injury the first, and most of them the second season of their growth; but no injury after the second season has been noted.
With the view of making southern varieties better adapted to planting in northern area, experiments have been made in propagating them on stocks from northern nuts. This stock has thus far proved unsatisfactory for southern varieties either budded or root grafted. The trees from northern nuts go dormant earlier in the fall and remain dormant later in the spring than trees from southern nuts. Northern trees in the nursery rows in early spring, in a perfectly dormant condition, are in striking contrast with the southern trees and their fresh, green foliage. Though the growing period in the North is nearly a fourth shorter for the northern than for the southern varieties, the native trees in the North make equal growth with the southern trees there during the same season. Northern varieties budded on northern stocks grown at Petersburg the past summer made nearly as much growth during one season as root-grafted trees of the same varieties on southern stocks grown in Florida two seasons. The trees at Petersburg were from dormant buds set the previous fall. They were just starting into growth in May when the trees in Florida had made a growth of six to twelve inches.
The northern seedlings in the North make better growth in a season than the northern seedlings in the South, as far as has been observed. When the growing period begins in the northern climate, the native trees respond at once to the quick growing season and outgrow the trees that have been accustomed to a slower growing climate. When their growing period is over, they begin promptly their preparation for the winter. The long, slow growing climate of the South does not seem to give the quick growing tree of the North an opportunity for its greatest growth at the important period. There appears to be too much difference between the growing habits of the southern and the northern pecans for either to be suitable stock upon which to grow the other.
Two choice trees of Moneymaker and one of Stuart, all well grown and giving every promise of success, were selected out of a large number of these varieties budded on northern stocks, and were transplanted in orchard two years ago for experiment. The Moneymaker trees have made little growth and the Stuart tree practically none. All have an unhealthy appearance and are left standing only for further experiments.
The section of Virginia in which these experiments have been made affords very severe climatic tests. The temperature in winter sometimes goes below zero, the temperature in spring is variable, changing suddenly from warm to freezing. Pecan trees seem able to endure almost any degree of cold when they are in a thoroughly dormant condition. The winter-killing from which they often suffer in the South, as well as in the North, is due to the effect of sudden freezing temperatures following warm periods in winter or spring.
Only well grown, vigorous pecan trees should be planted in the North. It is a waste of time and money to plant indifferent pecan trees in any locality, and especially in a locality where they have to contend with severe climatic conditions. The size of the tree is less important than its root system and vigor. The purchasers of trees grown on thin, sandy soil, with the root systems consisting almost entirely of straight tap roots, destitute of laterals, need not expect success. Most of these trees will die early, and many of those that live will linger on for several seasons without making much growth, tiring out the patience of the planter.
The work of transplanting should be very carefully done and the trees given proper care and culture.
It has been found that it costs more to grow pecan nursery trees in the North than in the South, but it is believed that planters in the North will find that these trees have a value which will far offset their additional cost.
Some of the methods of propagation and care are slightly different in the North from those that usually obtain in the South. But it is not practicable to go into the details connected with this work. The facts that have been mentioned are those that are believed to be of most importance for consideration by persons planting pecan trees in the North. Those who have gone thus far with the work upon which the conclusions are based are continuing as earnestly as they began.