I shall not try to cover the whole subject of propagation or describe methods of budding and grafting, as these will be covered by others and we are to have demonstrations of budding and grafting, which are far ahead of any descriptions that can be given. I will try to compare conditions in the North and South and give some of my experience with the problems that have confronted us.
We have been able to get very satisfactory results with the pecan, either by budding or grafting, under northern conditions. With good scions and good stocks we have been able to get nearly, if not quite, as good results in Pennsylvania as we were able to get in Florida or Louisiana. The growth of the tree is also quite satisfactory. From dormant buds on good stocks we are able to get a growth of four to six feet the first year in the nursery and six to seven feet is not unusual. The growth is also quite stocky and altogether very satisfactory. Any of the methods of propagation as practiced on the pecan in the South are successful in the North, but budding by the patch method has given us the best results. Grafting is quite successful so far as the live or stand is concerned, but, on account of our shorter growing season, the growth is not nearly so satisfactory as that of the dormant bud which, being set the previous summer, is ready to start quickly into growth in the spring and gets the full benefit of our shorter growing season.
The shagbark hickory is essentially a northern tree and can only be propagated satisfactorily in the North. In Florida and Louisiana we could graft the shagbark on pecan stocks with fairly satisfactory results, so far as the live or stand was concerned, but the tree did not take kindly to the climate of the Gulf Coast and made little growth, a number dying out altogether the second and third years after being grafted. We have never gotten very satisfactory results from grafting the shagbark with scions taken from old, bearing trees, but with good scions from young thrifty trees, the shagbark may be grafted with fairly satisfactory results in the northern states. From the nature of the growth, it is not practical to bud the shagbark by the annular or patch bud methods as practiced so satisfactorily on the pecan, but last season (1913) in an experiment we got good results from ordinary shield budding by taking scions from a tree that had matured and ripened its growth up early and setting the buds on young, sappy growth of the pignut hickory, Hicoria Glabra. The scions from which those buds were taken were cut to test patch budding on the shagbark and when it was found that the growth had hardened and the bark would not peel, the buds were cut and inserted by ordinary shield budding, as practiced on the apple, peach, etc. This experiment was made with little or no hope of success, so that my surprise can well be imagined, when the wrapping was removed and it was found that every bud had united with the stocks! These buds have made better growth the present season than have the grafts set the past spring, as might be expected. This may be a freak and we may not be able to again duplicate the results, at least in more extensive practice, but I am inclined to think that we will, under similar conditions. The shagbark, without any manipulation, ripens and hardens up its growth early in the season and it would appear that these conditions could easily be duplicated, at least in average seasons. Young stocks of either the pecan or pignut hickory hold their sap much later than does the shagbark and are in good condition for budding after the shagbark is dormant. We have practiced this method on the chestnut for several years with very satisfactory results. The chestnut may be budded almost as easily as the apple or pear, and with nearly as good results, by ordinary shield budding, by taking scions for budding from an old bearing tree which has matured and ripened its growth up early and setting the buds on young, sappy seedling stocks growing under cultivation in the nursery. The paragon chestnut, especially, ripens its growth up very early when the tree is carrying a good crop of chestnuts, and there is a month, in average seasons, when buds may be taken from it and set on young stocks in the nursery. This condition might be brought about on younger trees from which buds are to be taken by withholding nitrogenous fertilizers and cultivation, or, if necessary, by root pruning. Root pruning should not be too severe as a sudden check on the growth in the growing season might interfere more or less with the storing up of "starch" or "dormant plant food" in the scion. Any condition or conditions that will serve to induce early maturing and ripening of the wood growth on trees from which buds are to be taken will be satisfactory, and by using nitrogenous fertilizers and liberal cultivation on the stocks to be budded, they may be kept in good condition of sap well into September in average seasons. Grafted at the proper time we were able to get good results without any manipulation of the seedling stocks. All that we ever did there was to remove the new growth occasionally to hold the stocks in good condition for grafting and prolong the grafting season, and it was always questionable whether this was a necessary precaution. My idea in keeping the new growth off the stocks till the grafts were set was not to control the sap flow, but to prevent, if it were possible by this means, the exhaustion of the stored up "starch" in the stock, by the new growth. In the northern states, the sap in the walnut stocks, and perhaps to some extent in other nut tree stocks, is inclined to come up in the spring with a rush. Some seasons at least, even before the buds push into growth, when the stocks are cut off for grafting a large number "bleed" or run sap very freely and this may continue several days, flooding and injuring the scion, and exhausting the vitality of the stock. This condition was especially noticeable the past spring, due presumably, to the lateness of the growing season. Making provision for the exit of the surplus sap was usually sufficient in the lower south and, we believed, would be farther north, but with the stronger flow of sap this is not sufficient in the northern states, at least some seasons. An examination of grafts, set on stocks which have bled freely after having been grafted, shows that the stock callouses very slowly, if at all, and the scion, unless it be of very heavy, solid wood, becomes dark colored and sour and the wood soon dies in the cleft, although the scion above this point may remain green for weeks. I am not able, at this time, to give any specific remedy for the correction of this trouble for the reason that I have not worked it out to my own satisfaction as yet, but now that we understand the trouble better, I feel sure that we will be able to correct it in the manipulation of the stocks before they are grafted. Keeping the new growth off the stocks may be found to be sufficient in most seasons, if the grafting is done rather late, but I am of the opinion that a rather severe cutting back of the stocks a few days before they are grafted, if the grafting is done early, will be found the best practice. For later grafting, my opinion is that two or three cuttings, say a week apart, will be better. Root pruning, where it can be practiced to advantage, will be found more effective still. I have never known newly transplanted stocks or those which had the tree digger run under them, to bleed freely when grafted, and we have sometimes gotten a good stand of grafts on such stocks, but such stocks may not always have sufficient sap for the best results in grafting, if they have been recently transplanted or root pruned. Fall planted As a matter of experiment, I want to try budding both the pecan and walnut by this method the present season, but I don't expect any results from walnut buds set in this way. For the information of those who may wish to try this method the present season, I will say that we cut the shagbark buds a little heavier than we cut apple or pear buds. The wood was left in the bud. The bark on the stock was split and the buds inserted just as in any other shield budding. The buds were wrapped very firmly, with waxed muslin, just as we wrap patch buds.
Our success with grafting the English or Persian walnut, under northern conditions, has been variable and not very satisfactory. With good scions and good stocks and other favorable conditions, we have sometimes gotten over 90 per cent to grow, but the stand is more often much below this and the present season we did not average over 25 per cent. The fact that we get good stands of grafts when all conditions are right, is not only encouraging but demonstrates that the English walnut can be grafted under eastern or northern conditions with at least a fair degree of certainty as to results, just as soon as we learn the causes of our failures and are thus able to apply the remedy. Perhaps the greatest drawback to the successful grafting of the English walnut is the difficulty of obtaining good scions. The annual growth of the walnut is much more pithy than that of the pecan or shagbark, and for this reason, only a comparatively small portion of the growth is available for grafting purposes if we are able to select scions that will give the best results. Like the pecan and shagbark, the two-year wood makes the best scions for grafting, provided that the wood has good buds on it, but under our conditions those buds that lie dormant are usually shed off during the summer and few good buds remain that will start quickly into active growth. It is true that adventitious buds will often form where these buds have shed off, and these will push into growth if the stock is kept free from sprouts, but usually too late in the season to make good trees, and keeping the seedling stock free from sprouts when it should be in leafage is more or less weakening and injurious and the grafts, starting into growth late in the season, do not mature and ripen their growth up properly before frost and are quite likely to be injured by early November freezes, unless they have some protection. To graft the English walnut with unvarying and satisfactory results, under northern conditions, we must not only have good scions and good stocks, but we must control the sap flow in the stocks. In Florida and Louisiana the sap came up more gradually in the stocks in the spring, and when or root pruned stocks would probably give the best results, as the sap would probably come up more gradually in the spring and, while the flow would probably be sufficient for the best results, it would not flow freely enough to injure the scion or stock.
We have not experienced any serious difficulty from an extreme flow of sap in pecan stocks, either in the North or South, but we have had grafts set on the pignut hickory fail from this cause. The English walnut may be budded with fair to good results, by the patch method, by selecting good buds on the best matured, round growth, but to propagate the tree economically and satisfactorily it is desirable to both bud and graft, otherwise both stocks and scion wood are wasted.
TOP-WORKING LARGE WALNUT TREES
W. C. Reed, Vincennes, Indiana
In top-working large native walnut trees to the Persian or English walnut, the first operation is to cut the trees back severely. This should be done while the trees are dormant, preferably in February or early in March. Cut them back two feet or more above where you wish to graft, then cut again to where you want them. This will avoid splitting. Usually we cut back to where the limbs are from two to four inches in diameter. We have cut some back that were six to eight inches with good results. However, limbs this size require careful attention to avoid decay as it takes so long for them to heal over.
Scions for Grafting