In the course of experimental work with trees I grafted scions of several species and varieties into stocks of their respective genera at times of the year when grafting is not commonly done.
Scions were taken directly from one tree and placed at once in another tree. To this method I gave the name of "immediate grafting" in order to distinguish it from grafting with stored scions which might be called "mediate grafting" indicating the intermediate step of storage. Immediate grafting was successful in mid-winter in Connecticut but I had no thought of making it a practical feature of our work beyond the recording of a research fact.
Immediate grafting was successful in mid-summer in Connecticut. The procedure was very different from that of winter grafting. In summer the new green growth of the year was cut away completely from a scion and the remaining wood of one or more previous year's growth was depended upon for sending out shoots from latent buds. That is what happens after accidents to limbs or to trunks of trees and it occurred in the same way with my scions. Furthermore, it seemed to offer new hope for the propagation of walnuts, maples, and grapes, for example, because the free flowing sap of such species in the spring and early summer has led to attacks upon the sap by bacteria and fungi which ruin repair cells.
I have already published elsewhere the statement that immediate grafting may be done in the way described in any month of the year with many kinds of plants. Exceptions to this rule will doubtless appear here and there. For example, the grafting of trees in August would not be safe in Connecticut because the new young shoots would be killed by September frosts. That is the reason for August cutting of brush by farmers. The tender new shoots that are sent out from latent stump buds become frosted and the entire plant may die.
On account of an illness that had kept me confined to the house most of the time for some months, I had allowed the spring grafting season to pass this year. Stored scions of many kinds lay under a heap of leaves at the rear of my garage. The drying-out process had been intensified by an employee who made a spring clean-up of the yard and who looked upon this heap of leaves as something upon which creditable showing for his work might be made. A month or so later I kicked over the few remaining broken remnants of scions for no reason in particular. Down near the ground I observed that two hybrid chestnut scions which had been trampled into the ground had retained some moisture. Each one had sent out a pale canary-colored shoot of the sort with which we are painfully familiar. The shoot on one scion was about an inch and a third in length with well-formed unfolding sickly yellow leaves. The other scion had a shoot of the same kind but only about one-third of an inch in length and with yellow leaves barely out of bud-bursting form. It occurred to me that my old method of waxing the entire scion, leaves and all in this case, might be done as an experiment in order to see how long these greatly started shoots would hold up if desiccation was prevented and always with the possibility of a surprise.
Some years ago I had waxed some hazel scions from the West that had burst their buds and they all grew but the test was by no means so severe as it was with these yellow chestnut upstarts. The rule of discarding scions that are not wholly dormant was about to be rudely broken; waxing changed the whole situation. A miser does not scrutinize his treasure more acutely than we horticulturists do when getting out scions that have been stored during the winter and the voice of Demeter is calling us to the side of our own wards. How sadly a million nurserymen have thrown away a billion started scions of valuable kinds. My two chestnut scions had gone far beyond the hopeless stage but now perhaps I could be a doctor to them. If my two canary birds could be made to sing then would I also sing.
They were dipped in a dish of melted parafin wax for an instant and then quickly shaken in the air before scorching could occur. The scions were then grafted into a small chinquapin stock. A few days later one of the larger leaves of the larger shoot had cleared itself from the wax coating and had begun to expand widely, turning to a natural green color. The stem of the shoot turned to a normal brownish red. Two tiny shoots then broke through the wax of the larger shoot, looking like axillary bud shoots until closer examination showed them to be scale bud shoots. That should interest plant physiologists. Eventually the cramped leaves remaining under wax coating that was unnecessarily dense finally dropped away useless. The single green leaf and the two scale bud shoots went on to natural development. The smaller shoot of the other scion managed to burst through the wax completely and made normal growth.
After these scions were well under way I went out and searched in the loose dirt and leaves of the old heap and found another hybrid chestnut scion that presented the allusive emblem of a canary bird. This one had a shoot of about half of one inch in length and it burst completely through the wax, to make a fine little twig.
So much for an experiment that led immediately to one of far greater importance. If canary bird shoots could be made to break rules of horticultural theory and of recorded fact perhaps we might note the principle and apply it to the experimental grafting of green shoots of the year in tree propagation. This is what lawyers might call a non sequitur. Such grafting had always been a failure so far as I knew, and certainly my own attempts had failed in former years. Grafting of new growth of the year upon new growth of the year in the growing season is an established feature of horticultural experiment with certain annual plants. Why had it so signally failed with perennial plants and most impressively with trees? Doubtless plants produce in their leaves a hormone which directs certain enzymes that conduct wound repair by cell division. If plants which do not lignify for winter manage to direct successful wound repair after grafting and if plants which do lignify for winter do not conduct successful repair of grafted new growth it occurred to me in a speculative way that the reason might perhaps be sought in the nature of the two different kinds of hormones or of enzymes belonging to annuals and to perennials respectively. The difference might possibly depend upon the arrangement of ions, anions and cations upon two sides of the permeable membrane of a repair cell. The cell is an electrolyte and therefore division of the cell in course of preparation for multiplication might perhaps depend upon an electric impulse so delicately in balance that Nature for some cryptic reason might prefer not to allow the necessary balance to go toward cell division in grafts consisting of green growth of the year in perennials. Perhaps I might defeat natural processes by leaving a leaf or part of one at the distal part of a green graft shoot. This leaf might perhaps elaborate the necessary hormones or enzymes for wound repair purposes—and also for conducting polarity of sap movement toward maintenance of that scion and leaf.
We need not speculate further upon the philosophy of the subject because I took it up at this point for pragmatic tests experimentally. The horticulturist does not have to go to the theatre for thrills. My advance report at this moment comes at a time when a scientist would demand more works along with faith and my only reason for presenting incomplete notes at this time is that they seem to be fascinating in their outlook and no one knows how much experiment may be permitted me for next year at Merribrooke.