An important phase of nut growing to which I have given little attention is the search for new varieties. I find my interest in this aspect growing as I associate with the group of nut growers in Ohio, who through prize contests and active personal work are trying to discover superior nut trees in nature, yet I do not find in this the opportunity I seek for experimentation unless it may be in the matter of hybridization.
Rootstock Propagation
Rootstocks for walnuts and hickories are very easily grown from seed. Chestnuts are grown with variable success, and it would seem that particular care in drainage of the seed bed, and possibly the use of one of the seed fungicides, should improve chestnut germination.
The present trend in the propagation of fruit trees is toward selection of particularly suitable rootstocks. Do some nut tree seedlings accept grafts more readily than others? We do not know. Numerous writers have discussed the idea of varying degrees of compatibility of rootstocks with scions and Jones[1] has brought together considerable evidence to relate incompatibility among plants with something parallel to allergy in animals. Initial growth of the scion leads to a flow of foreign bodies into the stock. The theory is advanced that the stock develops antitoxins to these foreign bodies which succeed in killing the scion a few weeks later.
If a particular strain of nut tree stock is some day found to be of particular value for grafting, or for propagation of a disease resistant type, as in the chestnut, the propagation of such stock vegetatively would be essential. A present illustration is the series of Malling apple rootstocks which are grown from cuttings.
I have tried many times to grow chestnuts from cuttings with no success. A few experiments now in progress are limited to Malling IX apple stocks which I assume are not especially difficult to root. I am trying several modifications of a principle of making the cuttings at some time after girdling the stem. The hope is that in this way there will be accumulated at the base of the cutting more than the usual reserve of nutritive elements together with whatever plant wound hormones and plant growth substances the twig is capable of synthesizing.
Scion Storage
In earlier papers I described the use of sodium sulfate crystals (Glauber's salt) for controlling the humidity in scion storage. This season I have adapted the practice to the shipping of fresh walnut bud sticks. A sack of Glauber's salt in the bottom of the mailing tube keeps the cuttings moist, and if, in addition, the container is kept in a refrigerator when not actually in transit, the buds have been kept in condition for use up to twenty-five days.
A low temperature is essential in storage of any scions. Variations in this factor may have been the cause of some of the objections which have been raised to the practice of coating scions with wax when they go into storage. If wax is to be applied over a scion, it can be done more uniformly and in a thinner coating by immersion of the scion in melted wax. The scion so coated seems to be in better condition than an uncoated scion when it comes out of storage provided the storage temperature has been low. However, if the wood has not been kept dormant by low temperature, gases are evolved which form blisters under the wax and injure the scion. It is quite probable that a wax coating then aggravates this damage.
Grafting and Budding