Growing Nuts in the North / A Personal Story of the Author's Experience of 33 Years with Nut Culture in Minnesota and Wisconsin

Making a scarf with a plane preparatory to grafting.

Selection of good scionwood and bud wood, a very important matter, is made according to definite standards. Some plants graft better if wood is used that has two seasons' growth, but, in general, wood of the current season's growth is used. It must have reached its maximum possible maturity before it is cut. Also, some attention should be paid to the vigor of the growth which it has made during the season. For instance, in choosing between wood which has made only two or three inches' growth and that which has made a foot or more of growth, both being equally sound and mature, the more vigorous should be chosen. Attention should be paid to the development of the buds, which should be plump and never immature.

It is advisable to label scions before they are stored to avoid the confusion that will result if they are mixed. I find that the best method of doing this is to get a sheet of zinc, from 20 to 30 gauge thick, and cut it into strips one inch wide by one and three-quarters inches long. I bore a small hole in one corner of each tag, through which I thread 18-gauge copper wire, doubled and with the bottom loop folded over (see page 40). In preparing these tags, it is important to remember that both wires must pass through the hole in the metal tag, otherwise, the slight movement due to winds will cause the metal to wear through. Two wires prevent this action indefinitely. Since a small wire cuts through a zinc tag in one or two years, heavy wire must be used. Wire such as I have indicated is satisfactory. I print the necessary information on each tag with a small, steel awl, and such labels are still legible after twenty-five years. Copper, brass or aluminum would also make good tags, but these metals are more expensive. Of course, these tags may be used for small trees as well as grafts and scionwood and it is always well to do a good job of labeling all work, since many errors may result from disregard to this important detail.

In the north, the time to graft nut trees is when the cambium layer of the host, or stock, is active, which is usually during the entire month of May. This cambium layer consists of those cells lying just inside of the outer bark, between it and the woody part of the tree. When these cells are active, the inner side of the bark feels slippery and a jelly-like substance can be scraped from it. Although this is the state in which the stock should be for grafting, the condition of the scions should be almost the opposite, rather dry and showing no signs of cambium activity. The bark should cling firmly to the woody part of the scions, whereas the bark of the stock should slip off readily. Another good and fairly satisfactory rule is never to graft the stocks of nut trees until after the young leaves appear.

In grafting young nursery trees not more than an inch in diameter, the whole tree is cut off at any distance from the ground convenient to the nurseryman. Sometimes they are cut within a few inches of the ground, sometimes two or three feet. In my work, I like to keep the scions as high above the ground as I can. When the top of a stock is cut off, there is a great deal of sap pressure and the tree bleeds. It is a poor policy to attempt grafting while this is happening. Rather, one should cut the tops off, then wait for several days before inserting any grafts. Tools must be kept very sharp. A good grafting knife is sharpened on one side only, so that the blade is flat along the side which lies next to the cut made on the scion when it is trimmed. If unaccustomed to handling a knife, one can obtain more accurate results by using a small plane. I do this by holding the scion firmly in my right hand and pulling it toward me, against the cutting edge of the plane which is held in the left hand. Illustrations show how this is done.

The only disadvantage in using a plane is that one must exchange it for a knife to make the receiving cut in the stock before inserting the graft. This necessitates exposing the graft to the air for a longer time than does using a single instrument.

Spring budding is done during the same period as grafting. Bud wood is usually much larger in diameter than scionwood, for it is easier to remove buds from big branches than from wood only one-quarter inch in diameter. When budding is to be done, take along only enough wood for half a day's work, leaving the rest safely stored. A piece of wood having a bud is prepared as shown in the illustrations "A" and "B" (next page). A T-shaped slot is made in the stock to receive the bud, a process called "shield budding." This is tied in place with either string, raffia or gummed tape, as shown in "C" and "D" (next page). The bud must be free to grow, and although it may be covered completely with wax, no part of the binding material should be close to it. Since it is not necessary to cut off all the tree in budding, enough of it may remain above the bud to brace the shoot that develops. Later, it may be necessary to cut back the tree to the bud so that a callus will form and cause the wound to heal properly.

Shield Budding.

Best results are obtained when a graft union is coated with melted beeswax. Another and cheaper wax may be made by combining four parts of rosin, one part of beeswax and one-sixteenth part of raw linseed oil. To this is sometimes added a little lampblack to color the mixture so that it can be seen on the graft. Again, care must be taken to prevent injuring the cells with wax that is too hot.

I have used many kinds of tying materials, but the one which gives me best results is gummed tape, which preparation I describe in another chapter. By wrapping it in spirals around a graft union, I have a material which holds the graft in place and at the same time excludes air. The rubber also seems to encourage the formation of that tissue which unites the stock and scion. In addition to tape, melted wax should be brushed into those crevices and cracks which always occur in making a graft.

It is usually advisable, although not necessary, to shade new grafts. To do this, cover them with light-colored or white paper sacks. Never use glassine alone for it causes the grafts to overheat and so destroys them. Whatever tying material is used, either to fasten on these bags or to support the grafts, it should be inspected at intervals during the summer, as it may constrict the graft or stock and injure or cut off the cambium.

After a scion begins to grow, it must be firmly braced against the force of the wind, for a heavy gale can rip out grafts made years before. Laths make good braces for growing shoots. They may be attached to the main branch by stout waterproof twine such as binder twine, and the growing graft tied with soft muslin strips to the lath. As the graft grows more muslin strips should be used to keep the excessive growth anchored to the lath. Grafts will often make three or more feet in growth in one season.

It is important to remember that sprouts or buds which start from the stock must be rubbed off. If they are allowed to flourish, they may prevent the scion from growing. When working over a tree several inches in diameter, it becomes an art to keep the tree stock satisfied, yet to encourage the growth of the scions. In large trees, a few sprouts must grow to nourish the root system, but this is not necessary if the stock is one inch, or less, in diameter.

Chapter 17

Holding a piece of tape by one end, submerge it in the rubber solution, forcing it down with a spatula or knife. Swishing it around or moving it up and down several times helps to fill the pores with rubber. Drag it from the solution by pulling it sharply over the rolled edge of the pail, using the spatula on the upper side of the strip to scrape off superfluous rubber. A little practice soon enables one to judge the amount of rubber needed on the tape. There should not be so much that it drips off. Hang the tape on the rack so that the ends are attached to the rails, the tape sagging slightly in the center. Space the pieces of tape so that they do not touch, for, if they do, they will be very difficult to separate later. After they have dried for twenty-four hours, wind the tape on pieces of cardboard about one foot square, being careful not to overlap the tape. The tape is now ready for field-work.

I want to mention some of the advantages I have found in using this rubberized tape rather than raffia. The tape is uniform throughout and is stronger than raffia. It does not fly around and frequently get tangled as the latter does. There is no necessity for keeping it slightly damp to be usable. It may easily be torn off at any convenient length or it may be cut without injuring the edge of the grafting knife. A last advantage is that it is self-sealing since it overlaps on itself slightly when wound around a graft union. Because of this, there is no necessity for painting the finished graft with melted wax as is absolutely vital when using raffia. Personally, I use wax in addition to the tape for I feel that it is probably safer with that extra protection. Also it gives me an opportunity to wax over the tip end of the scion when it is devoid of a terminal bud.

The only disadvantage in using tape is its cost which, I must admit, is very much higher than that of raffia. But if, by using tape, twice as many grafts can be made each day, and if the resulting takes are 50% better, as they have been in my experience, then the cost is justified and raffia is actually the more expensive to use.

Chapter 18

One instance in which the stock was apparently affecting the scions, occurred in the case of several varieties of black walnuts which had been grafted on wild butternut stock over a period of sixteen years. The walnut top flourished but tended to outgrow the butternut, so that the caliber of the walnut was greater than that of the stock a few inches below the graft union. I also noticed that, although the graft began to bear about as early as black walnuts do when they are grafted on their own species, the nuts did not mature at all during the first few years of bearing. In 1938, after a favorable season, I found mature nuts on one variety, the Thomas. These nuts varied in size more than they do when grafted on black walnut. The most surprising thing about them, though, was that they did not have the characteristic black walnut flavor. When properly dried and cured, they could have passed as an entirely different nut since they tasted like neither the black walnut, the butternut nor the Persian walnut.

The overgrowth of the Ohio black walnut, grafted on butternut, was even more apparent than that of the Thomas. These nuts were, as I have said, immature the first few years they appeared and they, too, lacked the usual black walnut flavor. In their case, however, the most striking change was in the shape and structure of their shells which were elongated like butternuts, with corrugations typical of those found on butternuts and nearly as deep and sharp. (See Illustration in Chapter 1, Page 5.)

In 1937, I made experimental graftings on native black walnut stocks of the Weschcke No. 4 butternut, a variety I found to be superior to hundreds of other native trees tested. The grafts grew luxuriantly and in 1940, produced about two pounds of nuts. These nuts were approximately 30% larger than those on the parent tree. They cracked well and the kernels were similar to those from the parent tree. They definitely distinguished themselves, however, by being a free-hulling nut, which is not true of the mother tree nor of most butternuts. Soon after the nuts had dropped to the ground and were still green, they were hulled and their hulls peeled off like those of the Persian walnut, leaving the nuts clean and free from remnants. Apparently this phenomenon was a transient one since later crops did not display this free-hulling feature.

I have mentioned, elsewhere, the seedling apricot which came into bearing in St. Paul, and how I obtained grafts before it died during a very cold winter. I have grafted scions of this apricot on both hybrid and wild plum stocks repeatedly and this apricot now exhibits a material gain in hardiness. It overgrows the plum stock, but this does not seem to inhibit its bearing, the fruit growing to greater size than that of the mother tree.

These are some of the instances in which I have seen stock exert a definite, and, mainly a beneficial influence on its grafted top. It may easily be that these are only of a temporary nature and until I have seen them maintained for many more years, I must consider them to be transient effects.

Chapter 19

It seemed to me that if scions could be maintained in an approximately fresh state, they would furnish a key by which any variety of graft could be determined as easily as it could by its nuts. I therefore set myself to preserve scionwood in its fresh state. First, I cut five-inch pieces of plump, healthy wood, each piece having a terminal bud. I placed these buds downward in large test tubes which I then filled with pure, strained honey. Such models did very well for a time, but after about a year, the honey crystallized and of course the scions were no longer visible. I emptied the tubes and washed them, cleaned the scions in warm water, replaced them and refilled the tubes with pure glycerine. I submerged a thin, zinc tag, stencilled with the varietal name and bent to conform with the contour of the tube, inside of each one as a name plate which could not easily be lost or removed. I also labeled each cork with the name of the variety enclosed so that any one of them could be located when looking down at a nest of tubes in a vertical position.

In order to display these preserved specimens at illustrated lectures, I had a rack made of redwood, of a size to hold twenty tubes. The tubes could easily be taken from the rack for closer observation by members of an audience. I find this to be an interesting adjunct to various nut culture exhibits I make in trying to promote nut culture education.

Since I was able to identify my unlabeled, hickory grafts by means of this catalogue of submerged scions, I consider it of great practical worth. At the present time, I have about 50 hickory specimens, a good catalogue, although not a complete one. I see no reason why the same thing could not be done with black walnut or any other kind of nut scions.

Chapter 20

Crosses made between filberts and hazels usually produce great changes in the resulting fruit. J. F. Jones won considerable horticultural fame from crosses he made between the wild American hazel known as the Rush hazel, and such varieties of the European filbert as the Italian Red and Daviana. Hazel and filbert cross readily and the resulting seedlings will usually bear after only three or four years. For both these reasons, they are good material for a beginner to work with. If the wild hazel is to be used as the female, or mother, of the cross, it is necessary to pick off all the male blossoms, or staminate blooms. This should be done long before they begin to expand. The pistillate, or female blossoms, should be enclosed in bags, about six of the three-pound, common kraft bags should be enough. These are slipped over those branches which bear female blossoms and are tied around a heavy packing of absorbent cotton, which has been wound around the branch at approximately the place where the opening of the bag will be. In fastening the mouth of the bag around the cotton, I find that No. 18 copper wire, wrapped several times around and the ends twisted together, is more satisfactory than string. This makes a pollen-tight house for the pistillate blossoms but not one so air-tight as to cause any damage to either the plant or blossoms.

In order to have pollen available at the proper time, it is necessary to cut a few filbert branches which bear staminate blooms and store them in a dark, cold place to prevent the pollen from ripening too soon. I recommend keeping such branches in dampened sphagnum moss until it is time for the pollen to ripen, or if a cold cellar is available, burying the cut ends of large branches carrying male catkins one foot deep in clean, moist sand. When the pollen is wanted, the branches should be placed in a container of water and set near a window where sunlight will reach them. Usually, after one day of exposure to bright sunlight, the staminate blooms will expand and begin to shed their pollen. The pollen may easily be collected by allowing an extended catkin to droop inside a vial or test tube and then, as the catkin rests against its inner wall, tapping the outside of the tube sharply with a pencil to jar the pollen grains loose. A separate test tube must be used for each variety of pollen to be experimented with. By following this procedure for several days with all the staminate blooms that have been gathered, the experimenter should have enough pollen for work on a small scale. The test tubes containing this pollen should never be stoppered with corks, but with plugs of absorbent cotton, which will allow the passage of air. Pollen may be stored in this manner for several days, possibly as long as two weeks, if it is kept dry. By a close observation of the blooming period of the wild hazels, one is able to determine the best time for placing the filbert pollen on the pistillate blossoms. No attempt should be made to do so until the male catkins of the wild hazel species are so entirely exhausted that no amount of shaking will release any grains of pollen. When this condition exists, it is time to move the stored filbert branches to strong sunlight. A quiet day should be chosen to pollinize the hazels for two reasons. If there is a wind, it will blow away the pollen and so make the work more difficult. A wind will also increase the danger of the hazels being fertilized by native hazel pollen which may still be circulating in the air and which the flowers may prefer to filbert pollen.

When good conditions are present, then, the hybridizer proceeds to his work. A brush with which to transfer pollen from the vial to the pistillate blossoms is made by wrapping a little absorbent cotton around the end of a match. The paper bag is removed from around a group of hazel blossoms, a small amount of pollen is dabbed on each blossom and the bag is immediately replaced, to remain on for two more weeks. When the bags are finally taken off, the branches should be marked to indicate that the nuts will be hybrids. Before receiving pollen, each pistillate blossom has, emerging from its bud tip, a few delicate red or pink spikes which are sticky enough to make pollen adhere to them. Within a few days after receiving pollen, these spikes may dry up and turn black, a fair indication that the pollen has been effective. If the pollen does not take hold, the spikes of the staminate blooms are sure to continue pink for a long time. I have seen them in the middle of the summer, still blooming and waiting for pollen which would let them continue on their cycle. This ability of hazel flowers to remain receptive for a long period allows the nut-culturist ample time to accomplish his work. It is not so true with all members of the nut tree group, some, such as the English walnuts, being receptive for such a short period that only by very frequent examination and many applications of pollen can one be sure of making a cross.

Early in the fall, the hybrid nuts should be enclosed in a wire screen to prevent mice and squirrels from taking them before they are ripe. Such wire screens may be used in the form of a bag and fastened around each branch. When the husks turn brown and dry, the nuts are ripe, and ready to be gathered and planted. Careful handling of the nuts is advisable to preserve their viability. They should be planted in an outdoor bed which has been fully protected against the invasion of rodents. A screen such as I described for other nut seed is satisfactory for these hybrid nuts but it need not be as large as that. After the nuts have sprouted and the plants have grown for one season, they may be transplanted into a permanent location where they should again be well protected against mice by a trunk screen, and against rabbits by driving a stout stake deep into the ground on the south side of the tree and tying it to the tree. This use of a stake discourages rabbits from cutting off the tree.

There are innumerable other crosses that can be made as well as those between hazels and filberts. It is possible, for example, to cross the English walnut with the black walnut. Many such crosses have been made although none of them is known to have produced superior nuts. Thousands of crosses exist between butternuts and Japanese heartnuts. Many of these are of some worth and are being propagated. Crosses between heartnut and butternut are easily made, following the same procedure used in crossing hazels and filberts, except that larger bags are necessary for covering the female blossoms. Also, these bags should have a small, celluloid window glued into a convenient place, so that the progress of the female blossoms toward maturity can be observed.

When hybridizing walnuts, it is necessary to use a pollen gun instead of removing the bag from around the female blossoms and applying the pollen with a cotton-covered applicator. Such a pollen gun can be made by using a glass vial which does not hold more than an ounce of liquid. An atomizer bulb, attached to a short copper or brass tube soldered into a metal screw-cap, is fitted to the vial. Another small copper or brass tube should also be inserted in the screw-cap close to the first one. The second tube should be bent to a right angle above the stopper and its projecting end filed to a sharp point. Without removing the bag from around the pistillate blossoms, the hybridizer forces the point of the atomizer through the cotton wadding between bag and branch. The pollen in the vial is blown through the tube into the bag in a cloud, covering all the enclosed blossoms. It is advisable to repeat this on several successive days to make certain of reaching the female blossoms during their most receptive period.

8 x 8 x 8 foot tightly woven sheet of unbleached muslin stretched over mother hazel plant during pollination period in the process of making controlled crosses between it and filbert parents. Photo by C. Weschcke.

How to make a pollen gun

Chapter 21

Many people have observed the detrimental effect of trees of the walnut family on alfalfa, tomatoes and potatoes, resulting in wilting and dying. It is the root systems of the walnut which are responsible for this damage. Apparently, there is some chemical elaborated near the surface of the roots, and sensitive plants, whose roots come in contact with either roots or ground containing this factor, are injured and sometimes killed by it. One must therefore be very cautious about trusting these trees as protectors of many of the ornamental and garden plants. I am certain, from my own observations, that their influence on evergreens is strongly antagonistic.

On another basis is the association between catalpas and chestnut trees growing adjacent to one another. Constructive symbiosis apparently develops when a young chestnut tree is planted within the radius of the root system of a catalpa. The latter very definitely influences the chestnut tree to grow more vigorously than it otherwise would.

I have recorded my observations of these antagonisms and friendships between trees and plants to show that they are a reality which should be taken into consideration in grouping and transplanting. Such warnings are infrequent because some people may mistake them as condemnations of certain favorite trees. I do not intend them as such, for these plants are often valuable and worthwhile. This ability which they have developed through the many years of their existence is a guarantee of the sturdiness and strength of their family and species, not at all a quality to be condemned.

CONCLUSION

Considering the nut tree as a dooryard tree, an ornament rather than a business, makes it possible to include many more species as suitable for growing in the north. For this purpose, I suggest heartnuts, chestnuts, pecans and hiccans. The heartnut tree is always one to draw attention and interest, picturesque in its leaves, blossoms and clusters of nuts.

Last, but certainly not least in it potentialities, is the English walnut. I am certain that we shall have some varieties of these which will be hardy enough to plant in the north. When these have been completely proven, they will be a delightful addition to the number of trees flourishing here. What family would not receive enjoyment and satisfaction from having, in its dooryard, a gracious English walnut tree, its spreading branches laden with nuts?

Although the commercial aspect of producing hazilberts is engrossing me at the present time, my greatest pleasure in nut culture still comes, as it always shall come, from actual work with these trees. It is both a physical and mental tonic. I recommend nut tree culture to everyone who enjoys spending his time out-of-doors, who is inspired by work of a creative nature, and who appreciates having trees, or even one tree, of his own. Suggested reading on Nut Tree Culture: