The objective of our chestnut evaluation plots is to identify seedling trees by cultivar selection that we hope will contribute to the establishment of a commercial sweet chestnut industry in southwestern Ontario. To date, we have had surprisingly good growth of all the various nut trees.
In the spring of 1992, I invited John Gardner (Horticultural Crop Advisor, OMAF) over to the farm to do some experimental grafting onto some of the established chestnut trees. Up to the start of winter we had 90% take of scions with some showing growth over one meter long. However, I know from previous years that winter can take a heavy toll. Graft rejection is common in chestnuts and not yet fully understood. In milder climates graft rejection seems to be less of a problem.
In the spring of 1992 we established a new 3 acre planting of Chinese chestnut seedlings at 20 feet spacing; some of the spaces having 2 seedlings. There has been very good growth with plenty of buds for 1993. Fortunately, we never had to water last season.
Rain, forever rain! Chestnuts at pollen time have a strong sweet smell. We can usually smell trees in the grove for 3 weeks starting at the end of June. Surprisingly, last summer, there was no smell, and the pollen was constantly wet. Some stamens that I brought indoors shed pollen the next day. However, the favoured trees that I hand pollinated did not take (fertilize) despite two attempts. Overall, yields were drastically reduced in 1992. This past July was also flyless. Indeed, mosquito alley was without flying insects at pollen time, which is very unusual. The bluebirds were eating sluggish, gypsy moth caterpillars crawling at the base of the chestnut trees at the time. Could the lack of insects/insect activities contribute to the decreased yields in the chestnut? Are chestnuts 100% wind pollinated? Interesting questions.
In summary, in 1991 our total chestnut production was 200 pounds (2.2 pounds = 1 kilogram). In
1992, between 20 and 30 pounds were recovered from predominately the Layeroka grafts. We
have 2 pounds in the fridge for Christmas dinner.
Evaluating the Nut Tree
Orientals are impressed with the ginkgo tree. Its form is simulated in their pagoda architecture. Like Emma K black walnut, it has a strong structure where main limbs sweep out from the central leader to form an open, airy structure. The fruit buds of ginkgos fan out fruit from second, third, etc. year wood. Secondary branchlets carry the crop on Emma K, but as years go by these decline due to shading, die and are sloughed.
Many species have the ability to bear heavy fruit interior of the vegetative wood where the tree is better able to support it. Fruit growers refer to flower buds (fruit wood) and vegetative buds (structural wood) as different organs of the tree. Most nut trees are terminal bearing on branchlets which extend many centimeters each year. Spurs only extend millimeters in a year. Most nut trees are upland trees, more concerned with gathering health for an eventual fruitful year where terminals bear, rather than setting up to bear each year like spurs bear. We find lateral bearing in river flat trees where nutrients and moisture are adequate for annual bearing and the side buds in the terminal are tricked by strong growth into setting flowers. That is why black walnut, shellbark hickory and pecan are often side bearing (or lateral bearing) trees, but more often bear on branchlets off third and fourth year wood. Ginkgo is the nut tree which has mastered spur bearing and lateral bearing because it bears on spurs which extend millimeters each year, as well as on the buds of last season's terminals.
We are nut consumers and want our nuts every year. This may not be possible because most nut trees need many centimeters of yearly growth to finish the attached nut cluster while setting flowers buds. Considering the cycle of bearing from branchlets, followed by their shade suppression, death and sloughing, one envies spur bearing for its economy. There should be a genetic trigger for branchlet sloughing to be economical, just like persimmons slough branchlets. Without genetic branchlet sloughing, branchlets which are healthy enough to fill their nuts may be too healthy to die before the tree becomes a clutter of branchlets. Weak branchlets consume more of the tree's energy than they produce in photo-food. We look at each nut tree for a natural renewal which allows regular crops, perhaps yearly, on a healthy productive tree. If we select a tree from the wild only for its nut, and put it in an orchard setting, we often have: structural disappointment, photon processing disappointment and photo-food storage disappointment.
North American winters with their warm spells and cold snaps defeat the less hardy nut trees. Imported walnuts, filberts and chestnuts suffer freeze-thaw injury. None of the local native chestnuts have been defeated by cold snaps even in early October.
Native chestnut is unusual in that it bears nuts on the current season's flush of growth. New terminal growths which receive enough energy to start seven catkins usually produce one or two with female bloom. To produce healthy nuts the new growth continues five fully formed leaves above the burr. A cluster of more than two burrs is unstable and can break off under unusual wind or animal loading. However, native chestnut usually has two spaced burrs on each of the sun drenched, stout terminals near the top of the tree.
European chestnuts differ from native in having a more stout tree form which carries a larger crop of heavier nuts. Besides growing a nut which is much like a potato, chestnuts hold the crop erect on green stems of current growth. The green stem is a stout cylinder of wood spread over star shaped pith. Above the burrs the stem is willowy, without pith, except at the leader, if one exists. Chestnut wood continues this stout, light wood pattern with many hollow tubes, larger than in red oak. This tree structure carries heavy nuts on many terminals which bend low in the final few weeks of the season.
Heartnut is sort of like chestnut in that it usually bears some of its crop on the same terminals which are the main leader and top of the tree. Heartnut sets its cluster at the fifth leaf out and continues the leader from there after leaving,, a branchlet behind to feed the cluster. The leader is usually projected out another ten leaves. The cluster of heartnuts may weigh a pound, so the new branch which supports the leader, and the cluster, is several centimeters thick. Heartnut branches bend mightily in the wind and under crop load without breaking. Unlike chestnut, heartnut has many growing-flowering tips throughout its canopy. Most support a cluster of nuts except where bug injured. The nuts are usually well filled except where shaded by overhanging limbs. The major overhung limbs must be pruned off. Because the heartnut is a leaning tree only a few branchlets are self pruned by shade each year. Host continue to find light as the center of the tree opens up as the leaning trunks and branches bend down under loads from wind, nuts and their own weight. Heartnut seldom grows a vertical trunk^or its center-of-tree would not effectively open to the light.
Persian walnut does not grow like a heartnut. It grows a vertical leader. It suffers all types of cold and frost injury. Once heartnut has produced green leaves these are subject to freeze injury. Once Persian walnut swells its buds these are killed in the core by a freeze. It is as though Persian walnut had become a subtropical tree. Cycles of freezing usually end bearing for that season. Persian walnut sap must be low in sugar to freeze so easily. To stop sap flow Persian walnut shades its bark from the sun with clusters of branchlets. The branchlets, many of which are dead or dying, cover the major branches as well as the trunk. Walnut blight lodges in the dead and dying branchlets and feeds on them, waiting to splash onto new growth and enter it. A drip of dew on the base of a nut is the usual site of a blight canker. Carrying dying branchlets and suffering many injuries it is difficult to expect good cropping, but there is enough cropping to keep growers interested.
If Persian walnuts can be kept in a healthy condition, they will crop heavily. Several are lateral bearing on the side buds of vigorous terminals. Although side bearing Persians consistently produce nuts along second year wood the ratio of leaf to nut is low, yielding smaller, more poorly constructed nuts. Side bearing trees are usually weak from cropping, winter injury, arid blight. They must be pampered with cultivation, spraying, feeding, pruning and irrigation which are finely tuned to insure winter dormancy.
Filberts are similar to heartnuts in that their major limbs lean wide to open the center-of-tree to light. Main problems are: bush types which travel underground, bush types which sucker from a crown, shrinking and gritty kernel quality rather than the melting kernel of tree hazel. Hybridizing with tree hazel moves from these flaws as well as gaining in bud mite and filbert blight resistance. Few of today's hybrids have the winter hardiness and dormancy of native hazel.
As you can see, the progress we make in nut growing is built on the progress we make in nut
trees. The tree is our foundation. It needs to be a very firm foundation. However, current trees are
temporary in nature's plan. Growers have to have a plan which is consistent with nature's
relentless change, or we will be swept away. A reasonable plan would be to decide on
approximately five nut types per species which are marketable. About five clones would mix nuts
to be marketed as one type. Europe now markets several chestnut varieties which are the mixed
nuts of several clones. The five original clones would be traded in on better models as succeeding
generations warrant. We have to have a plan to gain succeeding selections. Current selecting is a
failure because too few trees are grown from select seed. The base for selection is too small. The
time span of local programs is too short. Programs have to be located to cause trees slightly more
distress than at the proposed orchards. The solution proposed is conservation plantings from the
best nut seed. With tree shelters it is likely that we can grow any seed into a tree on a proper
meadow. All of a planting will eventually be harvested for lumber, but after selection. We have
to get foresters interested in a plan to plant nut trees. Nuts are interesting to children of all ages.
After we have a working group, and a planting out, as it is in Orangeville, we have to produce an
education packet to use the schools to produce seedlings and a continuing cycle of support. The
native chestnut is a local, touchable, endangered species. We need: conservation literature,
instructions, Pro-mix, containers and good ideas to add to the plan.
Provided by SONG. Feel free to copy with a credit.