Unbalanced mineral nutrition of trees is a very important factor in
determining the amount of injury they may sustain from cold weather. In
the various parts of the United States the soils on which fruit and nut
trees are grown generally do not supply in adequate amounts some one or
more of the essential elements required in their nutrition. This
condition results in unbalanced nutrition, in that too much of certain
elements is absorbed by the trees and too little of certain other
elements. Under severe conditions this causes the leaves to be abnormal
in size or in form, for them to be chlorotic or to scorch or burn, or
for them to drop prematurely. Such leaves do not function properly, they
are not able to carry on photosynthesis at a normal rate and hence do
not make sufficient plant foods of the proper kinds to properly nourish
the trees. This results in disorders of various kinds said to be due to
mineral deficiencies. Among these deficiencies that have been found to
reduce tree growth and yield and to increase susceptibility to cold
injury are (1) boron, (2) copper, (3) iron, (4) magnesium, (5)
manganese, (6) nitrogen, (7) phosphorus, (8) potassium, (9) zinc, and
others. In all cases the corrective treatment to be given consists in
supplying the trees with the element or elements in which they are
deficient. These must be supplied in an available form and by such
methods that they can be absorbed by the trees.
The size of the crop of fruit or nuts borne by a tree and the length of
time between harvest and a killing freeze are important factors in
determining the cold resistance of fruit or nut trees. In test winters
many cases have been observed in which trees that matured heavy crops
during the previous summer were severely injured. Cases have been
observed in which the degree of cold injury sustained has been largely
in proportion to the size of crop matured the previous growing season.
Trees that mature the crop of fruits or nuts late in the season may be
less hardy than those that mature the crop early. It seems not only that
some material or materials are made in the leaves during late summer or
early fall which move out of them into the wood and cause it become
resistant to low temperatures, but that when a tree is maturing a crop
so much of this material goes into the fruits or nuts that if the season
is not a favorable one the wood may not attain its maximum hardiness. We
have learned that a high percentage of certain of the minerals,
carbohydrates, and oil that go to make up the kernels of the oily nuts
are transported into them during a period comprising a month to six
weeks before they are mature. In the production of a heavy crop the
amount of minerals and elaborated food materials such as proteins,
carbohydrates, and fats removed from a tree is very large. If the trees
do not carry a large healthy leaf area at the time of harvest or if
there is a killing frost at that time, the leaves have no opportunity to
elaborate more carbohydrates and other materials to replace those
removed in the crop, and as a result the trees do not develop maximum
hardiness.
To cite an outstanding example of this effect of the crop on hardiness,
I want to describe some observations I made several years ago. The late
J. B. Wight of Cairo, Ga., had a few hundred Satsuma orange trees that
bore a very heavy crop of fruit. The fruit had all been harvested from
certain of these trees for two weeks or more before the occurrence of a
freeze the last of November. From other trees the fruit crop had only
been partially harvested and none had been harvested from most of them.
The day and night temperatures had been warm but there was a rather
sudden drop into the low 20's during one night with the result that all
of the trees from which no fruit had been harvested were killed to the
ground. The trees from which a part of the fruit had been removed were
defoliated and all but the large limbs were killed. The trees from which
all the fruit had been removed two weeks or more before the freeze were
defoliated, but little or no injury to the woods occurred. The severe
injury was probably because the materials making for hardiness in the
wood had been transported to the maturing fruits and the temperature
dropped quickly before the trees had time to develop cold resistance.
It is a well-known fact that many kinds of non-woody as well as many
woody plants develop hardiness or cold resistance on exposure to very
gradually falling temperatures. This change, in the case of non-woody
plants such as cabbage or wheat, is spoken of as "hardening off." It is
not known how important this is in developing cold resistance in flower
and leaf buds of woody plants. It is quite possible that buds that have
become extremely tender as a result of rapid growth might, if held for
some time at temperatures too low for further growth, become quite
resistant to low temperatures just as do wheat or cabbage.
Generally speaking, the greatest amount of cold injury to the buds or
above-ground portions of a tree occurs on a single night. The length of
the cold period is of only indirect importance as influencing the rate
of temperature fall or the acquiring of cold resistance by the trees.
Trees that are subjected to low temperatures over a considerable period
of time are not nearly so likely to be injured as are those that are
subjected to a low temperature suddenly. That is really why there is so
much severe cold injury to woody plants in the South. In the deep South
freezing weather may be uncommon but when freezes do occur usually they
follow a period of comparatively warm weather and the temperature falls
quickly. It is this sudden change in temperature that causes the severe
injury. Two different places may have had the same mean monthly
temperature yet at one place severe injury may have occurred and no
injury at the other place with plants normally having equal hardiness. A
careful analysis of the situation, however, would probably show that at
the place where the injury occurred a period of warm weather had existed
which was followed by a rapid drop in temperature to a killing low on a
single night, whereas the trees at the place where no injury occurred
were not subjected to such changes in temperature. On the other hand,
injury to the roots usually occurs only after prolonged periods of cold
weather. This is largely because the soil cools slowly and it requires a
long period of cold weather to reduce the soil temperature sufficiently
and to such depths as to cause injury to the roots.
Under northern conditions where low temperatures for a rather long
period are sometimes experienced, injury to the portion of the trees
above ground may occur as a result of drying out of the wood. It is well
known that a cake of ice will gradually evaporate and disappear when in
the open and exposed continuously to below-freezing temperatures. We all
know that the family wetwash when hung on a line and frozen will soon
dry, especially if the wind blows. The principles operating in these
cases may cause severe injury to trees. In the wintertime the root
systems of trees take up water from the soil that is not frozen and this
water moves in the tree to replace that lost by evaporation. Under
conditions where the soil is frozen to such an extent that the water
absorbed by the roots is continually less than that lost by the top of
the trees by evaporation, drying out of the top occurs. If this is
continued over a period of time a dryness of the wood and other tissues
occurs that causes death of the dried-out portions. This type of injury
does not show the typical symptoms of cold injury but rather those of
drying out. The conditions that are most likely to cause such injury are
a soil frozen to the effective rooting depths, a dry atmosphere, and a
moderately high wind velocity. Injury of a similar nature to that just
described very often affects trees transplanted in late fall or early
winter, especially those that did not have their tops cut back to
balance the loss of roots sustained in transplanting. During even very
mild winters the tops of such trees dry out to such an extent that the
small branches and even the leader may die. In extreme cases the entire
top may die back to the root. In planting bare-root trees regardless of
the time of the year they should be rather severely cut back immediately
after transplanting to prevent such drying out and dying back of the
wood. Cut-back trees generally will make more growth the first season
following transplanting than will similar trees not cut back.
One of the most common types of injury to young nut trees as well as
others is that known as "sun scald" or "winter injury". This occurs
generally on the south or southwest sides of the trunk and for some
distance between the ground and the head of the tree. Usually the injury
is not evident until a year or so after it occurred and then it may be
observed as a narrow strip of discolored and sunken bark which may crack
where it meets the live tissue. This dead or injured area is usually
invaded by borers of one or more kinds. This so-called sun scald injury
is thought to be caused by the alternate freezing and thawing of the
tissues on the south and southwest sides of the tree. On a bright,
sunshiny day, even though cold, the sun's rays striking the bark of the
tree quickly raise the temperature of the bark and wood. When the sun is
obscured by clouds or at nightfall the temperature of the tissues drops
rapidly and they may freeze again. It is thought that the rapid and
rather great change in temperature of the bark and wood is the primary
cause of sun scald. Whatever the cause, we know that it can be prevented
by shading the tree trunk. This can be done by heading the trees low so
that the branches shade the trunk, or by shading the south side of the
trunk with a board 6 or 8 inches wide, or by wrapping the trunk with
burlap or similar material. Much of the injury to Chinese chestnut,
pecan, and hickory trees, especially, is caused by inexperienced growers
who cut off the low branches in an effort to raise the head of young
trees. The Chinese chestnut generally forms a very low-headed or
bush-type tree. Most of the cold or winter injury I have seen on Chinese
chestnut trees has been on the trunks and has resulted from removing the
lower limbs so that they were not shaded.
Hardiness in woody plants is only a relative term and is determined by
the condition of the plant at the time the low temperature occurs. Woody
plants are most tender when they are most actively growing and most
resistant to cold injury when they are in deep or profound rest. Strong,
vigorous, well-nourished trees are much more resistant to cold injury
than weak, poorly-nourished trees. Hence, the successful grower makes an
effort through disease and insect control and proper fertilization and
cultivation to keep his trees strong. These practices should be so
carried out that the trees will make a strong, vigorous growth in the
spring and early summer and then go into rest without a second or third
flush of growth. The trees should carry their leaves until frost as
there are some things made in them that cause the trees to develop
resistance to cold injury. Winter or cold injury can destroy in a single
night the hopes and expectations of several years' work but, in the
main, if one grows well only those trees that are suited to the
environment such losses are only rarely experienced.
Nut Culture In Ontario
I. C. MARRITT, District Forester, Ontario Department of Lands and
Forests
It was suggested to me that a paper be prepared on nut culture in
Ontario. The Department of Land and Forests of Ontario has not done
specialized work on nut culture. The reason for this neglect is not that
various members did not realize the importance of nut culture, but that
there was always more work on general reforestation and woodlot
extension than could be done. The work with nut trees has been along
with their general work. We have not, as yet, had a member of the staff
who has gone "nutty" over nuts. It is hoped that your meeting here will
stir up interest in this worthy subject.
We are very proud in Ontario of the work that has been done on general
reforestation and woodlot management. This is a subject that all nut
enthusiasts are interested in, and we would like you to know what is
being done in Ontario.
The Province of Ontario has been distributing trees free to landowners
since 1907. There are three well-equipped tree nurseries, and a fourth
is being developed in the eastern part of the province. A fifth nursery
has been started in the northwest at Fort William on Lake Superior. The
number of trees distributed varies considerably from year to year. The
high distribution years were 1939 and 1940, when approximately seventeen
million trees were planted each year. During the war years, on account
of the labour situation and war activities, the distribution declined to
between ten and eleven million trees. This past season, the demand was
much larger than the supply. All the nurseries are expanding, as it is
anticipated there will be a heavy demand by private planters, and also
most of the counties are enlarging the area of their county forests.
The application form for forest trees includes seven evergreens and
nineteen deciduous trees. Walnut and butternut are the only nut trees on
the application form. Shagbark hickory has also been grown, but not in
large enough quantity to include it in the list of available trees. The
St. Williams tree nursery near Lake Erie has grown named varieties of
walnuts and hickories. These have been given out to interested parties,
and, in future years, will further the growing of the more desirable nut
trees. About ten years ago, the citizens of St. Thomas planted nut trees
two or three feet in height for seventy miles along No. 3 Highway which
crosses Elgin County. A large number of these trees have survived.
A large acreage of forest trees has also been planted under the Counties
Reforestation Act. Under this act the county purchases the land and the
province plants and looks after the plantations for thirty years. The
county then has three options _re_ paying back the cost of planting and
supervision. All the options are without interest charges. The county
forests are largely on light sandy soils that, in most cases, are a
liability to the municipalities if they are not growing trees.
The Ontario Government passed an act in 1946 that gave the counties the
right to pass a by-law to regulate cutting on privately-owned woodlots.
You will be interested to know that eleven counties have passed by-laws
to regulate cutting. They are all based on a diameter limit. We realize
that a diameter limit is a poor substitute for good forestry practice,
but it is better than unrestricted cutting. The diameter limits range
from ten to sixteen inches for most trees, and five to six inches for
cedars.
Considerable extension work was done on nut growing in the period from
1920 to 1930. Mr. James A. Neilson, an Extension Horticulturist
stationed at Vineland, became very interested and located many
individual trees and gave numerous lectures on nut culture. A bulletin
by Mr. Neilson on nut culture was published in 1925, and reprinted in
1930, by the Ontario Department of Agriculture. Mr. Neilson went to
Michigan and did extension work on this subject until his untimely
death. Mr. G. H. Corsan has also done considerable work to keep nut
culture before the public by writing letters to the different
newspapers.
There has always been a large demand for black walnut. The reason for
this is the high value placed on this wood and the planting of these
trees for shade and nut production, although the consumption of native
nuts is comparatively low. The black walnut grew, originally, south of a
line from Toronto to Sarnia. It has been planted as far north as Ottawa,
and is distributed quite widely in Old Ontario now--being planted
largely as shade trees. These shade trees are producing nuts, and with
the aid of squirrels, the walnuts are seeding up along fence rows,
around farm homes, and in woodlots. Walnut has been observed coming up
in a woodlot, and the only possible source is a shade tree half a mile
away. The walnut caterpillar defoliates the trees but seldom kills them,
although it does lower their value as shade trees.
Walnut has been a favorite species for forest tree planting. It is
planted in pure stands and in mixtures. The largest and best known
walnut plantation was put out by Sir William Mullock in 1926 on the
highway north of Toronto. There are numerous small plantations
throughout the province. Foresters in Ontario generally recommend mixing
walnut with other hardwoods and evergreens rather than planting in pure
stands.
It has been advocated to plant walnuts with white spruce. The idea is
that spruce will shade the ground, kill the side branches of the walnut,
and help to force the walnuts to grow long slender poles. It is
understood, and expected, that the spruce will be ruined, as their
leaders would grow into the branches of the walnut. As far as we know,
this experiment has not been undertaken.
The butternut tree is found growing naturally farther north than the
walnut tree. Its northern boundary is roughly a line drawn from Midland
on Georgian Bay to Ottawa. It is widely distributed, but is not in large
enough quantity to have commercial value for lumber. An expert wood
carver, who is employed by the Department of Lands and Forests, uses
butternut largely in his work.
The shagbark and bitternut hickories make up the large percentage of the
hickories growing in Ontario. The northern limit of the bitternut is
approximately the same as the butternut--that is, Midland on Georgian
Bay and Ottawa on the east; while the northern limit of the shagbark is
thirty to forty miles south of the bitternut. The pignut and the
mockernut hickories are found in the southern hardwood belt along Lake
Erie.
The American chestnut was quite plentiful in different sections of the
southern hardwood belt. It was valued quite highly for the nuts. It has
been killed out by the chestnut blight and it is very rarely that live
suckers are seen.
The beech was widely distributed in the woodland of southern Ontario. It
has rarely been planted as a shade tree and it is not seeding up
extensively in woodlots. There are many stories of hogs being fattened
on beechnuts in pioneer days.
The Japanese heartnut has been planted in various parts of the province.
A heartnut tree in Bruce County lived through a hard winter that killed
many sugar maples and beech in the same area. Nut trees are seeding up
in many pastured woodlots in southwestern Ontario. The reason for this
is that stock do not relish their foliage as they do the maple, beech
and basswood, etc., and because of this, it is likely that nut trees
will make up a larger percentage of trees in Ontario woodlots than
originally, as it is a sad fact that at least seventy-five percent on
the farm woodlots in Ontario are still being pastured.
It is hoped that more interest will be shown in planting nut trees by
farmers and home owners. The Department of Lands and Forests is
enlarging its staff of Extension Foresters, and no doubt they will
include the propagation of nut trees in their extension work.
Nut Growing at the Horticultural Experiment Station, Vineland Station,
Ontario
W. J. STRONG
There was very little interest in nut growing in the early days of the
Horticultural Experiment Station although back in 1914 a few filberts
and Persian (English) walnuts were planted.
The first nut orchard at the Station was set out in 1922 and since then
several lots of nut trees have been added from time to time, principally
filberts and Persian walnuts. Also a few black walnuts, Japanese
heartnuts, Chinese chestnuts, hickories, pecan and several hybrids were
planted.
In 1922 twenty varieties of filberts were obtained from a nursery near
Rochester, N. Y. These were reputed to be some of the better sorts
imported from Germany but when they came into bearing only one was true
to name, this being Italian Red. Another un-named variety in this lot
(field number 3 R 1 A T 10, 11, 12), proved to be hardy and very
vigorous. The nuts were only of medium size but very well filled and of
good quality. The rest of these were a nondescript lot of worthless
varieties or seedlings and so after a few years nearly all were uprooted
and discarded.
At this time (1922) four varieties of Persian walnuts were planted,
Franquette, Mayette, Hall and Rush. The Franquette and Mayette have not
grown very well here and have given very poor yields. Both Hall and Rush
made good growth the first 15 or 20 years from planting but latterly,
growth has been poor and yields have fallen off considerably, although
this year (1947) there is a very fair crop showing, but with rather
much dropping. The nut of the Hall variety is quite large but the husk
is thick and the shell is thick and coarse, also in some seasons the
kernel has not filled out very well. The Rush has given good crops of
medium-size nuts. It seems to be rather susceptible to bacterial blight.
Five named varieties of black walnuts also were planted at this time
(1922), Thomas, Ohio, Stabler, Ten Eyck and McCoy. The Thomas has proven
to be the best of these and the value of the others was pretty much in
the order named. The last two were quite inferior as to nut, while the
Stabler lacked vigour and did not yield very well, although it is a nice
nut and the kernel comparatively easy to extract.
Eight Persian walnut seedlings in the same plantation, set out in 1926,
have made poor to fair growth. They have given very few nuts until this
year (1947) when two of them are showing a very fair crop.
About 1928 twenty Japanese walnuts and hybrids with the butternut, and
about the same number of Persian walnut seedlings, which have been
brought in by the late Professor Jas. A. Neilson, were transplanted to
the permanent fruiting positions. The Japanese walnuts and hybrids were
worthless and so were discarded. The Persian walnuts, however, seemed to
be of more value, several are quite nice nuts and one, at least, looks
to be worthy of increase for further trial or limited distribution. This
seedling (field number 13R3T14) has made very fair growth and has shown
only slight winter injury. For the last five or six years it has given
moderately good yields of very nice looking nuts. The nuts are large,
rather long and oval, resembling somewhat the Franquette. The shell is
smooth and moderately thick, well sealed but easy to crack. Usually they
are quite well filled and the kernel is mild in flavour and of nice
quality.
Another Persian walnut, set out about the same time, is the McDermid.
The original tree was found on the property of a Mr. McDermid at St.
Catharines, Out. One grafted tree and four seedlings were planted on the
Station grounds. They grew well and showed very little killing back and
for several years gave quite nice crops of nuts, but of recent years the
yield has been rather small. The nut is blunt-oval in shape and of good
size with a fairly hard shell which is well sealed but not any too easy
to open. The quality is fairly good but the pellicle is rather strong
flavoured.
The year 1936 may be considered the high water mark in nut planting at
the Station. A variety block of filberts was set out that year and fifty
one-year-old Persian walnut seedlings (Carpathian strain) were planted
in a nursery row, and in permanent location in 1937. The filbert
planting consisted of from three to nine bushes each of twelve
varieties, including Aveline (white), Barcelona, Bixby, Bolwyller,
Buchanan, Cosford, Daviana, Du Chilly, Medium Long, Red Lambert (?) and
Jones hybrid. These were planted in a compact block, 18 feet apart each
way on the square. A lesser distance no doubt would be sufficient for
upright growing sorts like Du Chilly but some of the more spreading
kinds can use the greater distance.