 |
Practical Grower Lynn Long on .... |
|
Working with Weiroot |
|
| |
Practical Grower Lynn Long on .... |
|
Working with Weiroot |
|
For years, cherry growers have recognized the advantages of
growing small trees on dwarf rootstock. They've observed the revolution
that has taken place in the apple industry due to dwarfing rootstocks,
and longed to be a part of it. They've realized the potential
that these rootstocks provided the apple industry for increased
production and productivity. They've seen crops being produced
in the second or third leaf and mature trees harvested from the
ground, without tall ladders.
However, good dwarfing rootstocks have eluded the cherry grower.
That is, until recently. After 10 years of trials in the U.S.
and comprehensive scientific investigation in Germany, scientists
in the western U.S. finally have the data to justify grower trials
of a limited number of Gisela rootstocks. This is an important
and exciting step, but growers have yet to validate the results
of the scientists. Another German rootstock series has not had
the level of scientific scrutiny associated with the Gisela series,
but has been accepted and used commercially by foreign growers
for a number of years. This is the Weiroot series making up 80%
of the new plantings in the Franconia region of Germany. Weiroot
will soon be available to American growers and deserves a closer
look.
The Weiroot rootstocks were originally selected from wild sour
cherry (Prunus cerasus) seeds growing in the mountainous
regions of Bavaria. These alpine sources assured scientists that
the plant material would be winter hardy, a problem in Bavaria
for the more sensitive Colt rootstock out of England.
After years of testing by scientists and extension personnel,
two series of releases were eventually made. The first generation
of releases included Weiroot 10, 13, and 14 -- of which Weiroot
13 was the most popular and widely planted. All of these selections
were relatively vigorous, reducing growth by 20% to 30%. These
rootstocks introduced the concept of size control to Franconian
growers. Coupled with the poor soils of the area, they provided
increased precocity along with reduced tree height, giving growers
the ability to grow a 15-foot tree. In fact, Weiroot 13 became
so popular that it replaced Mazzard F 12/1 as the standard for
the region.
However, the goal of scientists was to provide growers with a
range of tree vigor and not simply a semi-dwarf tree. Therefore,
a second generation of releases was made, which included Weiroot
154, 158, 53 and 72. These rootstocks provided growers with true
dwarf alternatives to the standard rootstocks. From this series
of releases, Weiroot 154 and 158, providing 50% reduction in vigor,
have proven to be the most satisfactory. Weiroot 53 and 72, at
25% to 30% the size of F 12/1, have shown more problems with mortality
than the other selections and have not been as widely accepted.
Probably the most exciting aspect about the Weiroot rootstocks
are their ability to maintain fruit size while reducing tree size.
It is this factor alone that has caused disappointment in other
potentially promising cherry rootstocks. The data reported in
the table above was collected by Tobias Vogel, Extension Agent
for the Franconia area of Germany. Vogel states that years of
data substantiates that cherries grown on Weiroot 10 produce fruit
of similar size to that grown on F 12/1. He therefore considers
Weiroot 10 as the check.
While growers in the Franconia region of Germany have been successful
utilizing Weiroot rootstocks in their commercial production, scientists
and growers in other regions of Europe have not always shared
that success. Reports of high mortality rates, especially with
Weiroot 53 and 72, have caused scientists to speculate on the
reason for these failures. Concerns have been expressed over issues
of cultivar compatibility and virus susceptibility. Cultivar compatibility
has been suspected in both German and Swiss trials after significant
mortality occurred. However, Bavarian scientists successfully
combined 70 different cultivars with the Weiroot rootstocks. Compatibility
problems occurred only with Van, and that only on a limited number
of rootstocks such as Weiroot 14.
For good reason there is much excitement and expectation surrounding
the Weiroot rootstocks. German growers are successfully growing
excellent cherry crops with these rootstocks even now. However,
it must be remembered that these rootstocks have not been tested
in the U. S. Differences in soil, climate, and diseases can drastically
affect the way a rootstock will perform. In addition, tests have
not been conducted to determine whether these rootstocks are compatible
with our cultivars or whether they are sensitive to our viruses.
The Weiroot rootstocks will be included in the next NC-140 trial
for direct comparison against the better Gisela rootstocks. In
addition, a consortium of scientists from Oregon and Washington,
called the Genotype Research Consortium, will be testing the Weiroot
stocks for susceptibilities. As scientists evaluate these rootstocks,
growers should consider small test plots to determine their suitability
for their local conditions.
|
|
| Weiroot 13 -- Of moderate to high vigor, Weiroot 13 grows 70% to 80% the size of F 12/1. Mature tree height is 12 to 18 feet, depending on the training system utilized. Precocity is good as well as fruit size. It exhibits good anchorage and does not need staking. A good choice for poorer soils. |
| Weiroot 154 -- A moderate vigor rootstock exhibiting 50% to 60% the vigor of F 12/1. This rootstock is quickly gaining favor in Germany since it combines the best yields with good fruit size. Central leader trees on this stock typically grow 12 to 15 feet tall. Best results are obtained on good soils. No support is necessary. |
| Weiroot 158 -- An intermediate size rootstock growing 40% to 60% the size of F 12/1. Trees can be held to 10 to 15 feet in height. This is the most popular Weiroot stock in Germany. It exhibits good precocity, although somewhat less than Gisela 5. Fruit size is good and the propensity for ripening one or two days early that is exhibited by Gisela 5 does not seem to be a problem with this rootstock. Weiroot 158 does not generally need to be staked. |
| Weiroot 53 -- A weak-growing stock producing trees 30% to 50% of F 12/1. This rootstock should only be grown in good soils to prevent growth problems. Properly managed, this stock can provide high early yields with good fruit size. Staking is recommended. |
| Weiroot 72 -- The lowest vigor stock, producing trees 25% to 30% the size of F 12/1. The potential tree height is only 6 to 9 feet tall. Trees are very precocious and fruit size is slightly smaller than that produced by the other rootstocks listed above. This rootstock requires excellent soil and optimum tree, soil, nutrition and water management to maintain fruit quality. Trees need to be supported. |
|
Various Cultivars on Five Rootstocks |
|||
|
|
|
|
|
| Weiroot 10 |
|
|
|
| Gisela 5 |
|
|
|
| Weiroot 158 |
|
|
|
| Weiroot 53 |
|
|
|
| Weiroot 72 |
|
|
|
