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Sweet cherry rootstocks
for the Pacic Northwest
Lynn E. Long and Clive Kaiser
PNW 619 • September 2010
A Pacic Northwest Extension Publication
Oregon State University • University of Idaho • Washington State University
All commercial sweet cherry trees are either
budded or graed. e part of the tree above
the gra/bud union is known as the scion and
the part below the gra/bud union is known as the
rootstock. Sweet cherry scion cultivars have been
selected over millennia for many reasons, but over
the past century, breeding programs have concen-
trated mainly on achieving improved characteristics
such as yield, taste, fruit size, fruit rmness, fruit
color, precocity, and resistance to fruit cracking and
disease. In contrast, rootstock cultivars have only
recently received attention.
Indeed, it is believed that ‘Mazzard’ seedlings were
rst used as sweet cherry rootstocks more than 2,400
years ago by early Greek and Roman horticulturists.
e fact that ‘Mazzard’ continues to be used widely
throughout the Pacic Northwest (PNW) is testi-
mony to the success of this seedling variety as a root-
stock. Over the past few decades, however, several
new rootstocks have gained prominence, oering
important attributes lacking in ‘Mazzard’. Many of
these new semi-dwarng rootstocks, although reduc-
ing tree vigor, may impart some disease resistance,
induce precocity, and enable growers to harvest
premium-quality fruit from high-density orchards.
Furthermore, full production may now be achieved
on these semi-dwarng rootstocks within ve or six
years, compared to similar trees on ‘Mazzard’, which
may take up to twelve years to reach full production.
is publication presents the current level of
understanding of the major cherry rootstocks and
links it to their performance in the PNW.
Graft Compatibility
For millennia, it has been known that ‘Mazzard’
rootstocks are compatible with all sweet cherry scion
cultivars, and even in modern times, no evidence
exists to contradict this statement. Since the end of
the eighteenth century in France, ‘Mahaleb’ was also
used as a cherry rootstock. is was due in part to
the partial dwarng eect that it imparts on cherry
scions when compared to ‘Mazzard’. In the mid-
nineteenth century ‘Mahaleb’ became popular in the
United States, and by the early 1900s it was the most
popular cherry rootstock, due mainly to its ease of
propagation from seed and its resistance to some dis-
eases when compared to ‘Mazzard’. However, by the
mid-1920s ‘Mahaleb’ was found to be incompatible
with several scion cultivars, resulting in premature
tree death, and ‘Mazzard’ again became the root-
stock of choice.
Some modern-day rootstocks have been shown
to be incompatible with some scion cultivars—for
example, ‘Weiroot 13’ in combination with several
scion cultivars, and ‘Colt’ in combination with either
Lynn E. Long, Extension horticulturist, Wasco County Extension,
Oregon State University. Clive Kaiser, Extension horticulturist,
Umatilla County Extension, Oregon State University.
Sweet cherry trees on dwarf and standard rootstocks.
Photo by Lynn E. Long, © Oregon State University.
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‘Sam’ or ‘Van’. At this time there have been no reports
of scion incompatibility with any of the commercially
available ‘Gisela’ rootstocks, including ‘5,’ ‘6’ and ‘12’.
Cold Hardiness
Cold hardiness is a complex physiological attribute,
and ndings from cherry rootstock research trials
around the world are inconsistent. Indeed, one of the
main confounding problems is that damage to scion
bud wood in fall is due to incomplete acclimatization
of the trees. is in turn results in poor winter har-
diness as well as damage to the trees in early spring
as trees break dormancy too early in the year. at
said, multiple studies have shown that many scion
cultivars graed onto ‘Mahaleb’ rootstocks will accli-
matize earlier in fall/winter than on other rootstocks.
e parent material of the ‘Gisela’ rootstocks, P. cera-
sus and P. canescens, are both hardier than ‘Mazzard’
and impart that hardiness to the three ‘Gisela’ root-
stocks currently available in the United States. ‘Colt’
is perhaps the only rootstock used in the United
States that is less hardy than ‘Mazzard’.
Flowering and Fruiting Habit
Cherry trees produce only simple buds—that is, only
one (solitary) bud per node—and each bud may be
either vegetative or oral. Vegetative buds on one-
year-old wood may either develop into shoots or
remain dormant. In subsequent years, these dormant
vegetative buds may become spurs. In other words,
spurs are only formed on wood that is two years of
age or older. Spurs can remain productive for up to
ten years if they enjoy adequate light interception.
Floral buds may contain up to ve owers per
bud, and they develop either from an axillary (lat-
eral) bud on one-year-old shoots or an axillary bud
of a spur. Where axillary buds on one-year-old wood
become oral, owers will either abort or produce
terminal fruit. In either case, this will result in blind
wood in subsequent years. Where numerous axil-
lary buds on a one-year-old shoot become oral, this
will result in the entire shoot having blind wood
that supports neither leaves nor fruit. Some culti-
vars such as ‘Tieton’, ‘Lapins’ and ‘Sweetheart’ have
a greater propensity for the production of entire
shoots of blind wood than do other cultivars.
Many of the new semi-dwarng rootstocks change
the fruiting habit of the tree, resulting in increased
ower density and greater numbers of spurs on the
trunk and in the center of the tree. Unfortunately,
however, semi-dwarng rootstocks are prone to set-
ting solitary (axillary) ower buds on one-year-old
wood, which results in blind wood.
Frost and Bloom
Although trees on productive rootstocks are at least
as sensitive to frost as those on standard rootstocks,
the former will oen produce more fruit aer a
severe frost due to initially higher ower counts. Fur-
thermore, in situations where no frost protection is
in place, owers closest to ground level are aected
worse than those furthest from the ground. Conse-
quently, where spring frosts occur during owering,
and articial heating of the orchards does not take
place, fruit set on semi-dwarng rootstocks will be
more severely aected than on non-dwarng root-
stocks, simply because the non-dwarng trees are
taller and the owers are further from the ground.
Given the fact that cherries are such a high-value
crop, it is advisable to install propane heaters and
fans to protect the owers during spring frosts.
Growth Habit and Size
Many of the new rootstocks are also size-control-
ling. However, the degree to which a tree is dwarfed
depends not only on the rootstock but also on scion
cultivar selection, soils, pruning severity and train-
ing system choice.
When coupled with ‘Bing’, ‘Gisela 12’ is more
dwarng than ‘Gisela 6’. However, a ‘Regina’/‘Gisela
12’ combination produces a tree that is approxi-
mately 10 percent larger than ‘Regina’/‘Gisela 6’.
Other varieties appear to exhibit similar inuences,
but observations are inconclusive at this time.
e site or location can also play a role in the
relative size of the tree. For example, in the eastern
United States, ‘Gisela 6’ produces a tree that is only
60 percent the size of a standard tree, whereas in the
PNW it produces a more vigorous tree growing to 90
percent of full size. Soil type and growing conditions
probably play a role in this discrepancy. Likewise,
‘Maxma 14’ grows more vigorously in the rich soils
of the PNW than in the calcareous soils of southern
France. Similarly, ‘Colt’, released in Europe as a semi-
dwarng rootstock, was found to produce a full-size
tree on irrigated sites in the PNW.
‘Gisela 5’ is the most dwarng commercially grown
rootstock in the PNW, reducing the tree to approxi-
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mately 50 percent that of standard size. Indeed,
research undertaken by the sweet cherry research lab
at Washington State University found that ‘Gisela 5’
and ‘Gisela 6’ had, respectively, 45 percent and 20 per-
cent lower-trunk cross-sectional areas aer seven sea-
sons when compared to ‘Mazzard’.
Knowing that a rootstock will decrease tree size
to 50 or 90 percent of the size of a standard tree can
be helpful; however, it doesn’t tell the whole story.
For example, with proper pruning and training
system inuence, a tree on ‘Gisela 6’ can easily be
maintained at a height of only 8 feet. When severely
pruned, many of the productive rootstocks such as
the ‘Gisela’ and ‘Krymsk’ series respond with mod-
erate, controlled growth, whereas a tree on ‘Maz-
zard’ will become invigorated through the growth
of water-sprouts. is moderate response, in con-
junction with a naturally wider branch angle, makes
trees on many of these productive rootstocks much
easier to manage.
Anchorage
Although typically grown without support, trees on
‘Gisela 6’ and sometimes ‘Gisela 5’ will oen tilt away
from the prevailing winds. is is especially true for
the more top-heavy central leader trees. Support,
through stakes or a trellis system, may be benecial
with these two rootstocks. Anchorage seems to be
adequate for all other rootstocks.
Planting Depth
Although scion rooting has been noted in limited
cases, it does not seem to be as serious or as prevalent
in cherries as in apples where the benets of the root-
stock are lost. Nevertheless, except for trees grown
on ‘Mazzard’ rootstock, it is wise to plant the gra
union several inches above the soil level in order to
prevent scion rooting.
Root Suckers
Most commercial cherry rootstocks used in the PNW
express limited to no root suckering. Occasionally,
depending on the conditions, ‘Mazzard’ can show low
levels of suckering. is has also been observed with
‘Krymsk 5’ and several of the ‘Weiroot’ clones such
as ‘Weiroot 158’. To date, however, this has not been a
problem with other cherry rootstocks.
Yield and Fruit Quality
One of the main advantages of the semi-dwarng
rootstocks is precocity when compared to traditional
rootstocks. Indeed, research results from the sweet
cherry research laboratory at Washington State Uni-
versity, comparing ‘Bing’ on ‘Mazzard’, ‘Gisela 5’
or ‘Gisela 6’, found that aer seven seasons, ‘Bing’
graed on ‘Gisela 6’ were the most productive, yield-
ing between 13 and 31 percent more than those on
‘Gisela 5’, and 212 to 657 percent more than those on
‘Mazzard’, depending on the year. Both ‘Gisela’ root-
stocks improved precocity compared to ‘Mazzard’,
bearing fruit in year 3 in the orchard.
Bacterial Canker
Bacterial canker, caused by Pseudomonas syringae,
is a pathogen of sweet cherries found in all cherry
production areas around the world. Infection rates
of 50 to 80 percent have been reported in some of the
wetter regions of the PNW, such as the Willamette
and Hood river valleys in Oregon. Even in the drier
regions of Central Washington and Oregon, infec-
tion and mortality rates can approach 10 percent or
more in some years.
e P. avium clone F 12/1 has shown tolerance to
this pathogen. erefore it is used in the Willamette
Valley as a high-budded stock in order to slow down
or stop a branch infection before it infects the trunk
and threatens the entire tree. In this situation, the
stock is grown out to the point of branching and
scion wood is budded onto the branches of the root-
stock.
Reports from the literature (Spotts et al., 2010) as
well as limited grower experience would indicate that
‘Colt’ rootstock shows greater tolerance to the dis-
ease than ‘Mazzard’, while ‘Krymsk 5’ shows greater
to similar tolerance to the disease than ‘Mazzard’.
Additionally, trees grown on ‘Gisela 6’ were less toler-
ant than ‘Mazzard’.
Virus Susceptibility
Prune dwarf virus (PDV) and prunus necrotic ring-
spot virus (PNRSV) are commonly found in mature
orchards throughout the PNW. Most strains of these
two viruses show few if any symptoms when trees
on ‘Mazzard’, ‘Mahaleb’ or ‘Colt’ rootstocks are
infected. However, some of the newer rootstocks,
such as ‘Gisela 7’ and ‘Weiroot 158’, show varying
degrees of sensitivity to one or both of these viruses
4
when inoculated in a controlled trial (Lang et al.,
1998). In this same trial, ‘Gisela 5’, ‘6’ and ‘12’ were
shown to have varying levels of tolerance to these
two viruses, with only a slight reduction in vigor
when infected.
Two Russian rootstocks, VSL 2 (‘Krymsk 5’) and
LC 52 (‘Krymsk 6’), were found to be hypersensi-
tive to these viruses (personal communication).
Much debate has taken place over the past few years
concerning the importance of these ndings. Since
hypersensitive trees die quickly when infected, some
scientists believe that hypersensitivity may ultimately
be benecial to an orchard block since infected trees
die before the virus can be transmitted to surround-
ing trees. In addition, a limited number of the hyper-
sensitive ‘Gisela 7’ trees were planted by PNW grow-
ers in the mid-1990s without reports of widespread
mortality. However, it would be wise not to plant
trees on hypersensitive rootstocks in an interplant
situation among mature trees or close to blocks of
older trees that may be infected with one or both of
these viruses.
Choosing the Right Rootstock
Several factors must be taken into account when select-
ing rootstocks for a new orchard (Table 1). Soil fertility,
scion cultivar choice and desired training system are
some of the more important aspects. In most cases you
will want to avoid the most dwarng rootstocks, such
as ‘Gisela 5’ and ‘Krymsk 6’, where soils are shallow or
low in fertility. Other productive rootstocks such as
‘Gisela 6’, ‘Krymsk 5’ or even ‘Maxma 14’ may perform
more satisfactorily on these sites, but higher planting
densities should be considered where soils are poorest.
In addition, it is best to avoid planting ‘Mahaleb’ root-
stocks in heavy soils. ‘Mahaleb’ will do poorly under
these conditions, and will potentially die out, whereas
‘Krymsk 5’ and ‘6’, although not adapted to wet soils,
will survive in heavier soil conditions than ‘Mahaleb’
or even ‘Mazzard’.
Full-size rootstocks such as ‘Mazzard’, ‘Maha-
leb’ and ‘Colt’ are best suited to standard-density
orchards of 120 to 160 trees per acre. However, when
trained as a Spanish bush or modied Spanish bush
(KGB), all three of these rootstocks may be grown
at densities of between 300 and 340 trees per acre.
Commercial plantings at these higher densities, in
the PNW as well as in Australia and Spain, have
proven successful using these training systems. Due
to the increased vigor of these rootstocks, a spindle
or central leader system is usually not recommended
since these trees tend to grow very tall. Furthermore,
scion cultivars of low productivity, such as ‘Regina’
and ‘Tieton’, have not produced satisfactory yields on
these rootstocks.
Most modern-day rootstocks such as ‘Gisela 6’,
‘Gisela 12’, ‘Krymsk 5’ and ‘Krymsk 6’ are semi-
dwarng, resulting in trees ranging in size between
‘Gisela 5’ and the grouping of ‘Mazzard’, ‘Mahaleb’
and ‘Colt’. Soil depths of 3 feet to greater than 5 feet
are normally recommended for semi-dwarng root-
stocks. On shallower soils it is necessary to increase
the tree density. All of the semi-dwarng rootstocks
are well suited to the modern training systems grown
in the PNW. Although ‘Maxma 14’ is precocious, it
produces a full-size tree and is therefore not recom-
mended for some of the higher-density systems such
as the UFO (upright fruiting oshoots) system or
single leader trees such as the Vogel central leader.
e moderately vigorous rootstocks are also more
widely adapted to and grow well with most variety
combinations. It is true that the most productive
varieties such as ‘Sweetheart’ and ‘Lapins’ can be a
challenge with any size-controlling rootstock, but
even with these combinations, growers have been
successful at consistently growing high-quality fruit.
e key is to pay close attention to pruning principles
(see PNW 592) and to perform required procedures
in a timely fashion. While productive varieties can
be challenging, these moderate size-controlling root-
stocks are just right for varieties of lower productiv-
ity such as ‘Regina’ and ‘Tieton’, and perform well
with moderately productive varieties such as ‘Bing’,
‘Skeena’ and ‘Benton’.
‘Colt’ (P. avium x P. pseudocerasus)
‘Colt’ was released by the research station in East
Malling, England, in the 1970s as a semi-dwarng
rootstock. However, in the irrigated orchards of the
PNW it produces a vigorous tree that is similar in
size to ‘Mazzard’ with similarly low precocity. In
addition, ‘Colt’ is sensitive to droughty soils and to
cold winter temperatures.
‘Colt’ has been widely planted in California due
to its resistance to cherry stem pitting, a debilitating
virus disease readily found in that state. It has also
shown resistance to Phytophthora root rot, bacte-
rial canker and gopher damage, but is susceptible
5
to crown gall. In the PNW, ‘Colt’ performs well in
replant situations where cherries follow cherries on
non-fumigated sites (Long, 1995).
‘Gisela 5’ (P. cerasus x P. canescens)
Although it is the most popular rootstock in Ger-
many and other parts of Europe, ‘Gisela 5’ has failed
to gain widespread acceptance in the PNW. It is the
most dwarng rootstock currently available com-
mercially in the United States. In the PNW, ‘Gisela 5’
is known to reduce vigor by up to 50 percent or more
compared to ‘Mazzard’ seedlings. e medium-low
vigor of this rootstock coupled with very high fruit
production has caused fruit size and quality issues.
is problem is accentuated when ‘Gisela 5’ is com-
bined with productive cultivars such as ‘Lapins’ and
‘Sweetheart’. When properly pruned and grown on
deep, fertile soils, it may be suitable for very high-
density plantings of 400 to 800 trees/acre and is
probably best suited to spindle systems such as the
Vogel central leader, or to the UFO system developed
at Washington State University.
More than any other commercial rootstock,
‘Gisela 5’ tends to advance both owering and fruit
ripening by two to four days, a potential advantage
for early-ripening cultivars where an early harvest
window provides higher returns. is may, however,
be disadvantageous in a frost-susceptible site or when
the harvest of a late-ripening cherry is advanced.
‘Gisela 5’ produces trees that are open and spread-
ing with wide branch angles, but branching may
be sparse. Anchorage is usually adequate, but some
growers have taken the precaution to support the tree.
Some suckering may occur, depending on growing
conditions, but this is usually not a problem. Trees on
‘Gisela 5’ rootstock have shown good winter hardi-
ness, and scion compatibility has not been an issue.
‘Gisela 5’ does not perform well in heavy soils
and needs good drainage. Trees show sensitivity to
replant stress so should only be planted on virgin
sites or where the soil has been properly treated with
fumigants prior to planting.
‘Gisela 6’ (P. cerasus x P. canescens)
‘Gisela 6’ is the most popular rootstock for new plant-
ings in Oregon. Even though it is a relatively vigorous
rootstock, it is easy to manage. Recommended plant-
ing densities are 300 to 500 trees per acre. Although it
Table 1. Planting parameters for various commercially available cherry rootstocks
Variety
super high
density
moderately
high density*
low density*shallow or
poor soils
low-productive
varieties
highly productive
varieties
‘Colt’ No No Yes Yes No Yes
‘Gisela 5’ Yes No No No Yes No
‘Gisela 6’ No Yes No At higher
densities
Yes Needs proper
management
‘Gisela 12’ No Yes No At higher
densities
Yes Needs proper
management
‘Krymsk 5’ No Yes No At higher
densities
Yes Needs proper
management
‘Krymsk 6’ Needs proper
management
Yes No At higher
densities
Yes Needs proper
management
‘Mahaleb’ No No Yes Avoid heavy
soils
No Yes
‘Maxma 14’ No Yes No At higher
densities
Yes Needs proper
management
‘Mazzard’ No No Yes Yes No Yes
*See text
Best suited for...
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exhibits medium-high vigor, it is also very precocious,
producing harvestable crops by the third leaf with full
production possible by the h leaf. Due to these high
production levels, trees on ‘Gisela 6’ need to be prop-
erly pruned from an early age in order to maintain
fruit size and quality. Premium fruit quality is pos-
sible with cultivars of moderate to low productivity,
such as ‘Bing’, ‘Skeena’ and ‘Regina’, but more dicult
with very productive cultivars. As with all size-con-
trolling rootstocks, it is imperative to maintain ade-
quate levels of vigor in order to produce high-quality
fruit. e production of new shoots is much easier to
achieve with ‘Gisela 6’ compared to ‘Gisela 5’ and is
one of the reasons for the popularity of this rootstock.
‘Gisela 6’ tends to advance owering and fruit rip-
ening only slightly compared to ‘Mazzard’. Trees are
open and spreading with good branching. Anchorage
can be a problem, especially on windy sites, although
most growers in the PNW do not provide support.
‘Gisela 6’ is well suited for a wide range of soil types
from light to heavy; however, good drainage is essen-
tial. Trees grown on this rootstock have not been prone
to suckering and scion compatibility has been good.
‘Gisela 12’ (P. cerasus x P. canescens)
Tree vigor and size on ‘Gisela 12’ is variable depend-
ing upon cultivar combination. Several years of test-
ing in e Dalles, Oregon, and in Prosser, Wash-
ington, indicated that when combined with ‘Bing’,
‘Gisela 12’ produced a tree intermediate in size to
‘Gisela 5’ and ‘6’. However, grower experience with
‘Regina’ indicates that ‘Gisela 12’ produces a tree
approximately 10 percent larger than ‘Gisela 6’. For
this reason some growers prefer a ‘Regina’/‘Gisela 12’
combination as they nd it easier to maintain shoot
growth and ultimately fruit size.
‘Gisela 12’ is both precocious and productive, pro-
ducing early heavy crops, with full production pos-
sible by the h leaf. Good fruit size and quality are
possible with proper pruning.
‘Gisela 12’ is adapted to a wide range of soils,
resists suckering and is well anchored. e tree struc-
ture is open and spreading and new branches form
readily. Scion compatibility has not been a problem.
‘Krymsk 5’ (P. fruticosa x P. lannesiana)
is precocious, semi-dwarng rootstock originated
in the Black Sea region of Russia. Grower experience
in the PNW suggests that ‘Krymsk 5’ is comparable
in size to ‘Gisela 6’ with slightly less precocity and
yield. Production of ‘Lapins’ on ‘Krymsk 5’ through
the eighth leaf in Oregon indicates that premium-
quality fruit can be produced consistently on this
rootstock when properly managed.
‘Krymsk 5’ is adapted to a wide range of soil types,
with reports that it will grow well in heavier soils than
‘Mazzard’. Accounts out of Russia indicate that the
rootstock is well adapted to cold climates. In addition,
Table 2. Attributes of various commercially available cherry rootstocks
Variety Tree size*Precocity Advance bloom/
harvest
Compatibility Root suckers Anchorage
‘Colt’ 100 No No Good No Good
‘Gisela 5’ 50–60 Yes 2–4 days Good No Fair to good
‘Gisela 6’ 85–90 Yes 0–1 day Good No Fair
‘Gisela 12’ 80–100 Yes No Good No Good
‘Krymsk 5’ 85–90 Yes No Limited data Moderate Good
‘Krymsk 6’ 65–70 Yes No Limited data Moderate Good
‘Mahaleb’ 90 Slight No Fair to good No Good
‘Maxma 14’ 100 Yes No Good No Good
‘Mazzard’ 100 No No Good Low Good
*Percent of full size
7
early indications suggest that trees on this rootstock
might also perform well in hotter climates, as leaves
remain turgid in extreme heat and don’t show the char-
acteristic cupping of ‘Gisela’ trees in hot conditions.
Trees are well anchored and do not need support. Low
to moderate levels of root suckers can be found grow-
ing from the crown, but usually not in the tree row. e
tree form is excellent, with wide branch angles.
‘Krymsk 6’ (P. cerasus x (P. cerasus x P. maackii))
‘Krymsk 6’ produces a tree that is only 75 to 80 per-
cent the size of ‘Krymsk 5’ or ‘Gisela 12’. In one com-
mercial orchard in Oregon, ‘Lapins’ fruit size and
quality through the eighth leaf on this rootstock has
been excellent.
Like ‘Krymsk 5’, ‘Krymsk 6’ rootstocks seem to
be adapted to both cold and hot climates as well as
heavier soils. Trees are well anchored, but there is low
to moderate root suckering. Tree form is good, with
wide crotch angles. Like ‘Krymsk 5’, ‘Krymsk 6’ is
sensitive to PDV and PNRSV.
‘Mahaleb’ (P. mahaleb)
‘Mahaleb’ is slightly more precocious and slightly
less vigorous than ‘Mazzard’ and it is one of the most
drought-tolerant cherry rootstocks, having deep-set
roots. ‘Mahaleb’ is, however, extremely sensitive to
water-logged soils as well as soils that may be anaerobic
for a short time during the winter months. ‘Mahaleb’
is best suited to deep, well-drained loams and sands
as well as the calcareous soils typical of Spain and
southern Italy. ere, and in similar locales around
the world, ‘Mahaleb’ is the preferred rootstock. In the
PNW, ‘Mahaleb’ rootstocks are generally used only in
light, sandy-loam soils and readily die out in ravines
and other low-lying areas where water collects.
Incompatibility of some sweet cherry cultivars can
be a problem with ‘Mahaleb’, as this condition has
been detected up to six years aer planting. ‘Chelan’
and ‘Tieton’ have expressed incompatibility symp-
toms when grown on ‘Mahaleb’. In addition, ‘Maha-
leb’ is attractive to gophers. Consequently, control
measures must be pursued with diligence.
‘Maxma 14’ (P. mahaleb x P. avium)
‘Maxma 14’ originated in Oregon from an open-
pollinated ‘Mahaleb’ tree. However, it has been most
widely accepted in France due to its precocity, semi-
dwarng nature and resistance to iron-induced chlo-
rosis caused by calcareous soils.
Oen a change in growing location modies root-
stock characteristics. In a trial conducted in Oregon
on loamy soils, ‘Maxma 14’ rootstock produced a tree
larger than ‘Mazzard’ through the h leaf when
combined with ‘Bing’. For this reason it is not rec-
ommended for super-high-density plantings in the
PNW. Fruit size was statistically similar, although
trending smaller, but production in the h leaf was
signicantly greater with an average of 46 pounds
per tree compared to only 2.8 pounds per tree for
‘Mazzard’. Due to high yields, trees must be properly
pruned each year.
‘Maxma 14’ shows good scion compatibility and
a broad adaptation to soil types and environmental
conditions. Very little suckering has been noted.
‘Mazzard’ (Prunus avium)
Growers in the PNW have a long tradition of plant-
ing ‘Mazzard’ rootstock. It is well adapted to PNW
soils, it is winter hardy, and due to the fact that it is
the same species as sweet cherry, there have been
no cases of incompatibility. In addition, due to high
vigor and moderate productivity, premium fruit
quality can be obtained with only moderate inputs in
pruning and management.
Unfortunately, it lacks precocity, oen not coming
into production until the h or sixth leaf or into full
production until the twelh leaf. Vigorous growth
makes it dicult to control in high-density plantings,
and the large tree size reduces picker eciency and
increases the hazards associated with harvest.
‘Mazzard’ does well in a wide range of soils from
sandy-loam to clay-loam. However, as with other
cherry rootstocks, it does not perform well in poorly
drained or wet soils. Root suckers are usually not a
problem except in limited situations.
F 12/1 (P. avium)
F 12/1 is a vegetatively propagated selection of ‘Maz-
zard’ used in many locations around the world
instead of the seedling-propagated ‘Mazzard’. West-
ern Oregon growers prefer F 12/1 to ‘Mazzard’ due
to its resistance to bacterial canker. e F 12/1 root-
stock forms the trunk from the branch union down
and the scion is budded onto each lateral branch. e
bacteria-resistant rootstock slows the progression of
8
canker infection that develops on the branches and
hinders the infection from proceeding to the trunk.
Many nurseries, however, prefer not to grow this
selection due to sensitivity to crown gall caused by
Agrobacterium tumefaciens. F 12/1 is more vigorous
than ‘Mazzard’ seedling in many locations where it
is grown.
Summary
Unfortunately, no one rootstock can satisfy all the
requirements for consistently producing copious
amounts of large, rm fruit of premium quality.
Growers are strongly advised to consider carefully
the eects of each specic rootstock/scion combi-
nation as a function of environmental and cultural
practices when replanting an orchard (Tables 1 and
2). Selecting the proper rootstock depends not only
on the management skills of the grower but also on
the scion cultivar, training system and site selected
for the orchard. Furthermore, it is oen possible for
semi-dwarng cherry rootstocks to be highly pro-
ductive. However, when these rootstocks are com-
bined with productive scion cultivars, it can lead to
an over-cropping situation. In addition, productive
scion/rootstock combinations are only recommended
for fertile soils. For more information about the
attributes of specic cultivars, please see PNW 604,
“Sweet Cherry Cultivars for the Fresh Market.”
Semi-dwarng rootstocks do, however, have
major economic advantages. A recent study con-
ducted among several Oregon growers (Seavert
and Long, 2007) found that growers could recover
their entire cost of establishment in eight years with
a high-density orchard on productive rootstocks,
compared to een years for a standard-density
orchard on ‘Mazzard’ rootstock.
e development of these new semi-dwarng,
precocious rootstocks has been almost as signicant
to the sweet cherry industry as to the apple industry
several decades ago. When compared to ‘Mazzard’,
‘Colt’ and even ‘Mahaleb’, size-controlling rootstocks
have allowed sweet cherry growers an opportunity to
plant high-density, pedestrian orchards that aord
high early yields, easier management and a safer and
more productive working environment.
References
Lang, G., W. Howell, and D. Ophardt. 1998. Sweet cherry
rootstock/virus interactions. Acta Horticulturae
468:307–314.
Long, L. E. 1995. Colt rootstock may be answer for cherry
replant disease. Good Fruit Grower 46 (4).
Seavert, C. F., and L. E. Long. 2007. Financial and economic
comparison between establishing a standard and high
density sweet cherry orchard in Oregon, USA. Acta
Horticulturae 732:501–504.
Spotts, R. A., K. Wallis, M. Serdani, and A. Azarenko. 2010.
Bacterial canker of sweet cherry in Oregon: Infection
of horticultural and natural wounds, and resistance of
cultivar and rootstock combinations. Plant Disease,
March.
For More Information
Long, L. E. 2003. PNW 543: Cherry training systems, selection
and development. Corvallis, OR: Oregon State University.
Long, L. E. 2007. PNW 592: Four simple steps to pruning
cherries on ‘Gisela’ and other productive rootstocks.
Corvallis, OR: Oregon State University.
Long, L. E., M. Whiting, and R. Nunez-Elisea. 2007. PNW
604: Sweet cherry cultivars for the fresh market. Corvallis,
OR: Oregon State University.
© 2010 Oregon State University
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University, Washington State University, and the University of Idaho. Similar crops, climate, and topography create a natural geographic unit
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