North American Fruit Explorers mailing list at ibiblio

["dwalsh/wchase" <wchase@interchange.ubc.ca>]

Del,

I don't know anything about rootstock hardiness (coming from rainy PNW), but 
I am
just reading a book Rootstocks for Fruit Crops by Roy C Rom and Robert F 
Carlson.
1987 and I've scanned the chapter on hardiness.

As far as I can see there is no mention of Malus prunifolia.  They do mention 
M
baccata and M robusta, but usually in reference to breeding programs.   (Rom 
is
from U of Arkansas and Carlson is from Michigan State U )

Chapter 4 Rootstocks by David Ferree and Robert f Carlson

 3.2. Rootstock Adaptation to Climate

Hardiness. There are genetic differences among apple rootstocks in cold 
hardiness.
Generally, however, in the principle apple-producing regions of North 
America, the
commonly used Malling and Malling Merton rootstocks have proved sufficiently
winter hardy for commercial use. In an occasional test winter, especially in 
areas
of more extreme temperature fluctuations like the Great Plains, mortality of 
the
rootstocks has occurred.

In New York State, field nursery observations following air temperatures of 
-31
to -34°C revealed a relatively more hardy group of rootstocks (M.1, M.2, M.3, 
M.4,
M.5, M.7. M.12, and M.16), a relatively less hardy group (M.9 and M.13), and a
group not hardy at these temperatures (M.6, M.8, M.10, and M.15). In western
United States and Canada, Delicious on M.7 survived -44°C, while trees on M.2
showed severe injury. In other cold-hardiness trials, Ottawa 4, Ottawa 3, 
MM.106,
and C52 have been tolerant of -35°C but intolerant of -40°C.

Predisposition of rootstocks may affect their response to cold temperatures, 
for
example, M.26 has appeared to be very cold hardy in some tests and relatively
sensitive in others. Roots discernible at the soil surface and arising from
burrknots or nodes on M.26, M.27, MM.106, and CG.10 have been killed at
approximately -15°C. Unfortunately, this type of injury may serve as infection
sites for root-rotting fungi. Factors such as previous crop load and 
temperatures
leading up to the extreme may be equally important in determining ultimate 
injury,
and these factors no doubt account for much of the variability among 
rootstocks.

Fruit-producing areas of the world subject to extremely cold winter 
temperatures
have served as rootstock cold-hardiness test sites. In Poland, in a test year
without snow cover, and with a soil temperature of -11°C at a depth of 5 cm,
nearly 75% of trees on M.9 were killed, while only 15-20% of trees on M.26 and
Bud.9 were killed. The Polish rootstocks P.2 and P.22 were as hardy as 
Antonovka
seedlings and retained considerable hardiness during fluctuating warm and cold
periods. In Minnesota field studies that purposely removed snow from test 
sites,
the rootstocks M.7, M.9, M.26, MM.104, and  MM.106 were hardy at -18°C. Both
root-freezing tests and field observations indicated that M.26 was more hardy 
and
M.7 less hardy than the other clones.

Winter-hardy cultivars have been used as rootstocks and as trunk and scaffold
systems for less hardy cultivars. During a test winter in Washington State 
with
temperatures of -44°C, Robusta 5, Antonovka, 'Hibernal', and 'Red Astrachan'
survived and demonstrated more cold tolerance than scaffold systems of 
'Mcintosh',
'Delicious', 'Haralson', and 'Canada Baldwin' . Apparently in addition to the
hardiness provided by the trunk stock itself, some hardiness can be imparted 
to
the scion cultivar by 'Hibernal'. In Oregon during a November freeze of -18°C,
trunk stocks of 'Transparent', 'Hibernal', 'Haralson', 'Canada Baldwin',
Antonovka, 'Charlamoff', and 'Hyslop Crab' prevented tree crotch and trunk 
injury.
Lapins classified the hardiness of various frame builders as follows: Very 
Hardy:
'Anis', 'Charlamoff', 'Heyer 12', 'Hibernal'; Hardy: Antonovka, 'Beautiful
Arcade', 'Borovinka', 'Duchess', 'Haralson', Malus robusta No. 5, 'Robin', 
'Yellow
Transparent'; Moderately Hardy: 'Anoka', 'Canada Baldwin', 'McIntosh', 
'Melba',
'Red Astrachan', 'Winter St. Lawrence'.

One of the most important ways that rootstocks can influence hardiness of the
scion cultivar is by speeding maturity in the fall and delaying budbeak in the
spring. Rootstocks that induce early maturity of the scion, such as M.9 and 
M.7,
tend to protect trees from fall freezes, but this may not relate to protection
against midwinter cold. M. 1, M.4, M5, and M.7 have been shown to attain cold
hardiness nearly two months earlier than M.2, which is most cold sensitive 
early
in the autumn

Several rootstocks, such as M. 13 or M.16, when left to develop into fruiting
trees, bloom as much as two weeks later than the bloom of most commercial 
apple
cultivars. However, the time of bloom characteristic apparently isn't 
conveyed to
the scion, as scions on these stocks generally bloom at their normal time. 
Another
factor to be considered is precocity, or the earliness in the life of the tree
that flowering begins. 'Northern Spy' is notoriously tardy, as a cultivar, to
begin flowering and fruiting. However, as a rootstock, it tends to induce
precocity similar to seedling rootstocks. M.9 tends to be precocious both as a
scion and rootstock, and as a rootstock induces precocity in the scions. Thus 
it
appears that the flowering characteristics of a given clone cannot be 
predicted to
have the same influence as a scion as when the clone is used as a rootstock.


p 111. Texture. In whole-tree excavation studies, Rogers and Vyvyan found that
depth of rooting increased from sand to loam to clay. In loam and sand, the 
root
system had the same general conformation - a shallow scaffold with vertically
descending roots. While in clay, most roots sloped downward and grew in the
subsoil. The total amount of root/tree was greatest in loam soils, followed by
clay, with the least amount of root in sandy soils. On all soil types, roots
spread farther than the branches, and in sand, root spread was 2 to 3 times 
branch
spread, but in loam and clay, it was only 1 to 1.5 times. In sand, roots were
long, thin, straight, and spreading, while in clay the roots were fairly 
short,
tapering, rapidly branching, and twisting in all directions. In the loam, the
roots were intermediate in appearance between those in sand or clay. The
rootstocks grown in these various soil types maintained their unique character
with only slight changes on various soil types. For example, on the sandy 
soil,
depth of rooting was greatest for the experimental rootstock (DF5) and least 
for
M.9 and M.1, while on the loam, M.9 had the deepest roots.

Hope this helps the discussion,

Derry

Derry Walsh & Bill Chase  email:wchase@interchange.ubc.ca
Aldergrove,  B. C.,  Canada
phone/fax (604) 856-9316
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Home web page  http://www.interchange.ubc.ca/wchase/HTML
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Sent: Saturday, December 02, 2000 9:01 PM
Subject: Re: [nafex] Tender rootstocks in zone 3


im ignorant on the subject of cold tolerance as relates to
: soil type. We're on hilly heavy clay, ( 340' deep to be exact! having had a
: well dug)   i dont know where there is a snow belt in this area, last year
: we looked at grass all winter-sad skis., so i guess any slightly tender
: trees would have been snuffed.  so far i have 100 apples ive grafted onto
: malus prunifolia. What is anyones opinion about it and its use in heavy
: soil?   i heard its one of the origional 4 apples, true?    any knowledge of
: its origin location? i was taught to graft just below the soil line, for
: varietal regeneration , but is this advisable  in heavy soil
thanks, minnesota del
:



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