North American Fruit Explorers mailing list at ibiblio

[Douglas Woodard <dwoodard@becon.org>]

From internet references, Roselow Crab appears to be Malus sargentii,
described as originating in Japan, though it's not clear exactly what
its exact range actually is. A USDA site shows its zone of adaptation 
stopping slightly short of the Canadian border in Minnesota. One 
internet reference says that it is not hardy beyond minus 33 degrees 
Farenheit, although perhaps you (Gerald) have the most solid information 
about that.

It is said to be best adapted to sandy soils.

The references seem to mostly agree that M. sargentii is a shrubby dwarf
growing to about 8 feet high or a little more, though one says 22
feet. It may be relevant that according to some statements nursery
sources often offer open-pollinated seedlings.

In what appears to be a chapter extracted from "Fruit Breeding: Trees
and Tropical Fruits" by Jules Janick and J.N. Moore,

<http://www.hort.purdue.edu/newcrop/pri/chapter.pdf>

it is stated

"Orchard evaluation [evidently as rootstocks] of seedlings from the 
M.sargentii x 'M.9' selections has not been encouraging; yields have 
been low and fruits small ([Hannah] Schmidt, 1988)."

There is an article "Field performance of Malus sargentii as a Rootstock 
for Four Commercial Apple Varieties" by W. C. Olien, W. C. Stiles, and 
R. C. McCrum in Fruit Varieties Journal (now Journal of the American 
Pomological Society) Volume 40 Number 4, October 1986 (quarterly) pp. 
140-143.

If you wish you should be able to get a photocopy through the 
interlibrary loan service of your public library. If not, contact me and 
I will see what I can do.

My take is that Roselow crab does not look like a good risk from the 
limited information I have.

If you have any difficulty getting small numbers of cheap hardy 
rootstocks, then seedlings of one prairie-hardy crab which has mainly 
common apple and Siberian crab Malus baccata in its breeding (or 
Antonovka) pollinated by another should do. From tests by Agriculture 
Canada some years ago, the pollen parent (father) makes a considerable 
difference to the hardiness of the offspring. Antonovka or Robusta 5 
crossed with Osman crab gave pretty good results. The classical apple 
rootstock for the Canadian prairies used to be Columbia crab seedlings, 
naturally with a prairie-hardy pollen parent.

I would test the seedlings through a least one winter at your site, 
preferably with the snow removed from the soil around the seedlings. One 
would expect some variation in coldhardiness. It might be wise to 
discard unthrifty or excessively vigorous (much more than their fellows) 
seedlings.

If you want a semi dwarf rootstock one solution might be an interstem of 
Ottawa 3 or Budagovsky 9 on a crab seedling. If necessary the dwarfing 
interstem might be obtained from a tree grown from a root cutting. 
Ottawa 3 is said to be sensitive to common apple viruses.

If you can get it, in a trial at Palmer, Alaska, Budagovsky 118 (I 
believe a semi-dwarf) showed up well for winter survival even compared 
to Malus ranetka.

Ottawa 8, another semi-dwarf mentioned by Bob Bors was trialed by some 
commercial orchards in Eastern Ontario and I would expect Quebec, I 
think in the 1960s. I talked to a grower in Eastern Ontario in the late 
1970s who was pleased with his early experience of it. If you ask around 
 among apple growers and the Quebec scientists you might be able to 
find a source. Even if you can just get scionwood of it you could graft 
it on a dwarf or semidwarf nurse root (maybe your Roselow seedlings) 
planted deep for scion rooting, if you have the time for that.

Doug Woodard
St. Catharines, Ontario, Canada
<dwoodard(at)becon.org>


Gérald Tremblay wrote:
> What do you think about using Roselow Crab has a cold climate dwarfing 
> apple rootstock?  I have 10 graftied this spring and doing very well for 
> now and a bunch of young seedlings.
>  
> Gerald, Quebec Z3