By Bernie Nikolai
I’ve always felt that the magnificent Siberian Crab has received a “bum rap” over the years. Here we have a tree that can take -50°F with zero snowcover, and come out smiling the next spring without any injury! It has a tough corky bark which makes it virtually immune from spring sunscald injury, and it has an excellent root structure, making for an extremely tough, solidly anchored tree.
Perhaps we tend to look for the exotic in cold climates. Perhaps rumors of incompatibility with other apple cultivars, or fragile graft unions are to blame. I thought I’d relate the experience people have had using Siberian Crab as a rootstock for over 50 years here on the Canadian prairies.
Siberian Crab is extremely tough! I visited the 100-tree orchard of an elderly fruit enthusiast last fall. He claims that in 84 years he had never seen tip dieback on this cultivar, despite temperatures well in the -50°s (Farenheit) over the decades. If you are growing trees in central Alberta or Alaska, this is the sort of stuff we need!
As a rootstock the problem people are afraid of is potential incompatibility. I’d say 90% plus of the older apple trees here in the city of Edmonton are on Siberian Crab rootstock. Many of my trees are on this rootstock, and I’ve yet to see any evidence of incompatibility. Perhaps this is because all the prairie-hardy Canadian apples (Parkland, Norland, Westland, PF51, etc.) have a fair amount of Siberian Crab in their acestry. I have heard that after a few years in Alaska a few years in Alaska a few Siberian Crabs have had their grafted-on cultivars “blow off” in a windstorm. Perhaps the answer is budding. I have never heard of this happening here in Alberta, but all Siberian Crab rootstocks are budded with the desirable cultivar at about ground level or slightly higher. Perhaps a whip-and-tongue graft just might blow off in a few trees after a few years at the graft union.
I have had good success using an interstem of a prairie-hardy tree on Siberian Crab rootstock, and grafted “exotic” apples onto the interstem. Again I have never experience a single incompatibility problem. Cultivars like McIntosh, Discover. Summerred, Jersey Mac, etc. All seem perfectly at home on my Parkland or September Ruby frame trees on Siberian Crab roots.
I understand that last year was a test winter in Alaska due to -40°F with little or no snowcover in parts of the state. I’m confident if you check your survivability reports you will find that the trees on Siberian Crab faired far better than those on other rootstocks. Clair Lammers in Fairbanks mentioned in his orchard very few Siiberian Crab trees were killed, but there was wholesale slaughter on other rootstocks.
If you put a gun to my head and made me choose another rootstock besides Siberian, Ranetka would get the nod. But my suggestion is why risk it? Use Siberian Crab. It’s tough, compatible, and a close to kill-proof in a cold climate as exists among apple cultivars. I’d suggest “budding” on young trees is the way to go, not whip and tongue grafting, which may cause a “blowout” in a small percentage of trees a few years down the line.