Italian vs Mount Royal: Picking a European Plum for Cold Country

These are the two European plums we'd plant first. Italian is the classic prune plum: big, purple, freestone and very sweet when it's fully ripe, and the best plum we grow for drying and baking. It's hardy to zone 3b. Mount Royal is the tough one, rated zone 2b, with a light blue plum that's best fresh. If you're in a cold spot, Mount Royal. If you want prunes and pies, Italian. If you can, plant both, since Mount Royal is a good pollenizer for Italian.

Hardiness

Mount Royal is rated zone 2b, winters to -45F. It has come through -44F in west central Minnesota and -42F in Columbus, Montana, and it has survived and cropped consistently at MSU's Lodgepole Fruit Research Site in Montana, where it has seen colder than -45F.

Italian is rated zone 3b, winters to -35F. It took -25F in Missoula on January 13, 2024 with no sign of injury. Its absolute limit is likely around -35F, possibly -40F on a good site free of frost pooling. It's a fine plum for most of western Montana, but not the colder pockets like Potomac. Check your site with the cold hardiness calculator.

Pollination

Mount Royal is self-fertile and fruits as a single tree. Italian is partially self-fertile. It sets some fruit alone, but it crops better with another European plum nearby, like Mount Royal. Both are bloom group 4 of 7. Neither will cross with Asian or American plums, so a hybrid plum won't pollenize them. See the plum pollination map.

Ripening

Mount Royal ripens about August 31 to September 12 in Missoula. Italian ripens later, about September 9 to September 29. In Missoula we let the first frost hit Italian before we pick, since it softens and sweetens the fruit. Don't leave it out for a lot of frosty nights in a row, though, or it goes bland. The ripening map has the dates for your town.

Fruit and Uses

Italian is a large, purple-skinned freestone plum. It scores 10/10 for drying, 9/10 for pies and baking, 9/10 for cooking and roasting, 8/10 for sauce and butter, 8/10 for canning and freezing and 7/10 fresh.

Mount Royal is a light blue, juicy, semi-freestone plum with sweet flesh. It scores 8/10 fresh and 7/10 for jams, canning, drying, cooking and sauce. It's excellent fresh and just okay dried.

Rootstock and Size

Italian comes on Lovell, full size, about 12 to 20 ft unpruned. Lovell doesn't like wet feet or high-lime soil. Mount Royal comes on Native Plum or Prairie Red Plum, both semi-dwarf, about 10 to 15 ft unpruned, and both hardy to at least -50F. Both of those roots sucker, so plan on mowing or pulling suckers. Our rootstock guide covers all three.

Deer

Deer love both. Fence or cage them.

	Italian	Mount Royal
Hardy to	Zone 3b (-35F), took -25F with no injury	Zone 2b (-45F), survived -44F
Bloom group	4 of 7, mid	4 of 7, mid
Pollination	Partially self-fertile	Self-fertile, pollenizes Italian
Ripens in Missoula	Sep 9 to Sep 29	Aug 31 to Sep 12
Fruit	Large, purple, freestone	Light blue, juicy, semi-freestone
Rootstock and size	Lovell, 12 to 20 ft	Native Plum or Prairie Red, 10 to 15 ft, suckers
Best uses	Drying 10/10, pies 9/10, cooking 9/10	Fresh 8/10
Deer	Favorite, fence it	Favorite, fence it

What We'd Plant

In Missoula, the Bitterroot or anywhere in zone 3b to 4, plant Italian for prunes, pies and roasting, with Mount Royal next to it so Italian crops heavier and you get a fresh-eating plum a week or two earlier. In zone 2b or 3a, or a frost pocket, Mount Royal alone. It's self-fertile and it's proven well past -40F.