Zone 4a: What Grows and How to Garden There

What a zone 4a winter means

Zone 4a is cold, but it opens up choices that zone 3 does not have: more apple varieties, some dwarfing rootstocks, and a long list of perennials rated to zone 4. The risk shifts from steady deep cold to winters without snow. Wisconsin Extension describes how a snowless winter froze soil deeper than normal and caused dieback and death, while snow-covered plants came through. Snow also has a downside: voles and rabbits work under it and chew bark, so guard young fruit trees.

Where zone 4a is

Zone 4a takes in much of North Dakota, including Fargo, Bismarck, Grand Forks and Williston; northern Minnesota and Wisconsin; northern Montana and Wyoming; the Upper Peninsula of Michigan; northern New York in the Adirondacks; northern Vermont and New Hampshire; and northern Maine. In the West it includes high valleys in Idaho, Colorado and Utah, and in Alaska the southwest around Bethel and Dillingham.

Fruit trees and small fruit

• Apples: NDSU’s zone 3 list plus zone 4 choices such as ‘Wolf River’ and ‘SnowSweet’; ‘Honeycrisp’ and ‘Zestar!’, only marginal in zone 3, are better suited to zone 4. SDSU warns that ‘Delicious’, ‘Fuji’, ‘Gala’ and ‘Braeburn’ are not reliably hardy.
• Pears: ‘Golden Spice’, ‘Summercrisp’ and ‘Ure’.
• Plums: hybrids such as ‘Pembina’, ‘Pipestone’, ‘Underwood’ and ‘Waneta’, with ‘Toka’ as a pollinator.
• Cherries: tart ‘North Star’, ‘Meteor’ and ‘Mesabi’, and Saskatchewan bush cherries.
• Grapes: hardy hybrids only. SDSU notes that areas with longer seasons and milder winters suit grapes best, and NDSU’s Carrington station names ‘Valiant’ as the easiest for North Dakota.

Perennials, bulbs and shrubs

Common lilac (zone 2), Pekin lilac (zone 3) and rugosa rose (zone 2) are dependable shrubs. Peonies, daylilies, hostas, Siberian iris, baptisia and daffodils are long-lived perennials. Plant tulips and daffodils 6-8 inches deep in fall.

Short-season vegetables

Montana State’s frost tolerance ratings are a good guide: peas are very hardy; beets, broccoli, carrots, kale, lettuce and onions are hardy; beans, cucumbers, peppers, squash and tomatoes have no frost tolerance. Use transplants for tender crops, and plastic mulch and row covers to warm them. Maine Extension notes row covers raise daytime air temperature by up to 10°F but must come off for pollination.