Growing Potatoes in Montana

Potatoes are a great crop for Montana!

Did you know that Montana is typically the #3 or #4 top producer of seed potatoes in the US, and Gallatin County accounts for almost half of the potato-growing acreage in the state?

Potatoes prefer cool, sandy soil and grow well in our climate.

When to Plant

• Plant when soil is workable and 40–55°F+ (early/mid May in-ground, or earlier in raised beds/bags)

• You can plant potatoes about two weeks before the last frost if soil is well-draining, not soggy. (Our average last frost in Bozeman is around June 3, but it can be as early as mid-May)

• If your soil is well-draining, you can plant potatoes as early as it can be worked, and they’ll come up when soil temperatures are high enough. Potatoes are cool-tolerant but if you want to get a jump on the season, plan on protecting potato sprouts from hard frosts or heavy snow (though potatoes can take a very light frost and recover)

How to Plant

Cut seed potatoes into chunks with at least two eyes (sprouts) per piece. Allow to dry overnight to form a skin to prevent rotting.

1. Trenches (Planting In-Ground)

• Make sure soil is well-worked and loose. Dig trench 4–6” deep

• Space seed pieces 8–12” apart (6” for smaller potato varieties)

• Cover with soil, then hill soil up as plants grow

2. Raised Beds

• Follow depth & spacing instructions for Trenches

• You can plant several weeks sooner in raised beds since they thaw sooner than the ground

• Water more frequently as raised beds will dry out faster

3. Containers / Grow Bags

• Follow depth & spacing instructions for Trenches

• Use 6+ gallon container with drainage, add 1/2 and 1/2 mix of potting soil and compost

• Start about 1/3 to 1/2 full, and add soil in layers as plants grow (“hilling”)

What are Determinate vs Indeterminate Potatoes?

• Determinate (usually marked early/short season)

  • All tubers develop at once

  • Faster (great for short growing seasons in Montana), mature in 70-90 days

• Indeterminate (usually marked long season)

  • Keep producing as you hill

  • Larger yield but need longer season (90-120 days)

What Potatoes Need

• Sun: 6+ hours daily

• Soil: loose, well-drained

• Water: consistent moisture (about 1–2”/week)

• Fertilizer: moderate; avoid excess nitrogen (compost is best!)

• “Hilling”: piling loose dirt, compost, or straw/leaf mulch around plants as they grow taller to protect tubers from sun/heat and also encourage more production (in long-season varieties)

• Weeding: Potatoes don’t like competition, but be careful of shallow roots or tubers near the surface!

What Types to Get

All varieties generally grow well here, so choose based on how long your season is and how you want to use them:

• Russet: used for baking & fries (store longest, 4-6+ months)

• Yellow (Yukon): all-purpose, buttery flavor (store 2-4 months)

• Red: used for boiling, salads (store 2-3 months)

• Purple/Blue: all-purpose, high in antioxidants, denser than other potatoes (store 2-3 months)

• Fingerling: roasting, tender texture (shortest storage, 1-2 months - best eaten fresh)

How & When to Harvest

• You can steal “new potatoes” as soon as you feel in the soil that they’re big enough: 60–70 days after planting

• Full Harvest:

  • Short Season/Determinate: After potatoes flower (check for tuber size)

  • Long Season/Indeterminate: After leaves die back (usually after first frost)

• Store in cool, dark place (not fridge)

Troubleshooting

• Too Small / Too Few Potatoes

  • Possible causes: Planted too late, not enough sun/water, too crowded, too much nitrogen (lots of leaves but few tubers)

• Potato Scab (Rough/Corky/Scabby Patches)

  • Common in our alkaline soil, can be caused by using seed potatoes that aren’t certified disease free or exacerbated by using fresh manure or infrequent watering.

  • Scab is a cosmetic issue. It’s ok to eat these potatoes, but the scab-causing bacteria live in the soil, so don’t re-plant potatoes in the same area.

• Rotting

  • Soil too wet and cold - make sure you have better drainage, or amend your soil to make it looser

• Green/Bitter Potatoes

  • Exposed to sunlight (fix by hilling soil higher)

• Blight (Brown/Black Spots on Leaves)

  • Don’t get water on leaves; rotate crops each year

• Frost Damage

  • Protect from heavy frost - plants will recover from light damage, but may yield less. Frost cover can help with this & extend your growing season.

Final Notes:

• Potatoes may form small, tomato-like fruit after they bloom - fruit is not edible, so keep away from children and pets

• Protect growing tubers and stored potatoes from sunlight so they don’t turn green. Green potatoes are very bitter and also can cause stomach upset.

• Some people plant the whole potato and get great results! Feel free if you want to experiment (and save some time)