When To Plant Potatoes In Idaho

Knowing when to plant potatoes in Idaho is the first step to a great harvest. Getting the timing right means your spuds grow strong and produce plenty of tubers before the first fall frost. This guide will walk you through the best planting times for your specific area and give you the tips you need for success.

Idaho’s climate varies a lot, from the short seasons in the mountains to the longer, warmer summers in the valleys. This means planting time isn’t the same everywhere. We’ll break it down by region so you can plan your garden with confidence.

For most of Idaho’s populated agricultural valleys, the classic planting window is from late March through mid-April. However, soil condition is just as important as the calendar date.

Understanding Your Idaho Growing Zone

Idaho spans USDA hardiness zones 4 through 7. Your zone is a key factor in your planting schedule.

Zone 6 & 7 (Treasure Valley, Lewiston area): These are the warmest regions. You can often plant as early as late March if the soil is ready.
Zone 5 (Idaho Falls, Pocatello, much of the Snake River Plain): Aim for mid to late April. Frosts can linger here into May.
Zone 4 (Higher elevations, like McCall or Island Park): Wait until late May or even early June. The soil takes much longer to warm up.

The Best Soil Test: Temperature and Texture

Potatoes need cool, but not cold, soil to begin growing. A soil thermometer is your best tool.

Plant when soil temperature is consistently at least 45°F (7°C). A range of 45-55°F is ideal.
The old-timer’s test works too: grab a handful of soil. If it’s soggy and forms a muddy ball, it’s too wet. If it’s crumbly and falls apart, it’s perfect. Planting in cold, wet soil can cause seed pieces to rot.

Working Around the Last Frost Date

Potato foliage can handle a light frost, but a hard freeze will damage it. Know your area’s average last spring frost date.

You can plant potatoes 2-4 weeks before your last expected frost date, as long as soil conditions are good.
If a severe frost is forecast after planting, you can protect emerging plants with a light covering of straw or a frost cloth.

Choosing the Right Potato Variety for Idaho

Selecting varieties suited to your season length improves your harvest. Here’s a few popular choices for Idaho gardens:

Early Season (70-90 days): ‘Yukon Gold’, ‘Red Norland’, ‘Irish Cobbler’. These are excellent for shorter seasons or for getting new potatoes early.
Mid Season (90-110 days): ‘Russet Burbank’ (the classic Idaho baker), ‘Kennebec’, ‘Purple Majesty’. These are the mainstay for storage.
Late Season (110-135 days): ‘Butte’, ‘Canela Russet’. Need the longest, warmest growing seasons, best for southern Idaho.

Step-by-Step Planting Guide

Follow these steps for a strong start.

1. Preparing Seed Potatoes

Always use certified disease-free seed potatoes from a garden store. Don’t use potatoes from the grocery store.

About a week before planting, “chit” or green-sprout your seed potatoes. Place them in a cool, bright spot to encourage short, sturdy sprouts.
On planting day, cut larger seed potatoes into pieces. Each piece should be about the size of a golf ball and have at least 1-2 eyes (sprouts).
Let the cut pieces air-dry for a day to form a callus over the cut surface. This helps prevent rot.

2. Preparing the Garden Bed

Potatoes need loose, well-drained soil with lots of organic matter.

Choose a spot that gets full sun (at least 6-8 hours).
Work the soil deeply, breaking up any clods. Mix in several inches of compost or well-rotted manure.
A slightly acidic soil pH of 5.0 to 6.0 is perfect for potatoes.

3. The Planting Process

Dig a trench about 6 inches deep.
Place seed pieces cut-side down, with the eyes facing up, about 12 inches apart in the row.
Space rows about 2.5 to 3 feet apart to allow for hilling later.
Cover the seed pieces with 4 inches of soil. Leave the trench slightly depressed; you’ll fill it in as the plants grow.

Caring for Your Potato Plants

Consistent care after planting is crucial for a good yield.

Watering and Hilling

Potatoes need even moisture, especially once they start forming tubers.

Water deeply once a week, providing about 1-2 inches of water. Avoid letting the soil dry out completely, then flood it.
When plants are about 6 inches tall, begin “hilling.” Mound soil from between the rows up around the base of the plant, covering about half the stem. This protects developing tubers from sunlight (which turns them green and toxic) and encourages more potatoes to form.
Hill again every few weeks as the plants continue to grow.

Fertilizing and Pest Watch

A balanced approach keeps plants healthy.

Use a balanced, low-nitrogen fertilizer at planting. To much nitrogen encourages leafy growth instead of tubers.
Watch for Colorado potato beetles. Hand-pick the yellow eggs and orange larvae off leaves. Row covers can also prevent them from reaching plants.

Harvesting Your Idaho Potatoes

Harvest time depends on what type of potato you want.

New Potatoes: For tender, thin-skinned new potatoes, harvest about 2-3 weeks after the plants finish flowering. Gently dig around the edges of the plant with your hands.
Storage Potatoes: For mature potatoes, wait until the plant vines have completely died back. This allows the skins to toughen up for storage. Use a digging fork to carefully lift the entire plant.

Let your storage potatoes cure in a dark, well-ventilated place for 1-2 weeks before putting them in long-term storage in a cool, dark cellar or garage.

Frequently Asked Questions

Can I plant potatoes in the fall in Idaho?

Fall planting is generally not recommended for most of Idaho. Our winters are to cold, and the ground freezes solid, which would kill the seed potato. Spring planting is the reliable method.

What if I planted my potatoes to early and a frost comes?

If a light frost is expected, you can cover the emerged plants with straw, old blankets, or specialized row cover. If the tops get nipped, the plant will often send up new growth from below the soil. A hard freeze is more damaging, so watching the forcast is key.

How late is to late to plant potatoes?

You need enough time for the variety to mature before the first hard fall freeze. Count back 90-120 days (depending on your variety) from your average first fall frost. In much of Idaho, planting after late June is risky for full-size tubers.

Can I grow potatoes in containers in Idaho?

Absolutely! Container growing is a great option, especially if you have limited space or heavy soil. Use a large container (at least 10-15 gallons), ensure excellent drainage, and follow the same timing guidelines as in-ground planting. The soil in containers often warms up a bit faster in spring.

By paying attention to your local conditions and following these guidelines, you’ll be well on your way to harvesting a bumper crop of homegrown Idaho potatoes. There’s nothing quite like the taste of potatoes you’ve grown yourself.