When To Plant Potatoes In Northern California

If you’re a gardener in Northern California, figuring out when to plant potatoes is the key to a great harvest. Getting the timing right for when to plant potatoes in northern california means you work with the unique climate, not against it.

Our region’s mild winters and long growing seasons are a big advantage. You can actually grow potatoes twice a year in many areas. This guide will walk you through the best planting windows, varieties, and steps for success.

Northern California’s prime potato planting times are late winter and late summer. The goal is to let potatoes grow during cool, not cold, weather and mature before the heat of summer or the chill of winter.

Primary Planting: Late Winter to Early Spring

This is the main planting season for most gardeners.

Best Time: Plant from late January through March.
Key Signal: Soil is workable and no longer soggy from winter rains.
Goal: Harvest in early summer before the hottest weather arrives.

Secondary Planting: Late Summer

For a fall harvest, you can plant a second crop.

Best Time: Plant from late July through early August.
Key Signal: After the peak summer heat has passed.
Goal: Harvest in late fall before the first heavy frost.

Microclimate Matters

Your specific location makes a big difference:

Coastal Areas (SF, Monterey): Mild year-round. You can plant almost any time, but early spring and late summer are still best. Frost is rarely a issue.
Inland Valleys (Sacramento, Napa): Hotter summers, colder winters. Stick strictly to the Jan-Mar window for spring planting. Fall planting is trickier due to early frosts.
Mountain/Foothill Areas: Shorter season. Wait until April or May, after all danger of frost is gone, for a single summer crop.

Using Soil Temperature as a Guide

A soil thermometer is your best friend. Plant your seed potatoes when the soil at planting depth (about 4 inches) consistently reaches 45°F to 50°F. This is more reliable than calendar dates alone.

Choosing the Right Potato Variety

Pick types that match the season and your taste.

Early Season (60-80 days): ‘Yukon Gold’, ‘Red Norland’. Great for spring planting for a quick harvest.
Mid Season (80-100 days): ‘Kennebec’, ‘Purple Majesty’. Excellent all-purpose choices for our main seasons.
Late Season (100+ days): ‘Russet Burbank’. Need a long, cool growing period. Best for coastal areas with very mild summers.

Always buy certified disease-free seed potatoes from a garden center, not grocery store spuds.

Step-by-Step Planting Guide

Follow these steps for a healthy start.

1. Prepare the Soil

Potatoes need loose, well-draining soil. They prefer a slightly acidic pH of 5.0 to 6.0.

Work the soil to a depth of 12 inches.
Mix in generous amounts of compost or well-rotted manure. Avoid fresh manure, it can cause scab.
Create raised rows or hills about 10 inches tall. This improves drainage and warms the soil faster.

2. Prepare Seed Potatoes

About a week before planting, encourage them to sprout.

Place seed potatoes in a bright, airy spot indoors.
If they are larger than a golf ball, you can cut them into pieces. Each piece must have at least 2-3 “eyes” (sprout buds).
Let the cut pieces sit out for a day or two so the cut surface dries and forms a callus. This prevents rot.

3. Plant Correctly

In your prepared hill or row, dig a small hole 4 inches deep.
Place the seed potato piece with the eyes facing up.
Space pieces 12 inches apart in the row, with rows 3 feet apart.
Cover gently with 3-4 inches of soil.

4. The “Hilling” Process

This is crucial for good tuber production.

When green shoots reach about 6-8 inches tall, mound soil around the base, leaving just the top leaves exposed.
Repeat this process every few weeks. This protects developing tubers from sunlight, which turns them green and toxic.
Continue hilling until the plants begin to flower.

Caring for Your Potato Plants

Consistent care leads to a bigger yeild.

Watering

Keep soil consistently moist, but never waterlogged. Water deeply once or twice a week, depending on weather. Inconsistent watering leads to misshapen tubers. Reduce watering once plants start to yellow and die back.

Fertilizing

They are moderate feeders. At planting, use a balanced organic fertilizer or one higher in phosphorus (for root growth). Avoid high nitrogen fertilizers later on, which encourages leaves, not potatoes.

Pest and Disease Watch

Colorado Potato Beetle: Hand-pick adults and larvae. Check undersides of leaves.
Blight: A fungal disease. Ensure good air circulation and avoid overhead watering. Rotate your potato crop location each year.
Gophers & Voles: Plant in raised beds lined with hardware cloth if these are a problem in your area.

Harvesting Your Potatoes

Knowing when to harvest is as important as knowing when to plant.

For “New” Potatoes

You can gently dig around the plant and steal a few small, tender potatoes about 2-3 weeks after the plants finish flowering. This doesn’t harm the main plant.

For Mature, Storage Potatoes

Wait for the plant’s foliage to turn yellow, brown, and die back completely.
Stop watering to let the skins toughen up.
On a dry, sunny day, use a garden fork to carefully dig up the entire plant, starting far out from the stem to avoid spearing tubers.
Let potatoes cure on the soil surface for 2-3 hours, then move to a dark, well-ventilated place for 1-2 weeks to cure further.

Store cured potatoes in a cool, dark, and humid place. Properly stored, they can last for months.

Frequently Asked Questions (FAQ)

Can I plant potatoes from the grocery store?

It’s not recommended. They are often treated with sprout inhibitors and may carry diseases that can stay in your soil. Certified seed potatoes are a safer investment.

What if I plant potatoes too late in spring?

If planted too late, the tubers will try to form during the peak summer heat. This can lead to poor tuber set, smaller potatoes, or increased pest problems.

How do I grow potatoes in a container?

Use a large pot or grow bag (at least 10-15 gallons). Follow the same steps, but you’ll “hill” by adding more potting mix instead of soil. Container potatoes need more frequent watering.

Why are my potato leaves turning yellow?

Late in the season, it’s a natural sign of maturity. If it happens early, it could be overwatering, a nutrient deficiency, or the start of a disease like blight.

Can I save my own seed potatoes for next year?

You can, but select tubers from your healthiest plants. Store them properly and check for disease. There is a risk of carrying over viruses, so many gardeners prefer to buy new certified seed each year.

By following these timing and care tips, you can enjoy two productive potato seasons in Northern California. The key is observing your garden’s conditions and getting those seed potatoes in the ground at the right moment. With a little planning, you’ll be digging up homegrown potatoes in no time.