When To Plant Potatoes In Southern California

If you’re a gardener in Southern California, knowing when to plant potatoes is the key to a great crop. For optimal harvest timing, you need to sync your planting with our unique coastal and inland climates.

Our long growing season is a big advantage, allowing for multiple planting windows. This guide will walk you through the best times, varieties, and methods to get the most from your potato patch.

You have two primary planting seasons here: late winter and late summer. The best time for you depends on whether you live near the coast or further inland.

Primary Planting Windows

For most of Southern California, the first and main planting is in late winter. Aim for January through early March. The soil is starting to warm, and the threat of a hard frost is usually past.

Your second chance comes in late summer for a fall harvest. Plant from late July through early September. This is especially good in hotter inland areas, as the potatoes mature during cooler fall weather.

Coastal vs. Inland Timing

Coastal gardeners have a more forgiving schedule. You can often plant from January all the way into April. The cool, foggy summers are perfect for potatoes, which dislike extreme heat.

Inland gardeners must be more precise. Plant your first batch as early as January, but be prepared to cover sprouts if a late frost hits. For your summer planting, wait until the peak summer heat starts to fade, often in mid to late August.

Using Soil Temperature as Your Guide

The most reliable method is to check your soil temperature. Potatoes grow best when soil is between 45°F and 55°F. You can use a simple soil thermometer. If you don’t have one, a good rule of thumb is to plant when you can comfortably work the soil and it’s no longer soggy from winter rains.

Choosing the Right Potato Variety

Not all potatoes are created equal, and some perform better in our climate. You’ll want to select varieties based on your planting season.

Early Season (60-80 days): These are excellent for a quick harvest. Try ‘Yukon Gold’, ‘Red Norland’, or ‘French Fingerling’. They’re great for both winter and summer plantings.
Mid-Season (80-100 days): A reliable choice for our long season. ‘Kennebec’, ‘Purple Majesty’, and ‘All Blue’ are fantastic options.
Late Season (100+ days): These require the longest, coolest growing period. ‘Russet Burbank’ does well in inland areas if planted very early. They can be trickier near the coast if summers are too cool.

Always buy certified disease-free seed potatoes from a garden center. Don’t use potatoes from the grocery store, as they are often treated to prevent sprouting.

Step-by-Step Planting Guide

Follow these steps to get your potatoes off to a strong start.

Prepare the Soil: Potatoes need loose, well-draining soil. Work the area to a depth of 12 inches. Mix in several inches of compost or aged manure. They prefer slightly acidic soil (pH 5.0-6.0).
Chit Your Seed Potatoes: About 2-3 weeks before planting, set your seed potatoes in a cool, bright place. This encourages short, sturdy sprouts, which gives them a head start.
Cut and Cure (Optional): Larger seed potatoes can be cut into pieces, each with at least 2-3 “eyes.” Let them cure for a day or two so the cut surface calluses over, preventing rot.
Planting Depth and Spacing: Dig a trench or individual holes 4-6 inches deep. Place the seed potato piece sprout-side up. Space them about 12 inches apart in rows that are 2-3 feet apart.
Watering In: Give them a thorough watering after planting. Then, hold off on heavy watering until you see sprouts emerge, usually in 2-3 weeks.

The “Hilling” Method for Success

Hilling is crucial. It protects developing tubers from sunlight, which turns them green and toxic, and encourages more potatoes to form along the buried stem.

When green shoots reach about 6-8 inches tall, gently mound soil around the base, leaving the top few inches exposed.
Repeat this process every few weeks as the plant continues to grow. You can also use straw or shredded leaves for hilling, which is especially helpful in heavy soil.
Stop hilling when the plant starts to flower, as the tubers are beginning to form en masse then.

Watering and Feeding Your Crop

Consistent moisture is vital, especially once tubers start forming. Water deeply once or twice a week, allowing the soil to dry slightly between watering. Inconsistent watering leads to knobby or cracked potatoes.

Avoid over-head watering which can promote fungal diseases like blight. Use drip irrigation or soaker hoses instead.

For fertilizer, use a balanced, low-nitrogen mix at planting. To much nitrogen gives you lots of leaves but few potatoes. A side dressing of compost when you start hilling is usually sufficient.

Pests and Problems in Our Region

Keep an eye out for a few common issues:

Colorado Potato Beetle: Less common here but possible. Hand-pick the orange larvae and adults.
Aphids: Blast them off with a strong stream of water or use insecticidal soap.
Potato Blight: A fungal disease that thrives in humid conditions. Water at the soil level, ensure good air circulation, and rotate your crops each year. Don’t plant potatoes where tomatoes or peppers grew the previous season.
Gophers and Voles: These can be a major nuisance. Planting in raised beds with hardware cloth at the bottom is the most effective defense.

Harvesting for Optimal Timing

You can harvest “new” potatoes about 2-3 weeks after the plants stop flowering. Gently dig around the edges of the plant with your hands to steal a few tender spuds.

For your main harvest, wait until the plant’s foliage turns yellow and begins to die back. This is the sign that the potatoes have reached maturity. Stop watering about two weeks before you plan to harvest to help toughen the skins for storage.

Use a garden fork carefully to loosen the soil, starting far from the plant’s center to avoid spearing tubers. Let the potatoes cure in a dry, shaded, well-ventilated place for 1-2 weeks before storing them in a cool, dark location.

Year-Round Potato Planning Calendar

January – March: Primary planting window. Plant early and mid-season varieties.
April – June: Hill and maintain spring-planted potatoes. Begin harvesting new potatoes from early plantings by late spring.
July – Early September: Second planting window. Prep soil and plant for fall harvest, especially inland.
October – December: Harvest main summer crop and fall-planted potatoes. Cure and store properly. Rest and amend beds for the next cycle.

FAQ: Southern California Potato Planting

Can I grow potatoes in a container?

Absolutely. Use a large pot or grow bag at least 15 gallons in size. The process is the same, but container soil dries out faster, so monitor water closely.

What if my potato plants flower?

Flowering is normal and often signals that tuber formation is beginning. It doesn’t effect the edibility of the potatoes underground.

Why are my potatoes green?

Green skin means the tuber was exposed to light. The green parts contain solanine, which is bitter and can be toxic in large amounts. Always hill properly and store potatoes in complete darkness. You can cut away small green spots before cooking.

Can I save my own seed potatoes for next year?

It’s possible but not always recommended. Disease can carry over from one year to the next. If you want to try, save small, undamaged potatoes from your healthiest plants and store them seperately. But for beginners, buying new certified seed potatoes each year is safer and more reliable.

How do I get the biggest potato yield?

The keys are loose, fertile soil, consistent watering after plants are established, and diligent hilling. Choosing a variety suited to our climate and your planting season makes a huge difference too.

Planting potatoes in Southern California is a rewarding project with a delicious payoff. By timing your plantings for late winter or late summer, choosing the right varieties, and following simple steps for care, you’ll be well on your way to a succesful harvest. Remember, the perfect timing for optimal harvest timing starts with getting those seed potatoes in the ground at the right moment for your microclimate.