When To Plant Potatoes In Phoenix

If you’re gardening in Phoenix, knowing when to plant potatoes is your first step to a great harvest. The unique desert climate here means timing is everything to avoid the extreme heat. Get it right, and you’ll be digging up homegrown spuds in no time.

Potatoes are a cool-season crop. They grow best in mild temperatures and need to be harvested before the summer heat arrives. In Phoenix, that gives us two distinct planting windows each year.

The best times to plant potatoes in Phoenix are during the cooler months. You have a primary season and a secondary, more challenging one.

Primary Planting (Late Winter): This is your best bet. Plant seed potatoes from mid-January through mid-February. The goal is to get them in the ground so they can grow during the cool of late winter and spring, maturing before the June heat.
Secondary Planting (Fall): You can try a fall crop by planting in early to mid-September. This is trickier, as the soil is still very warm. It requires more attention to watering and shading when they first start.

Missing these windows often leads to poor results. Potatoes exposed to soil temperatures above 80°F will stop developing tubers underground.

Why Phoenix Timing is So Specific

Our desert environment presents special challenges. Understanding them helps you see why the calender matters so much.

Heat: Intense summer heat cooks the plants and halts tuber growth.
Soil Temperature: Potatoes tubers form best when soil is between 60°F and 70°F. Our soil stays in this range during the late winter planting period.
Frost: While rare, a late frost can damage young foliage. Planting after mid-January usually avoids this risk.

Choosing the Right Potato Variety

Selecting a variety suited to our shorter, cool season improves your success. Look for types labeled “early” or “mid-season” maturing.

Early Season (70-90 days): ‘Yukon Gold’, ‘Red Norland’, ‘Irish Cobbler’. These are excellent for Phoenix as they mature quickly.
Mid-Season (90-110 days): ‘Kennebec’, ‘Viking Purple’. These can work well in the winter/spring planting if get them in early.
Avoid Long Season: Late varieties (over 110 days) often run into the heat before finishing.

Always buy certified disease-free seed potatoes from a garden center, not grocery store potatoes, which may be treated to prevent sprouting.

Step-by-Step Planting Guide

Follow these steps for a healthy potato patch.

1. Preparing Seed Potatoes

About a week before planting, “chit” or sprout your seed potatoes. Place them in a cool, bright spot. This gives them a head start. Cut larger seed potatoes into pieces, ensuring each piece has at least 2-3 “eyes” or sprouts. Let the cut pieces dry for a day to form a callus, which prevents rot.

2. Site and Soil Preparation

Potatoes need full sun (at least 6-8 hours) and loose, well-draining soil. Phoenix soil is often heavy clay, so amending it is crucial.

Loosen the soil to a depth of 10-12 inches.
Mix in 3-4 inches of compost or aged manure. This improves drainage and fertility.
A slightly acidic soil pH (5.8 to 6.5) is ideal to help prevent scab disease.

3. The Planting Process

Dig a trench about 6 inches deep.
Place seed potato pieces cut-side down, with eyes facing up, spaced 12 inches apart.
Cover with 4 inches of soil. Rows should be about 3 feet apart.
Water deeply after planting to settle the soil.

Caring for Your Potato Plants

Consistent care is key, especially as temperatures begin to rise in April and May.

Watering

Potatoes need even moisture. Water deeply 1-2 times per week, depending on rainfall (which is rare). The soil should be moist but not soggy. Inconsistent watering leads to misshapen tubers. Reduce watering as the plants begin to yellow and die back near harvest time.

Hilling

This is the secret to a bigger harvest. When plants are about 8 inches tall, mound soil around the stems, leaving just the top few leaves exposed. Repeat this every few weeks. Hilling protects developing tubers from sunlight (which turns them green and toxic) and encourages more potatoes to form along the buried stem.

Fertilizing

Use a balanced, low-nitrogen fertilizer at planting. To much nitrogen encourages leafy growth instead of tubers. A side dressing of compost when hilling is often sufficient.

Pest and Heat Watch

Watch for aphids and use a strong spray of water to dislodge them. As late spring heat arrives, consider using a 30-40% shade cloth to protect plants and extend the growing season by a week or two.

Harvesting Your Bounty

Harvest time depends on the variety and planting date. For your winter-planted crop, expect to harvest from late April through May.

New Potatoes: You can gently dig for small, tender “new” potatoes about 2-3 weeks after the plants finish flowering.
Mature Potatoes: For full-sized spuds, wait until the plant foliage turns yellow and dies back completely. Stop watering, and after about two weeks, carefully dig up your potatoes on a cool, cloudy morning if possible.

Let potatoes cure in a dark, well-ventilated place for 1-2 weeks before storing. This toughens their skin for longer storage.

Common Challenges and Solutions

Even with perfect timing, you might face these issues:

Green Potatoes: Caused by tubers exposed to light. Hill more diligently and store harvest in complete darkness.
Poor Yield: Often due to planting too late, extreme heat, or soil that is too compact or nitrogen-rich.
Early Dying Foliage: In Phoenix, this is usually caused by the onset of intense heat, not disease. It’s your signal that harvest time is near.

FAQ: Planting Potatoes in the Desert

Can I grow potatoes in a container in Phoenix?
Absolutely. Use a large container (15+ gallons) with excellent drainage. It’s a great way to control soil temperature and quality. You may need to water container potatoes more frequently.

What if I missed the January-February window?
After mid-February, its generally too late for a spring crop. Your best option is to wait for the fall planting window in September, though it requires extra care with cooling the soil initially.

How do I prepare my soil for a fall potato planting?
For September planting, soil will be hot. Pre-moisten the soil a few days before, and plant in the cooler evening hours. Consider using a thick layer of straw mulch or shade cloth immediately after planting to keep soil temperatures down.

Do potatoes need full sun in Phoenix?
Yes, but during the hottest part of the spring, some afternoon shade can prolong the plants life and boost yield. Morning sun with afternoon shade is a good compromise in late season.

By following these timing and care guidelines, you can enjoy the satisfaction of harvesting your own potatoes. The key is respecting the desert seasons and getting those seed potatoes in the ground at just the right moment.