When to Plant Sweet Potatoes: Timing for Warm Climates and Short Seasons

Planting sweet potatoes at the right moment is the key to a successful harvest. After growing sweet potatoes for years in my warm Sonoma Valley garden—and helping short-season gardeners find the right timing—I’ve learned that the calendar matters far less than soil temperature, frost dates, and variety choice. Sweet potatoes need consistent warmth from planting through harvest, and even small timing adjustments can make a big difference.

Here’s how to choose the best planting window for both long, warm climates and shorter, cooler growing seasons.

Table of Contents

Start With the Most Important Factor: Soil Temperature

In every climate, the true planting date begins when soil reaches 70°F (21°C) at 4 inches deep. Sweet potato slips planted too early simply sit and stall; sometimes they rot.

My experience in Sonoma:
Most years, I’m planting in late May, even though the weather feels warm in April. When I’ve planted earlier, slips have always lagged behind the later-planted ones.

My tip: Use a simple soil thermometer—I rely on mine every spring. It removes the guesswork.

Timing for Warm Climates (Long Seasons)

If you garden where summers are long and consistent—California, the South, much of the Southwest—you have a wide planting window.

Warm-climate planting timeframe:

Ideal: 2–4 weeks after your last frost date
Soil: 70–85°F
Air temperatures: Nights consistently above 55°F

In my region, slips planted between late May and mid-June grow fast and produce large, well-shaped roots. Warm climates can even support successive plantings into early July for staggered harvests.

My experience:
Later plantings often catch up because warm soil accelerates early growth. I get some of my biggest crops from June slips.

Timing for Short Seasons (Cooler Climates)

Short-season gardeners—those in the northern U.S., mountain regions, or coastal cool zones—need to match slip planting carefully with their reliable warmest weather.

Short-season planting timeframe:

Plant: As soon as soil reaches 70°F (never earlier)
Typical window: Late May to late June
Minimum frost-free days needed: 90–120

If you have fewer than 110 frost-free days, choose early maturing varieties like ‘Beauregard,’ ‘Georgia Jet,’ or ‘O’Henry.’

Use black plastic to pre-warm soil.
Use row covers early to hold night warmth.
Plant slips next to a south-facing wall or fence to build a warmer microclimate.
Choose raised beds—they warm earlier and faster.

These methods have helped many of my readers in Montana, New England, and the Pacific Northwest harvest solid crops.

Frost Dates Still Matter

Sweet potatoes are frost-tender at both ends of the season.

Plant after:

Your last spring frost
Night temperatures reliably above 55°F

Harvest before:

Your first fall frost
Cold nights that drop below 50°F consistently

My insight:
In Sonoma, my slips tolerate a cool night or two, but anything below 50°F slows growth sharply.

A Simple Planting Rule You Can Trust

I’ve learned this rule applies everywhere:

Plant sweet potatoes only when the soil is warm enough to make slips grow immediately.

If the soil is too cool, waiting just one more week can mean the difference between a patch of struggling vines and a bed full of vigorous growth.

Final Thought

Timing sweet potato planting is all about warmth—warm soil, warm nights, and a long enough frost-free window. Whether you garden in a heat-rich climate like mine or in a region with unpredictable summers, using soil temperature as your guide ensures your slips root quickly and grow steadily. Plant at the right moment, and you’ll set the stage for a strong harvest of sweet, flavorful tubers.