Pennsylvania planting calendar

When to plant sweet potatoes in Pennsylvania — sow, transplant & harvest dates

Pennsylvania is mostly USDA zone 6b (range 5a-7b). Dates below are derived from sweet potatoes's frost tolerance and Pennsylvania's frost window — not generic national averages.

Sweet potatoes planting timetable for Pennsylvania

Stage	When in Pennsylvania	Anchor
Start seeds indoors	mid-March (March 14)	6 weeks before the last frost (late April)
Transplant outside	mid-May (May 16)	21 days after the last frost (late April)
First harvest (estimate)	late August (August 29)	~105 days from transplant

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Pennsylvania's climate shifts the sweet potatoes dates

Pennsylvania's last spring frost averages late April and first fall frost mid-October, which sets the whole planting clock. Pennsylvania runs from cold northern mountains to a mild southeastern corner. Philadelphia gardens almost two zones warmer than the northern tier. Wait for warm soil — sweet potatoes stall in cold ground even after the air warms, so don't rush them out.

Sweet potatoes are extremely frost-tender and demand warm soil — do not transplant slips until soil temperature at 4-inch depth holds at 18 °C (65 °F) or above, typically 3 weeks after the last spring frost. Short-season zones (z5-6) should start slips indoors under lights 5-6 weeks early to ensure 100-120 frost-free days. Avoid zones 3-4 without a floating row cover season-extension strategy; in z9-11 slips can go out as early as late March.

Frost-risk note

Don't plant before late April — even a light frost will kill seedlings overnight. In the northern Allegheny plateau (zone 5a) the safe date runs a week or two later.

Regional variation within Pennsylvania

the northern Allegheny plateau (zone 5a) runs roughly 1-2 weeks behind the state average; the southeast around Philadelphia (zone 7b) can plant 1-2 weeks earlier.

Philadelphia — USDA zone 7b
Pittsburgh — USDA zone 6b
Harrisburg — USDA zone 7a
Allentown — USDA zone 6b
Erie — USDA zone 6b

What else to plant in Pennsylvania around then

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Quick-grow guide

Sun: Full sun — 6-8 hours direct.
Soil temperature for germination: Soil 18-24 °C (65-75 °F) for slip rooting.
Spacing: 12-18 inches (30-45 cm) between plants.
Days to harvest: ~105 days from planting out.

Frequently asked questions

When is the best time to plant sweet potatoes in Pennsylvania?

In Pennsylvania (mostly USDA zone 6b), sow sweet potatoes indoors around mid-March, transplant outdoors mid-May (after the last frost, late April), and harvest from late August. Sweet potatoes are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

What USDA zone is Pennsylvania?

Most of Pennsylvania sits in USDA hardiness zone 6b, with the state spanning roughly 5a-7b from the northern Allegheny plateau (zone 5a) to the southeast around Philadelphia (zone 7b). The last spring frost averages late April and the first fall frost mid-October.

Can you grow sweet potatoes in Pennsylvania?

Yes. Pennsylvania's dominant zone 6b supports sweet potatoes — the key is timing. Sweet potatoes are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

Does the planting date change across Pennsylvania?

the northern Allegheny plateau (zone 5a) runs roughly 1-2 weeks behind the state average; the southeast around Philadelphia (zone 7b) can plant 1-2 weeks earlier.

What else can I plant in Pennsylvania around the same time?

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.