When to Plant Kale in Pennsylvania: Zone-by-Zone Planting Calendar

You are staring at a pack of kale seeds, checking the weather app every few hours, and trying to figure out if it is finally safe to plant. Too early and the seedlings sit in cold mud going nowhere. Too late and you miss the sweet spot before summer heat makes spring kale bitter. The timing question is even trickier if you want a fall crop — start those seeds too late and the first frost catches plants before they reach picking size. In Pennsylvania, getting the dates right is the difference between two full harvests per year and one mediocre one.

The good news is that kale gives you a wider planting window than almost any other vegetable you can grow in PA. Seeds germinate in soil as cool as 45 degrees, transplants handle frost down to 20 degrees without flinching, and fall-planted kale actually improves after your first freeze. The challenge is not whether kale can handle our climate — it is dialing in the exact dates for your specific zone so each planting peaks at the right time.

Below you will find zone-by-zone spring and fall planting calendars for all four PA growing regions, soil temperature germination data, indoor seed-starting schedules, succession planting timelines, and a month-by-month task calendar you can pin to the garden shed wall. Every date is calibrated to Pennsylvania zones 5a through 7a using historical frost data from the past 30 years.

Spring Planting Window by Zone

Spring kale goes into the ground earlier than most people expect. Because kale handles frost down to 20 degrees Fahrenheit without damage, you can transplant hardened-off seedlings 2 to 3 weeks before your last expected frost. This is a significant advantage over warm-season crops like tomatoes and peppers that cannot go out until all frost risk has passed.

The table below shows the spring planting window for each PA region. “Earliest transplant” is the date you can safely set out hardened-off seedlings with minimal frost risk to the plants. “Last practical transplant” is the latest date that still gives kale enough cool weather to produce a good spring harvest before summer heat arrives.

Zone 7a gardeners in the Philadelphia suburbs and Delaware Valley have the biggest advantage here: a spring transplant window that opens in late March gives kale nearly three full months of cool-weather growing before summer heat arrives. In the northern tier (zone 5a), the spring window is tighter — roughly 6 to 8 weeks of ideal growing conditions between the last frost and the onset of 80-degree days. For a complete growing guide covering all techniques, see our kale growing hub.

Fall Planting Window by Zone

The fall planting window is where most PA kale growers should focus their energy. Fall kale produces sweeter leaves, faces fewer pest problems, and can be harvested for three to four months compared to the spring crop’s six to eight weeks. The key to a successful fall planting is counting backward from your first expected frost date.

How to Calculate Your Fall Planting Date

Use this formula: First frost date minus days-to-maturity minus 14 days. The extra 14 days accounts for the slower growth that happens as day length decreases in September and October. For a variety like Winterbor (60 days to maturity) in zone 6a (first frost around October 15), the math works out to: October 15 minus 60 minus 14 = July 22 seed-start date.

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Indoor Seed-Starting Schedule

Starting kale seeds indoors gives you the most control over timing. Indoor-started transplants are 4 to 6 weeks ahead of direct-sown seeds, which means earlier spring harvests and better-established fall plants. The schedule below covers both spring and fall indoor starts for all four PA zones.

Spring Indoor Start Dates

Fall Indoor Start Dates

For detailed instructions on indoor seed starting technique — light requirements, container selection, temperature management, and feeding — see our step-by-step how to grow kale in PA guide.

Soil Temperature and Germination

Soil temperature is the single most reliable predictor of whether your kale seeds will germinate and how quickly. Air temperature fluctuates wildly in a PA spring — a 70-degree afternoon can follow a 35-degree morning — but soil temperature changes much more slowly and gives a more accurate signal of when conditions are ready for sowing.

Germination Rate by Soil Temperature

Check soil temperature by inserting a soil thermometer 2 inches deep at 8 AM for three consecutive mornings. Morning readings give you the daily minimum soil temperature, which is the number that matters for germination. If the average of those three readings is 45 degrees or above, you can direct sow kale. If it is 55 or above, germination will be fast and reliable.

Direct Sowing Timing

Direct sowing eliminates the indoor setup entirely but requires more precise timing. You need soil that is warm enough for germination (45 degrees minimum) but air temperatures that are still cool enough for kale to thrive. In Pennsylvania, this creates two optimal direct-sowing windows: mid-April through mid-May for spring and mid-August through early September for fall.

Spring Direct Sow Schedule

Fall Direct Sow Schedule

Fall direct sowing is trickier because you are sowing into warm summer soil that often exceeds 85 degrees at the surface — too hot for reliable kale germination. The workaround is to sow in a shaded outdoor bed or in cell trays placed on a shaded porch, then transplant seedlings to the garden once they have 3 to 4 true leaves.

If you want to direct sow fall kale into the garden, wait until late August or early September when soil temperatures in most of PA drop below 80 degrees. At that point, germination will be reliable, but you lose 3 to 4 weeks compared to starting indoors in July. For zones 5a and 5b, direct sowing fall kale is generally not recommended because the shortened growing season does not leave enough time for plants to reach full size.

Transplant Timing and Hardening Off

Transplanting gives you the most flexibility in timing because you control the environment during the critical first 4 to 6 weeks of growth. Indoor-grown seedlings are ready to transplant when they have 4 to 5 true leaves and stand 3 to 4 inches tall — typically 4 to 6 weeks after sowing.

The 7-Day Hardening-Off Calendar

Hardening off is the process of gradually exposing indoor seedlings to outdoor conditions. Skipping this step is the most common reason spring kale transplants fail — they cannot handle the sudden shift from a 68-degree kitchen to a 45-degree windy April morning. Start hardening off 7 days before your target transplant date.

Transplant on a cloudy day or in the late afternoon. Full midday sun on freshly transplanted seedlings causes temporary wilting even when the soil is adequately moist. Water each transplant with at least one pint of water immediately after planting to collapse air pockets around the roots. For the full step-by-step transplanting process, see our how to grow kale guide.

Succession Planting Schedule

Succession planting means starting new kale seeds at regular intervals so you always have plants at different stages of growth. Instead of one big planting that peaks and fades, succession planting gives you a steady supply of fresh kale from April through December. For PA gardeners, three strategic sowings cover the full year.

Three-Sowing Plan for Pennsylvania

Running all three sowings provides kale from May through February — roughly 10 months of continuous harvest. The spring crop carries you through early summer. The fall crop covers September through December with the best-tasting leaves. The winter crop, protected with row cover or a cold frame, fills in the gap from January through the first spring transplants.

Baby Kale Succession (Every 2 Weeks)

For tender baby kale that is milder than mature leaves and perfect for salads and smoothies, sow a short row (3 to 4 feet) every 2 weeks from April through September. Space seeds 2 to 3 inches apart and harvest entire plants at 3 to 4 inches tall, about 25 to 30 days from sowing. This rapid cycle means you can fit 12 to 14 baby kale sowings into a single PA growing season from one small bed.

Variety Selection by Planting Season

Not all kale varieties perform equally across spring and fall plantings. Some handle heat better for spring growing; others have superior cold tolerance for fall and winter harvests. Choosing the right variety for each season maximizes your yield and eating quality.

Frost Dates and Season Extension

Understanding your local frost dates is critical for timing both spring and fall kale plantings. The dates below are 30-year averages based on USDA weather station data for representative PA locations. Your specific frost dates may vary by a week or more depending on elevation, proximity to water, and urban heat island effects.

PA Frost Date Reference

Season Extension for Kale

Kale does not stop producing at first frost — it gets better. But eventually, sustained temperatures below 10 to 15 degrees will kill unprotected plants. Simple frost protection extends your harvest window by 4 to 8 weeks beyond the first frost date, pushing kale production into December and even January for much of PA.

For a full breakdown of overwintering techniques and what to expect from kale that survives a PA winter, see the overwintering section in our kale growing hub.

Month-by-Month Task Calendar

Pin this to your garden shed. Dates assume central PA (zone 6a) — adjust 2 weeks earlier for zone 7a and 2 weeks later for zones 5a-5b.

Common Timing Mistakes in PA

Most kale timing problems in Pennsylvania fall into a handful of predictable patterns. Avoiding these saves you an entire season’s worth of frustration.

Mistake 1: Waiting Until After Last Frost to Transplant

Many new gardeners treat kale like tomatoes and wait until all frost risk passes. This wastes 2 to 3 weeks of prime spring growing weather. Kale handles frost down to 20 degrees without injury. Transplant 2 to 3 weeks before your last frost date, not after it.

Mistake 2: Starting Fall Seeds Too Late

This is the single most common kale timing error in PA. Gardeners wait until August to think about fall kale, but by then the clock is already running short — especially in zones 5a and 5b where the first frost arrives in late September. Start fall kale seeds in early July. If you miss July entirely, transplant purchased seedlings from a nursery in early August rather than starting from seed.

Mistake 3: Direct Sowing Fall Kale into Hot Soil

Soil temperatures above 85 degrees suppress kale germination. Mid-July garden soil in full sun often exceeds 90 degrees at the surface. Direct sowing into this heat produces spotty germination or outright failure. Start fall seeds in cell trays in shade or indoors, then transplant once seedlings are established.

Mistake 4: Not Adjusting for Day Length in Fall

A kale variety listed at 60 days to maturity will actually take 70 to 75 days in fall because decreasing day length slows photosynthesis. Always add 10 to 14 days to the seed packet’s days-to-maturity when calculating fall planting dates. This adjustment prevents the common problem of fall kale that is still immature when the first hard freeze arrives.

Mistake 5: Giving Up After Spring Kale Turns Bitter

Spring kale develops a stronger, sometimes bitter flavor once daytime temperatures regularly hit the 80s in June. Some gardeners conclude that kale does not grow well in PA and stop planting it. The reality is that the fall crop is where kale excels here. If spring kale disappointed you, try a fall planting — the difference in flavor is dramatic. Cold-sweetened October and November kale tastes nothing like heat-stressed June kale.

Plan your full season: See our monthly planting guide for a month-by-month schedule, or browse all crops in our Pennsylvania vegetables hub. For frost timing, check our PA frost dates by region.

Frequently Asked Questions About Planting Kale in Pennsylvania