In Pennsylvania, you can plant spinach as early as mid-March in the southern part of the state and late March to early April in northern and western regions. Spinach is one of the hardiest cool-season crops, tolerating heavy frosts and even brief dips into the 20s, so you don’t need to wait for your last frost date. The goal is to get seeds in the ground while temperatures are still cool and days are short, giving the plants time to mature before summer heat triggers bolting.
Spring Planting Dates by Region
Pennsylvania spans a wide range of climates. Philadelphia in the southeast has a median last frost date around April 6, while areas in the Poconos, northern tier, and higher elevations may not see their last frost until mid-to-late May. Spinach doesn’t need frost-free conditions, though, so your planting window opens well before that last frost date.
For southeastern PA (Philadelphia, Lancaster, Chester County), you can direct-sow spinach seeds from mid-March through late March. In central PA (Harrisburg, State College), aim for late March through the first week of April. In western and northern PA (Pittsburgh, Scranton, Erie), early to mid-April is typical. If you’re unsure about your specific location, a good rule of thumb is to plant four to six weeks before your average last frost date.
Spinach seeds germinate in soil as cool as 35°F, but the optimal soil temperature range is 45 to 75°F, with 70°F being the sweet spot. In early spring, germination will simply be slower. Seeds that take five or six days at 70°F might take two to three weeks at 40°F. That’s fine. The plants will establish and grow as the soil warms.
Fall Planting for a Second Harvest
Fall is actually the easier season to grow spinach in Pennsylvania. Shortening days and cooling temperatures work in your favor, reducing the risk of bolting almost entirely. Penn State Extension recommends sowing fall spinach in mid-July through mid-August, depending on your region. Earlier in that window works better for northern counties, where cold arrives sooner.
Count backward from your expected first fall frost (typically mid-October in much of PA) and give your spinach about 45 to 50 days. That puts your ideal sowing window in late August for the southeast and mid-August or earlier for the north. If you’re planting in July or early August when soil is hot, keep in mind that spinach germination drops off sharply above 85°F. Watering the bed the evening before and sowing in a partially shaded spot can help. Some gardeners pre-sprout seeds on a damp paper towel in the refrigerator for a few days before planting.
Why Spinach Bolts and How to Delay It
Bolting is when spinach sends up a flower stalk, turning the leaves bitter and signaling the end of your harvest. Two things trigger it: rising temperatures and lengthening days. Once daytime highs consistently hit the upper 70s and low 80s, bolting accelerates. Day length matters too. Research has shown that bolting rates increase significantly once photoperiods reach about 16 hours. In central Pennsylvania, days hit 16 hours around late May, which is why spring-planted spinach typically runs out of time by early to mid-June.
Large swings in temperature, like a warm spell followed by a cold snap, can also push spinach toward bolting. This makes Pennsylvania’s unpredictable spring weather a real factor. Planting as early as possible gives your crop the most growing time before these triggers kick in. Choosing slow-bolt varieties also buys you an extra week or two.
Choosing the Right Type
Common spinach comes in two main leaf types: smooth and savoy (crinkled). Both bolt when days get long and temperatures climb. For spring planting, look for varieties labeled “slow bolt” or “long standing” on the seed packet. Savoy types tend to be more cold-hardy, making them slightly better for very early spring and fall plantings.
If you want spinach-like greens through the summer, consider alternatives. New Zealand spinach thrives in heat and should be planted after all frost danger has passed. Malabar spinach is a vine with glossy leaves that produces well through hot weather, especially with some afternoon shade. Perpetual spinach, which is actually a type of chard, also handles summer conditions far better than true spinach. These aren’t the same plant, and the flavor differs, but they fill the gap between your spring and fall spinach harvests.
Preparing the Soil
Spinach is a leafy crop, so it’s hungry for nitrogen. Aim for a soil pH between 6.0 and 6.5. If you’ve worked compost or aged manure into the bed, you may not need any additional fertilizer beyond a light nitrogen boost. Without compost, apply a balanced granular fertilizer (something with roughly equal parts nitrogen, phosphorus, and potassium) before planting, working it into the top few inches of soil.
Spinach has shallow roots, so loose, well-drained soil in the top six inches matters more than deep preparation. If your garden soil is heavy clay, which is common across much of Pennsylvania, mixing in a few inches of compost improves both drainage and texture. Raised beds warm up faster in spring, giving you a slight head start on germination.
Planting and Harvest Timeline
Sow seeds about half an inch deep and one inch apart in rows spaced 12 inches apart. Once seedlings have a couple of true leaves, thin them to three to four inches apart. You can eat the thinnings.
Most spinach varieties reach harvest size in 37 to 50 days from planting, depending on temperature and variety. In cool early-spring conditions, expect the longer end of that range. You can start picking individual outer leaves as soon as they’re big enough to use, typically when they reach three to four inches long. This “cut and come again” approach lets the center of the plant keep producing. Alternatively, you can harvest the whole plant at once by cutting it at the base.
For a spring planting in mid-March in southeastern PA, you’re looking at a first harvest in late April to mid-May, with continued picking into early June before bolting ends the season. A fall planting sown in mid-August can produce from late September through November, since spinach tolerates hard frosts and even light freezes. A simple row cover or cold frame can extend fall harvests well into December in milder parts of the state.
Quick Planting Calendar for PA
- Southeast PA (zones 7a/7b): Spring sow mid-March to early April. Fall sow mid-August to early September.
- Central PA (zones 6b/7a): Spring sow late March to mid-April. Fall sow early to mid-August.
- Western and northern PA (zones 5b/6a): Spring sow early to mid-April. Fall sow late July to mid-August.
Succession planting, sowing a new short row every 10 to 14 days, stretches your harvest window on both ends. In spring, start your first sowing as early as the soil is workable and keep going until daytime highs are regularly in the 70s. In fall, two or three staggered sowings ensure you’re not harvesting everything at once.