Knowing the right time to get your seed potatoes in the ground is the single most important factor for a successful harvest. For gardeners in Pennsylvania, timing your planting correctly ensures your potatoes get the cool weather they love to start growing, without the risk of a late frost killing the sprouts. This guide will give you the clear, practical advice you need to nail the planting window for your specific area.
The climate across Pennsylvania varies significantly, from the colder USDA Hardiness Zones 5 in the north and mountains to the milder Zone 7 in the southeast. This means the best planting time isn’t the same for someone in Erie as it is for someone in Philadelphia. Generally, you should plant potatoes in Pennsylvania about 2-4 weeks before your last expected spring frost date. For most of the state, this falls between early April and mid-May.
When to Plant Potatoes in Pennsylvania
To simplify, let’s break the state down into three general regions. Keep in mind, these are estimates—always watch your local weather forecast and soil conditions.
Southwestern & Southeastern PA (Zones 6b-7):
This includes cities like Philadelphia, Lancaster, and Pittsburgh. Your last frost is typically around mid-April. The ideal potato planting window here is late March to early April. You can often be the first in the state to get your seed potatoes planted.
Central PA (Zone 6a):
This covers areas like State College, Harrisburg, and Scranton. Your last frost usually arrives in late April. Aim to plant your potatoes from mid-April to early May.
Northern & Mountainous PA (Zones 5a-5b):
This region includes Erie, the Pocono Mountains, and higher elevations. Frosts can occur into early May. Here, you should wait until early to mid-May to plant. Patience is key to avoid frost damage.
How to Know Your Soil is Ready
Potatoes need cool soil, but not cold, wet mud. Planting in soggy soil can cause seed pieces to rot before they sprout. A good old-fashioned test is more reliable than any calendar.
* The Squeeze Test: Grab a handful of soil from about 4 inches deep. Squeeze it in your hand.
* If it holds together in a muddy ball, it’s too wet. Wait a week.
* If it crumbles apart easily, it’s perfect for planting.
* Temperature Check: For a more precise measure, use a soil thermometer. Potatoes can be planted when soil temperatures consistently reach 45°F (7°C). A reading of 50-55°F (10-13°C) is even better for strong sprouting.
Step-by-Step Planting Guide
Once your date and soil are aligned, follow these steps for a great start.
1. Choose and Prepare Seed Potatoes: Always use certified disease-free seed potatoes from a garden center, not grocery store potatoes. A week or two before planting, “chit” or green-sprout them. Place them in a cool, bright spot (like an egg carton on a windowsill) to encourage short, sturdy sprouts.
2. Cut and Cure (Optional): Larger seed potatoes (egg-sized or bigger) can be cut into pieces. Each piece must have at least 1-2 “eyes” or sprouts. Let these cut pieces cure for 1-2 days in a cool, dry place so the cut surface forms a callus. This helps prevent rot.
3. Prepare the Planting Site: Potatoes need full sun (at least 6 hours) and loose, well-draining soil. Work in several inches of compost or aged manure to improve soil structure and fertility. Avoid fresh manure, as it can promote scab disease.
4. Plant Correctly: Dig a trench or individual holes about 6-8 inches deep. Space seed pieces about 12 inches apart in the row, with rows 2-3 feet apart. Place each piece with the eyes facing upward. Cover with 4 inches of soil.
5. Hill as They Grow: As plants grow to about 6-8 inches tall, gently mound soil from around the plant up around the stems, leaving just the top few leaves exposed. Repeat this process every few weeks. Hilling prevents sunlight from reaching the developing tubers (which turns them green and toxic) and encourages more potatoes to form along the buried stem.
Choosing the Right Potato Type for PA
Planting time can also be influenced by the type of potato you choose. They are catagorized by how long they take to mature.
* Early Varieties (70-90 days): Like ‘Yukon Gold’ or ‘Red Norland’. These are great for an early summer harvest and can be planted a little earlier in the spring. They also escape some late-season pest problems.
* Mid-Season Varieties (90-110 days): Like ‘Kennebec’ or ‘Purple Majesty’. These are reliable workhorses for a main crop harvest and store well.
* Late Varieties (110-135 days): Like ‘Russet Burbank’. These need the longest growing season. In Pennsylvania, it’s crucial to plant these as early as your zone allows to ensure they mature before fall frosts.
Can You Plant Potatoes in Fall?
While spring is primary season, a fall planting is possible in Pennsylvania, especially in the warmer southeastern zones. The goal is to plant 2-3 weeks after the summer heat breaks, usually in late August, so tubers develop in the cool autumn weather. You’ll harvest in late fall. It’s a more advanced technique and success depends heavily on a mild early winter.
Common Mistakes to Avoid
* Planting Too Early: This is the most common error. Cold, wet soil leads to rot.
* Ignoring Crop Rotation: Never plant potatoes in the same spot where tomatoes, peppers, or eggplants grew the previous year. They are all in the nightshade family and share diseases.
* Not Hilling Enough: Green potatoes are inedible. Consistent hilling is non-negotiable.
* Overwatering at Planting: Keep soil moist, not waterlogged, until sprouts emerge.
FAQ: Pennsylvania Potato Planting
Q: What is the latest you can plant potatoes in Pennsylvania?
A: For a main crop that needs to mature fully for storage, aim to have them in the ground by late June at the absolute latest. For early varieties, you might try a planting in early July for a small fall harvest, but this is risky.
Q: Can I plant store-bought potatoes that have sprouted?
A: It’s not recommended. Grocery potatoes are often treated with sprout inhibitors and may carry diseases that can persist in your soil for years. Certified seed potatoes are a safer investment.
Q: How do I protect early planted potatoes from a late frost?
A: If sprouts have emerged and a frost is forecast, gently cover the plants with a thick layer of straw, floating row cover, or even old blankets. Remove the covering once the frost threat passes in the morning.
Q: When are potatoes ready to harvest in PA?
A: For “new” potatoes, you can gently dig around plants about 2-3 weeks after they finish flowering. For mature potatoes for storage, wait until the plant vines have completely died back, usually in late summer or early fall.
Getting your planting timing right sets the stage for everything that follows. By aligning your efforts with Pennsylvania’s unique climate zones and following these simple steps, you’ll be well on your way to a bountiful harvest of homegrown potatoes. Remember, gardening is part science and part observation—so keep an eye on your soil and your local weather for the best results each year.