If you’re a gardener in the Garden State, knowing when to plant potatoes in NJ is the first step to a great harvest. Getting the timing right means your seed potatoes will grow strong and produce plenty of tubers for you to enjoy later in the year.
New Jersey’s climate varies from the cooler northwest to the warmer coastal areas, so planting time isn’t the same everywhere. But don’t worry, we’ll break it down simply. This guide gives you the clear, practical steps you need for success.
When to Plant Potatoes in NJ
For most of New Jersey, the ideal potato planting window is from late March to mid-April. The classic sign is when the soil is workable and has warmed up a bit.
Here’s a more detailed look by region:
- North & Northwest NJ (Zones 6a-6b): Aim for early to mid-April. Frost can linger here, so waiting until the soil temperature is consistently above 45°F is smart.
- Central NJ (Zones 6b-7a): This is the sweet spot. Late March through early April is usually perfect.
- South & Coastal NJ (Zones 7a-7b): You can often start a bit earlier, in late March. The warmer coastal influence gives you a longer growing season, which is great for late varieties.
The single best indicator is soil temperature. Use a soil thermometer. When the soil at planting depth (about 4 inches) holds at 45-50°F for a few days, it’s go time. Planting in cold, soggy soil can cause seed pieces to rot instead of sprout.
Understanding Your Planting Cues
Old-time gardeners use natural signs. One reliable rule is to plant potatoes around the time of your last expected spring frost. You can find your area’s average last frost date from local extension services.
Another traditional marker is when dandelions start to bloom. It’s a natures signal that the ground is warming. While not as precise as a thermometer, it’s a helpful clue to look for.
Choosing the Right Potato Varieties for NJ
Picking varieties suited to our climate improves your results. Potatoes are catagorized by how long they take to mature: early, mid-season, and late.
- Early (70-90 days): Great for getting a quick harvest. Plant these first. Examples: ‘Yukon Gold’, ‘Red Norland’, ‘Irish Cobbler’.
- Mid-Season (90-110 days): These are reliable workhorses. Examples: ‘Kennebec’, ‘Viking Purple’.
- Late (110-135 days): Need the longest season, best for storage. Plant these at the same time as early ones. Examples: ‘Russet Burbank’, ‘German Butterball’.
For a continous harvest, plant a mix of early and mid-season types. You can also do a second planting of early varieties in early August for a fall crop, especially in South Jersey.
Step-by-Step Planting Guide
Follow these steps to plant your potatoes correctly.
1. Prep Your Seed Potatoes
Always use certified disease-free seed potatoes from a garden center, not grocery store spuds. About 1-2 weeks before planting, “chit” or green-sprout them. Place them in a cool, bright spot (like a windowsill) to encourage short, sturdy sprouts.
Cut larger seed potatoes into pieces, each with at least 1-2 eyes. Let the cut pieces cure for a day or two so the cut surface calluses over. This prevents rot.
2. Choose and Prepare the Site
Potatoes need full sun (at least 6 hours) and loose, well-draining soil. They thrive in slightly acidic soil with a pH of 5.0 to 6.5. Work the soil deeply, removing rocks and clumps.
Mix in several inches of compost or aged manure. Avoid fresh manure or high-nitrogen fertilizers, as they promote leafy growth instead of tubers. A balanced organic fertilizer worked into the soil is a good choice.
3. The Planting Process
- Dig a trench about 6-8 inches deep.
- Space seed pieces 10-12 inches apart in the trench, with the eyes facing up.
- Cover the seed pieces with 3-4 inches of soil.
- Space trenches about 2-3 feet apart.
As the plants grow, you’ll “hill” soil around them, which we’ll cover next.
Caring for Your Potato Plants
Consistent care is simple but crucial for a good yield.
Watering and Hilling
Keep soil consistently moist, but not waterlogged. About 1-2 inches of water per week is ideal, more if it’s very hot and dry. Water at the base of plants to keep foliage dry and prevent disease.
Hilling is essential. When plants are 6-8 inches tall, mound soil from the sides around the stem, leaving a few inches of leaves exposed. Repeat this every few weeks. Hilling protects developing tubers from sunlight (which turns them green and toxic) and encourages more potatoes to form.
Fertilizing and Pest Watch
Side-dress plants with a low-nitrogen fertilizer when they are about a foot tall. Simply sprinkle it alongside the row and water it in.
Keep an eye out for Colorado potato beetles. Hand-pick the yellow-and-black striped adults and the red larvae off leaves. Row covers early in the season can prevent them. Also, rotate where you plant potatoes each year to reduce soil-borne diseases.
Harvesting Your New Jersey Potatoes
Harvest time depends on the type you planted and what you want.
- New Potatoes: For tender, small “new” potatoes, you can carefully dig around plants about 2-3 weeks after they finish flowering.
- Mature Potatoes: For full-sized, storage potatoes, wait until the plant tops turn yellow and die back completely. Then stop watering and wait about 2 more weeks for the skins to toughen up.
Harvest on a dry day. Gently dig with a fork, starting far from the plant to avoid spearing tubers. Let potatoes cure on the soil surface for a few hours, then brush off dirt—don’t wash them until you’re ready to use them.
Store cured potatoes in a cool, dark, humid place with good ventilation. Properly stored, your homegrown potatoes can last for months.
FAQ: Planting Potatoes in New Jersey
Can I plant potatoes in July in NJ?
Yes, but only for a fall crop. Plant early-maturing varieties in very early August. This works best in South Jersey where the first frost comes later.
What happens if I plant potatoes too early?
Planting in cold, wet soil can cause seed pieces to decay before they sprout. It’s better to wait a week than to rush and lose your seed.
Can I grow potatoes in containers?
Absolutely. Use a large container (like a 15-gallon pot) with drainage. Plant 1-2 seed pieces per pot and follow the same hilling process, adding soil as plants grow.
Why are my potato leaves turning yellow?
If it’s near harvest time, it’s normal. If it’s early in the season, it could be a sign of overwatering, a nutrient issue, or a disease like early blight. Check your watering and ensure plants have good air circulation.
How do I prevent green potatoes?
Green potatoes are caused by exposure to light. Always hill your plants thoroughly to cover tubers, and store harvested potatoes in complete darkness.
By following these timing and care tips, you’ll be well on your way to harvesting a bumper crop of delicious, homegrown potatoes right from your New Jersey garden.