Gardening in New Jersey: zones, frost dates and when to plant

Five climates in 166 miles

The Office of the New Jersey State Climatologist at Rutgers divides the state into five climate regions. Each one grows a slightly different garden.

• Northern. The highlands and valleys of the northwest rise to about 1,800 feet and have a continental climate with little ocean influence. In winter this region can average more than 10°F colder than the coast. It also has the shortest growing season in the state, and valley spots can see killing frost well outside the usual window.
• Central. This belt runs from New York Harbor to the Trenton area. It is heavily built up, and the pavement and buildings hold heat, so nights in developed areas stay warmer than in nearby suburbs.
• Pine Barrens. The interior south has sandy, porous, infertile soil that dries quickly and loses heat fast on clear nights. Atlantic City Airport, surrounded by sand, can be 15 to 20 degrees colder than the bayfront marina about 13 miles away.
• Southwest. The low land along Delaware Bay has the state’s highest average temperatures and longest growing season. Fall frost typically arrives about four weeks later than in the north, and spring frost ends about four weeks earlier.
• Coastal. The ocean keeps the shore cooler in spring and warmer in fall and early winter. Sea breezes often reach 5 to 10 miles inland. Nor’easters are most frequent from October through April.

Check the frost dates for your city above. A garden in Sussex County and one in Salem County can be weeks apart.

What limits New Jersey gardens

Summer heat and humidity. Areas south of the central belt have nearly twice as many days above 90°F as central New Jersey. Rutgers’ Growing Tomatoes in the Home Garden (FS678) recommends disease-resistant varieties. It also advises keeping tomatoes, peppers, eggplant and potatoes out of the same spot for at least two years to limit soil-borne disease. Planning a Vegetable Garden (FS129) adds that good air movement dries leaves faster and can reduce disease.

Uneven moisture. Annual precipitation ranges from about 40 inches on the southeast coast to 51 inches in north-central New Jersey. FS678 links blossom end rot to uneven soil moisture and fruit cracking to heavy rain after a dry spell. Its remedy for both is steady watering of at least 1 inch a week, plus mulch.

Cold early weather. Rutgers warns that tomatoes set out too early are stressed by cool air and soil. Cold during flowering also causes catfacing, which is more common on large-fruited and early varieties. If you must plant early, use row covers or hot caps.

Deer and wildlife. FS129 suggests planning for fencing wherever deer are around.

Rutgers planting guidance

Rutgers’ Planning a Vegetable Garden (FS129) includes a planting table that gives spacing, transplant-or-seed method, planting months and expected yield for more than 40 crops. It treats the garden as two seasons, with early spring crops followed by plantings for late summer and fall harvest. Some highlights from the table:

• Peas are sown in March and April.
• Spinach goes in during April and again in September.
• Lettuce can be planted in April, May, August and September.
• Tomato and eggplant transplants go out in May and June. Peppers go out in June.
• Brussels sprouts and cauliflower are set out in July. Kale is sown in July and August, both for fall harvest.

The same fact sheet asks for full sun and good drainage, with no standing water even after heavy rain. Put tall crops on the north side so they don’t shade shorter ones.

For varieties, Varieties for New Jersey Home Vegetable Gardeners (FS681) lists cultivars that did well in New Jersey research trials. For tomatoes these include Early Girl, Fourth of July and Moreton for early crops. Midseason choices include Better Boy, Celebrity, Jet Star and Ramapo. Heirlooms include Brandywine Red and Mortgage Lifter. For sweetpotatoes the list includes Beauregard, Covington and O’Henry. For tomato mulch, FS678 suggests straw, salt hay or grass clippings laid 3 to 4 inches deep once the soil warms in late spring. Black plastic is another option, and it warms the soil.

Soil testing through Rutgers

Rutgers strongly advises a soil test before liming or fertilizing, especially for a new garden. Kits are available from most county Extension offices and from the Rutgers Soils Laboratory in New Brunswick. In a few weeks the report returns pH and levels of phosphorus, potassium, calcium, magnesium and several micronutrients, usually with lime and fertilizer recommendations. Fertilizing the Home Vegetable Garden (FS626) says a slightly acid soil near pH 6.5 suits most vegetables. It recommends sampling after fall harvest or before spring fertilizing and retesting every three years.