Temperature has much to do with success growing in containers. Root vegetables are cool-season crops. Leaf and stem crops prefer cool weather. Warm temperatures—and longer days—are needed for fruiting vegetables to grow and mature.
Knowing the average last frost date in spring and the average first frost date in fall will help you plan when to sow seed or set out starts or seedlings—those dates help define the cool-weather crop season and the warm-weather crop season. Mark your calendar with the frost dates, then schedule your planting and harvest. Each crop may have a different start and end date, but a simple calendar will help you keep the garden running smoothly—planting and harvesting.
To make sure you have plenty of time for fruiting crops such as tomatoes, peppers, eggplant, and melons to ripen, you may want to jump start the season by starting seeds indoors before the last frost.
Container Planting and Harvest Times:
Here are suggested seed sowing and harvest times for crops you can grow in containers on a patio, balcony, or roof top.
- Asian Greens: Plants prefer to grow in cool weather; sow seed in early spring and again in late summer. Some can grow inside during winter under lights or in a windowsill; keep temperatures below 70°F (21°C). Most Asian vegetables require 30 to 50 days to reach harvest—depending on variety.
- Asparagus: Start with one-year old plants from a nursery (sold as roots in late winter). Plant roots as soon as danger of frost is past. Harvest comes in second year after planting; plant can remain productive for 20 years.
- Beets: From seed, crop is ready in 8 to 10 weeks; time sowing so that harvest is complete before or well after summer heat.
- Beans: Sow seeds in late spring and early summer; beans are cold sensitive and should not be planted until after the last expected frost. Beans are ready in 60 to 70 days.
- Broccoli: Grow broccoli from seedlings. In cold-winter regions, starts can go into the garden two weeks before the last expected frost. Put in a second planting in midsummer for fall harvest. In mild-winter regions, set out starts from early fall through late winter. Time planting so that crop matures before it becomes really hot. Broccoli is ready to harvest in 8 to 10 weeks.
- Brussels sprouts: Start from seedlings. Brussels sprouts require four to five months of cool weather to mature or summer temperature of 65°F (18°C) or less. In hot summer regions start in early summer to mature in cool fall weather. Brussels sprouts are ready for harvest in 2 to 3 months.
- Cabbage: Late winter and early spring plantings should be timed to reach maturity before the arrival of hot summer days. Start crops for fall and winter harvest in mid-summer. Cabbage is ready for harvest in 60 to 110 days depending upon the variety.
- Carrots: Start in spring about the time of the last frost and continue until 60 days before the first frost in fall; with ample moisture they can be grown in summer heat. Provide shade where exceptionally hot. Carrots mature in 8 to 12 weeks depending on the variety.
- Cauliflower: Bring cauliflower to harvest in cool weather. From seed to harvest allow 12 weeks; from starts to harvest allow six to eight weeks. In cool spring and early summer regions, start plants in late winter or early spring. In warm spring and summer regions, start from seedlings in mid-summer for a fall harvest.
- Celery: Seeds are very slow to germinate so it’s easier to start with seedlings from the garden center. In mild-winter regions, grow celery for winter harvest. In warm-summer regions, plant celery in late summer for fall harvest. Celery is ready for cutting 16 to 18 weeks after sowing.
- Collards: Sow seed in early spring and summer. From seed to harvest allow eight or nine weeks.
- Corn: Sow seed in late spring after frost danger is past or set out starts two weeks after the last frost; in mild winter regions sow in late summer for a fall crop. Corn is usually ready 65 to 80 days after sowing.
- Cucumbers: Sow after temperatures rise to a constant 60°F (15°C) Make a second sowing one month later. Cucumbers are ready to harvest 50 to 60 days after sowing.
- Eggplant: Start with young plants from a nursery or by seed sown indoors at least two months before you plan to transfer them to outdoor containers. Eggplants are ready for harvest 60 to 75 days after sowing—if days and night temperatures stay consistently warm, 70°F (21°C).
- Garlic: Sow cloves in fall to harvest large bulbs the following summer. In cold-winter regions protect the crop form freezing by covering and insulating the container.
- Horseradish: Start with root cuttings from established plants after the danger of frost has passed. Horseradish is a perennial; protect the container from freezing in winter.
- Jicama: Start seed indoors three months before setting out in container after danger of frost has passed. Jicama requires three months of warm temperatures to reach harvest.
- Kale: If summers are cool with an average daytime temperature of 75°F (24°C) or less sow in spring, otherwise sow in midsummer to grow in cool of fall. Frost improves flavor. Kale is ready for harvest in 55 days.
- Leeks: Sow indoors at least two months before the last frost. Starts that are 8 inches/ 20 cm tall can be set out in containers from early to mid-summer and can grow on for up to 3 months.
- Lettuce: Sow seed in succession from early sprig to fall; seed germinates rapidly but starts can be planted where time is short. Allow 50 to 70 days from seed sowing to harvest.
- Melons: Start seed indoors 4 to 6 weeks before setting them out in container. Seed can be planted outdoors after weather warms to 60°F (15°C). Cantaloupes, honeydews, and watermelons require at least 70 days to come to harvest.
- Okra: Okra loves warm weather; sow seed after nighttime temperatures average 65°F (18°C). Allow 55 days to harvest.
- Onions: Plant onion sets or seed in early spring and make successive sowing. Grow for stems in cool weather—below 70°F (21°C)–for bulbs into warm weather. Bulb onions are ready to harvest in 100 to 110 days; shallots are ready to harvest in 60 to 70 days.
- Peas: Start seed indoors or sow outdoors three weeks before the last expected frost. Fall sowing is recommended for areas with mild winters. Peas are ready for harvest in 55 to 70 days.
- Peppers: Sow seed indoors eight weeks before you plan to set plants out; set out transplants after average temperatures reach 60°F (15°C). Sweet peppers are ready for harvest in 70 days; hot peppers require 60 to 100 days depending on variety.
- Potatoes: Sow seed potatoes in early spring; potatoes are cold tolerant so you can plant them before frost has passed. In mild-winter areas plant potatoes in mid-summer for a winter harvest. Potatoes are ready between 75 and 130 days to harvest.
- Pumpkins: Sow seeds in container after the danger of frost has passed or set out starts two or three weeks after the last frost. Most varieties require 100 days or more from sowing to harvest.
- Radishes: Sow radishes indoors anytime during the year; outdoors avoid growing in midsummer and sow the last outdoor crop three to four weeks before the last killing frost. Harvest in 25 to 50 days depending on variety.
- Rutabaga: Crop will mature from seed in three months; time sowing so that harvest comes before or after summer heat.
- Spinach: Sow seed in early spring and early fall for windowsill and outdoor containers. Make successive plantings ten days apart. Temperatures in the 80°sF (26°C) will cause the crop to bolt. Spinach requires 45 to 50 days from sowing to harvest.
- Squash: Sow seed indoors three to four weeks before the last expected frost; set plants out two weeks after all danger of frost has passed. In warm-winter areas start seed in late summer or set out transplants for fall harvest. Zucchini and other summer squashes require 40 to 45 days to reach harvest from sowing; winter squashes require 70 to 100 days depending on the variety.
- Sweet Potatoes: Start from slips outdoors after all danger of frost has passed. Crop requires 100 to 120 days to reach harvest.
- Swiss Chard: Sow in containers year round except where winters are harsh, then sow in late spring. From seed to harvest allow 55 days.
- Tomatillo: Sow seeds indoors a month before the last expected frost. Set out plants two weeks after all danger of frost has passed. From sowing to harvest allow 85 days.
- Tomatoes: Transplant starts to outdoor containers about two weeks after the last frost. Start seed indoors 8 weeks before you plan to transplant to containers outdoors. Tomatoes require 55 to 100 days to reach harvest depending on the variety.
- Turnips: Crop will mature from seed in two months; time sowing to mature crop before or after summer heat.