Posted: June 26, 2025
Your vegetable garden may be planted for the summer, but for an extended harvest of different crops, try succession planting. Smart gardeners enjoy spring greens, followed by warm-season plants like tomatoes and peppers, then segue into planning for a long fall harvest.
Produce and leafy greens shown (clockwise from top): romaine lettuce, cabbage, cilantro in a bed of broccoli sprouts, spinach and other leafy greens, green onions, tomatoes, and green leaf lettuce. USDA photo by Peggy Greb.
Growing cool-season crops such as brassicas in the spring is difficult as weather can become unpredictable, transitioning quickly from cooler weather directly to hot, humid summer temperatures. The rapid transition to warmer temperatures causes brassicas such as broccoli and cabbage, and Asian greens to bolt. Bolting means plants go to seed and become bitter before they can be harvested. A more reliable plan is to plant later in the summer and harvest during the cooler days of fall.
Understanding days to maturity (DTM) is a must for knowing when to plant fall vegetables. You can find this information on seed packets and in catalogs. For crops that are seeded directly in the ground, DTM is based on the time of sowing; for crops that are grown from seedlings, DTM is determined from the time of transplanting. Fall brassica seedlings may be difficult to find at local nurseries. If growing your own transplants, sow the seeds indoors 4-6 weeks prior to hardening off and planting them in the garden. While you can direct sow broccoli, cauliflower, and cabbage, growing transplants indoors provides a stronger start. Plants are better equipped to withstand weather as well as insect and disease damage. The DTM ranges from 60-90 days from transplant. In transplanting these seedlings out in mid-to-late July, be sure to water and mulch to retain moisture around the plants. Leafy greens such a kale and collards can be direct seeded or started indoors as transplants.
Average fall frosts in our region occur from mid-to-late October. Typically, early frosts do not kill fall crops. Leafy greens such as kale, collards, and some root vegetables become sweeter with a light fall frost. Carrots and beets, in particular, store energy as they grow in the form of starches. As the temperature begins to cool, these starches are converted to sugars and can act as a protection from freezing. Carrots and beets can remain in-ground with protection right up until the ground is frozen. Use straw or a hoop-house and enjoy the harvest potentially well into December.
Many vegetables that like cool spring temperatures can be grown in the fall. For the following crops, days to maturity refers to direct sowing. The DTM provided here is approximate and can vary by variety or seed vendor for each vegetable. Carrots- 70 days, beets- 50, radishes- 25, turnips- 45/50, spinach- 35/40, Asian greens such as mustards, pak choi, tatsoi and Chinese cabbage- 40/60, peas- snap, shell or snow- 60/70, fava beans- 70/100, endive- 40/45, Swiss chard- 50/60. Note that for chard, the white varieties tolerate cold better than the multi-colored Bright Lights series.
Lettuce typically will not germinate in temperatures of 70°F or above. Optimal germination temperature ranges from 40-70°F. Head lettuces should be planted indoors and seedlings planted in mid to late July or later, depending on their DTM. Romaine and butterhead lettuces grow better in cold temperatures. Artic King and Winter Density lettuces have been bred to be extra cold-hardy.
Specialty greens that tolerate colder temperatures may be of interest, especially if you are intending to do some growing in a cold frame. Claytonia, 40 DTM, also known as miner's lettuce or winter purslane, is rich in calcium and vitamin C. Mache, known as corn salad or lamb's lettuce, 45 DTM, has a unique nutty flavor. New Zealand spinach, 52 DTM, will withstand frosts into the low 20s.
The biggest challenge will be narrowing down which varieties to choose, especially if ordering seeds from catalogues. Vegetables that will extend the length of your harvest and please your palate can be an exciting new aspect of vegetable gardening.
Barbara Kline is a Penn State Master Gardener. This volunteer program supports the outreach mission of Penn State Extension and provides research-based information on best practices in sustainable horticulture and environmental stewardship. For more information, contact the Penn State Extension of Allegheny County at alleghenymg@psu.edu or 412-482-3476.
