Early Indoor Planting

• Many plant species fare well if planted indoors early in the fall, potentially to be transplanted outdoors later. If you have a greenhouse, spare delicate seedlings from frost by starting them in trays indoors. While ideal planting time will vary by location, in cooler climates you may begin as early as late summer, while in milder places, it's best to wait until summer temperatures have dropped significantly, potentially waiting until September to plant your cold weather crops indoors. For example, if you're planting lettuce, spinach and other popular leafy greens, check that the soil's temperature has dropped to 85 degrees Fahrenheit or lower.
  
  

Transplanting

• In milder climates, you may be able to transplant your winter crops from the greenhouse to the outdoors once they have developed past the seedling stage. While planting times vary widely by region, as a rule of thumb, you should be able to transplant after six to eight weeks in the greenhouse. In the Pacific Northwest, Oregon State University recommends transplanting winter crops quite early, between June and August.
  
  

Winter Gardens for Warm Climates

• In warmer climates, a winter garden may be a necessity, as summer heat would scorch more delicate plants. For example, the University of Arizona Cooperative Extension of Maricopa County recommends planting vegetable gardens to produce their main yields in the fall and the spring. As a result, the winter is a busy time for the vegetable gardener, finishing up the fall's harvest and then planting in mid to late winter for the spring garden. Depending on the vegetable, planting dates range from late fall through the winter months.
  
  

Individual Plant Calendars

• While the specific timing for individual plants varies according to your location, some general rules apply. Calculate the ideal planting dates for individual plants based on their cold hardiness and the winter temperatures in your area. When planting vegetables, use the maturation period as a guide. For example, broccoli will average 120 to 130 days from seed to maturity. On the other hand, if you start the broccoli plant indoors and then transplant the seedling, it will only require 90 to 100 days of growth, outdoors. If you're trying to plan your a winter garden for before the coldest months or after the warmth of late summer, you may need to stagger plantings of various vegetables according to their maturation periods.