Overwintering cover crops can be sown to provide nutrients and organic matter for next year’s garden. Sowing salad greens from late September into the first weeks of October is important because small plants (1 or 2 inches tall) overwinter better than larger plants. Overwintering plants have unique soil fertility needs to help them survive the cold and thrive come spring. Excessive nitrogen produces fast growth full of water, so don’t provide too much nitrogen because this will make plants more susceptible to frost damage. The goal is balanced growth throughout the fall and early winter, then in the spring, add top dressings of high nitrogen organic fertilizers or composted manure to spur faster spring growth.

In an established garden, the nutrients necessary for fall plant establishment can be supplied by cover crops and compost. Incorporate well-rotted compost into the entire garden bed. The comparatively warm soil temperatures of fall allow soil bacteria to mineralize the nutrients in the compost, making them available to winter vegetables.

For plant lists and full details on gardening in September, order your copy of Seattle Tilth's Maritime Northwest Garden Guide, a planning calendar for year-round organic gardening.