September marks a shift in the garden, transitioning from the intensity of summer growth to a cooler, more productive second season. This period is a final window for planting that extends the harvest well into late fall and sets the stage for the following spring. Focusing on crops and ornamentals suited to the cooling soil and shortening days maximizes garden output. This allows for the enjoyment of fresh produce and vibrant blooms in the coming months and after winter dormancy.
Quick-Maturing Vegetables for Fall Harvest
September is the ideal time to sow seeds for a rapid autumn harvest, focusing on crops that mature quickly, generally within 4 to 8 weeks, before the first significant frost arrives. Leafy greens are particularly well-suited for this late-season planting because cooler temperatures improve their flavor, making them sweeter and less prone to bolting. Direct-seeding varieties like spinach, arugula, and loose-leaf lettuce yield tender, harvestable leaves in as little as 30 to 45 days.
Arugula is one of the fastest options, often ready for harvest within a month of sowing. Spinach also thrives in the cooling weather and can be harvested as baby greens about four weeks after planting. For a continuous supply, implement succession planting by sowing a small batch of seeds every two weeks throughout September.
Root vegetables can also be planted now for a fast turnaround. Radishes offer the quickest gratification, maturing in only 25 to 30 days, and they become crisper when grown in cool soil. Turnips are another excellent choice, with many varieties developing usable roots in 40 to 50 days, and their greens can be harvested sooner.
Baby carrots and beets can also be sown in early September, targeting a harvest window of 50 to 75 days. The reduced daylight and dropping temperatures cause these root crops to convert starches into sugars, resulting in a sweeter flavor profile. Ensuring the soil remains consistently moist is necessary for good germination and rapid growth.
Overwintering Crops and Next Year’s Staples
September is the time for planting crops that rely on winter cold to prepare for next year’s growth. Garlic is the most prominent example, requiring fall planting to establish a robust root system and undergo vernalization. This prolonged cold exposure, typically 6 to 8 weeks below 40°F (4°C), signals the plant to divide its single clove into a fully segmented bulb.
Planting garlic cloves, pointy-side up, four to six weeks before the ground freezes allows them to establish roots. This timing prevents excessive top growth that could be damaged by heavy frost. Without this chilling period, hardneck varieties may only produce a single, round bulb instead of the desired cloves.
Once planted 2 to 4 inches deep, apply a thick layer of straw or shredded leaf mulch. This insulates the soil and keeps temperatures consistently cold, preventing freeze-thaw cycles that can heave the cloves out of the ground.
Perennial Herbs and Cover Crops
Some perennial herbs, such as chives and parsley, benefit from fall planting, allowing them to establish roots for an early spring harvest. September is also an appropriate time to sow cover crops, such as winter rye or clover, which enrich the soil. These crops prevent erosion over winter and, when tilled under in spring, add valuable organic matter and nutrients to the garden beds.
Autumn-Planted Flowers and Spring Bulbs
September is the ideal month for planting spring-blooming bulbs, which require a cold dormancy period to flower successfully. Bulbs must be planted before the ground freezes to ensure they receive the necessary chilling hours. The soil is generally still warm enough in September and October for the bulbs to develop roots before becoming dormant for the winter.
Bulbs should be buried two to three times their height. Larger bulbs, such as tulips and daffodils, typically go 6 to 8 inches deep. Smaller bulbs, like crocuses and snowdrops, require a shallower planting of 3 to 4 inches. Proper drainage is important, as bulbs will rot if left sitting in waterlogged soil.
Spring-Blooming Bulbs
The following bulbs must be planted now:
- Daffodils
- Crocuses
- Hyacinths
- Most tulips
Immediate Color and Perennials
Gardeners can introduce immediate color by planting cool-season annuals and perennials that thrive in autumn temperatures. Pansies and violas can be planted now to provide color until a hard freeze and often survive winter to bloom again in early spring. September is also a suitable time to divide and transplant existing perennials, allowing them to settle into new locations before winter dormancy.