September in Missouri signals the end of summer heat and the beginning of a second, cooler growing season. Moderating temperatures and diminishing daylight create a favorable environment for plant establishment and growth. While the summer harvest winds down, the focus shifts to planting crops for a late-fall yield and establishing plants that require a winter chilling period. Planning plantings around the first expected hard frost, which typically arrives between mid-October and early November, is the main challenge. This transitional period offers a crucial window for both quick-maturing food production and long-term garden investment.
Fall Vegetables for Quick Harvest
The cool, moist conditions of September are perfect for sowing seeds of leafy greens and root crops that mature rapidly. These vegetables are intended for consumption before the deep freeze sets in, providing a fresh harvest well into autumn. Many gardeners focus on varieties with short days-to-maturity, often under 60 days, to maximize the window before a hard frost.
Leafy greens like spinach, kale, and leaf lettuce varieties can be directly sown now. Spinach is particularly cold-hardy, and a mid-September planting can sometimes successfully overwinter to provide an early spring harvest. To improve germination in soil that may still be warm, plant the seeds slightly deeper than recommended and ensure consistent moisture.
Root vegetables such as radishes and turnips are also excellent choices for fall planting. Radishes mature quickly, often ready for harvest in under a month, making them ideal candidates for succession planting throughout September. Turnips can be grown both for their greens and their roots, with the milder flavor of the roots often enhanced by a touch of frost.
For brassicas like broccoli and cabbage, it is generally too late to start from seed in September for a proper fall head, but small transplants can still be planted. These starts benefit from the cooler temperatures, which minimize bolting and improve the flavor of the developing heads. Using row covers can extend the harvest of all these quick crops, insulating them from the initial light frosts and pushing the production window into late fall.
Overwintering Crops and Spring Bulbs
September is the beginning of the planting window for crops and ornamentals that require a cold period to initiate growth or flowering next spring. The goal is to allow root systems to establish in the warm soil before the ground freezes, leading to vigorous spring growth and a successful harvest or bloom.
Garlic, both hardneck and softneck varieties, should be planted from late September through November. The cloves require a period of vernalization—exposure to cold temperatures—to properly divide and form large bulbs the following summer. Plant individual cloves with the pointed end facing up, approximately one to three inches deep, ensuring the planting site offers well-drained soil to prevent rot.
Overwintering onion sets and shallots can also be planted now, giving them a head start on an earlier summer harvest. Like garlic, they benefit from developing a robust root system before dormancy. Fall-planted perennial herbs, such as chives or oregano, also establish roots in September to withstand winter and emerge strong in the spring.
Spring-flowering bulbs, including tulips, daffodils, and crocus, should be planted from late September to late October, or once soil temperatures cool below 60 degrees Fahrenheit. These bulbs also need a sustained chilling period to trigger their internal blooming mechanisms. Plant the bulb at a depth that is two to three times its vertical height, ensuring the pointed tip is aimed toward the sky.
Soil Improvement and Turf Maintenance
September is the most opportune time for improving soil health and establishing cool-season turfgrasses in Missouri gardens. The combination of warm soil and cooler air temperatures creates ideal conditions for seed germination and root development. Focusing on these non-ornamental plantings now prepares the garden for a healthier, more productive season next year.
Overseeding cool-season lawns, such as tall fescue and Kentucky bluegrass, should be completed early in the month. Warm soil promotes rapid germination, while mild air temperatures reduce stress on emerging seedlings. Preparing the seedbed with core aeration or dethatching before spreading the seed ensures successful establishment through better seed-to-soil contact.
For vegetable beds that are finished producing, planting a cool-season cover crop is an excellent form of soil enrichment.
Cover Crop Options
- Winter annuals like cereal rye are hardy and can be sown late into the fall to prevent erosion and scavenge excess nutrients.
- Oats and oilseed radishes are popular choices because they typically winter-kill in Missouri, simplifying spring planting since no tilling is required.
- Leguminous cover crops, such as crimson clover or hairy vetch, fix atmospheric nitrogen into the soil.
- These cover crops break down over winter and in the spring, adding organic matter and improving fertility.
For any newly sown seeds, whether grass or cover crop, the soil must be kept consistently moist until germination is complete.
Adding Autumn Color and Perennials
The moderate temperatures of September provide a perfect opportunity to add immediate color and establish perennial plants. Planting woody ornamentals and perennial flowers now allows root systems to grow and anchor themselves before the ground freezes, significantly reducing transplant shock. This establishment is crucial for the plant’s health and resilience.
For instant autumn color, garden centers offer cool-season annuals like pansies, violas, and ornamental kale that thrive in the declining temperatures. Pansies can provide continuous color through the fall and often survive the winter to bloom again briefly in the early spring. The classic fall chrysanthemum provides a dense flush of color and is best planted when the buds are just beginning to show color.
September is an ideal time to plant new perennial flowers, shrubs, and trees. Native Missouri perennials, like coneflower and black-eyed Susan, benefit from the warm soil that encourages root growth without the stress of summer heat. Planting now means the plants will be fully established and ready to put energy into top growth and flowering when spring arrives.
When planting shrubs and trees, create a wide planting hole and backfill with native soil to ensure good drainage. The root ball must be kept moist until the plant enters dormancy, which encourages the development of fine root hairs necessary for nutrient uptake. This fall planting window ensures a strong, well-rooted foundation for future garden displays.