What to Plant in September: Fast-Growing Veggies for a Second Harvest

Autumn, a season of falling leaves, jack-o'-lanterns leering in grimaces, and pumpkin spice, is not leaving anytime in the next millennium or two. It brings with it a host of autumn-themed drinks, including novel concoctions such as the green-apple lineup from 7 Brew, with the apple butter chai latte featuring green syrup, melted white chocolate, spiced chai, and a mountain of whipped cream. To some people, it sounds like a sensory car-wreck; to others, it sounds like a riot at the candy store. 

Whatever your stance might be on this drink, it doesn’t negate the fact that planting in September continues to be one of the joys of many gardeners. Escaping the torrid heat of summer, the fall seasons come in pleasing currents, heralding cooler temperatures. 

If you want to extend your harvest well into the chilly months, here is your ultimate guide to the best fast-growing vegetables to plant in September.

Why September is Perfect for a Second Harvest

Cool-season vegetables, the strongest of which have survived harsh Russian winters, don’t mind when the winter wind blows cold. Roots establish quickly because the ground has retained months of summer heat. Many common summer pests that plague gardens, such as squash bugs and tomato hornworms, begin to decline in numbers as temperatures drop. 

Cool-weather crops undergo a process where starches convert into sugars when exposed to light frosts, resulting in sweeter, crisper greens and root vegetables. Shorter days and cooler ambient temperatures mean plants lose less moisture through evaporation, reducing your watering workload.

To maximize your success, look for short-season varieties that mature in 30 to 60 days so you can harvest them before hard winter freezes set in. Raised garden beds are a high-yield enterprise, resulting in  impressive harvests before winter sets in. 

Top Fast-Growing Veggies to Plant This Month

1. Leaf Lettuce and Mesclun Mixes

Leaf lettuces are living life on the fast lane, with varieties like Black Seeded Simpson, Salad Bowl, and colorful mesclun mixes going from seed to salad bowl in as little as 30 to 45 days. Plant seeds in succession every two weeks throughout September and October. You can harvest them using the "cut-and-come-again" method by snipping the outer leaves and letting the center continue to grow.

2. Spinach

Spinach thrives in cooler weather. When planted in September, it develops a deep, rich flavor that tastes far superior to midsummer crops. Varieties like Bloomsdale Long Standing mature in about 40 to 50 days. Spinach can tolerate light frosts remarkably well. In milder climates, a light layer of mulch or a simple cold frame can help you harvest fresh spinach straight through winter.

3. Radishes

Radishes are reviled today, but in Western Europe, they had royal backing. In the 8th century, the Holy Roman Emperor Charlemagne held the vegetable in such high regard that he explicitly decreed his subjects must grow them in their gardens. To continue the tradition of Rome, you can grow radishes in your own yard – quick-maturing varieties like Cherry Belle or French Breakfast can be ready to harvest in a mere 21 to 30 days. Plant them in loose, well-draining soil. Because they grow so fast, ensure they receive consistent moisture so they don't turn woody or overly spicy.

4. Kale

Often derided as bitter garbage, kale is admittedly not to everyone’s taste, and many wholeheartedly prefer steak to its bitter leaves, but there’s always those who can stomach its taste. It does get sweeter after frost. Varieties such as Lacinato (Dino kale) or Red Russian can be harvested as tender baby greens in 30 days, or left to mature into full-sized plants in 50 to 60 days. 

5. Arugula (Rocket)

Arugula brings a delightful, peppery punch to autumn salads and pastas. It germinates rapidly in warm September soil and is ready to harvest in roughly 35 to 40 days. Harvest arugula leaves when they are young and small. Older leaves can become intensely bitter as the plant matures and days grow shorter.

6. Swiss Chard

While Swiss chard is typically grown as a summer crop, it handles dropping temperatures exceptionally well. Varieties like Bright Lights produce colorful, nutritious stems and leaves that mature in about 50 to 55 days. Chard is a heavy producer. A single planting in September can easily provide continuous harvests until the ground freezes solid.

Essential Tips for September Planting Success

Transitioning your garden beds from summer leftovers to autumn crops requires a little strategy:

1. Clear Out Spent Crops: Remove any diseased or exhausted summer plants (like spent tomato vines or yellowing squash) to prevent pests and diseases from wintering over in your soil.

2. Amend the Soil: Your soil has worked hard all summer. Replenish its nutrients by mixing in a generous layer of compost or organic, slow-release fertilizer before planting your new seeds.

3. Keep Seeds Moist: September can still bring unexpected warm, dry spells. Because seeds need consistent moisture to germinate, water your newly sown beds daily until seedlings are well established.

4. Prepare for Frost Protection: Keep row covers, old bedsheets, or cloches on hand. While the veggies listed above love cool weather, sudden hard freezes early in the season can damage tender young seedlings. For the ultimate winter protection, greenhouses reign.