Written By Lara Wadsworth

August is that time of year when everyone is getting a little sick of the heat. Many people are looking forward to pumpkin spice lattes and wearing their favorite sweater. However, the heat has not passed yet, and while summer may be beginning to wind down, don’t hang up your gardening gloves just yet. August brings intense heat in many regions, but it also marks the opening of a critical window for fall preparation. So, whether you’re sneaking in late summer crops or getting a jumpstart on cool-weather planting, now’s the time to act!

Understanding First and Last Frost Dates

By August, most zones are squarely focused on the first fall frost. Your growing window is closing fast, so pull up your frost date (via the Farmer's Almanac or your local extension office) and count your weeks. Microclimates, such as shaded areas, high elevations, or urban heat islands, can shift your actual frost date earlier or later than that listed for any individual zone. Adjust accordingly and stay flexible. So, keep a close eye on the weather forecast for your area and take action if needed! Depending on where you’re growing, extreme heat or even an early frost can occur and should be guarded against. The best source for new gardeners to understand this information as it relates to their area is your local extension office.

Remember, frost dates aren’t the only metrics important to plant selection and planting times. In August, zones 7 through 11 need to be thinking about the intense heat of summer that can stunt plant growth. The hot summer sun can be too much for some plants. Shade cloth, mulching, smart species selection, and proper watering practices are your best defenses as you ride out the last blast of summer.

What are USDA Hardiness Growing Zones?

The United States Department of Agriculture (USDA) zone hardiness map assigns a zone number to each region of the United States based on the average winter low temperatures experienced annually. Your zone number helps you determine what perennial plants will thrive in your area when that winter low is considered. However, the information you gain from identifying your growing zone should also be paired with understanding your first and last frost dates, as this will determine the length of your growing season.

USDA zones reflect average winter lows. However, for summer planting, use frost dates and your understanding of the local climate to inform your decisions. Two regions that fall within the same zone designation could still have very different summer experiences! Keep both winter and summer conditions in mind.

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What to Plant in August

Zone 3

If you’ve been in zone 3 for any length of time, you know how short the summers can be. While August typically brings warm(ish) weather, it is also a critical time for planning your fall garden and getting any other warm-weather crops cycled through as needed. Your first freeze could hit in less than two months, so this month is about short-term payoff and prepping for fall.

• First Frost Date Window: Early to Mid-September
• Approximate Weeks Until First Frost: 5-9
• Seeds to Start Indoors: Microgreens, quick-growing herbs like basil and cilantro, start brassicas (like broccoli, cauliflower, and cabbage) indoors and move them outside as soon as daytime temps stay below 75 F. Also start lettuce and any other more hardy herbs for fall transplanting.
• Seeds to Sow Outdoors: Fast-maturing greens like radishes, arugula, spinach, and mustard. Try a final round of bush beans or peas if you think you can. Consider cover crops like buckwheat if your garden beds will be left fallow soon.

Zone 4

By August in zone 4, you can already start to see signs of summer winding down. Yet, you have at least a couple of months before the frost really sets in. That’s plenty of time to get some more gardening in. August is a transition month. You can find a beautiful balance between late-summer productivity and planning your fall garden.

• First Frost Date Window: Mid-September to Early October
• Approximate Weeks Until First Frost: 7-11
• Seeds to Start Indoors: Start brassicas like kale, broccoli, Chinese cabbage, and late cabbage to have them ready for fall planting. Start herbs, microgreens, and sprouts for use throughout the summer season.
• Seeds to Sow Outdoors: Direct sow root crops like beets and carrots (at the beginning of the month), brassicas like broccoli and cauliflower, and leafy greens like lettuce and spinach (as long as daytime highs stay below 75F).

Zone 5

August is usually the peak garden maintenance month for Zone Five dwellers. The final harvests of warm-season crops are being made, and the window for fall planting is wide open. You can enjoy the fruits of your earlier work while also investing in your fall garden.

• First Frost Date Window: Mid to Late October
• Approximate Weeks Until First Frost: 9-13
• Seeds to Start Indoors: Start brassicas and hearty greens indoors to prepare for late summer or fall transplanting. Microgreens, sprouts, and herbs are also great options for indoor growing at this time of the year.
• Seeds to Sow Outdoors: Direct sow carrots, beets, turnips, and radishes. You may even be able to get one more harvest of things like beans, mustard greens, and arugula. This is also your last chance to direct sow any other fast-growing warm-season crops. Get your fall cover crop planted and growing this month as well.

Zone 6

August in zone 6 still features many warm days, but by the end of the month, things are starting to calm down (heat-wise). Keep a close eye on the weather and watch out for unexpected heat waves, but expect August to mark the beginning of the end of summer. Start thinking about fall growing!

• First Frost Date Window: Late October
• Approximate Weeks Until First Frost: 11-15
• Seeds to Start Indoors: Grow herbs, microgreens, and sprouts indoors. Cool-weather crops like brassicas and leafy greens can also be sown to prepare for fall harvesting.
• Seeds to Sow Outdoors: Quick greens like spinach, chard, and lettuce; shade helps reduce bolting. You can still plant summer squash and cucumbers early in the month for a short window of harvesting. Fall root crops, such as carrots, beets, and radishes, should be planted now.

Zone 7

August in zone 7 brings more heat and potential for heat-related issues. The cooler fall days are still a ways away, but the peak of summer has also passed. This means that there is still much to be done, but planning for fall is also critical.

• First Frost Date Window: October to November
• Approximate Weeks Until First Frost: 13-17
• Seeds to Start Indoors: Start herbs, microgreens, and sprouts for a quick, high-nutrient-density harvest. Sprouts and microgreens make a great addition to traditional summer sandwiches, BBQ, and salads. Sow brassicas like cauliflower and brussels sprouts in individual pots to prepare for fall transplanting.
• Seeds to Sow or Transplant Outdoors: Legumes like beans, as well as beets, carrots, turnips, cucurbits like cucumbers and summer squash. Plant quick-growing greens like lettuce, but provide shade during the midday hours. Plant heat-tolerant greens like amaranth and Malabar spinach. Herbs like basil, thyme, and oregano love the warmth, so go crazy with those. Be sure to mulch well and consider some shade for tender plants during the hottest parts of the day.

Zone 8

Zone 8 in august is still very hot, but temperatures will begin to decline slightly throughout the month. Daily high and low temperatures will begin to cool down by the end of August, but for most of the month, heat stress is still a concern. It will soon be time to prep fall transplants indoors, but it might still be a bit too hot for sowing.

• First Fall Frost Date Window: November - December
• Approximate Weeks Until First Fall Frost: 15-19
• Seeds to Start Indoors: You can start brassicas, such as broccoli and cauliflower, indoors late in the month for transplanting in the fall. The indoors is also the perfect place to keep growing herbs, sprouts, and microgreens throughout the heat of summer. These crops can be ready in a matter of days to weeks for a refreshing touch to your summer meals and aren’t limited by outside weather.
• Seeds to Sow or Transplant Outdoors: Southern peas, summer squash, cucumbers, and basil are still thriving. Late in the month, consider direct sowing kohlrabi, rutabaga, and Chinese cabbage.

Zone 9

August is the peak of the heat season for zone 9. Heat stress is a real concern, but we know that more tolerable days are around the corner! However, for the time being, August is not the best time for planting new crops outside.

• First Frost Date Window: November - December
• Approximate Weeks Until First Fall Frost: 21-26
• Seeds to Start Indoors: Start cool-weather crops like kale, broccoli, spinach, and cabbage indoors to prep for fall transplanting.
• Seeds to Sow Outdoors: Basil, peppers, eggplant, cucurbits (such as melons and squash), beans, and corn. Plant out any other warm-season annuals you haven’t yet, including peppers and okra. Consider trying out some unique, heat-tolerant greens, such as roselle or malabar spinach.

Zone 10

Due to continuous high heat, it is not a good time to plant much of anything new outside at this point. Focus on heat-resistant crops and varieties to get you through this time. Many gardeners even take a hiatus during June through August by planting a heat-tolerant cover crop, such as cowpeas. Be sure to keep everyone, the plants, and yourself well hydrated!

• First Frost Date Window: Does not typically experience frosts.
• Approximate Weeks Until First Frost: N/A
• Seeds to Start Indoors: Only things you can grow entirely indoors, such as microgreens, sprouts, baby greens, and herbs. It is still a bit early to start fall crops. Instead, try your hand at growing leafy greens as microgreens for mixing into salads, stuffing sandwiches, or making refreshing wraps.
• Seeds to Sow or Transplant Outdoors: Avoid outdoor planting unless absolutely necessary. If you must, choose heat-tolerant crops like amaranth or Malabar spinach and protect them from extreme heat.

Whether you’re just getting into the swing of summer gardening, gearing up for your fall crops, or just trying to survive the heat, the month of August is full of opportunity. Thoughtful planning and determination can make a big difference in your gardening experience. Prioritize fast growers, prep fall transplants, and protect your crops from sun and drought. Your summer garden may be maturing, but August is anything but idle. Keep it growing!

Lara Wadsworth, True Leaf Market Writer

I am a native of Southwestern Michigan, where I currently reside. I love all things plants! After completing a Bachelor's Degree in Horticulture, I found a dream work-from-home job that allows me to share my passion. Now, I spend my days writing for TLM, playing with my dog, eating delicious food with my husband, and plotting my next landscape or gardening move. I believe everyone should get down and dirty in the soil now and then. Happy Gardening!