When Should You Start Planting Zucchini This Season?
Are you planting zucchini this season? Before you start putting seeds into the ground, it's important to understand that the best time to plant zucchini will depend on your planting location. In this article, organic gardening expert Logan Hailey examines the best times to plant zucchini broken down by each USDA hardiness zone!
Zucchini is a prolific summer squash that keeps on giving in the garden: Just a single plant can yield up to 10 pounds of zucchini squash! As an added bonus, zucchini is easy to grow, quick to mature, will easily outcompete weeds, and don’t require much tending.
But zucchini is a warm-season crop that really can’t handle the cold. This makes spring plantings a little tricky, especially for northern growers. Luckily, we’ve got quite a few tricks up our sleeves for getting zucchini in the ground at the perfect time.
Here’s everything you need to know about when to plant zucchini based on your climate, including a simple 4-step guide to planning your squash garden and a quick-reference chart of zucchini planting dates.
Zucchini is a member of the Cucurbitaceae family along with cucumbers, pumpkins, and melons. Considered a summer squash, zucchini loves the heat and sunshine and loathes the cold. But thanks to its vigorous growth, zucchini can be cultivated in USDA growing zones 3 through 11 as long as it’s planted at the proper time.
If you plant zucchini too early, you may risk losing your whole crop to late spring frosts. On the other hand, planting zucchini too late may result in not having enough time to enjoy the fruits of your labor.
To grow zucchini in the north, you need at least 60 frost-free days (preferably with nights above 40°F). In the south, as long as temperatures don’t go above a sweltering 110°F, zucchini will thrive almost year-round.
Is Zucchini Cold Sensitive?
Although zucchini grows rapidly, you get the most bang for your buck (and work) by planting it as early as the weather allows. These squash plants take 40 to 60 days to mature and require completely frost-free, settled weather to thrive.
Temperatures below 40°F can significantly stunt or damage the crop. And these tender annuals definitely don’t tolerate frost. In fact, zucchini is a bit of a tropical diva. In a perfect world, zucchini plants would grow at a cozy 60°F to 85°F.
But, alas! We don’t live in a perfect world. Every gardener knows that the weather is unpredictable and a bit of educated guessing is key to getting your plantings right. Thankfully, crops are willing to adapt if we give them a little extra attention.
Follow These Tips:
- Decide how you want to plant zucchini.
- Find your hardiness zone.
- Determine the last spring frost date.
- Consult our quick-reference chart on when to plant zucchini.
Planting your spring garden is the most exciting part of the growing season, but you don’t want to jump the gun and risk losing out on all your hard work.
The most common mistake amongst beginner gardeners is planting their garden on the first warm sunny day of spring. Oftentimes the weather tricks us and will suddenly turn cold again, killing back all those fragile baby crops planted after on that random hot day.
To ensure this doesn’t happen, it’s best to approach gardening with a game plan. After all, Nature is our friend, but her weather whims are not always in our favor.
To create a weather-resilient garden, plan ahead by choosing exactly how and when you’re going to plant zucchini.
Nursery Starts vs. Indoor Sowing vs. Direct Seeding
The zucchini starting route you choose will determine your exact planting date. Weigh the pros and cons of each option, then use our handy quick-reference chart below to decide the best time to plant.
When it comes to planting zucchini, you have three main options. You can buy seedlings from a nursery, start your seeds indoors and then transplant, or you can direct seed into your garden. Let’s look at the pros and cons of all three methods.
Buying zucchini seedlings is by far the easiest way to get started with your garden. This beginner-friendly method ensures that you only have to tuck those babies into the ground.
This also removes a lot of the guesswork out of seeding dates. As long as you know your ideal transplant date, your local nursery, farm, or garden store did the pre-planning work for you. The starts should come already hardened off with strong roots and vigorous leaves. Just be sure to double-check with the grower that the plants are ready to go in the ground.
Timing: Purchase nursery starts 1-7 days before planting.
Pros of Nursery Starts
- The easiest option for beginners.
- No nursery, or greenhouse needed.
- Nursery timed seeds for you.
- Starts come already hardened off.
- Seedlings grown by professionals.
Cons of Nursery Starts
- Most expensive option.
- Limited varietal selection.
- Risk of getting rootbound starts.
This is the best option for cold-season growers or intermediate-level gardeners. It requires a little bit more preparation (including a mini-nursery, greenhouse, or seed starting set up in your home), but it can save you a lot of money and open up the door for a wider diversity of zucchini varieties.
To start your own zucchini seedlings, begin with a protected seed starting area. This can be a miniature greenhouse or an indoor setup. If you are starting seeds indoors, you will probably need supplemental grow lights to ensure that the seedlings don’t get spindly or “leggy”. Some gardeners can get by with a large south-facing window with ample sunlight.
Zucchini seeds are most commonly sown in 3” or 4” square pots filled with a quality seed starting mix. Sow seeds ½” to 1” deep in the mix and place the pots in a bottom tray to catch the water. Keep the starts thoroughly moist until germination, which usually takes about 7 to 10 days when the soil is warm. A heating mat beneath the trays can ensure faster, more uniform germination.
After 2-4 weeks, zucchini plants should have several true leaves and roots that fill out their container. They need to be hardened off (slowly adjusted to outdoor temperatures) about 1 week before transplanting. I usually start hardening off summer squash seedlings 1-2 weeks after the estimated last frost date. A protected sunny patio or an outdoor table with row cover are suitable.
Once your starts are adjusted to outdoor temperature fluctuations and the weather has thoroughly settled to above 40°F at night, you can transplant zucchini into the garden on a date that fits within the planting window for your zone.
Be very gentle with the roots and provide at least 2 to 3 square feet per plant. Cover newly transplanted zucchini with row cover for added protection from cold weather and pests.
Timing: Start zucchini seeds indoors for 2 to 4 weeks before planting them outside. An easy metric is to start seeds right around the estimated last frost date. Harden off zucchini seedlings 1 week before planting. Transplant 1 to 3 weeks after the last frost date.
Pros of Growing Starts
- Get a head start on the season.
- Cheaper than buying nursery starts.
- Can sample different varieties.
- Closer to the planting process.
- More control over plant health.
Cons of Growing Starts
- Is more time-intensive.
- Summer squash are prone to transplant shock.
- Requires a seed-starting setup.
- You will need to plan for hardening off.
Like many of its Cucurbit cousins, zucchini doesn’t like root disturbance. When possible, direct seeding is better than transplanting in regard to root health and vigor. It is the cheapest and most traditional option that requires the least amount of handling or specialized equipment.
However, direct seeding poses a lot more risks than transplanting. It is only reasonable for warmer growing zones with minimal pest pressure and reliably warm weather.
To direct seed zucchini, wait until the weather is as warm as possible (ideally above 60°F). Prepare a loamy, loose seedbed by weeding the soil, amending it with compost, and raking it flat.
Seeds should be sown at a depth of ½ to 1” deep and about 12-18” apart in every direction. Gently cover the seed with soil and keep evenly moist. Zucchini seeds usually take 7 to 10 days to germinate, but they can be more erratic in an outdoor garden setting. I usually sow extra seeds and thin them out later on.
I prefer to use row cover to buffer against temperature and moisture extremes while also excluding pests from the young emerging squash plants.
Timing: Wait to direct seed zucchini until at least 3-4 weeks after the last frost date. Use a soil probe to be sure that s temperatures are at least 70°F. Consult the chart below for the ideal date range in your growing zone.
Pros of Direct Seeding
- Cheapest option.
- Most plant vigor.
- No risk of transplant shock.
- No specialized equipment needed.
- Least amount of handling.
Cons of Direct Seeding
- Rodent risk.
- More temperature fluctuations.
- Less control over conditions.
- Soil can dry out more easily.
- Later planting date and harvests.
Remember, the younger the seedling, the more fragile it will be to temperature and moisture fluctuations. Just like animals, young plants get stronger and more resilient with time.
All in all, direct seeding zucchini is only ideal if you have an abundance of cheap zucchini seeds and a long growing season. For northern gardeners, I’d almost always recommend going the transplanting route or buying starts from a reputable source. It takes a little extra effort, but this will ensure the longest possible harvest window and the greatest chance for success.
Determining your hardiness zone and frost dates can help you decide which option is ideal for your specific climate.
Finding Your Hardiness Zone
The United States Department of Agriculture (USDA) first defined plant hardiness zones in 1960. They created a recommended growing map that tells us which plants can grow in which places. These colored regions are called “hardiness zones.”
The hardiness zones are based on average minimum winter temperatures. They are divided into 10-degree F zones, which are numbered 1a to 13b. You can find these USDA growing zones referenced on seed packets, in growing guides, and on nursery plants to help farmers and gardeners gauge whether certain species will thrive in their location.
Follow These Steps to Find Your Hardiness Zone:
- Visit https://planthardiness.ars.usda.gov/
- Enter your address or zip code in the top white search bar
- Reference the color legend to determine your zone
If you are on the edge of a hardiness zone, choose the colder one just to be safe. For example, Lubbock, Texas, borders the lime green 7b (5 to 10°F) and slightly darker green 7a (0 to 5°F) zones.
If I lived in that area, I’d plant my garden based on zone 7a planting dates. You don’t want to accidentally seed cold-sensitive crops like zucchini too early during a chilly spring.
As another example, a mountain gardener in Whitefish, Montana, may live on the border of zone 5a (-20 to -15°F) and zone 4b (-25° to -20°F). I’d choose a planting date based on zone 4b. Recall that these temperatures are the extreme lows and they don’t tell us the frost dates.
Determining Your Last Frost Date
A frost date is the average day of the last spring frost or first fall frost. Based on historical weather data, frost dates tell us when to expect the spring weather to warm in our area and when we predict the fall weather will turn cold.
Spring frost data is usually based on the last light freeze, but it’s important to understand the different types of frosts that can occur:
- Light Freeze: 29 to 30°F (will kill or damage tender plants like zucchini)
- Moderate Freeze: 25 to 28°F (kills most vegetation except hardy crops)
- Hard Freeze: Below 24°F (heavy damage to most garden plants except hardy perennials)
The Old Farmer’s Almanac is the most widely trusted source for last frost dates. They use government-collected weather data from the NOAA National Center for Environmental Information.
To find your last frost date:
- Head to https://www.almanac.com/gardening/frostdates
- Type in your zip code or city and state in the search bar
- Reference the chart for your estimated frost dates
This is basically just another way to determine when you want to plant your frost-sensitive crops. You can use your hardiness zone and last frost date in combination to make the best-educated guess possible.
As a general rule of thumb, transplant tender warm-weather crops like zucchini 1-3 weeks after the last frost date. This means that seedlings would be started indoors about 3-4 weeks before the planting date. If you want to direct seed zucchini, double-check that soil temperatures are at least 70°F using a soil thermometer.
When in doubt, just wait another week. Unlike tomatoes or melons, you don’t have to rush to get zucchini in as early as possible. These plants grow so fast that putting off the planting date won’t set back your harvests by much.
In fact, my experiments have shown that zucchini transplanted one week apart often end up the same size. The later planting enjoys slightly warmer weather and catches up to the first planting very quickly.
Continuing with our example in Lubbock, Texas, the earliest I’d plant zucchini outdoors would be around April 16. This is exactly two weeks after the estimated last frost date (April 2), however, I’d also want to keep an eye on nighttime temperatures in my garden.
If I was starting seeds indoors, I’d aim to get them in their trays about 2-4 weeks before planting, which is somewhere between March 19 and April 2.
Quick Reference Chart
The two major ways to determine planting dates are the hardiness growing zone and the last frost date. Use the guide above to determine both before deciding your garden planting dates.
When the planting time comes around, a soil temperature probe is the most reliable means of gauging whether or not your soil has warmed enough. Remember that growing zones and last frost dates are only estimates and every year is different.
- Transplant zucchini 1-3 weeks after the last frost date.
- Direct seed zucchini 3-4 weeks after the last frost date.
- Check that the soil temperature is at least 70°F.
- The ambient (air) temperatures should be reliably above 40°F at night.
For true zucchini lovers or market gardeners, succession planting is an excellent way to ensure you have a continuous supply of this tender summer squash.
While zucchini plants are crazy vigorous, they do tend to peeter off with their production as they age. It’s often easier to stagger the plantings so you have baby and teenager plants maturing as the older ones run out of steam.
Professional growers typically plant a new zucchini succession every 2-3 weeks throughout the summer. You can alternate seedings as close or spread out as you’d like.
Succession planting is ideal for areas with long growing seasons (100+ frost-free days) and may not be logical for extra cold climates.
Bottom Line: Don’t Plant Zucchini Until Outdoor Temps are Above 40°F at Night and Soil Temperature is at least 70°F
Ultimately, growing zucchini is equal parts art and science. A little bit of experimentation and educating guessing will help you determine the best time to plant your squash garden. These plants are very forgiving as long as they get the warmth that they crave.
So wait to plant until the temperatures are reliably above 40°F at night and soil temps are at least 70°F. However, if you have protection (a greenhouse, low tunnel, or thick row cover), zucchini can be planted even earlier.
Once you determine your ideal zucchini planting date, document it in your garden records for future years. Then, count backward 2-3 weeks to determine when to start zucchini seeds indoors. This will ensure that your zucchini seedlings are ready to go at the right time. And don’t forget to harden off the seedlings a week before planting!