When you think of a zucchini, you probably think of a long, dark-green, soft-skinned squash, but this is only one of many varieties of summer squash. All summer squash share the same basic growth requirements. And they all grow fast! So what are the 9 zucchini growth stages, and how long does it take them to reach maturity?
What is Zucchini?
Zucchini are typically oblong and dark green, or they can be patterned in green and white. But there are also small round zucchini in shades of green and yellow. Yet other zucchini are oblong and bicolored: half yellow and half green!
Yellow squash is oblong and yellow with narrower, slightly curved necks. Patty Pan squash is flattened and rounded with lumpy edges and can be found in yellow, green, and white shades.
Zucchini is one of the easiest vegetables to grow.
9 Growth Stages of Zucchini Plants
| Stage | Key Notes | Photo |
| Selecting Seeds | Flattened, firm, shiny, off-white Use fresh seeds no more than 4 years old Choose from many varieties | |
| Sowing Seeds | Sow seeds outdoors (recommended) Also possible to sow indoors in peat pots Sow in loose, moist soil Cover with 1 inch of fresh soil Keep seeds warm and moist | |
| Germination | Roots sprout Keep warm and moist Seeds take 10-14 days to germinate | |
| Cotyledons | The first leaves (cotyledons) emerge from the soil New plant requires bright light Cotyledons appear after germination and last for just 5-7 days | |
| True Leaves | The first true leaves emerge Cotyledons will fall off Plant will start growing rapidly True leaves emerge 3-5 days after cotyledons Time for thinning Time to transplant indoor seedlings | |
| Vegetative growth | Harvest 6 to 10-inch-long fruits Begin harvesting 50 to 60 days after planting Use a sharp knife or pruners to cut fruits from plant Store fruits in refrigerator for up to 1 to 2 weeks Find creative ways to consume your harvest! | |
| Flowering | Flowers emerge Separate male and female flowers Flowers require cross-pollination Flowers very attractive to pollinator insects Flowers are edible Good time to fertilize plants Flowers begin to appear 45 to 55 days after planting Healthy plants continue flowering all summer | |
| Fruiting | Fruits form with female flowers Fruits grow very quickly Fruits are ready within 3 to 8 days after flowering | |
| Harvest | Harvest 6 to 10-inch-long fruits Begin harvesting 50 to 60 days after planting Use a sharp knife or pruners to cut fruits from the plant Store fruits in the refrigerator for up to 1 to 2 weeks Find creative ways to consume your harvest! |
A zucchini seed takes 50 to 60 days to sprout, grow, develop, and produce its first fruit. In ideal growing conditions, your plants will reach maturity within this timeframe. If conditions aren’t ideal, such as cooler weather causing slow plant growth, it may take your plants a little longer to reach fruiting maturity.
Let’s dig a little deeper into the details of each growth stage of a zucchini plant and see what you can expect during each stage.
Selecting Seeds
When choosing seeds, consider your space limitations and preferences.
If you’ve ever stood in front of a seed display trying to choose one seed packet from a vast array of beautiful options, feeling paralyzed with indecision, you are certainly not alone! You may think that all zucchinis are the same, but there is a huge diversity of cultivars. You may know the exact variety you are looking for or want to browse before selecting something for your garden.
Selecting seeds can be very enjoyable or stressful, depending on how you look at it. First, be realistic. Zucchini can grow to be very large plants. If you have room for only one or two plants, buy just one pack of seeds, perhaps of a more compact variety. If you have a lot of space to dedicate to zucchini, you could try a couple of different varieties.
Buy your seeds from a reputable seed source and plant them within 4 years. Using seeds within two years will yield the best results. Seeds will lose viability as they age, and the germination rate will decline. Store your seeds in a cool, dry location. When you examine them, they should appear fresh and firm. If your seeds become damp, mushy, or moldy, throw them out and buy fresh ones.
Sowing Seeds
Once you’ve selected the seeds you want, you can start thinking about planting them. Zucchini can be started indoors or outdoors. It is generally recommended to start them outdoors, directly sown where you want them to grow.
You can get a slight head start by planting seeds indoors, but zucchini don’t always transplant well, and they will readily germinate outdoors, so this is still the preferred option.
Pro Tip: Cut your seeds before you start planting.
Starting Inside
Start your zucchini seeds indoors in late spring, ensuring a 3 to 4-week gap before transplanting.
If you prefer to start your zucchini seeds inside, start them in mid-to-late spring. Allow anywhere from 3 to 4 weeks between sowing and your planned transplant date. So if you want to plant them outside in mid-July, start them inside towards the end of June. Plan to wait until the temperatures outside have warmed and the soil temperature is at least 60 degrees before transplanting.
The minimum supplies you need will be:
- Seed packet,
- Peat pots
- Quality seed-starter soil mix
Zucchini doesn’t like any root disturbance, and using peat pots will greatly help minimize soil and root disturbance during transplanting. You’ll want to carefully remove or open up the bottom of the peat pot when planting just to ensure the roots can freely access the rest of the soil!
Fill your peat pots with loose, well-drained seed-starting soil. Sow seeds 1 inch deep and cover them loosely with soil. Plant 2 to 3 seeds per pot and keep them in a warm, well-lit location. Give the soil a thorough watering to get them started, and then keep the soil moist until the seeds sprout.
Sowing Outside
Choose a sunny, well-drained location, sow seeds 1 inch deep, and space them appropriately.
Starting zucchini seeds outdoors is the preferred method. Wait until after any chance of spring frost has passed before you plant your seeds outside. But don’t be in too much of a hurry to get your seeds in the ground in early spring. Some pests, like squash vine borers, can be more of a problem early in the season. If you wait until mid-summer to plant, you will still have time to grow a hefty crop with less risk of these pesky insects.
Prepare your garden plot. Plant in a location with full sun and high-quality, well-drained soil. Sow your seeds 1 inch deep directly into the garden soil. Cover them loosely with fresh soil. Sow one seed every 3 to 4 inches if you want a row of zucchini. You can also sow them in low mounds of soil with 3 to 4 seeds per mound (or hill) spaced 3 feet apart.
If you sow your seeds outdoors earlier in the spring, cover them with a small portable greenhouse or floating row cover to help preserve some warmth. Zucchini is very sensitive to cold, and you don’t want to kill your seeds as they’re trying to sprout or seedlings as they’re trying to grow. Keep them moist if you sow them later in the season when it’s already hot outside. You will probably need to water them every day.
Germination
Seeds need air, moisture, and the right temperature to germinate.
Germination is the stage all seeds go through to start growing a new plant. To germinate, a seed needs three basic elements:
- Air
- Moisture
- The right temperature.
Some seeds need extremely specific conditions to sprout, but zucchini is less picky, so as long as your seeds are fresh and have air, moisture, and warmth, they should germinate just fine.
During germination, the seed swells a bit with moisture, the tough outer coating of the seed breaks open, and a tiny root begins to grow. The baby root (radicle) will naturally grow down into the soil, so you won’t see this stage of germination. After the root anchors the seed into the soil, a tiny green shoot emerges and grows.
After planting your zucchini seeds, be patient. It can take between 10 and 14 days to see the first green shoots emerging from the soil. Within a few days of seeing the first green shoots, the first leaves, called cotyledons, unfurl.
Cotyledons
Squash cotyledons are broad and oval, lasting only until true leaves develop before turning yellow and falling off.
The cotyledon phase is something every garden plant experiences. This is the phase after the seed sprouts but before the first set of true leaves appears.
Cotyledons are the first set of leaves that usually look different from the true leaves. So, if you expect large leaves with toothed edges, and instead, the first leaves you see are smooth and round, don’t panic!
Zucchini cotyledons typically appear once the stem emerges from the soil, just a few days after the seed germinates. They look like a pair of broad, oval leaves. The cotyledons will stay around just long enough for the first true leaves to grow, then turn yellow, wither, and fall off. Don’t panic; this is what’s supposed to happen.
True Leaves
Within a few days, the first true leaf of your zucchini plant will emerge between the cotyledons.
It may take only a couple of days from when the cotyledons emerge to when you see the plant’s true leaves. The first true leaf will appear as a single, slightly wavy-edged leaf. It will emerge from the stem, usually between the pair of cotyledons. This will be a single true leaf, quickly followed by other new leaves. Once your plant has developed a couple of true leaves, it’s time to do some thinning.
Thinning Seedlings
Thinning is crucial for strong and healthy zucchini plants, ensuring enough space for growth.
Thinning is an important step you need to take to help ensure that your zucchini plants are strong and healthy. Since only some seeds will sprout, you probably planted many more seeds than you intend to grow to maturity. If multiple seeds sprout, you must thin them to allow more space for large, vigorous plants to grow.
How should you select which seedlings to thin and which to keep? Look carefully at your new seedlings. Thin the weaklings, leaving only the strongest and healthiest-looking seedlings. Rather than pulling out the unwanted seedlings by the roots, use a sharp, clean knife or scissors to trim off the seedlings you are removing. This will allow you to remove extra plants without disturbing the soil and negatively affecting the remaining seedlings.
If you started seeds outside: After the seeds sprout and develop their true leaves, thin them to 1 seedling every 1 foot (for compact varieties) to 3 feet (for larger vining varieties). Choose the healthiest-looking seedlings to keep. You don’t want them to be too crowded together because they will compete for sun, water, and soil nutrients. You also want to allow plenty of airflow between plants to give you full access and minimize the risk of pests and diseases.
If you started seeds inside: After they sprout and develop their first true leaves, thin them to 1 seedling per pot. When seedlings have grown to have a couple of true leaves each, you must begin a process known as “hardening off.” Hardening off helps a seedling adapt from steadily controlled indoor temperatures to harsher outdoor conditions.
A few days before you intend to plant your seedlings outside, take your young plants outdoors for a few hours each day, gradually increasing the time they spend outside.
Give them a little extra protection from direct sunlight for the first few days so they don’t burn, and make sure to keep them watered because those small peat pots will dry out quickly. Bring your plants back inside during any temperature extremes. Once your young plants are acclimated to a full day and night outside, it’s time to transplant!
You can transplant them outside when the soil is warm and after any chance of frost. In a sunny garden location with high-quality well-drained soil, dig a small hole the size of your peat pot and gently place the entire pot in the hole.
Fill in around the edges up to the edge of the pot. Don’t bury your seedling or its stem in the soil; allow it to stay at the same soil level as in the pot. Leave at least 1 to 3 feet between seedlings so they have enough room to grow.
Vegetative Growth
During the rapid growth phase, zucchini plants need constant moisture, sunlight, and warmth.
This is the phase where your plant is growing very fast. It requires steady soil moisture, bright sunlight, and consistent warmth during this time. Your plant will be performing a lot of photosynthesis and converting sunlight into energy. It will also be absorbing nutrients from the soil.
The plants can grow 2 to 3 feet tall and 2 to 3 feet wide. Some longer vining varieties of zucchini can grow to 6 feet or more. These fast-growing crops can grow a couple of inches each day!
Plants tend to sprawl along on the ground but can also be carefully tied to a pole or trellis and trained to grow upwards. This style of vertical gardening requires a bit of extra work but can be useful if you are trying to conserve space in your garden.
Pests and Diseases
Zucchini plants are susceptible to powdery mildew disease that appears as a white powdery coating on the leaves.
While your zucchini plant is actively growing, it is susceptible to several pests and diseases. Some of the most common zucchini problems are:
| Powdery Mildew | Causes grayish-white mildew to form on leaves Leaves wither and die Maintain good air circulation around plants Choose cultivars that are resistant to powdery mildew |
| Leaf Spot and Anthracnose | Causes brown spots and holes in leaves Choose cultivars that are disease resistant Destroy (don’t compost) infected plants Try to keep leaves dry when watering |
| Squash Bugs | Clusters of sap-sucking insects on leaves and stems Keep garden area clear of dead and diseased plant debris (leaves, stems, flowers) Destroy eggs found on undersides of leaves Spray with insecticidal soap |
| Squash Vine Borer | Caterpillars that burrow into stems and vines and quickly kill entire plants Plant zucchini in mid-summer to avoid early-season pests Fill a yellow container with soapy water to attract and kill adults (they are attracted to yellow) Cover plants with lightweight row cover fabric to prevent egg laying |
Flowering
Squash plants produce separate male and female flowers that are attractive to pollinators.
Zucchini plants are “monoecious,” which means that these plants produce separate male and female flowers. The first several flowers that bloom are male flowers. It may be 1 to 2 weeks after the first male flowers appear until your plant produces its first female flowers. The flowers are very attractive to a large number of pollinators, which is not only great for your squash production but also your other garden plants.
Both male and female flowers will be large, showy, and yellow-orange. The male flowers will appear at the end of a thin stem, and at the center of the flower, you will see large pollen-covered anthers.
The female flowers will have a mini-zucchini at their base and a prominent stigma emerging from the flower. Pollinators will visit both male and female flowers, transferring pollen from the male anthers to the female stigma. If the flowers are successfully cross-pollinated, you will get a fruit!
Each flower lasts for a couple of days. After a couple of days of blooming, the male flowers wither and fall off the vine. Female flowers also wither and fall off, but if successfully pollinated, they will form a small fruit before fading.
When your plants start to flower, this is a good time to give your plant some extra compost or fertilizer. It requires a lot of energy for a plant to produce fruits. Adding some fertilizer during the flowering stage will give it an extra energy boost to help it produce healthy fruits. Use organic compost or a general vegetable garden fertilizer.
Fruiting
Check daily during fruiting for optimal size and abundance.
Once your plant starts fruiting, you can expect to harvest fresh zucchini regularly! The female flowers are the ones that have tiny fruits at the base. So by the time your plant has its first female flowers, it is already starting to produce fruit. And once the plant starts to produce, the fruit grows very quickly!
When the flowers wither, you will have tiny zucchini fruits, and you can even pick them when they are small like this. You can also wait a few more days but don’t wait too long. Zucchini is the most tender when picked young, within a week after flowering. If you want really big fruits, you can wait longer, but the longer you wait, the tougher the fruits will be. Larger fruits will also contain bigger seeds which are not as appetizing.
Fruits can grow approximately an inch or more per day. You should check your summer squash plants daily during the fruiting phase. If you visit your garden only once per week, you will find yourself with some super-jumbo-sized zucchini. It can be pretty amazing to watch how quickly your plant can produce an abundance of fruits.
Harvest
Pick zucchini when they’re 6 to 8 inches long for optimal tenderness.
You can expect to harvest your first zucchini fruits approximately 50 to 60 days after you plant the seeds. There will, of course, be some variability in first harvests. Plants grown in warmer climates will grow, develop, and ripen sooner than plants grown in cooler climates. Similarly, healthy plants grown in ideal conditions will produce fruits sooner than those in less-than-ideal conditions.
For a standard long green zucchini, I like to pick them when they are 6 to 8 inches long. At this point, they are still small and tender, and easy to work with. Any fruit left on the plant will continue growing and will get noticeably bigger each day. Even if you find yourself with an overgrown foot-long fruit, you should still harvest it so the plant continues to use its energy to produce new fruits.
Squash vines, stems, and leaves have sharp, stiff hairs that can irritate the skin. I recommend wearing gloves when handling the plants. Use a sharp knife to cut the stem just above the fruit. If you look at a ripe zucchini and don’t have a knife handy, you can also firmly grasp the fruit and slowly twist it at the stem until it breaks away from the plant. Be sure to check under those large leaves; a fruit might be hiding underneath!
Zucchini is a soft-skinned summer squash. Winter squash has hard skin and can be stored for several months. Summer squash spoils quickly and doesn’t last long once harvested. You can expect a freshly picked zucchini to last from one to two weeks — store fruits in a paper or plastic bag in the crisper drawer in your refrigerator. After one week, the skin will likely start to shrivel, but you can still eat it.
With such abundant yields, you might wonder what to do with all that produce. If you like baked goods, try fresh zucchini bread or muffins. For savory meals, chop your squash and add it to a sautee, stir-fry, or baked veggie medley. Grill them in large chunks or on a kebab. If you have eaten your fill of zucchini, give them away to your neighbors or bring your surplus to give away at the office.
Final Thoughts
Zucchini is an easy-to-grow summer squash. This plant matures rapidly, grows large, and can be extremely productive. Zucchini plants grow readily from seed in any warm climate, and you can watch them develop from the first sprout to the final harvest. Give them a warm sunny spot in the garden with consistent moisture, and you’ll be harvesting an abundance of your own tender and tasty squash throughout the summer!
