Zucchini Plant Growth Stages | Life Cycle

Zucchini is just one type of summer squash (Cucurbita pepo), although I’m willing to bet it’s the most popular. This heat-loving vegetable is a must-grow largely because it requires minimal care and a single plant can produce an impressive harvest.

All summer squash share the same life cycle and I think knowing the details of the zucchini plant growth stages is the first step in optimizing your annual squash harvest. Keep reading to learn more!

Conditions for Growing Zucchini

As the name implies, all types of summer squash – such as zucchini – grow best in warm weather. You’ll see the best harvest from your zucchini plants when the average temperature is between 65 and 75°F. 

Plant zucchini somewhere that receives at least 6 to 8 hours of full sun per day. Strong winds can interfere with pollination later in the season, so take this into account when planning your vegetable garden in the spring.

Zucchini thrive on moisture, especially during active fruit development. Irrigate with at least an inch of water per week and be sure to water deeply to reach the entire root system. Inconsistent watering can result in misshapen fruit.

The ideal soil pH for zucchini is typically between 6.0 and 6.5. Unless a soil test indicates otherwise, amend beds prior to planting with aged compost and throughout the growing season with a balanced fertilizer, something like a 4-4-4 NPK formula will work well.

Most zucchini plants have vining growth habits, however, compact bush varieties are becoming more and more popular. When growing the former, you’ll need to provide plenty of empty space to sprawl out or give them a supportive trellis to climb upwards.

Growth Stages Of Zucchini

Zucchini is an incredibly fast-growing vegetable, often needing only 50 to 60 days to produce ripe fruit when grown from seed. This trait can be taken advantage of by succession planting zucchini throughout the growing season. Just be sure you have a use for all of the fruit you’ll be harvesting!

Summer squash is annual, meaning that individual plants sprout and die off all in a single year. The growing season typically starts when the soil reaches 60°F in the spring. Most zucchini plants start to die back when temperatures drop to 45°F in the fall.

Fortunately, zucchini will continue producing fruit as long as the weather permits. You should expect the average zucchini plant to produce fruit for about 90 days during the summer. This can vary depending on your climate’s season length, the cultivar you’re growing, and overall plant health.

1. Seed Germination 

Zucchini seeds are quite easy to germinate. With adequate warmth, zucchini seeds germinate within 7 to 10 days.

According to Oregon State University, the minimum temperature for germination is 60°F. However, temperatures between 70 and 95°F are ideal.

As long as the soil temperature is above 60°F and all threat of frost has passed, seeds can be direct-sown in the garden. Only cool-climate gardeners like myself need to start zucchini seeds indoors to make the most of the growing season.

2. Seedlings

Sprouted zucchini seeds start out with two special leaves called cotyledons. These ‘baby’ leaves are present throughout germination, even existing inside the seed itself, and support the first days of growth. 

Contrary to popular belief, cotyledons are capable of photosynthesis. However, the seedling’s adult foliage will take over this job after about 7 to 14 days.

Keep an eye on vining varieties as they grow. Particularly vigorous growers may require trellis or stake supports before leaving the seedling stage. In form, they are almost identical to cucumber, winter squash, and pumpkin and grow with equal vigor.

Seedlings with Cotyledons and Adult Leaves Emerging) Zucchini Plant Growth Stages
Zucchini seedlings, look almost identical to pumpkin and squash

3. Vegetative Growth

Healthy vegetative growth is necessary to support fruit development later on, as these hungry plants need their huge leaves to fuel fruit production. The bulk of the vegetative growth occurs in the first 45 days of the plant’s life. 

During this stage, the zucchini plant requires adequate nutrition to support its rapid growth. While you might be tempted to lay the fertilizer down thick, too much nitrogen will trigger excess vegetative growth while sapping resources from flower and fruit production.

While bush-type zucchinis usually only grow about 2 feet tall and wide, vining varieties can spread to over 6 feet wide. Training the latter type up some sort of support isn’t always necessary but can help keep future fruit from sitting on the soil and potentially rotting or being eaten by pests.

4. Flowering

Most zucchini plants begin flowering 45 to 55 days after germination. The flowers are bright yellow and emerge from the center of the plant. They are easily hidden by the large leaves and sometimes go unnoticed.

Like all summer squash, these plants produce separate male and female flowers, and only the female flowers are capable of developing fruit. The male flowers are the first to appear, so don’t be alarmed if your zucchini fails to set fruit early on. 

5. Pollination

Zucchini is a type of fruit, so pollination is required to achieve any sort of harvest. Zucchini plants are self-fertile, meaning that a female flower can be pollinated by pollen from the same plant. But pollinators are still needed to transfer the pollen from a male flower to a female one.

Technically speaking, you only need one zucchini plant for pollination. However, be warned that the male and female flowers of a single plant often emerge at different times. 

Efficient pollination can make or break a zucchini crop. I recommend planting multiple plants and manual cross-pollinating if necessary to ensure future fruit development.

Developing Zucchini Fruit
Fruit developing from the stem behind the flower

6. Fruit Development and Ripening

Don’t blink, or you might miss your zucchini’s fruit development stage! It only takes 4 to 8 days on average for a pollinated flower to produce a ripe zucchini.

Zucchini fruit develops below the pollinated flower. At first, the fruit just looks like a swollen segment of the stem. Since the fruit can grow up to an inch per day, however, it doesn’t take long to look like a bona fide zucchini.

Zucchini Growth Timeline – Video Timelapse

This plant is grown under artificial grow light on 24hrs of daylight which reduces the growth time significantly.

Growing Zucchini Time Lapse - Seed To Fruit in 78 Days

When To Harvest Zucchini

Most zucchini plants start producing ripe fruit 50 to 60 days after seed germination. The harvest continues as long as the plant remains healthy and the weather is warm, usually lasting at least 90 days.

A good rule of thumb is to start harvesting zucchini when they are about 6 inches long. The fruit may grow larger throughout the season. 

Ripe zucchini fruit is typically dark green with shiny, semi-firm skin. Mature fruit size and color can differ between varieties, so I always recommend following any cultivar-specific advice for the best results.

Ripe zucchini ready to harvest
Ripe zucchini ready to harvest

As the growing season draws to a close, be sure to harvest any fruit before potential frost. Zucchini is very sensitive to cold temperatures and exposure to freezing conditions will damage fruit still on the plant.

FAQ Zucchini Plant Growth Stages

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.