Pumpkin Plant Growth Stages | Life Cycle

Did you know that there’s no true botanical definition of a pumpkin? A ‘pumpkin’ is simply any type of round winter squash traditionally used to make pies or as decor. 

Accepted pumpkin varieties tend to be tougher and more flavorful than other squashes but, otherwise, it’s more or less a case of you’ll know a pumpkin when you see one!

As a subcategory of winter squash, there are obviously a lot of similarities in how these gourds grow in the garden. So, for the purposes of this article, I’ll be getting stuck into the specifics of pumpkin plant growth stages.

Conditions for Growing Pumpkin

Pumpkins require at least 8 hours of bright, direct sunlight per day to grow to their full potential and grow on large, sprawling vines that tolerate cool temperatures much better than they do the heat. 

The best climates for growing pumpkin plants are USDA zones 3 to 7. Of course, gardeners can still cultivate pumpkins outside of these zones but will need to take extra steps to protect their plants from extreme weather conditions.

One of the biggest considerations when planting pumpkins is the amount of space each plant needs at maturity. According to the University of Illinois, the average vining pumpkin plant requires at least 50 to 100 square feet. Planting even a couple of pumpkins can eat up valuable garden space very quickly.

Pumpkin plants are often grown in hills. This practice raises the average soil temperature and improves drainage around the root system. 

According to the University of Massachusetts, pumpkins prefer pH levels of 6.0 to 6.8. Sandy soil containing lots of organic material is ideal for drainage and soil temperature.

The vast majority of pumpkin cultivars grow by spreading along the soil’s surface. Smaller varieties, however, may be trained up supports to save space and protect the fruit from damage.

Amend the soil using aged compost, manure, or a 10-10-10 fertilizer before planting and again when the vines start to bear fruit. Keep in mind that pumpkin plant roots are quite extensive. 

Pumpkins need about 1 inch of water per week on average. When irrigating pumpkins, take steps to keep the leaves and fruit dry.

Growth Stages Of Pumpkin Plant

As annual plants, pumpkins complete an entire life cycle within a single year. They do have a long growing season, however, with most varieties requiring 75 to 100 days to produce ripe fruit. 

The length of a pumpkin’s growing season is largely determined by fruit size. It’s not uncommon for particularly large cultivars to take 120+ days to reach maturity. Popular examples of giant pumpkins include ‘Big Max’, ‘Atlantic Giant’, and ‘Big Moon’.

Start pumpkins in late spring or summer, depending on your local climate, for a mid-fall harvest. The fruit should be harvested before the year’s first frost, so it’s important to get seeds or seedlings in the ground at the right time. Keep in mind that all winter squash, including pumpkins, must fully ripen on the vine.

1. Seed Germination 

I’m willing to bet you already know what a pumpkin seed looks like, even if your only hands-on experience has been eating them! Pumpkin seeds are flat and oblong and can be anywhere from ½ inch to over 3 inches long depending on the variety.

Most pumpkins produce seeds with a white or cream outer husk. The seed itself is light green. There are also some pumpkin varieties with huskless seeds — these types are often grown specifically for their edible seeds.

The outer husk of a pumpkin seed acts as a protective coating that prevents germination until the growing environment is right. In addition to warm temperatures, moisture is also needed to penetrate and soften the husk.

2. Seedlings

Following germination, your pumpkin plant will turn into a small seedling with two simple leaves. These leaves are known as cotyledons and develop in the seed embryo before pushing through the soil’s surface and growing upward.

Pumpkin cotyledons are a vital source of energy throughout the germination and sprouting processes. They can also perform some photosynthesis while the plant waits for more leaves to develop.

Pumpkin plant seedling with its first true leaf

Pumpkin seeds require soil temperatures above 65°F to germinate. However, temperatures between 70 and 85°F are generally considered ideal. In these conditions, germination should occur after 7 to 10 days.

After the cotyledons, all new foliage will consist of ‘true’ or adult leaves. You should see the first adult leaf emerge from the top of the seedling about 7 days after sprouting. 

Over the next 7 or so days, several other adult leaves will grow from the seedling. It’s normal for the cotyledons to die off as the other leaves take over metabolic functions.

3. Vegetative Growth

A pumpkin’s primary vegetative growth period takes place over the next 50 to 60 days. During this stage, the plant’s main goal is to produce strong vines, new foliage, and a healthy root system to support future flowering and fruit sets.

Particularly vigorous vines can grow up to 6 inches in a single day. Some gardeners opt to trim the main vine when it reaches 10 to 15 feet long.

4. Flowering

Most pumpkin plants begin flowering 55 to 70 days after sprouting. Pumpkins produce bright yellow, trumpet-shaped flowers along the length of the vines. 

Like other squash varieties, pumpkin plants have separate male and female flowers. The first several flowers to emerge from a vine are almost always male. Female flowers then open up shortly thereafter.

pumpkin flowers
Male flower

While you need both a male and a female flower to produce fruit, only the female flowers are actually capable of turning into pumpkins. Male flowers supply the pollen.

You can differentiate between male and female pumpkin flowers by taking a close look at the point where the blossom connects to the stem. The stem of each female flower features a noticeable bulge. This bulge is the flower’s ovary or the part of the flower that will transform into a pumpkin after fertilization. 

5. Pollination

For effective pollination, the female pumpkin flower needs to come into contact with pollen from a male flower in order to set fruit. Pollen can be transferred from one flower to another via insects, the wind, or by hand.

The Missouri Botanical Garden has a simple yet effective visual guide on the hand-pollinating pumpkin and squash flowers.

Pumpkins are self-fertile, meaning that a male flower can pollinate a female flower on the same plant. In other words, you technically only need one pumpkin plant in the garden to produce fruit.

However, I still recommend growing multiple plants if you have the available space. The reasoning behind this is that male and female flowers may open at different times. Planting several pumpkins in one area increases the odds of successful pollination.

Female pumpkin flower
Pumpkin ovary developing into fruit behind the flower

Pumpkin blossoms open up for about 4 hours in the morning or afternoon before wilting and falling from the plant. Pollinated female flowers will immediately begin developing into fruit. New flowers continue growing until the year’s first frost.

6. Early Fruiting

Visible fruit development can occur as little as 7 days after flowering begins. Early fruiting presents as swelling at the base of the fertilized female flower (where the ovary is located).

Pumpkin plant early fruit development
Note the fruit tip where the flower petals have fallen

For large pumpkins, it’s common practice to pinch off female flowers that grow after the first fruit set. Culling all but a couple of pumpkins per plant will divert energy to producing the largest fruit possible.

7. Fruit Development and Ripening

The fruit will continue to grow in size for at least 45 to 55 days before ripening. 

When a pumpkin reaches its mature size, it will start to produce a compound called ethylene. Ethylene is an important part of the ripening process and its presence will trigger color changes and cause the stem connecting the pumpkin to the vine to harden and die off.

Ripe pumpkin on the vine

When To Harvest Pumpkin

Most pumpkin cultivars ripen at least 45 to 55 days after flower fertilization. Pumpkins should always be allowed to ripen on the vine. 

Achieving the mature size and color expected of the specific variety is the clearest sign that a pumpkin is ready for harvest. Other signs include:

  • A rind that produces a hollow sound when thumped
  • A rind that resists piercing with a fingernail
  • A stem that is hard and dry (e.g., woody)

You might also be interested in 13 Mini Pumpkin Varieties That Are Delicious and Fun

FAQ Pumpkin Plant Growth Stages

How Long Does It Take To Grow A Pumpkin?

The average pumpkin takes up to 100 days to be ready for harvest. Small, decorative varieties may reach maturity in as little as 75 days. If you want to grow a giant pumpkin, however, it could take 120 days or longer for the fruit to ripen. 

How Long Does A Pumpkin Vine Grow?

Traditional pumpkin varieties produce vines that can grow up to 20 to 30 feet long by the end of the year. This is why it’s important to allocate at least 50 to 100 square feet per pumpkin plant at the start of the growing season.

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.