How Fast Do Watermelons Grow

If you’re planting watermelons for the first time, you’re probably wondering just how fast do watermelons grow. The journey from seed to sweet fruit is surprisingly quick under the right conditions, but it requires some know-how. This guide will walk you through the timeline and the steps to get those vines sprouting and expanding rapidly in your garden.

Understanding the growth stages is key. Watermelons are warm-season crops that thrive on heat, sunlight, and consistent care. Their speed depends heavily on the variety you choose and your local climate. With a little attention, you can enjoy the satisfaction of watching them develop from tiny seeds to large, juicy fruits in a single season.

On average, a watermelon takes 70 to 90 days to reach full maturity from the day you plant the seed. This is known as its “days to maturity.” Some smaller, icebox types can be ready in as little as 70 days, while larger picnic varieties may need 90 days or slightly more. The initial sprouting phase is the quickest part; you’ll see seedlings emerge in just 3 to 10 days if the soil is warm enough.

The 4 Key Stages of Watermelon Growth

Let’s break down the timeline into clear stages. Each one has its own needs and visual cues.

1. Germination & Sprouting (Days 1-10)

This is where speed is most apparent. Watermelon seeds need warm soil to wake up. For the fastest germination, ensure your soil temperature is at least 70°F (21°C), with 80-90°F (27-32°C) being ideal.

Seeds will typically sprout and emerge from the soil in 3 to 10 days.
You’ll first see two small oval seed leaves (cotyledons).
Keep the soil consistently moist but not soggy during this critical phase.

2. Vine Growth & Flowering (Days 10-45)

After sprouting, the plant focuses on building its engine: the vines. True leaves will replace the seed leaves, and vines begin to run across the ground.

Vines can grow several inches in a single day during peak warmth.
Flowers start to appear around day 30-45. You’ll see both male and female flowers; only the female ones (which have a tiny bulge at the base) will develop into fruit.
This stage requires ample sunlight and nutrients to support the coming fruit.

3. Fruit Set and Development (Days 45-70)

Once pollinated, the female flower’s bulge begins to swell into a tiny fruit. This is when you’ll see the most dramatic visual expansion.

The young watermelon can grow to near full size in just 2-3 weeks under ideal conditions.
The fruit’s growth rate is incredible, sometimes noticeable from one day to the next.
The plant is using huge amounts of water now, so consistent watering is non-negotiable.

4. Ripening (The Final 2-3 Weeks)

The fruit stops expanding and begins the internal process of ripening. Sugars develop, and the rind color matures. Look for these signs of ripeness:

The curly tendril nearest the fruit turns brown and dries up.
The spot where the fruit touches the ground changes from white to a creamy yellow.
The rind loses its glossy shine and becomes dull, and it becomes tough to pierce with a fingernail.

How to Speed Up Watermelon Growth

You can’t rush nature, but you can definately create the perfect environment for maximum speed. Here are the most effective tactics.

Start Seeds Indoors (In Cool Climates)

If your growing season is short, get a 3-4 week head start by sowing seeds indoors.

Plant seeds in biodegradable pots 3-4 weeks before your last frost date.
Use a heat mat to keep soil at 80°F for best germination.
Provide strong light so seedlings don’t get leggy.
Transplant carefully outdoors after all frost danger has passed and soil is warm.

Warm the Soil

Since heat is the biggest accelerator, warming your garden soil early makes a massive difference.

Cover your planting area with black plastic mulch 1-2 weeks before planting. It absorbs sun and heats the soil beneath.
Consider using a floating row cover after planting to trap warmth around young plants.
Plant in raised beds, which naturally drain better and warm up faster in spring than flat ground.

Choose a Fast-Maturing Variety

Your seed selection sets the baseline timeline. Look for these quicker options:

‘Sugar Baby’ (75 days): A classic small, round icebox type.
‘Golden Midget’ (70 days): Turns yellow when ripe and has pink flesh.
‘Blacktail Mountain’ (70-75 days): Known for good cold tolerance and early production.
‘Mickylee’ (70-75 days): A popular hybrid with sweet, crisp flesh.

Perfect Your Planting Technique

Give seeds the best possible start right from day one.

Wait until soil is reliably above 70°F. Planting in cold soil will delay or prevent germination.
Plant seeds 1 inch deep in small hills or mounds for improve drainage.
Space hills 3-6 feet apart, as vines need ample room to run.
Water the soil thoroughly after planting.

Essential Care for Rapid Expansion

Once your plants are growing, consistent care keeps the momentum going. Neglect can slow things down significantly.

Watering: Deep and Consistent

Watermelons are about 92% water, so they need plenty to fill out.

Provide 1-2 inches of water per week, focusing on deep watering that encourages deep roots.
Use drip irrigation or soaker hoses to keep foliage dry and prevent disease.
Water consistently, especially during fruit set and development. Inconsistent watering can lead to bland fruit or cracking.
Reduce watering slightly during the final ripening week for sweeter melons.

Feeding: The Right Nutrients at the Right Time

These heavy feeders need a balanced diet but too much nitrogen can give you all vines and no fruit.

Mix compost or well-rotted manure into the soil before planting.
At planting, use a balanced, all-purpose organic fertilizer.
When vines begin to run, switch to a fertilizer lower in nitrogen and higher in phosphorus and potassium to promote flowering and fruiting.
A side dressing of compost halfway through the season can give plants a helpful boost.

Sunlight and Space

Never underestimate there need for sun and space.

Plant in the sunniest spot possible. Watermelons require a minimum of 6-8 hours of full, direct sun daily.
Respect their sprawling nature. Crowded plants compete for light and nutrients, slowing growth and increasing disease risk.

Common Problems That Slow Growth

Even with good care, issues can arise. Here’s how to troubleshoot a slow-growing patch.

Cool Weather: Growth stalls below 60°F. Use row covers for protection during unexpected cold snaps.
Poor Pollination: If fruits aren’t setting, you might have a lack of pollinators. Hand-pollinate by transferring pollen from male to female flowers with a small brush.
Pests: Cucumber beetles and squash vine borers can weaken plants. Use row covers early in the season and monitor regularly.
Disease: Fungal diseases like powdery mildew can hamper growth. Ensure good air circulation, avoid wetting leaves, and choose resistant varieties.
Weed Competition: Weeds steal water and nutrients. Mulch heavily around plants to suppress weeds and retain soil moisture.

FAQ: Your Watermelon Growth Questions Answered

What is the fastest growing watermelon?

Varieties like ‘Golden Midget’ and ‘Sugar Baby’ are among the fastest, often maturing in 70-75 days from seed.

Can you speed up watermelon growth?

Yes, by using black plastic mulch to warm soil, starting seeds indoors, choosing early varieties, and providing perfect watering and feeding.

How long does it take for a watermelon to grow after flowering?

After successful pollination, it typically takes about 30-35 days for the fruit to reach full size and then an additional period to ripen fully.

Why are my watermelons growing so slow?

The most common causes are cool temperatures, inconsistent watering, poor soil nutrition, or insufficient sunlight. Check these factors first.

How many watermelons do you get per plant?

Typically, a healthy vine will produce 2-4 fruits, depending on the variety and growing conditions. For larger varieties, gardeners often limit it to 2-3 fruits per plant for best size and quality.

Growing watermelons quickly is a rewarding summer project. By focusing on warmth, consistent moisture, and rich soil, you can optimize there growth from a quick sprout to a rapidly expanding fruit. Remember, patience in the beginning—waiting for warm soil—pays off with remarkable speed later in the season. Keep a close eye on your vines, and you’ll be rewarded with the perfect homegrown treat.