When To Plant Watermelon In Kansas

If you’re planning to grow watermelon in Kansas, timing is everything. Knowing exactly when to plant watermelon in Kansas is the first step to a succesful harvest of sweet, homegrown fruit.

Our state’s weather can be tricky, with late frosts and hot summers. This guide will walk you through the optimal planting windows, variety selection, and care tips tailored for Kansas gardens.

The optimal time to plant watermelon in Kansas depends heavily on your location within the state and the spring weather. The key is soil temperature, not just the date on the calendar.

Understanding Your Kansas Climate Zone

Kansas spans USDA Hardiness Zones 5b to 7a. This means the last spring frost date can vary by several weeks from north to south.

Northern Kansas (Zones 5b-6a): Average last frost around May 5-15. Target planting from mid-May to early June.
Central Kansas (Zone 6b): Average last frost around April 25 – May 5. Target planting from early to mid-May.
Southern Kansas (Zones 6b-7a): Average last frost around April 10-20. Target planting from late April to early May.

Always treat these dates as estimates. Watch the forcast, not just the calendar.

The Golden Rule: Soil Temperature

Watermelon seeds germinate poorly in cool soil. The magic number is 70°F. Planting before the soil reaches this temperature risks slow germination, seed rot, and weak plants.

Use a soil thermometer to check the temperature at a 4-inch depth in the morning.
If you’re impatient, using black plastic mulch can help warm the soil faster a few weeks before planting.

Direct Seeding vs. Transplants

You have two main options for getting your watermelons started.

Direct Seeding (Recommended)

This is often best for Kansas, as watermelons have sensitive roots that don’t always like being transplanted.

Wait until all danger of frost has passed and soil is at least 70°F.
Plant seeds 1 inch deep in small hills or rows.
Space seeds about 2 feet apart, with rows 5-6 feet apart.
Thin seedlings to the strongest 2-3 plants per hill once they have a few leaves.

Using Transplants

Transplants can give you a slight head start, especially in shorter-season areas of Northern Kansas.

Start seeds indoors in peat pots about 3-4 weeks before your expected outdoor planting date.
Harden off seedlings gradually for a week before transplanting.
Transplant very carefully to avoid disturbing roots, planting at the same depth they were in the pot.

Choosing the Right Watermelon Variety for Kansas

Selecting a variety suited to Kansas’s growing season length is crucial. Look for “days to maturity” on the seed packet.

Shorter Season (70-85 days): Ideal for Northern Kansas. Examples: ‘Sugar Baby’, ‘Blacktail Mountain’, ‘Yellow Doll’.
Mid-Season (85-95 days): Good for Central and Southern Kansas. Examples: ‘Crimson Sweet’, ‘Charleston Gray’.
Longer Season (95+ days): Best for Southern Kansas with a long, hot summer. Examples: ‘Jubilee’, ‘Allsweet’.

Step-by-Step Planting Guide

Follow these steps for the best chance of success.

Site Selection: Choose the sunniest spot in your garden. Watermelons need full sun (8+ hours daily) and well-drained soil.
Soil Preparation: Work in several inches of compost or aged manure. Watermelons prefer a slightly sandy loam, but any well-drained soil amended with organic matter will work. Aim for a soil pH of 6.0 to 6.8.
Planting: Create small mounds or hills about 3 feet apart. This aids drainage and soil warming. Plant 4-6 seeds per hill, 1 inch deep.
Initial Care: Water gently but thoroughly after planting. Keep the soil consistently moist until seeds germinate and seedlings are established.

Caring for Your Kansas Watermelon Patch

Consistent care through the summer is key to big, juicy fruit.

Watering

Water deeply (1-2 inches per week), especially during fruit set and growth. Use drip irrigation or soaker hoses to keep foliage dry and prevent disease. Reduce watering as fruit mature for sweeter flavor.

Fertilizing

Use a balanced fertilizer at planting. When vines begin to run, switch to a lower-nitrogen, higher-phosphorus fertilizer to encourage flowering and fruiting. To much nitrogen early on will give you all vines and no fruit.

Weeding and Mulching

Keep the area weed-free, especially early on. Apply a layer of straw or other organic mulch after the soil is warm to retain moisture, suppress weeds, and keep fruit clean.

Pest and Disease Watch

Common Kansas issues include cucumber beetles, squash vine borers, and powdery mildew. Row covers early in the season can protect young plants from pests. Rotate your crops each year to help prevent soil-borne diseases.

Harvesting Your Watermelons

Harvest time is the best reward. Look for these signs of ripeness:

The curly tendril nearest the fruit turns brown and dry.
The spot where the melon rests on the ground changes from white to a creamy yellow.
The rind loses its glossy shine and becomes dull.
You hear a deep, hollow sound when you thump it (this takes practice).

Use a sharp knife or pruners to cut the stem, leaving an inch attached to the fruit.

Frequently Asked Questions (FAQ)

What is the latest you can plant watermelon in Kansas?

In Southern Kansas, you can plant as late as early July for a fall harvest. In Central Kansas, aim for before mid-June. In Northern Kansas, planting after late June is risky due to early fall frosts.

Can I plant watermelon seeds straight from a store-bought melon?

You can, but it’s not recommended. Many commercial melons are hybrids, so seeds may not produce fruit true to the parent. It’s better to buy seeds from a reliable supplier for predictable results.

How long does it take for watermelons to grow in Kansas?

From planting to harvest, it typically takes 70 to 100 days, depending on the variety you choose and the summer weather conditions.

Why are my watermelon plants flowering but not producing fruit?

This is common early in the season. Watermelons produce male flowers first, followed later by female flowers (which have a tiny fruit at the base). Lack of pollination by bees is also a common cause. Avoid using pesticides that harm pollinators.

Growing watermelon in Kansas is a rewarding summer project. By paying close attention to the right planting time for your area, choosing a suitable variety, and providing consistent care, you’ll be well on your way to enjoying the taste of summer from your own garden. Remember, patience with the soil warmth in spring is your first and most important step.