When to plant melons in Sunnyside, Grandview and Prosser, WA

Plant melons in the garden in Sunnyside, Grandview and Prosser May 1–22, either as seeds or as young plants started indoors Apr 3–10.

Tricky here Plant seeds or young plants

Why these dates

Sunnyside, Grandview and Prosser's typical last spring frost is May 1. Frost kills melons, so planting starts once frost risk drops, around May 1. Keep row cover or a frost blanket handy for the first couple of weeks, since a late frost is still possible.

Columbia Basin and low eastern valleys. Hot, dry summers and quick spring warm-up. Warm crops go in earlier than west of the Cascades, and irrigation matters more than rain.

Difficulty: Tricky here
Sun: Full sun; the hottest spot you have
Spacing: 24 to 36 inches apart
Planting depth: 1 inch deep
Frost: Killed by frost
First harvest: About 85 days after planting

Step by step

Start seeds indoors Apr 3–10 in trays or small pots under a grow light or in your sunniest window. Or skip this step and buy young plants (starts) at a garden center.
Harden off the young plants: about a week before planting, set them outside for a few hours a day, a little longer each day.
Plant them in the garden May 1–22, 24 to 36 inches apart. If you plant seeds instead, sow them 1 inch deep.
Water deeply once or twice a week rather than a little every day, and mulch once the soil is warm.
Harvest: Cantaloupes are ripe when the stem slips off with a gentle push. Watermelons are ready when the curly tendril nearest the fruit turns brown and dry.

Varieties that do well here

Sugar Baby (watermelon)
Minnesota Midget (cantaloupe)
Halona (cantaloupe)

Watch out for

Cool soil and cool nights are the main obstacle west of the Cascades. Black plastic mulch and row cover until flowering make the difference.

The toughest heat lover for west-side gardens: choose short-season varieties and use black plastic and row cover. Eastern valleys grow them easily.

Common questions

When is the last frost in Sunnyside, Grandview and Prosser, WA?

Typically May 1. In 9 years out of 10, frost is over by May 18. These are 1991–2020 NOAA climate normals for Sunnyside.

Is it too late to plant melons in Sunnyside, Grandview and Prosser?

The spring planting window runs through May 22. Later plantings may not have time to produce before the first fall frost, which usually arrives around October 6.

When should I start melons from seed indoors in Sunnyside, Grandview and Prosser?

April 3 to April 10, which is 4 to 3 weeks before the May 1 planting date. Or buy young plants at a garden center instead.

Also plant in Sunnyside, Grandview and Prosser around the same time

Planting dates for melons in nearby areas

Yakima, WA May 8–29
Tri-Cities (Pasco, Kennewick, Richland), WA May 1–22
Walla Walla, WA May 1–22
Moses Lake, WA May 1–22
Ellensburg, WA May 20 – Jun 10
Ephrata and Quincy, WA May 1–22

Full planting calendar for Sunnyside, Grandview and Prosser · Melons in every city