When To Plant Flowers In Washington State

Knowing when to plant flowers in Washington State is the key to a vibrant and successful garden. Our unique climate, split by the Cascade Mountains, means timing is everything for your blooms.

This simple guide breaks down the best planting times for annuals, perennials, and bulbs across Washington’s main regions. We’ll cover both spring and fall planting so you can plan your garden calendar with confidence.

Understanding Washington’s Gardening Zones

Washington isn’t just one garden; it’s several. The Cascade Range creates two primary climates. West of the mountains, you have a mild, maritime climate with wet winters and dry summers. East of the mountains, the climate is continental, with hotter summers, colder winters, and less rainfall.

Your specific USDA Hardiness Zone is crucial. Coastal and western valley areas are generally in zones 8a to 9a. The interior east ranges from zones 6a to 7b, with higher elevations even colder. Always check your zone before buying plants to ensure they can survive your winter.

Spring Planting Guide for Washington

Spring is the most common planting time. The goal is to wait until the soil is workable and the danger of a hard frost has passed.

For Western Washington (West of the Cascades)

Your last frost date typically falls between mid-March and mid-April. Here’s a general timeline:

Early to Mid-March: You can start sowing seeds for cool-season flowers directly in the ground. Think of sweet peas, calendula, and poppies. It’s also safe to plant hardy perennials and shrubs.
April: This is a prime planting month. The soil warms up. You can plant most nursery-grown perennials and sow seeds for cosmos and zinnias indoors for later transplant.
After Mother’s Day (Mid-May): This is the traditional safe date for tender annuals. Now you can plant marigolds, petunias, geraniums, and impatiens without worry of a late cold snap.

For Eastern Washington (East of the Cascades)

Your spring arrives later, and frosts can persist. The last frost date often ranges from late April to late May.

April: Focus on cool-season crops and hardy plants only. The soil may still be too cold and wet for much else.
May: Begin planting hardy perennials and shrubs in early May. Wait until after your last frost date (check local averages) for tender items.
Early June: This is generally the safest bet for planting all your summer annuals, like vinca and begonias, which love the heat that’s coming.

Fall Planting: A Secret for Stronger Flowers

Many gardeners forget about fall planting, but it’s fantastic for Washington. The soil is still warm from summer, autumn rains provide moisture, and plants can establish roots without the stress of summer heat.

This leads to earlier blooms and stronger plants the following spring. It’s an excellent time for planting perennials, trees, shrubs, and spring-blooming bulbs.

Best Fall Planting Times

Western WA: Aim for September through early October. This gives plants a solid month or more of root growth before winter dormancy. You can sometimes plant as late as November if the weather stays mild.
Eastern WA: Target early September. You need to finish before the first hard freeze, which can come much earlier than in the west. Getting plants in by mid-September is a wise goal.

Season-by-Season Flower Recommendations

Knowing what to plant when simplifies your trips to the nursery.

Early Spring Bloomers (Plant in Fall or Very Early Spring)

Daffodils (bulbs planted in fall)
Tulips (bulbs planted in fall)
Pansies & Violas (can often be planted in fall for early color)
Bleeding Heart (perennial)

Summer Stars (Plant After Last Frost)

Dahlias (tubers planted in spring after frost)
Lavender (perennial, plant in spring or early fall)
Black-Eyed Susans (perennial)
Sunflowers (seeds sown in late spring)
Zinnias (seeds or transplants after frost)

Fall Color (Plant in Spring or Early Summer)

Sedum ‘Autumn Joy’ (perennial)
Asters (perennial)
Chrysanthemums (often treated as annuals here, planted in spring)

Step-by-Step Planting Tips for Success

Getting the timing right is half the battle. Doing the planting correctly is the other half.

Test Your Soil: Washington soils vary from sandy coastal to heavy clay. A simple test can tell you if you need to add compost or adjust pH.
Amend the Soil: Mix in 2-4 inches of compost or well-rotted manure to your planting area. This improves drainage and provides nutrients, which is especially important in our heavy clay soils.
Water Deeply at Planting: After placing your plant in the ground, water it thoroughly to settle the soil and eliminate air pockets around the roots.
Mulch: Apply a 2-3 inch layer of mulch around your plants. This conserves moisture, suppresses weeds, and regulates soil temperature. It’s vital for helping plants through both summer droughts and winter chills.

Common Mistakes to Avoid

Even experienced gardeners can make these errors in our unique climate.

Planting Too Early: Enthusiasm can lead to planting tender flowers before the last frost. Patience saves money and plants.
Ignoring the “East vs. West” Rule: A planting schedule for Seattle will not work in Spokane. Always tailor advice to your side of the state.
Forgetting About Watering in the “Dry Side”: Eastern Washington gardeners must plan for irrigation. Summer rainfall is scarce, and new plantings need consistent water.
Overwatering in the “Wet Side”: Conversely, western WA gardeners can drown plants in heavy, wet clay soil. Ensure good drainage to prevent root rot.

FAQ: Your Washington Flower Planting Questions

What month is best to plant flowers in Washington?

For spring planting, April through May is ideal in western WA. In eastern WA, May through June is safer. For fall planting, September is the best month across much of the state.

Can I start planting flowers in March in Washington?

In western Washington, yes, but only the hardiest cool-season flowers and perennials. In eastern Washington, it’s usually too early unless you’re working in a protected greenhouse or cold frame.

When should I plant perennials in Washington State?

The optimal times are early spring (April-May) and early fall (September). Fall planting allows them to establish roots before winter and often results in better performance the next year.

Is it too late to plant flowers in July in Washington?

For most perennials and shrubs, July is too hot and dry, especially east of the Cascades. You can plant heat-loving annuals from containers, but they will need frequent watering to establish. It’s better to wait for early fall.

When do you plant fall bulbs in Washington?

Plant spring-blooming bulbs like tulips, daffodils, and crocus in the fall. The best time is from late September through November, once the soil has cooled down. This gives them the chilling period they need to bloom.

By following these regional guidelines and paying attention to your local frost dates, you can create a stunning flower garden that thrives in Washington’s beautiful and varied landscapes. Remember, successful gardening here is all about working with our seasons, not against them.