Best Time To Plant Begonia In Washington

Washington’s cool, moist climate makes late spring the optimal window for setting out begonias. Finding the Best Time To Plant Begonia In Washington depends on your specific region, but the general rule is to wait until after the last frost date. This guide will walk you through everything you need to know for success.

In Washington state, the weather can be tricky. You might think you can plant early, but begonias are tender perennials. They cannot handle frost at all. The best time to plant begonia in washington is typically from mid-May to early June.

This timing works for most of the state. It includes the Puget Sound lowlands, the Columbia River Gorge, and even parts of Eastern Washington. The key is to check your local frost dates. A simple online search for your zip code will help.

Understanding Washington’s Climate Zones

Washington has diverse climates. The west side is mild and wet. The east side is drier and hotter. Your planting window shifts based on where you live.

Western Washington (Seattle, Tacoma, Olympia): Plant after May 15. Soil is usually warm enough by then.
Eastern Washington (Spokane, Yakima, Tri-Cities): Plant after May 1. The risk of frost ends earlier here.
Coastal Areas (Port Angeles, Aberdeen): Plant in late May or early June. Cool ocean air can delay warming.
Mountain Foothills (Leavenworth, Winthrop): Wait until June. Higher elevations have later frost dates.

Why Timing Matters So Much

Begonias are not cold-hardy. If you plant them too early, a late frost can kill them. If you plant them too late, they might not bloom before fall. The sweet spot is when soil temperatures reach about 60°F (15°C).

You can check soil temperature with a simple thermometer. Stick it two inches into the ground. If it reads below 55°F, wait a bit longer. Begonias will sulk in cold soil.

Types Of Begonias And Their Planting Windows

Not all begonias are the same. Different types have slightly different needs. Here is a breakdown.

Tuberous Begonias

These are the showy ones with big flowers. They grow from tubers, not seeds. You can start them indoors in March or April. Then transplant them outside after frost danger passes.

Start tubers indoors: March to April
Plant outdoors: Mid-May to early June
Bloom time: July to October

Wax Begonias

These are smaller, more compact plants. They are often used in bedding displays. They are slightly more tolerant of cool weather. But still wait until after the last frost.

Start seeds indoors: February to March
Plant outdoors: Mid-May
Bloom time: June to October

Rex Begonias

These are grown for their colorful leaves. They are very sensitive to cold. They prefer indoor or shaded outdoor spots. Plant them outside only when night temperatures stay above 55°F.

Plant outdoors: Late May to June
Bloom time: Summer (flowers are small)
Best for: Containers and hanging baskets

Dragon Wing Begonias

These are vigorous growers with angel-wing shaped leaves. They are heat-tolerant but not frost-tolerant. They do well in Washington’s summer warmth.

Plant outdoors: Mid-May
Bloom time: June to frost
Best for: Large containers or garden beds

Step-By-Step Guide To Planting Begonias In Washington

Follow these steps for the best results. They work for all types of begonias.

Check your frost date. Look up the average last frost date for your area. Add one week to be safe.
Prepare the soil. Begonias like rich, well-draining soil. Mix in compost or peat moss. Avoid heavy clay.
Choose a spot. Most begonias prefer partial shade. Morning sun with afternoon shade is ideal. Full sun can burn the leaves.
Space them properly. Tuberous begonias need 12 inches apart. Wax begonias can be 8 inches apart. Check the tag for specifics.
Plant at the right depth. For tubers, place them with the concave side up. Cover with 1 inch of soil. For seedlings, plant at the same depth as the pot.
Water thoroughly. After planting, water well. Keep the soil moist but not soggy. Begonias hate wet feet.
Add mulch. A thin layer of bark or straw helps retain moisture. It also keeps the roots cool.

Common Mistakes To Avoid

Planting too early in cold soil
Overwatering after planting
Placing in full, harsh sun
Forgetting to harden off indoor-started plants
Using heavy clay soil without amending it

How To Harden Off Begonias Before Planting

If you started your begonias indoors, they need to adjust. This process is called hardening off. It takes about 7 to 10 days.

Start one week before planting day.
Place plants outside in a shaded spot for 1 hour.
Bring them back inside at night.
Each day, increase outdoor time by 1 hour.
After 3 days, move them to partial sun.
After 7 days, leave them out overnight if no frost is forecast.
Now they are ready to plant.

This step is critical in Washington. Our spring weather can be unpredictable. A sudden cold snap can shock tender plants. Hardening off reduces that risk.

Best Time To Plant Begonia In Washington For Containers

Container planting gives you more flexibility. You can move pots indoors if frost threatens. This means you can plant a bit earlier.

For containers, you can plant begonias as early as late April. Just keep an eye on the forecast. If temperatures drop below 40°F at night, bring the pots inside. A garage or covered porch works fine.

Container begonias also need more frequent watering. Pots dry out faster than garden soil. Check the soil daily. Water when the top inch feels dry.

Best Container Mix For Begonias

Use a high-quality potting mix
Add perlite for drainage
Mix in slow-release fertilizer
Avoid garden soil in containers

Caring For Begonias After Planting

Once your begonias are in the ground or pots, they need regular care. Here is what to do.

Watering

Begonias like consistent moisture. Water when the top inch of soil is dry. In Washington’s rainy summers, you might not need to water much. But during dry spells, water deeply once a week.

Water at the base of the plant. Avoid getting water on the leaves. Wet leaves can lead to powdery mildew. This is common in our humid climate.

Fertilizing

Feed begonias every 2 to 4 weeks during the growing season. Use a balanced liquid fertilizer. Look for one with equal parts nitrogen, phosphorus, and potassium. For tuberous begonias, switch to a high-phosphorus fertilizer once buds appear.

Start fertilizing 2 weeks after planting
Stop fertilizing in late August
Use half-strength for container plants

Deadheading

Remove spent flowers regularly. This encourages more blooms. For tuberous begonias, pinch off the entire flower stem. For wax begonias, just snap off the old flowers.

Deadheading also keeps plants looking tidy. It prevents them from wasting energy on seed production.

Pest And Disease Control

Begonias are generally pest-resistant. But watch for these issues:

Slugs and snails: They love begonia leaves. Use organic bait or hand-pick them at night.
Powdery mildew: Improve air circulation. Avoid overhead watering.
Root rot: This happens from overwatering. Ensure good drainage.
Aphids: Spray with a strong stream of water or use insecticidal soap.

Extending The Bloom Season

In Washington, you can enjoy begonia blooms from June until the first frost. To extend the season, try these tips.

Plant in containers that can be moved indoors
Choose late-blooming varieties
Provide afternoon shade to prevent heat stress
Keep up with deadheading and fertilizing
Cover plants if an early frost is predicted

The first frost in Washington varies. In Seattle, it is usually mid-November. In Spokane, it can be late September. Check your local frost date to know when to bring plants inside.

Overwintering Begonias In Washington

Begonias are perennials in warm climates. In Washington, they are treated as annuals. But you can overwinter them indoors. This saves money and gives you a head start next year.

Overwintering Tuberous Begonias

Before the first frost, dig up the tubers.
Cut back the stems to 2 inches.
Let the tubers dry in a warm, airy place for a week.
Remove any loose soil.
Store in a paper bag or box with peat moss.
Keep in a cool, dark place at 45-55°F.
Check monthly for rot or drying out.
Replant in spring after frost danger passes.

Overwintering Wax And Rex Begonias

These can be kept as houseplants. Bring them indoors before temperatures drop below 50°F. Place them in a bright window. Water sparingly during winter. They will go semi-dormant.

In spring, cut them back and repot. They will grow again. You can also take cuttings in fall to start new plants.

Frequently Asked Questions

When is the best time to plant begonias in Washington state?

The best time is mid-May to early June, after the last frost. For containers, you can plant a few weeks earlier if you can move them indoors during cold snaps.

Can I plant begonias in April in Washington?

It is risky. April often has late frosts. Only plant in April if you use containers and can bring them inside at night. Otherwise, wait until May.

Do begonias need full sun or shade in Washington?

They prefer partial shade. Morning sun with afternoon shade is ideal. Too much sun can scorch the leaves. Too little sun reduces blooming.

How do I know if the soil is warm enough for begonias?

Use a soil thermometer. Insert it 2 inches deep. If the temperature is at least 60°F, it is safe to plant. Cold soil can stunt growth.

Can I plant begonia tubers directly in the ground in Washington?

Yes, but wait until late May. Tubers need warm soil to sprout. Starting them indoors in pots gives them a head start. Direct planting works but blooms come later.

Regional Tips For Washington Gardeners

Different parts of Washington have unique conditions. Here are specific tips for each region.

Western Washington (Puget Sound Area)

Our climate is mild and wet. Begonias love it. Plant in raised beds or containers to improve drainage. Watch for slugs. Use copper tape or organic bait.

The best time to plant begonia in washington for this region is mid-May. Soil warms slowly here. Be patient.

Eastern Washington (Inland Empire)

Summers are hot and dry. Plant begonias in partial shade. Water more frequently. Mulch heavily to keep roots cool. The planting window is early May.

In Spokane, the last frost is usually around May 10. In the Tri-Cities, it is earlier. Adjust your planting date accordingly.

Coastal Washington

Cool ocean breezes keep temperatures moderate. Plant in late May or early June. Choose wind-protected spots. Begonias can tolerate some wind, but not strong gusts.

Coastal fog can cause powdery mildew. Space plants well apart for air circulation.

Mountain And High Elevation Areas

These areas have short growing seasons. Plant in June. Use black plastic to warm the soil. Choose fast-growing varieties. Consider starting tubers indoors in March.

Frost can occur even in July in some mountain valleys. Be prepared to cover plants at night.

Final Thoughts On Planting Begonias In Washington

Timing is everything for begonias in Washington. Wait for warm soil and frost-free nights. Mid-May to early June is your safest bet. With proper care, you will enjoy vibrant blooms all summer long.

Remember to harden off indoor plants. Water consistently but not too much. Feed regularly. Deadhead spent flowers. And protect from slugs and mildew.

Whether you grow tuberous, wax, rex, or dragon wing begonias, the principles are the same. Give them the right start, and they will reward you with color until the first frost.

So mark your calendar for mid-May. Prepare your soil. Get your tubers or seedlings ready. Then plant with confidence. Your Washington garden will thank you.