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When to Plant Boysenberries in Multnomah County, OR

Boysenberries are a cross between raspberries, blackberries, and loganberries, producing large, dark, intensely flavored berries. They are excellent for jams and pies.

Multnomah County, Oregon is in USDA Zone 9a. The average last spring frost is April 14 and the first fall frost is October 27, giving you a growing season of approximately 196 days.

At an elevation of 357 feet, Multnomah County receives approximately 35.9 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Boysenberries to ensure they mature before fall.

Multnomah County, OR (Zone 9a) Moderate season
196 days
Last Spring Frost April 14
196 growing days
First Fall Frost October 27

Multnomah County Soil Profile

Soil Type

Silt Loam

Soil pH

6.0-7.0

Drainage

Well Drained

Boysenberries Planting Timeline — Multnomah County, OR

Boysenberries Planting Calendar

Activity When Date Range
Transplant Outdoors April 28 Apr 28 – May 12

· 24" apart · Rows 72" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Transplant Outdoors
May Transplant Outdoors
June
July
August
September
October
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

Moderate — regular watering

📅 Days to Maturity

365–730 days

🧪 Soil pH

Needs 5.5–7 · Your soil: N/A

🗺️ USDA Zone

Zone 9a

📆 Growing Season

196 days in Multnomah County

Growing Tips for Multnomah County

Provide strong trellising for vigorous canes. Prune spent canes to ground after harvest. Mulch heavily to retain moisture. Protect from wind to prevent cane damage.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Boysenberries in Multnomah County, OR?

Multnomah County is in Zone 9a with an average last frost of April 14. Plan your Boysenberries planting based on this frost date — see the calendar above for exact timing.

What planting zone is Multnomah County, OR?

Multnomah County, Oregon is in USDA Hardiness Zone 9a. The average last spring frost is April 14 and first fall frost is October 27.

🌱

Your Multnomah County Garden Planner — Free

A 22-page printable planner built for Multnomah County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Multnomah County, OR. Local conditions may vary. Last updated: July 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.