Growing Blueberries in Portland, Oregon – My Advice to Clients

A Care & Fertilizing Guide for Growing Blueberries in Portland, Oregon Gardens, from your landscape designer — for clients with backyard blueberries (and maybe a dog or two).

1. Safety First — For Dogs and Plants

Before adding any fertilizer or mulch, think about how curious your dog is. If your pup tends to dig or eat odd things, test new fertilizers in an area you don’t mind being disturbed first.

Avoid these dog temptations:

• Bone meal and blood meal — dogs love them (my Irish Setter once ate half a bag!)
• Chicken manure — not good for blueberries and can be too alkaline.

2. Blueberry Fertilizer Basics

Blueberries need acidic soil (pH 4.5–5.5) and a steady source of organic, slow-release nitrogen.
They also appreciate mulch to retain moisture and keep the roots cool.

Skip fresh manure — it can introduce pathogens.
Do not use ammonium nitrate (NH₄NO₃).
Yes to ammonium sulfate — it helps maintain acidity if your soil pH is above 5.5.

If your soil pH is below 5, use urea or cottonseed meal instead.

3. Safe, Organic Fertilizer Options

These fertilizers and mulches work beautifully for blueberries and are dog-safe when used properly:

Local sources:

• Best Buy in Town, Hillsboro — Garden Compost (apply twice a year; expect ~1″ annual settling)
• The Worm Farm — Blueberry Mulch Mix

4. Easy Year-Round Fertilizer Program

Option 1: Simple & Effective (recommended for growing blueberries in Portland)

Use Down to Earth Acid Mix (4-3-6) — easy to find and made for acid-loving plants.
This organic fertilizer releases nutrients slowly and safely.

Schedule:

• Late Fall: 1 cup per plant
• Mid-March: 1 cup per plant
• Mid-April (before flowering): ½ cup per plant

Sprinkle evenly around each plant and scratch it lightly into the soil. Water thoroughly afterward.
Each application takes about a month to break down and become available to your plants.

Option 2: DIY Mix

Visit Concentrates Inc. in SE Portland to create a custom fertilizer blend — their staff can help you mix cottonseed meal, feather meal, and fish bone meal for a more hands-on approach.

5. Liquid Fertilizer Option

If you prefer liquid feeding:

• Use fish fertilizer at half the label strength, once a week.
• Apply in the evening, then water it in well.
• Keep an eye on your dog for a week — if they lose interest, it’s likely safe to continue.

This method provides the right nitrogen, but it requires consistency.

6. Mulch Tips

Mulch keeps roots cool, holds moisture, and protects against weeds.

When to apply:

• Late Fall and Mid-Spring

What to use:

• Clean yard debris compost (ask for “edible garden-safe”)
• Manure compost (cow or horse)
• Blueberry mulch mix (from The Worm Farm)

Avoid bark dust meant for ornamental beds — it may not provide enough organic content.