Rain-Proofing Your Grow: Battling Mold and Mildew in Washington’s Wet Season

Washington’s wet season is no joke—and neither is losing your crop to a mold outbreak. If you’re growing cannabis at home anywhere from Olympia to Bellingham (or braving the rain in Forks), this guide is your must-have umbrella for your buds.

---

Why Mold and Mildew Love Washington

Washington’s maritime climate—especially west of the Cascades—serves up frequent rain, high humidity, and long stretches of overcast skies. While great for ferns and foggy vibes, this combo creates the perfect storm for:

• Powdery Mildew (PM): Looks like your leaves got dusted in flour. It spreads fast in cool, damp, stagnant air.

• Bud Rot (Botrytis): A silent killer that starts inside the cola and works its way out. Once you spot it, it’s often too late.

• Leaf Spot & Downy Mildew: Less common but still a threat in long rainy seasons, especially in shaded backyards.

---

Step 1: Build a Shelter, Not a Sauna

Rain protection doesn’t mean suffocation. Here’s how to protect your plants from above without choking them out.

What Works:

• DIY PVC Greenhouse with Clear Poly Panels
   Affordable, easy to assemble, and allows light while keeping rain off. Just make sure you leave gaps for air to flow.

• Tarp Awnings with Side Venting
   If you’re on a budget, a taut tarp angled for runoff will do—but don’t block the sides. Think “rain umbrella,” not “plastic prison.”

• Pop-Up Canopy with Mesh Walls
   Perfect for temporary setups in yards or patios. The mesh keeps airflow steady while blocking splash-up from rain.

What to Avoid:

• Fully Enclosed Plastic Greenhouses (Unless vented or climate-controlled)
   You’ll just be breeding moisture. Cannabis is not a terrarium plant.

---

Step 2: Let That Air Flow

Humidity + still air = mildew magnet. Moving air helps dry surfaces and strengthen stems.

• Use Outdoor-Rated Clip Fans (weatherproof if possible)
   Mount them under the canopy to keep air circulating between plants.

• Thin Your Plants
   Don’t be afraid to remove lower fan leaves and open up the middle of the plant. If your plant is too bushy to see through, it’s too bushy for Washington rain.

• Avoid Overcrowding
   Leave space between plants—think “social distancing” but for colas.

---

Step 3: Early Detection = Prevention

Catch mold early, and you might save the harvest. Let it go, and you'll be cutting your losses—literally.

What to Look For:

• Gray fuzz in dense buds (Botrytis)

• White powder on leaf tops (Powdery Mildew)

• Random yellow or brown spots that seem to spread fast

Tools for Detection:

• Jeweler’s Loupe or Microscope: Look at trichomes and spot mold at a microscopic level.

• Moisture Meter for Soil: Overwatering during a rainy week can make things worse below the surface.

---

Step 4: Use Natural Defenders

Don’t wait for mold to arrive. Treat your plants regularly during rainy spells with preventative sprays.

Organic Options:

• Neem Oil – Great for PM prevention. Spray early in the day so it dries before nightfall.

• Lactobacillus Serum (LABS) – Beneficial bacteria that outcompete bad fungi.

• Bacillus subtilis – A biological fungicide found in products like Serenade.

• Potassium Bicarbonate – Works like baking soda to stop mildew from spreading.

Pro tip: Rotate your treatments every week to prevent fungal resistance.

---

Step 5: Time Your Harvest Wisely

You might be tempted to push for fatter buds, but once the forecast turns to daily drizzle, early may be better than ruined.

• Check the 10-Day Forecast Religiously

• Start Flush Early if Needed

• Harvest Before the Mold Does

A slightly early harvest still smokes better than soggy rot.

---

Bonus Tip: Clean Up Post-Season

Don’t let spores linger for next year.

• Sanitize pots, shears, and support stakes.

• Turn over your soil or solarize it if reusing an outdoor bed.

• Compost mold-free trimmings, but trash any infected bud.

---

Grow Strong Through the Storm

Growing cannabis during Washington’s wet season might feel like you're fighting the sky itself—but with the right setup, airflow, and a little mold-mindfulness, you can beat the gray and still bring in green. Whether you’re nestled in the Olympic Peninsula or perched on a Seattle rooftop, your weed can thrive—even in the rain.

From soggy soil to stubborn strains, we help Washington homegrowers thrive—rain or shine. We’re here with practical advice, local know-how, and zero judgment. Check out our website for more details.