How to Grow Oyster Mushrooms From Starbucks Coffee Grounds Using Takeout Deli Cups

Growing oyster mushrooms at home doesn’t have to be complicated. One of the simplest and most regenerative methods uses nothing more than Starbucks “Grounds for Your Garden” bags, a little mushroom spawn, and old takeout deli cups. This low-tech setup turns everyday waste into fresh gourmet mushrooms and living mycelium your garden will love.

This is a perfect beginner project and a great way to connect people to fungi using materials that cost almost nothing. We also have them for sale here if you'd prefer to buy some ready to go.

Why Coffee Grounds Are Ideal for Mushrooms

Used coffee grounds are:

• Pre-pasteurized during brewing

• Naturally moist

• Nitrogen-rich and full of minerals

• Easy for oyster mycelium to colonize

• Completely free

Starbucks even gives them away, just ask for a “Grounds for Your Garden” bag.

What You’ll Need

• 1 bag of fresh Starbucks used coffee grounds

• Oyster mushroom spawn (grain spawn works best)

• Clean deli cups with lids (16–32 oz takeout cups)

• Something to poke holes with

• Spray bottle for misting

Step-By-Step: The Easiest Coffee-Ground Oyster Grow

1. Break Up the Coffee Grounds

Open your Starbucks bag and break up any clumps with clean hands or a spoon. You want the grounds to be loose and evenly hydrated.

2. Mix in the Mushroom Spawn

Instead of layering, the simplest method is just to mix the spawn directly into the entire bag.

Add roughly 10–20% spawn by volume.

Seal the top of the bag back down and shake it up like you’re coating popcorn. Massage it so the spawn distributes evenly through all the coffee grounds.

This gives the mycelium full contact with the substrate right away, speeding colonization and reducing contamination.

3. Fill the Deli Cups

Scoop the inoculated coffee grounds into your takeout cups.

Leave about ½ inch of headspace on top so your mushrooms have room to form.

4. Add Air Holes

Use a clean nail, knife tip, or scissors to make:

• 4–6 small holes around the sides

• 2–3 small holes in the lid

These allow oxygen exchange while keeping humidity inside.

5. Incubate

Place the cups somewhere warm and out of direct sun — 65–75°F is ideal.

Over the next 7–14 days:

• The mycelium will spread through the coffee

• The entire cup will turn white

• It will smell pleasantly earthy (not funky)

If you see green, black, or fuzzy colors, that’s contamination — just toss it and start again.

6. Fruiting Time

Once the cup is fully colonized:

• Remove the lid or cut 1–2 slits in the cup for mushroom clusters to pop out.

• Place it where there’s airflow and indirect light.

• Mist lightly daily if the surface starts drying out.

Oyster mushrooms are fast. Once pins form, they double in size every 24 hours.

Harvest when the caps are still curled downward for the best texture.

7. Reuse the Myceliated Coffee Grounds

After your harvest, the leftover mycelium block isn’t trash — it’s living compost. Mix it into:

• Garden beds

• Mulch rings around trees

• Compost piles

• Hugelkultur beds

Oyster mycelium keeps enriching soil long after it finishes fruiting.

Tips for Better Results

• Always use fresh grounds, same-day is best.

• If your home is dry, put cups inside a tote with the lid cracked for extra humidity.

• Blue, pink, golden, and phoenix oysters all love this method.

• Don’t compact the coffee; keep it fluffy for airflow.

Why This Method Works

This is one of the cleanest introductions to home mushroom cultivation. The heat of brewing gives you a naturally pasteurized substrate, oyster mushrooms do the rest, and you get:

• Homegrown gourmet food

• A deeper connection to fungal ecology

• A simple way to recycle an overlooked waste stream

All using materials that cost almost nothing.

Want to Go Deeper?

If you want to learn how to turn this into buckets, totes, or low-tech farm-scale production, check out our MycoSymbiosis cultivation classes. We cover culture to fruiting using accessible tools that work anywhere.