You’d be surprised how many things in your kitchen are secretly gold-tier fertilizer. In our efforts to boost the sustainable practices of the Greenhaus community, we’re starting a 3 part series on practical and easy ways to incorporate sustainability into your plant care. We can truly make an impact by beginning with small tweaks to our regularly scheduled programming & save money at the same time! Tune in every Sunday for the next few weeks for more! So without further ado, here are 8 plant-friendly kitchen scraps, how to use them, and how long it takes to see the resulting glow-up in your houseplants afterwards. Groceries are way too expensive lately not to have multi-functional purposes for them!

1. Rice Water

How to use it: After rinsing your rice, save that cloudy water and let it cool. Water your plants with it every couple of weeks.
Why it works: It’s full of starches that feed soil microbes, which in turn make nutrients more available to your plants.
Absorption time: About 3–5 days to perk up your soil biology, and you might see subtle growth boosts in a week or two.

2. Eggshells

How to use it: Rinse, dry, and crush ‘em up. Mix directly into the topsoil or steep in water for a “calcium tea.”
Why it works: Eggshells are packed with calcium, which helps build strong cell walls (aka sturdier stems and leaves).
Absorption time: Slow and steady. Crushed shells take weeks to break down, so this is a long-game fertilizer.

3. Used Coffee Grounds

How to use it: Let them dry out, then sprinkle a thin layer on top of your soil or mix into your potting mix.
Why it works: They’re slightly acidic and full of nitrogen, which leafy green plants adore.
Absorption time: Expect to see benefits in about 1–2 weeks if used consistently (and not too thickly).

4. Banana Peels

How to use it: Chop into tiny pieces and bury them a few inches deep in the soil. Or soak in water for a couple days and use that liquid as fertilizer.
Why it works: High in potassium and phosphorus which are great for flowering and root development.
Absorption time: Chopped peels decompose in 2–3 weeks. The soaked version, which I use quite frequently & highly recommend, acts faster in around 5–7 days.

5. Vegetable Scraps Broth

How to use it: Boil your clean veggie scraps (no salt or seasoning!), let cool, then water your plants.
Why it works: Leaches vitamins and minerals like magnesium and iron into a super gentle broth.
Absorption time: Almost immediate. Plants absorb the minerals through the soil within a few days.

6. Used Tea Leaves (or Tea Bags)

How to use it: Dry and sprinkle into soil or steep again for a weak tea fertilizer. Just make sure it’s caffeine-free if your plant prefers less acidity.
Why it works: Adds nitrogen and trace minerals, and helps soil retain moisture.
Absorption time: This takes about a week to two depending on the plant and soil condition.

7. Onion and Garlic Skins

How to use it: Steep the papery skins in water for a few hours and use as a natural pest-repelling, nutrient-rich tonic.
Why it works: They contain potassium and sulfur which are great for disease resistance and overall plant strength.
Absorption time: Fast. You’ll see benefits within a week, and bugs might back off sooner.

8. Aquafaba (Chickpea Water)

How to use it: Dilute it 1:3 with water and give your plants a drink with no salt or seasoning, please.
Why it works: Packed with plant-based protein, it nourishes soil microbes and helps improve soil structure.
Absorption time: Within a few days, especially helpful for depleted potting mix.

One Caveat: Organic vs. Non-Organic

If your kitchen scraps come from conventionally grown produce, they could carry residual pesticides or preservatives that your plant’s root systems don’t love. Over time, these chemicals can mess with soil microbes, throw off your pH balance, or even slow growth rather than help it.

If you can, go organic with the things you plan to use on your plants, especially peels, skins, or anything that gets buried or soaked. And definitely rinse well. Your plants don’t need a side of synthetic fungicide with their banana tea.

Final Tip: These kitchen cast-offs are more “slow release” than commercial fertilizers, but that’s what makes them gentle and sustainable. For best results, rotate a few different methods and always pay attention to how your plants respond. If they look a little meh, ease up or mix in some compost to balance things out.

So next time you’re about to throw out those scraps, remember: your kitchen trash is your plants’ treasure.

With Love,

Zoé & The Greenhaus Team

Sustainable Plant Practices: Repurposing Kitchen Scraps