Comparison: Best Organic Plus Potting Mix (Updated | Nov 11th)

Look for blends that match the plant’s environment: indoor mixes should have moisture‑retaining agents like yucca extract and be low‑gnat, while outdoor mixes need good drainage and added slow‑release fertilizer. Also consider whether the mix is peat‑free for a smaller carbon footprint, and check for pH‑balancing components such as dolomitic limestone.

Back to the Roots emphasizes a peat‑free formula with yucca extract for moisture control and mycorrhizal fungi for root health, while Miracle‑Gro relies on responsibly sourced peat, coir, and a quick‑release natural fertilizer. The Back to the Roots mix is also marketed as pet‑safe and less prone to indoor gnats, whereas Miracle‑Gro focuses on protecting against over‑ and under‑watering.

Back to the Roots offers a 12‑quart bag at a lower volume, which can be more cost‑effective for small indoor gardens, while Miracle‑Gro’s 16‑quart bundles provide more soil for larger outdoor containers and include two bags for added convenience. Price per quart may be similar, but the larger Miracle‑Gro packs reduce the frequency of repurchasing for extensive outdoor setups.

Both Miracle‑Gro Organic Outdoor and Indoor mixes contain a quick‑release natural fertilizer that feeds plants for up to two months, whereas Back to the Roots relies on organic nutrients from its blend without a separate fertilizer component. If you prefer a longer‑term feeding schedule, you may need to supplement Back to the Roots with additional organic fertilizer.

Back to the Roots’ 100% organic, peat‑free mixes use upcycled plant matter and wood fines, resulting in a lighter carbon footprint compared to the peat‑based Miracle‑Gro options. Additionally, Back to the Roots highlights a “Grow One Give One” program that donates educational kits, adding an extra layer of social responsibility.

Mycorrhizal fungi enhance nutrient uptake and root development, especially for indoor plants; Back to the Roots Indoor Mix explicitly includes root‑boosting mycorrhizae, while Miracle‑Gro’s formulas do not list this component. If you’re growing delicate houseplants or seedlings, the added mycorrhizae can improve overall vigor.

While you can technically use an outdoor mix indoors, it may retain too much moisture and promote gnats, whereas indoor mixes are formulated to balance moisture and reduce pest issues. Conversely, indoor mixes might lack the drainage and slow‑release nutrients needed for hardy outdoor containers, so matching the mix to the environment yields the best results.

Back to the Roots mixes combine wood fines, yucca extract, and limestone for a light, well‑aerated texture, whereas Miracle‑Gro mixes incorporate peat, coir, and perlite for a more traditional, moisture‑retentive feel. The Michigan Peat topsoil adds sand for extra drainage, making it suitable for heavier planting scenarios where excess water must escape quickly.