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

The indoor mix is formulated with yucca extract for moisture retention and includes mycorrhizal fungi to boost root development, while the outdoor version adds dolomitic limestone for pH balance and is designed for a broader range of plants, including vegetables and flowers. Both are 100% organic and peat‑free, but the indoor blend omits added fertilizer to reduce gnats, whereas the outdoor blend contains a quick‑release natural fertilizer that feeds plants for up to two months.

Miracle‑Gro’s indoor mix combines sphagnum peat moss, coir, and a built‑in natural fertilizer that helps regulate water uptake, reducing the risk of both drought stress and waterlogging. Back to the Roots relies on yucca extract for moisture control, which also improves water retention but does not include a fertilizer, so you may need to supplement nutrients yourself.

Miracle‑Gro’s 25‑quart outdoor mix fills three 10‑inch containers and includes a quick‑release fertilizer, offering a low cost per quart and long‑lasting nutrition. The Back to the Roots 12‑quart bags are smaller but premium‑blend and peat‑free; for large‑scale planting, the larger Miracle‑Gro bag typically provides better value.

Peat‑free mixes, like Back to the Roots, use upcycled plant material and wood fines, which reduces carbon emissions associated with peat extraction. While Miracle‑Gro’s mixes contain responsibly sourced peat, they still rely on peat moss, so a peat‑free option generally has a lighter environmental footprint.

Mycorrhizae form a symbiotic relationship with plant roots, extending the root network to improve nutrient and water uptake, especially phosphorus. Both Back to the Roots indoor mix and Espoma’s potting soil include mycorrhizal blends, giving plants a head start on healthy root systems.

Mixes with built‑in fertilizer, like Miracle‑Gro’s outdoor and indoor blends, simplify care by providing nutrients for up to two months, which is convenient for beginners. If you prefer precise nutrient control or want to avoid any added chemicals, a fertilizer‑free mix such as Back to the Roots indoor blend lets you customize feeding schedules.

Miracle‑Gro offers bundle packs (two 16‑qt bags or two 8‑qt bags) that reduce the price per quart by roughly 10‑15% compared with single bags. Back to the Roots currently sells only single 12‑qt units, so while the product is premium, the per‑quart cost is higher than the bundled Miracle‑Gro options.

Back to the Roots indoor mix is marketed as pet‑ and child‑safe because it lacks bark, compost, and synthetic chemicals that can attract gnats or cause irritation. Miracle‑Gro’s mixes contain natural fertilizers but no harmful additives, making them generally safe, though it’s wise to keep them out of reach of curious pets and kids.

Herbs often prefer a well‑draining, slightly alkaline mix, so a blend with dolomitic limestone (found in Back to the Roots outdoor mix) can be beneficial. Flowering plants typically thrive with richer nutrient content, making Miracle‑Gro’s fertilizer‑infused mixes a good choice for sustained bloom production.

Back to the Roots mixes include dolomitic limestone to maintain a stable pH, which is especially helpful for indoor plants that can experience pH drift. Miracle‑Gro’s blends rely on peat moss, which naturally leans acidic, so you may need to monitor pH levels or add lime if growing pH‑sensitive crops.