Organic additives without the myths.
Compost, worm castings, kelp, neem, soap, BTI, gypsum, lime, and Epsom salt all have a place. None of them should be treated like magic.
Additive guide
| Additive | Best use | How to use | Caution |
|---|---|---|---|
| Compost Must-have |
All-purpose soil biology and slow nutrient support. | Top-dress containers lightly or mix into garden beds. | Do not bury stems; unfinished compost can burn roots. |
| Worm castings Must-have |
Gentle microbe-rich amendment for indoor/outdoor plants. | Use as a light top-dress or small percentage of potting mix. | Too much can make mixes heavy and wet. |
| Kelp / seaweed Must-have |
Trace elements and stress support. | Use liquid seaweed or kelp meal at label rate. | Not a complete fertilizer by itself. |
| Fish emulsion Should-have |
Quick organic nitrogen boost. | Dilute strongly and use during active growth. | Can smell and can overfeed soft growth. |
| Bone meal / fish bone meal Should-have |
Slow phosphorus and calcium support. | Use for bulbs, roots, flowering/fruiting crops if soil needs it. | Avoid overuse; excess phosphorus can lock out iron/zinc. |
| Gypsum Should-have |
Adds calcium and sulfur without raising pH much. | Use where calcium is needed and pH is already acceptable. | Not a cure for all blossom-end rot. |
| Dolomitic lime Should-have |
Raises pH and adds calcium/magnesium. | Use only if soil is too acidic. | Bad fit for acid-loving plants or already alkaline media. |
| Epsom salt Should-have |
Magnesium sulfate for confirmed magnesium issues. | Use lightly and only when symptoms/context fit. | Not a universal green-up cure. |
| Neem oil Must-have |
Low-toxicity pest management tool for some soft-bodied pests. | Spray in shade/evening; cover undersides. | Can damage stressed plants; avoid heat, intense light, and open pollinator blooms. |
| Insecticidal soap Must-have |
Contact control for aphids, mites, whiteflies, mealybugs. | Spray direct contact and rinse sensitive plants later. | No residual control; repeat is required. |
| BTI Should-have |
Biological larvicide for fungus gnat larvae and mosquitoes. | Use mosquito bits/dunks as a soil drench according to label. | Does not kill adult gnats. |
| Beneficial nematodes Should-have |
Biological soil pest support. | Apply to moist soil and protect from sun/heat. | Must be fresh and species-appropriate. |