Black Tar-Like Substance on Garden Soil: Algae from Compaction and Acidity

Likely Algae

Grows on compacted, acidic soil. Check pH—target 6–6.5 for most plants, 5.5 for azaleas/hollies.

Rehab Plan

1. Till to loosen.
2. Spread 2+ inches bagged leaves this fall.
3. Lime if needed.
4. Till 4–5 inches deep.
5. Overseed with annual ryegrass.

Next Steps

If ryegrass prospers, till it in as green manure next spring. If it fails, test soil nutrients and follow recommendations. If still no growth, investigate drainage.