蛭石是一种天然矿物（水合镁铝硅酸盐），加热到高温时会膨胀成手风琴状的颗粒。在园艺中，它被用作生长介质的组成部分，在提供一定通气性的同时，保持水分和养分。与珍珠岩不同，蛭石能保持更多的水分，并具有适度的阳离子交换能力（CEC），这意味着它可以暂时保持和释放营养离子。
关键事实
- Retains 3–4 times more water than perlite — better for moisture-loving seedlings and cuttings
- Moderate CEC allows it to buffer and slowly release nutrients
- pH slightly alkaline (7.0–7.5) — can raise pH in acidic mixes
- Not suitable as a standalone hydroponic medium — too water-retentive for most systems
- Best uses: seed starting, propagation mixes, top layer over germinating seeds
- Often blended with perlite in propagation media (50:50) to balance moisture and aeration