Five common sources of perlite used in the North American horticultural industry were tested for their release of fluoride during five successive teachings with pH 5.2 sodium phosphate buffer (1 cc perlite/ml buffer). Soluble fluoride in the first leachate ranged from 0.05 to 0.8 mg/l and in the fifth leachate from 0.01 to 0.18 mg/l. Lilium Asiatic hybrids `Pixie Grange' and `Sunray', Chlorophytum comosum (Thumb.) Jacques `Variegatum', and Gibasis pellucida (Martens & Gal.) D. Hunt `Bridal Veil' were. grown in sphagnum peat moss plus perlite substrates ranging up to 50% perlite and at substrate pH levels from 4.6 to 7.0. No fluoride toxicity occurred in these crops in any treatments. The precaution against the use of perlite in substrates used for growing fluoride sensitive crops needs to be reconsidered.
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