Evaluating cherry (Prunus cerasus) pits as an alternative greenhouse substrate aggregate

An increased emphasis on sustainability has heightened interests in finding uses for agricultural by-products such as cherry pits (CP) produced by Michigan's tart cherry (Prunus cerasus 'Montmorency') industry. The objectives were to determine 1) if CP can be used as an alternative aggregate to PL in greenhouse substrates; 2) if CP can be used fresh (FCP) or dried (DCP) and; 3) if there are any phytotoxic plant growth effects on seedlings or greenhouse bedding plants. Fresh CP was either stored in sealed containers to maintain 'freshness' (FCP) at 2.2 C or oven-dried (DCP) at 71 C for three days and stored in sealed containers until used. Peat moss (PM) was amended with either (by vol.) 20% FCP, DCP, or PL, thus formulating three 80:20 pm:FCP, PM:DCP, or PM:PL substrates. Germination bioassays were used to determine the potential presence and effect of phytotoxins of FCP- and DCP-amended substrates. Seedling germination count, phytotoxicity ratings, and seedling dry mass were evaluated and no visual detrimental effects were observed. A plant growth trial with basil (Ocimum basilicum), geranium (Pelargonium × hortorum), and petunia (Petunia × hybrida) were conducted. In general, substrate pH and electrical conductivity (EC) were significantly higher in substrates amended with FCP and DCP than with PL. Plant height and width, growth index, and dry mass were unaffected by aggregate type. Geranium and petunia plants grown in substrates amended with FCP or DCP and developed high pH-induced symptoms on the foliage. Results from this trial indicate CP can be used as a greenhouse substrate aggregate for production of basil, geranium, and petunia, but further investigations to improve pH and EC management and trial performance of other greenhouse crops is warranted.