Improved propagation methods greatly benefit conservation of rare cycads. Appropriate substrate conditions, especially excellent root aeration, are crucial to successful cultivation of most cycads. Typical cycad substrates include substantial portions of organic materials that will decompose over time, reducing drainage and increasing water retention. In this study, two inorganic substrates, arcillite (Turface® MVP®) and coarse silica sand, and one mixed cycad substrate (with organic and inorganic components) were evaluated for germination and growth of three rare Zamia species: Z. fairchildiana L.D. Gómez, Z. cunaria Dressler & D.W. Stev., and Z. aff. portoricensis Urb. over a period of 14 months from seed sowing. Substrate type affected leaves per seedling and leaf length. These factors also varied by species as did taproot length and germination rate. There were also significant interactions between substrate and species for caudex diameter and leaf variables, likely reflecting ecological differences among the species, two of which are from rainforest habitats and one from dry forest. All three substrates performed adequately for germination, survival, and growth of Zamia. Turface® and possibly the silica sand likely require additional watering to improve their performance as cycad substrates.
Claudia Calonje, Chad Husby and Michael Calonje
Judy Kay, Arantza A. Strader, Vickie Murphy, Lan Nghiem-Phu, Michael Calonje and M. Patrick Griffith
Horticulture is an essential part of plant conservation programs, and botanic gardens are uniquely suited for conservation horticulture work. Here, we present a case study of a successful cycad (Cycadales) propagation program at Montgomery Botanical Center (MBC, Miami, FL), using palma corcho (Microcycas calocoma) as an example. This species is highly sought in the nursery trade, and overcollection of wild plants is one factor leading to imperilment of natural populations. Thus, propagation and distribution of palma corcho can make a strategic contribution to in situ conservation. Provenance history of the living collections is reviewed, and techniques for propagation and establishment are detailed. An innovative botanic garden/industry partnership to provide seed for cultivation is discussed. Finally, we present analysis of market forces with regard to rare plant availability and conservation, using palma corcho as an example. Average price per seed has fallen by over half since offered on public auction. This inversely correlates with seed supply, which has been steadily increasing during the last 15 years and helping meet the high market demand. We project the cost of palma corcho will fall further to a point where collection from the wild has no further economic incentive.