Microsite and rooting depth are more important than water-holding gel for establishment of restoration plantings of Ilex vomitoria on barrier islands in the Gulf of Mexico

Abstract

Restoration of woody plants to barrier islands requires development of production and outplanting protocols as well as determination of “safe sites” for reestablishment. Yaupon (Ilex vomitoria Aiton [Aquifoliaceae]) is a shrub associated with scrub dunes and shallow, interdunal swales of barrier islands along the northern Gulf Coast. We studied the effect of microsite (lowest point of the depression within interdunal swale versus low dune ridge around swale), rooting depth (production container depth), and absorbing gel on seedling survival and subsequent growth of I. vomitoria planted at 5 sites associated with barrier island swales of Santa Rosa Island, Florida. Survival of I. vomitoria was greater in depressions than on ridges and with greater rooting depths. Survival on ridges did not improve with addition of hydrogel but survival for standard pots was increased in depressions. When outplanted in depressions with gel, plant height increased by as much as 6 cm (2.4 in) compared to all other outplanting combinations. Plants on ridges were half the height of plants in depressions in 2006 but no differences were found in 2007. Plants grown in Treepots were more than twice as tall as plants grown in round containers in 2006 but did not differ in 2007. Plants had greater canopy area in depressions than on ridges and with greater rooting depth. For establishment and growth on barrier islands, I. vomitoria should be grown in pots 35 cm (14 in) deep (for example, Treepots) and planted in centers of shallow swales.