2019 ASHS Annual Conference

In 1931, the Main Fountain Garden opened at Longwood Gardens in Kennett Square, PA. After 83 years in operation, the centerpiece garden at Longwood underwent a massive revitalization. This project included the construction of a Grotto created with local Avondale Brownstone and was to feature a rock wall with ferns and mosses growing amongst the large stones. The Grotto would be a low light, damp, man-made environment with supplemental LED lighting. The objective of this work was to determine a method to grow moss on the rocks of the Grotto wall prior to the structure being complete. To mimic the suspected environmental conditions in the Grotto, moss trials were conducted in a basement under LED lights comprised of 80% red and 20% blue light. The lights were kept on 24-hours a day and light levels were 15 µmol·m^-2·s^-1. A preliminary trial developed a general recipe for a soil that would adhere to the rock face and provide a substrate for moss growth. The recipe was a 2:3 ratio by volume of Elmer’s Glue-All™ : Water, followed by mixing in potting media until a paste consistency was formed. The experiment tested two types of the sticky soil (created with SunGro propagation mix or pure peatmoss) with seven moss samples (5 different species) collected across Longwood Gardens property and with stone lying flat or at a 45-degree angle. Treatments were applied to same Avondale Brownstone used for Grotto construction. For each treatment, stick soil was applied at a thickness of 0.3 cm and at an area the size of each single piece of intact harvested moss (ranging from 6 to 26 cm²). Moss was watered 3 days a week and growth was measured 24 and 58 days after transplanting. The majority of moss species exhibited no growth over the course of the experiment regardless of angle or substrate. When comparing peat and propagation mix, more moss species grew on peat based sticky soil. The largest and most consistent growth occurred with Orthodicranum viride that showed positive grown with all treatments. Positive growth only occurred with two of the remaining 20 treatments. Based on the results Orthodicranum viride and one of the three Hedwigiaceae were recommended for use in the grotto. Both have successfully established and grown on the rocks.