Comparison of Herbaceous Perennial Plant Growth in Seaweed Compost and Biosolids Compost

Liners of angelonia ‘Pink’ (Angelonia angustifolia Benth.), shooting star (Pseuderanthemum laxiflorum), coreopsis ‘Early Sunrise’ (Coreopsis grandiflorum Hogg ex Sweet.), and scutellaria ‘Purple Fountains’ (Scutellaria costaricana H. Wendl.) were transplanted into containers filled with, by volume, 1) 100% compost; 2) 60% compost, 25% vermiculite, 15% perlite; 3) 30% compost, 30% sphagnum peat, 25% vermiculite, 15% perlite; 4) 0% compost, 60% sphagnum peat, 25% vermiculite, 15% perlite. Two compost products were evaluated: SW, a 1:1 by volume mixture of partially composted seaweed and partially composted yard trimmings and SYT, a 1:1 by weight mixture of biosolids compost and yard trimmings compost. There was no difference in angelonia shoot dry mass among the different percentages of SW compost but angelonia plants grown in 0 and 30% SYT had greater shoot dry mass than plants grown in 60 or 100% SYT. Shoot dry mass of shooting star plants increased as the percentage of SYT compost increased from 0 to 30 % and then decreased while shoot dry mass of plants grown in SW compost decreased as the percentage of compost increased. There was no difference in coreopsis shoot dry mass or scutellaria shoot dry mass between the two compost products and there also was no difference in shoot dry mass among the different percentages of either compost product.