Amelanchier spicata from Four Provenances in New England Differ in Early Seedling Growth and Are Insensitive to Fertilizer Nitrogen Source

Amelanchier spicata (dwarf serviceberry) is a shrub native to North America with multi-seasonal appeal. As part of a larger project to evaluate Amelanchier germplasm for horticultural merit, we evaluated variation in growth among seedlings of A. spicata from four provenances in Maine and New Hampshire, and assessed whether nitrogen source (NH₄-N, NO₃-N, or NO₃NH₄-N) affected growth and development of plants in container culture. Plants growing in a substrate of 1:1 perlite:vermiculite were supplied with nitrogen and other nutrients using modified and balanced Hoagland solutions. The pH of each solution was adjusted to 4.5 or 6.5, for a total of six treatment combinations. Seedlings were fertilized regularly for 61 days. Substrate pH was influenced by nitrogen form, but not by solution pH. Nitrogen form did not affect root dry weight, leaf dry weight, and stem length. Seedlings supplied with nitrogen in the form of NO₃NH₄-N or NH₄-N alone had slightly greater stem caliper, stem dry weight, SPAD, and foliar Fe content than those supplied with NO₃-N alone. Seedlings supplied with NO₃-N had marginally greater leaf number and foliar Al, Mg, and Ca than those provided with NH₄-N. Even though some traits varied by nitrogen source, the differences in means were not likely to be commercially important and overall plant growth was robust. In contrast, seedling provenance had a large impact on plant growth and development. Although maternal plants were shrub-like in indigenous populations, seedlings from three provenances produced single stems, whereas those from one provenance consistently branched at the cotyledonary node. Plants from the four provenances differed in leaf number, stem dry weight, leaf dry weight, root dry weight, stem length, SPAD, and stem caliper, as well as foliar N, P, K, Ca, B, Cu, Mg and Mn content. Our results indicate that notable variation in growth and development exists among provenances of A. spicata, even within a localized spatial scale, and that fertilizers containing either NH₄-N or NO₃-N are suitable for their production in containers.