Katherine Temus
When habitats have been destroyed or significantly damaged restoration efforts are often needed to return the habitat to a functional, usable, and healthy state. Use of the correct native plants is paramount to the success of the project. Seeds for use in revegetation projects are either collected from wild populations or harvested from commercial stands. For several species of native Utah forbs, collection of wild seeds is impractical and seeds are not available commercially in bulk amounts. This severely limits or eliminates the use of these native Utah forbs in wildland restoration projects.
We have sought to promote the commercial production of these species by gaining an understanding of their phenology (growth and reproduction) patterns. This information allows growers to choose seeds from a species that will grow best in an agricultural setting. It also gives them the information needed to choose the harvest date that will give them the greatest yield.
Seeds of 12 species of native forbs (two to three populations each) were collected from wildland sites throughout Utah in 2005. During the following winter and spring they were planted and grown out in a greenhouse until they were deemed hardy enough to be transplanted in the field. At this point (during in the summer of 2006) they were transplanted into a fenced plot at the BYU research farm near the mouth of Spanish Fork Canyon. Populations were organized by rows, surrounded by weed mat, and watered via a drip system. During the following growing season, (summer of 2007) phenology data were recorded for each individual plant every week for 14 weeks. The phenological stage(s) that were present for each plant was recorded at each reading. The phenology stages were categorized as vegetative, bolting, budding, bud color, flowering, early fruit, mid fruit, and late fruit (ripe fruit). The approximate number of flowers present on each plant was also recorded. In this way the flowering peak for each population was recorded, as well as peaks for ripe seed (Figure 1). With these peaks we could determine how many weeks following the flowering peak the best harvesting time could be expected. At the end of summer, as populations began to increase the number of late fruit, seed was harvested and seed production was quantified. Some species (Castilleja rhexifolia, Delphinium barbeyi, Potentilla gracilis, and Castilleja miniata) experienced heavy predation by insects and produced very little or no seed.
Variation existed between species in the distinctness of their flowering peaks. Some species peaked quickly and then abruptly stopped flower production (ex. Potentilla glandulosa), while others peaked more slowly and trailed off flower production (ex. Castilleja miniata). For instance, Iliamna rivularis did not peak; rather, the ripe fruit increased at the same rate as the increase in flowering, though a few weeks behind. As the number of ripe fruit increased, flowering continued to increase as well. This was a result of the type of inflorescence that I. rivularis has. As the lower, more mature flowers produce seed and ripen, younger flowers are still growing further up on the stalk.
Seed production and ease of harvest also varied between species. The species most suited for commercial production (as determined by the level of ease at which they were grown and harvested, the amount of seed they produced, and how predictable their harvest dates were) are: Chamerion angustifolium, Iliamna rivularis, Geranium viscosissimum, Erigeron speciosus, and Geranium caespitosum. The species that would be the most difficult to grow and harvest in a commercial setting are: Castilleja miniata, Polemonium folisissimum, Eriogonum heracleoides, Delphinium barbeyi, and Castilleja rhexifolia. Potentilla glandulosa, and Potentilla gracilis fall between the two ends of the spectrum.
Because the forbs were being grown in a habitat different than their origin, we were interested in knowing whether or not the difference in local pollinators would be a limiting factor in their reproductive success. Hence, during the same time that phenology data were being collected, data were also taken on the pollinator activity within each population. The types of pollinators that visited individual plants within a population and how frequently they visited were recorded. Pollinators proved to not be a limiting factor in the reproductive success of the forbs at the farm. The number of flowers a plant produced determined the number of pollinator visits (Figure 2). These forbs can be successfully pollinated by other pollinators when removed from their native pollinators.
I am presenting this data at the Botanical Society of America meeting in July of this year. I am also preparing a manuscript of this research to be submitted to the Native Plants Journal this fall.