Seed Propagation of Sphaeralcea (Globemallow)

Plants of Sphaeralcea are flowering perennials with bright orange to red flowers that add color to landscapes.  They are drought-tolerant and considered pioneer species because of their ability to establish quickly in harsh conditions. Three species are native to the Intermountain West and considered desirable for low-water landscapes: S. grossulariifolia, S. parvifolia, and S. munroana. While plants of Sphaeralcea are available in the industry, they are not widely distributed because of difficulty with seed propagation and dormancy breaking.  A reasonably successful strategy for breaking physical seed dormancy in Sphaeralcea is seed nicking.  However, this method is not cost-effective on a large scale because the seeds are small (<1 mm in diameter) and seed nicking is labor-intensive.  We hypothesized that seeds of Sphaeralcea might exhibit double dormancy.  In February 2009, seeds in lots of 50 each were exposed to physical (seed nicking, rock tumbling for 24 hr, and hot-water scarification) and physiological (6 weeks cold-moist stratification) dormancy breaking strategies, alone and in combination to test this hypothesis (n = 5).  After dormancy treatments were complete, seeds were germinated on moist filter paper in plastic Petri dishes held on a bench top at 21C.  Germination was recorded as radicle emergence from the seed.  We found no interaction between species and treatment in percent germination among the three species (P = 0.87).  Germination of seed after nicking alone was 52%.  Germination of seed after 6 weeks cold-moist stratification was only 5%.  However, the combination of nicking and 6 weeks cold-moist stratification significantly enhanced seed germination over either of these dormancy breaking strategies alone (84%). Seed germination percent after rock tumbling alone was 26%, significantly greater than hot-water scarification.  Cold-moist stratification did not improve germination when combined with physical dormancy breaking strategies other than nicking.  Our data suggest that Sphaeralcea may exhibit double dormancy.  Future work should focus on evaluating different rock-tumbler media and time of tumbling to find a viable alternative to nicking for breaking physical seed dormancy in these species.