Propagation research determined that plants do not form adventitious roots, suggesting that stem cuttings would not be successful. Seed germination and transplanting techniques should be focus for reintroduction techniques (Kaye and Greenlee, 1995).
Seeds germinate best with the fruit husk removed (Kaye, 1999)
Some seed lots require cold pre-treatment, while others may not. Germination requirements for this species differ from year to year, possibly due to annual variation in environmental conditions during maturation and while fruits are on the ground, prior to collection (Kaye, 1999).
Field propagation studies indicate that 30% of seeds sown between the surface and 1 inch (3 cm) deep in the sand germinate and establish as seedlings, while none buried 4 inches (10 cm) deep germinate and establish. Results indicate that scattering seeds on the surface or lightly raking them in is the best technique. Seeds are much easier to sow than plants are to transplant, so larger numbers of pink sandverbena plants can potentially be introduced, possibly outweighing the predictability of transplants (Kaye et al 1998, Kaye 1999).
Germination trials conducted at The Berry Botanic Garden resulted in 0% germination with 8 weeks of cold stratification followed by alternating 50F/68F (10/20C) treatment, but 17% under 8 weeks of cold stratification followed by constant 68F (20C). Without cold stratification, 20% germination was achieved with either a constant 68F (20C) or alternating 50F/68F (10/20C) temperatures (BBG File).
The seedling establishment rate using 50,000 seeds scattered in the sand per site, while low in absolute terms, was substantially greater than attempts with 5,000 seeds per site (0.54% establishment rate as opposed to 0.017%) (Kaye 2000).
Plants were very successful on dredged sand brought up and deposited on the beach. The nutrient-rich sand smothered the previously dominant European beachgrass (Amophila arenaria), thereby creating suitable habitat for the pink sandverbena (Kaye and Greenlee, 1995).
Transplanted individuals placed singly, or in clusters of three or six are equally capable of growth, flower production and seedling production the following year. They often grow larger than plants from the wild. Transplanting wild seedlings in the fall failed to produce vigorous plants (Kaye et al. 1998).
Propagation observations determined that the majority of individuals are annuals, but a small amount (3%) continued to grow the following year into large plants and produce several thousand seeds (Kaye and Greenlee, 1995).
Second year plants often produce more seeds than first year, and therefore may be especially important in re-introduction efforts (Kaye et al, 1998).
Low density transplants grow larger in the first year than high density plantings, and mortality is unaffected by density (Kaye 1999).
Natural population sizes vary widely over time and space. The total number of tagged plants surviving to reproduce varied from 3.9 - 30.5 % between years. The average plant size varied from 3.7 inches (9.4 cm) to 20.9 inches (53.0 cm). Inflorescence number varied from one to 153 (Kaye 1999).
A study was conducted in which seedlings were transplanted onto dredged sand and old sand with and without fertilizer added. Some plots were weeded and others were not. Fertilizer has a stronger positive effect in fresh (dredged) sand, while weeding helped more on older substrates. While fertilizer addition caused a significant difference in flowering on fresh sand, the improvement was relatively small. In general, fresh sand provided the most favorable conditions for pink sandverbena growth (Kaye 1999).
On coastal sand dunes, plants increase in abundance and diversity (species richness) as time since dredged-sand deposition increases (Kaye 1999).
Pink sandverbena tends to decline with substrate age, especially after 3 years (Kaye 1999)
Transplants and plants from field-sown seed can reproduce and recruit substantial numbers of seedlings the following year (Kaye 1999). Even with initial success with plant establishment from seed, long term population establishment is difficult to achieve. By the second year following reintroduction efforts, no plants were present at four re-established sites and only one or two plants were present at three other sites (Kaye 2000).
One re-established population has done remarkably well. More than 1700 plants were established in 1997, and 411 plants germinated the following year. In 1999, more than 50,000 plants had established and in 2000 the population consisted 33,916 plants in the monitored area plus an additional 15,000 plants throughout the rest of the spit (Kaye 2000).
Eleven natural and four reintroduced A. umbellata ssp. breviflora populations (232 individual plants total) were sampled and genetically analyzed using Inter Simple Sequence Repeat (ISSR) screening. Most populations had relatively high levels of genetic diversity with heterozygosity ranging from 0.13 to 0.26 and means of 0.19 and 0.15 for natural and reintroduced populations, respectively. The two largest reintroduced populations had levels of diversity comparable to the source population, while the other two reintroduced populations were genetically impoverished (McGlaughlin 2000).