The ability of honeyvine milkweed [Ampelamus albidus (Nutt.) Britt.] to establish and develop from seed was studied in laboratory and field experiments. Optimum germination temperature was 30 C. Seed incubated at cooler temperatures and then transferred to 30 C germinated equally as well as seed incubated continually at 30 C. Germination was unaffected at moisture stress levels between 0 and −4.6 bars, but was decreased at levels between −4.6 and −12.8 bars. The optimum pH range for germination was between 5 and 7. The greatest emergence of seedlings occurred at a depth of 0.5 cm with no emergence occurring at depths greater than 5 cm. Greater emergence was obtained with a loam than sandy loam at all planting depths except 0.5 cm. Field plots seeded on May 1 gave maximum seed production. Seed production decreased with each 2-week delay in planting. Planting dates of July 10 or later produced no seed. Seed germination was affected little by delayed planting. The following spring, regrowth from plants seeded on June 12 or later was less vigorous than regrowth from plants seeded earlier.

Virginia buttonweed seeds germinated at temperatures between 15 and 40 C, with optimal germination occurring at 25 or 30 C in 12 h light alternated with 15 to 25 or 20 to 30 C in darkness, respectively. Germination rate was lower in continuous darkness than in light. Germination was reduced under simulated water stress conditions with less than 10% of seeds germinating at osmotic potentials below −0.3 MPa. Overall seed germination was reduced under simulated flooding conditions; greater germination occurred in aerated water than in unaerated water. Maximum germination occurred at pH 6. Seedlings emerged from depths as great as 8 cm, with maximum emergence occurring from 2 cm.

When trifluralin [α,α,α - trifluoro - 2,6 - dinitro -N,N-dipropyl-p -toluidine] was manually incorporated in small field plots to a depth of 10 cm, ivyleaf morningglory [Ipomoea hederacea (L.) Jacq.] was controlled more effectively than when incorporation was only 5 cm deep. No significant differences in ivyleaf morningglory control were observed between different incorporation depths when trifluralin was mechanically incorporated in large field plots. Ivyleaf morningglory emerging from 10 cm deep was controlled to a greater degree than that emerging from 5 cm deep. Preplant incorporated (PPI) trifluralin plus alachlor [2 - chloro – 2′, 6’ - diethyl - N- (methoxymethyl)acetanilide ] applied preemergence (PE) controlled up to 92% of the ivyleaf morningglory compared to 33 and 15% respectively, when these herbicides were applied alone at equal rates. This indicates a synergistic interaction between these two compounds. Trifluralin PPI plus RH 8817 [5-(2-chloro-4-trifluoromethyl phenoxy) - 2 - nitrobenzoic acid ethyl ester] and alachlor applied PE controlled ivyleaf morningglory more effectively (88 to 94%) than all other treatments. Soybean [Glycine max (L.) Merr.] injury and stand reduction were less than 5% in all studies.

Wild oat (Avena fatua L.) seedlings from mature seeds emerged in silt loam from depths up to 17.5 cm in the greenhouse or 15 cm under field conditions. No emergence occurred from greater depths. Under field conditions, the greatest percentage of shoots emerged from seeds planted 5 cm deep. Wild oat in a space-planted nursery produced an average of 19 tillers, reached a maximum height of 79 cm, and produced an average of 1072 seeds. The number of tillers per plant, the number of seeds per panicle, and the total number of seeds per plant increased with an increase in annual precipitation. Wild oat seeds harvested as early as 3 days after anther extrusion germinated, but seeds harvested 6 or 7 days after anther extrusion germinated more rapidly.

Goatsrue is an introduced perennial plant which has proven to have great invasive potential, leading to its classification as a noxious weed in many states and at the federal level. Very little research has been done on its basic biology. Physical dormancy of mature goatsrue seed was tested through scarification with sulfuric acid for up to 60 min resulting in 100% germination. Comparison of dormancy for 26-yr-old and 6-mo-old goatsrue seed indicated that aged seeds had reduced dormancy levels compared to newly harvested seeds. Maximum germination was similar among the 6-mo old and 26-yr-old seed lots, suggesting no loss of viability had occurred in seed stored dry for 26 yr. Goatsrue seedling emergence was inversely related to burial depth, and decreased as burial depth increased. Emergence of seed buried at 0.5 to 3.0 cm soil depth was 93 to 87%, respectively, and no emergence occurred from 12 and 14 cm. When the soil seed bank of five goatsrue-infested areas was sampled, the largest density of seeds found was 74,609 seeds m−2 while the lowest was 14,832 seeds m−2. Viability and dormancy of seeds recovered from the soil seed bank survey ranged from 91 to 100% and 80 to 93%, respectively. Management, which reduces the soil seed bank and controls emerging seedlings, is as essential as control of mature goatsrue plants in order to avoid seedling establishment and reinvasion of a location.

Tropical signalgrass is one of the dominant weeds in the Florida turfgrass industry and is potentially troublesome for the southeastern turfgrass industry. Tropical signalgrass is especially problematic for St. Augustinegrass sod producers because of lack of control options. The objectives of our research were to determine the effect of light, pH, temperature, water potential, and planting depth on tropical signalgrass germination and emergence. Tropical signalgrass germination does not require light and is optimum at pH 5 to 6, temperature 25 C, and water potentials greater than − 0.4 MPa. Tropical signalgrass shoots emerged from depths of 0 to 7 cm, with maximum germination when placed on the soil surface. Tropical signalgrass seedlings emerged in the field during the second week of March in Ft. Lonesome, FL. Weekly mean soil and ambient air temperatures at the time of emergence were 20 C. Tropical signalgrass emergence was first observed at 118 and 73 growing degree-days (GDD) (13 C base temperature), with a peak emergence period at 222 and 156 GDD for 2001 and 2002, respectively.

Laboratory experiments were conducted to determine the effects of optimum temperature, depth of planting, and simulated moisture stress on smellmelon germination and subsequent emergence. Smellmelon germination increased with temperatures ranging from 20 to 30 C, with the highest germination of 83% occurring at 30 C. Germination percentages decreased to 49 and 15% with temperatures of 35 and 45 C, respectively. Emergence from depths of 9 to 15 cm was less than 25% for all temperatures. Highest emergence from depths of 1 to 6 cm occurred with 30 and 35 C. Smellmelon germination was reduced from 81 to 61% when the osmotic potential was reduced to − 0.2 MPa and was further reduced to 48 and 7% with solutions of − 0.4 and − 0.6 MPa, respectively. Field studies were conducted to evaluate smellmelon biomass production in 1999 and 2000 when competing with cotton (Gossypium hirsutum L.). End of season-smellmelon leaf area values were 16,280 and 22,053 cm2 per plant in 1999 and 2000, respectively, or 67 and 117 g of leaf dry weight per plant for 1999 and 2000, respectively. In 1999, smellmelon produced 60 g of stem dry weight per plant, and it increased to 75 g in 2000. Optimum germination temperature for smellmelon coincides with those for many annual crops. These data indicate that smellmelon germination and emergence can occur under a wide variety of environmental conditions. On the basis of biomass production values, smellmelon may also be a very efficient competitor with many cultivated crops.