More info for the terms: bog
, breeding system
, root crown
Sweetbay reproduces sexually through seed production and seedling establishment [51,102] and regenerates asexually by root and/or root crown sprouts following top-kill [111,137].
Pollination and breeding system: Sweetbay produces perfect flowers . No additional information on pollination or breeding system was available in the literature (2008).
Seed production: General statements on sweetbay seed production vary, and specific numbers were rarely reported. A review reported that sweetbay produced "good seed crops practically every year under normal conditions" and seed occurred on trees as young as 10 years old . Halls  reported that sweetbay produces seed annually but yields may be small. Little  also reported that sweetbay produces seed annually but "in what would seem to be abundant amounts". Sweetbay stems of sprout origin produced "appreciable amounts of seed when stems were only 1 inch in diameter".
Seed production may be affected by associated vegetation, shading, disturbance history, and/or population distribution; however, there are too few sweetbay seed production studies to determine which factors affect production most. Sweetbay seedlings planted in a thinned shortleaf pine (Pinus echinata)-loblolly pine stand in eastern Texas produced fruit at 6 years old in open sites but failed to produce fruit by 9 years old when beneath trees. Fruit yields were "never very large"; a maximum of 20 g of fruit was produced/plant . In the northernmost sweetbay population in Massachusetts, only 33% of the population produced fruits . Sweetbay failed to produce fruit in 3-year-old and recently burned slash pine plantations in southeastern Georgia. Burned plantations were 16 to 30 years old and visited 2 years after fire. Fire severity was not described. Researchers suggested that harvesting, fire, or shading in older stands may have affected fruit production .
Seed dispersal: Sweetbay seeds are likely dispersed by mammals, birds, heavy rains, and/or gusty winds [72,75,115].
Seed banking: Information on sweetbay's seed bank persistence and importance is lacking. In the few available seed bank studies, sweetbay was not dominant and did not emerge from soil samples. Although present in highly disturbed and undisturbed longleaf pine (P. palustris) stands on poorly drained soils in the Croatan National Forest, sweetbay seedlings did not emerge from any soil samples . In the Welaka Research and Education Center in north-central Florida, sweetbay made up 0.8% of the relative tree density, 0.4% of the relative basal area, and 0.04% of the relative seedling density but did not emerge from substrate samples collected in February and August from a variety of microsites .
Germination: Different findings were reported from the few studies of sweetbay seed germination. For sweetbay seeds collected on 13 October from Glouster, Massachusetts, time required to germinate decreased and germination percentages increased as exposure time to cold temperatures increased :
Germination time and percentages with increasing duration of cold exposure for sweetbay seeds [28
] Days of cold stratification Days to germinate Percent germination 0 60 12 14 57 14 27 42 80 42 34 84 58 33 93
Sweetbay seeds collected in the fall from southern New Jersey pine barrens germinated slowly and with low percentages. Seeds exposed to cold germinated at a lower percentage than those without cold exposure. Germination was 3% after 169 to 440 days with cold exposure and 15% after 78 to 420 days without cold exposure . Information from literature reviews, observations, and studies by Little  suggest that germination of sweetbay seed is often slow. When 100 sweetbay seeds collected in New Jersey were cut open, about 90% had embryos, but germination in the greenhouse was less than 18% .
Seedling establishment/growth: Sweetbay seedlings tolerate shading and typically develop in the understory of hardwood or conifer stands. Continued flooding and extended dry periods are not tolerated. A review reports that partial shading of first-year seedlings may increase sweetbay establishment but that regeneration is often best in natural openings or clearcuts. Generally, seedlings survive if there is not an "extended period" of inundation. Height growth of 12 to 24 inches (30-60 cm) is possible in the first year . In the northernmost sweetbay populations, seedlings were absent, even though about 33% of the population produced fruits .
Shading: Sweetbay seedlings often establish in the shade of pine and hardwood forests. In a greenhouse study, sweetbay seedlings in medium and heavy shade produced heights and taproot lengths similar to those of seedlings grown in light shade. Above- and belowground biomass and total root length were, however, negatively affected by shading. In heavy shade, total root length and root weight were 27% and 21%, respectively, those of seedlings grown in light shade :
Sweetbay seedling growth as a proportion (%) of seedlings grown in light shade (30-45% full sun) [71
] Attribute measured Medium shade
(12-25% full sun) Heavy shade
(6-16% full sun) Seedling height 93 99 Oven-dry weight of aboveground portion 49 45 Taproot length 97 94 Total root length 51 27 Oven-dry root weight 33 21
Sweetbay seedlings may occur in open, regenerating, and mature forest stands. On Bradwell Bay, Florida, sweetbay seedlings occurred on every transect sampled in an open, old-growth slash pine stand. Slash pine trees over 98 feet (30 m) tall dominated the canopy, and swamp tupelo and sweetbay saplings up to 39 feet (12 m) dominated the midstory . Abundant sweetbay seedlings (1,600-3,600 stems/acre) were produced in lowland forests of New Jersey receiving 1.3% to 17.7% of full sunlight. Seedling density was much lower (400 stems/acre) in an abandoned cranberry bog where light levels were 38.3%. Light intensities were measured at the seedling layer (about 4 inches (9 cm) above the soil surface). Studies showed that sweetbay saplings were also shade tolerant .
Moisture: Too much or too little water can reduce sweetbay seedling establishment. In bottomland hardwood forests on the floodplain of South Carolina's Upper Three Runs Creek, there were 0.32 sweetbay seedlings/mÂ² on unflooded sites but none on flooded sites. Flood events (overland water for 1-6 days) occurred 41 times at flooded sites and did not occur at unflooded sites. Mature sweetbay trees were also lacking in flooded areas . On an experimental tree island in Palm Beach County, Florida, 6-month-old sweetbay seedling transplants suffered high mortality during dry conditions. The island was above water for 2 months after planting, and researchers suggested that the low water table was the reason for sweetbay seedling survivorship of 3% or less .
Aboveground sweetbay seedling growth was relatively unaffected by water levels up to 6 inches (15 cm) below the soil surface in a greenhouse study. However, roots were heavier and larger where the top water level was lower .
Vegetative regeneration: Sweetbay sprouting after top-kill has been described as vigorous , and sprouts may originate from roots, root crowns [111,137], and/or lignotubers . While sprouting after stem damage is the most common type of vegetative regeneration by sweetbay, regeneration in the northernmost Massachusetts population occurred through the rooting of stems bent to the ground. New sweetbay clumps were found at 10-foot (3 m) distances from parent clumps. The largest sweetbay tree in the area produced 104 stems .
Sweetbay was described as "a particularly strong sprouter, producing large and vigorous sprouts on almost every stump" after cutting in a swamp tupelo-dominated floodplain in Alabama's Escambia River basin. Sweetbay stumps ranged from 3 to 50 inches (7.6-127 cm) in diameter, and larger stumps produced more sprouts (P=0.024). Two years after cutting, sweetbay averaged 11.5 sprouts/stump, and 8 years after cutting, sweetbay averaged 11 sprouts/stump. Eight years after cutting, the tallest sweetbay sprout measured 20 feet (6 m) .