Reproduction of the swamp cypress
The swamp cypress (Taxodium distichum (L.) Rich., 1810) is a conifer of the Cupressaceae, native to the southeastern United States where it grows in lowland woods with a mild oceanic climate, along river courses or in marshy areas. This plant was introduced to Europe in the mid-17th century.
Suitable breeding habitat –
The swamp cypress is a plant of southern and eastern North America, present in an area ranging from New Jersey to Florida, also from southern Missouri and Illinois to Alabama, Texas, Mexico and Guatemala.
Its habitat is that of wetlands and sites that are underwater for at least part of the year; it is often present on overhanging calcareous soils and frequently also where the water is brackish, at low altitudes in the temperate zone but which gradually rises up to about 2,000 meters or more as it moves towards the tropics.
Taxodium distichum is a temperate to tropical plant that grows best in areas where annual daytime temperatures are between 20 and 30 ° C, but can tolerate 8 – 34 ° C.
When the plant is dormant it can survive temperatures as low as about -10 ° C or more depending on where it comes from, but young plants or new sprouting can be severely damaged at -1 ° C.
The plant prefers an average annual rainfall in the range 1,200 – 1,400 mm, but tolerates 1,000 – 1,600 mm, and also grows best in areas with hot summers.
Although this plant can be grown in moist soil and shallow water, it thrives in any soil and trees actually grow faster in normal non-flooded soil.
From the pedological point of view it prefers a pH in the range 5.5 – 7, tolerating 4.5 – 8.5; it also tolerates air pollution and plants are tolerant of occasional very strong winds.
Propagation occurs by seed with sowing to be carried out at the end of winter in a cold seedbed. When they have reached the size that they can handle they should be planted in individual pots and grown in a greenhouse for at least their first winter. The definitive transplant must be carried out in late spring or early summer, after the last foreseen frosts.
It is also possible to prepare cuttings from branches in vegetation in the late summer period; the rooting is good.
The spread of Taxodium distichum occurs mostly through seeds which remain viable for less than a year and are dispersed in two ways. One is via the water: the seeds float and move on the water until the flood recedes or the cone settles on the shore. The second is by means of wildlife: squirrels eat the seeds, but often drop some scales from the cones they collect. The seeds do not germinate underwater and rarely germinate on well-drained soils; the seedlings usually settle on continuously saturated but not flooded soils for one to three months. After germination, the seedlings must grow rapidly to escape floodwaters; they often reach a height of 20-75cm (up to 100cm in fertilized nursery conditions) in their first year. Seedlings die if flooded for more than two to four weeks. Natural regeneration is therefore prevented in sites that are always flooded during the growing season. Although vigorous saplings and stump shoots can produce viable seeds, most specimens do not produce seeds until they are around 30 years old. In good condition it grows quite fast when young, then more slowly with age.
Taxodium distichum growing in swamps have a growth feature called cypress knees. These are woody projections of the root system above the soil or water. It was once thought that their function was to supply oxygen to the roots, which grow in the poorly oxygenated dissolved waters typical of a swamp (such as in mangroves). However, there is little scientific verification; in fact, the roots of the marsh specimens whose knees are removed do not diminish in oxygen and the trees continue to thrive. Another more likely function is structural support and stabilization. Taxodium distichum trees growing on flood-prone sites tend to form reinforced bases, but trees grown on drier sites may not have this feature. Reinforced bases and a strong intertwined root system allow them to withstand very strong winds; even hurricanes rarely eradicate them.
Regarding its conservation status, in 2002, the Indiana Department of Natural Resources identified T. distichum as a protected plant as threatened. Globally, the species is listed as Least Concern by the IUCN.