The bald cypress belongs to the Taxodiaceae family, and is a conifer native to swampy areas in Florida and the Gulf of Mexico, where the Mississippi branches into a network of channels. Areas that are flooded for long periods and where water reaches high levels, are usually colonised by evergreen, deciduous broadleaf and deciduous conifer woodland with three Taxodium species.

Bald cypresses are huge trees which may reach 40 metres, with reddish-brown bark, buttressed trunks, pyramidal heads, and leaves which turn red in autumn, still attached to the young shoots, and then fall, covering the surrounding ground. Their most peculiar characteristic is their root system, which grows deep into stagnant, poorly oxygenated mud, and sends woody projections (even quite far from the trunk), called “knees”, above the waterline. These may reach 2 metres and are specialised structures, also called pneumatophores. They have a specialised anatomical structure with pores (lenticels) in their bark, enabling air to enter and circulate in the roots through air spaces connected to the submerged parts, and reach the underwater tissues. Due to their love and need of water, bald cypresses are common in historic parks and gardens of the Po Plain, and along channels, ponds and small lakes, from which their respiratory roots emerge. In spontaneous woodland, the branches of bald cypresses and other trees are clad with hanging tufts and festoons of Spanish moss (Tillandsia usneoides L.), which are their only decoration in winter. Despite its name, this is not a type of moss, but an epiphytic Bromeliacea with flexible, threadlike stems (sometimes used, dried, as a substitute for horsehair). Various members of the Bromeliaceae (pineapple family) are used as ornamentals and, in Padova, may be seen in winter in the greenhouse bearing their name. The Botanical Garden hosts a few ancient specimens of bald cypresses, one in the quarter with plants from the Euganean Hills, near the south gate, and three near the entrance (Ponte delle Priare), along the canal, bearing visible pneumatophores. Along the same canal is a fourth specimen, which is slightly different from the others in that its coriaceous pine cones are not oval but round. It belongs to a different species, Taxodium ascendens Brongn. Near the entrance bridge is a spiny cryptomeria, or Japanese cedar (Cryptomeria japonica G. Don), of the Taxodiaceae family which, in cold temperate areas of the central Japanese islands, lives in humid beech woodland with oaks, ashes, maple trees and sorbs. This plant in the Botanical Garden of Padova is particularly interesting from the historical viewpoint, because in 1850 it was the first specimen brought to Italy. Today, this columnar tree, with reddish-brown bark and pyramidal head, is grown in southern Italy for reafforestation purposes, but it is also frequently cultivated in parks and gardens for the beauty of its needle-like evergreen leaves, which change colours with the seasons, from pale to blue-green, then violet in winter. Its pollen is highly allergenic. The Taxodiaceae are one of the most interesting conifer families, fossils of which date back 150 million years. They are presently scattered, and their populations are the remains of larger groups of the Tertiary epoch. They have persistent or deciduous needle- or scale-like leaves spiralling along branches and woody cones. The leaves of deciduous plants (Taxodium and Metasequoia) are inserted in short, lateral shoots – brachyblasts – with which they fall in autumn. The Arboretum also hosts two Taxodiaceae that may be considered, like ginkgo and dawn redwood, two living fossils: California redwood [Sequoia sempervirens (D. Don) Endl.] and big tree [Sequoiadendron giganteum (Lindl.) Buchholz]. California redwood produces a valuable reddish timber and is a typical species in woodland mixed with deciduous broadleaf trees of the western coast of the United States, from California to Oregon, where it is protected from excessively cold temperatures by the nearby ocean and is provided with water from fog, which is frequent even in dry summers. It forms spectacular woods, many of which are protected (National Park north of San Francisco), and is particularly impressive when its trees grow in dense, columnar shapes, like true vegetal monuments, the tops of which soar up in the sky. It is a long-lived species (the oldest tree is over 2200 years old) and, together with eucalyptus, may grow to the maximum height of the vegetal kingdom (110-115, up to 137 metres). Big trees form gigantic woods in parks (Yosemite National Park and Sequoia National Park) in the western Sierra Nevada in California. They are very tall and slightly less long-lived than redwood (although many specimens exceed 1500 years in age). They are never as tall as redwoods (maximum 100 metres), but their buttressed trunks may have a circumference of 12 metres. The two species are clearly different, owing to the characteristics of their leaves. Redwoods have linear, flat leaves, yellowish-green on the underside, and arranged in two rows. In big trees, leaves are arranged in three rows and are smaller, oval and blue-green, turning to brown after two or three years. Female cones in redwoods have a small number of scales, are erect and grow each year, followed by seed dispersion. Big trees, instead, have larger cones that mature every two years (they start hanging from the second year, but do not grow any larger) and, unlike any other conifer, their cones never open to release the seeds, which may be preserved for even 20 years before germinating. In the Arboretum, near and outside the circular wall, between the south and west gates, is an ultra-centenarian redwood, easily identified by the two large cables supporting it: in the late 1900s, it was struck by lightning twice, which reduced its stability and damaged a large portion of its canopy. However, it is still quite tall and keeps its towering shape, because its branches are not very long and the canopy is therefore dense. The Arboretum also houses one specimen of big tree, between the south and east gates. It is young, and not very large yet, but its presence is important for teaching purposes.