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Ornamental or utility value
the giant-sequoiaceae (Sequoiadendron giganteum) or mountain-sequoiaceae is the only living representative of the type Sequoiadendron from the family of the Sumpfzypressengewächse (Taxodiaceae). His home is the western mountain slopes of the Sierra Nevada in California, where he is known as “Giant Redwood”. It can be found at altitudes of up to 2,500 metres. Since the middle of the 19th century, the sequoia tree has also been found again in Central Europe, where it was already native before the Ice Age. There it was used as a park and landscape tree as well as in experimental extensions for forestry. In its natural range, however, the sequoia is threatened with extinction and is a protected species.
The evergreen sequoia is different from its siblings, the primeval sequoia and the coastal sequoia, also hardy here. It shows several characteristics in its growth. As the name suggests, the sequoia is a real giant and is considered the largest plant on earth in terms of plant mass. In addition, it forms not only a high, but also a very thick trunk. The most impressive living representative of its kind is the “General Sherman Tree” in Sequoia National Park with a height of 84 metres and a trunk diameter of over eight metres, resulting in a trunk volume of almost 1,500 cubic metres. In our latitudes, however, the sequoia tree rarely reaches its final height. It carries a narrow cone-shaped crown, with what the straight trunk often remains knotless up to big heights. Sequoia trees live to be over 3,000 years old and weigh up to two and a half thousand tons when fully grown. The sequoia tree is a so-called pyrophyte, which means that its fibrous, thick, resin-free bark is structured in such a way that it can protect the tree from forest fires. Burns to the tree heal almost completely after a few years. The root system of the mammoth tree is flat and can form a radius of 30 metres. The tree owes its characteristic reddish brown bark the English name “Redwood”.
The scale-like needles of the mammoth tree wind spirally in three rows around the branch. They are blue-green at first, later dark green in color and taper at the front. The narrow sequoia needles can grow up to one and a half centimeters long and are renewed every three to four years.
In view of its long life span, the sequoia tree becomes fertile very early at about ten years of age. On a tree there are both the inconspicuous green male and the yellow female flowers. The female flowers are cone-shaped and stand upright during flowering. Pollination is by the wind.
The cones ripen one year after fertilisation, are about eight centimeters long and ovoid. They contain the ludicrously small seeds of the sequoia tree, three to six millimetres in size. Young cones are green and stand upright, mature cones hang downwards. The cones of the mammoth tree are not only adapted to regular dry periods and forest fires, but even need them to release their seeds. They only open after heating, so that the seeds fall on fertile soil on which no other plants can compete for light or roots. This ensures that the sensitive plants have sufficient time and resources to establish themselves.
The sequoia loves a humid climate. It needs hot, dry summers, which are replaced by snowy winters. He also needs a reliable water supply. Waterlogging does not get the tree against it. The pitch should be sunny to semi-shady or sunny.
The right soil must be deep and rich in nutrients, as well as permeable and loose – the sequoia tree reacts sensitively to soil compaction. The soil may contain as little lime as possible.
When planting, pay attention to the large space requirement of the mammoth tree, both in width and in the root area. The planting hole should be three times the size of the root ball. Loosen the soil well and improve heavy loamy soil with some gravel or sand. Insert the sequoia just as deeply as it stood in the pot. After planting, scum the tree. A watering rim around the root disc also helps with later watering. A mulch layer reduces evaporation. Young trees should be given a light winter shelter after planting.
The sequoia tree is easy to care for and actually extremely frugal. As long as the water supply is secured, he does not need any further care. But beware: A sequoia requires considerable amounts of water and its extensive root system can also draw water from nearby plants. Therefore, make sure that the tree is permanently watered and that your neighbours are insensitive.
Regularly remove dead wood from your sequoia. Otherwise the tree will not be pruned.
Due to its size, the sequoia is only suitable for large gardens, where it is usually planted as a solitary tree. In extensive green areas and parks you can sometimes see it planted in small groups as a grove.
Since sequoia trees are much less vigorous in our latitudes than in the USA, some breeding forms are quite suitable for the domestic garden. The variety Sequoiadendron giganteum ‘Glauca’ is much weaker than the wild variety. A very low form of the mammoth tree with only 20 meters is the variety ‘Aureum’. It stands out due to its golden-yellow shining shoot tips. Pendulum’ is an almost 30 meter high, narrow columnar cultivar with a curved main shoot and wavy trunk.
A sequoia is grown from seeds. These must first be cooled, but need very warm temperatures to germinate. A heating mat or a heatable mini greenhouse is recommended for this purpose. Stratify the seeds in the refrigerator for about two weeks and then let them soak in some water. Finally, sow the light bucket in a seed tray, dust lightly with soil, cover with foil and keep moist. In a very warm, bright place without direct sun, the seeds germinate soon. Then convert the mini trees into single pots. However, it takes a few years until the sequoia is about one metre tall enough to move into the garden.
Diseases and pests
The sequoia tree is resistant to diseases as far as possible, only from time to time fungi spread on the tree. He suffers greater impairment from storms and lightning strikes, as his crown is very exposed due to its height. In winter the sequoia tree can suffer from snow breakage when there is a lot of snow and from frost dryness when there is no snow.