Small, olive-green cones are hidden between the needles of the sequoia. They are particularly valuable for propagation because they contain the seeds. They also serve as food for wild animals and have long aroused the interest of researchers.
A sequoia bears several thousand cones per year
Structure of the sequoia cone
The cone of a sequoia has the following properties:
- Length: up to 8.5 cm
- Width: up to 5.5 cm
- Shape: obtuse and ovate
- Colour: olive green, later turning brown
- Quantity: 10,000 to 30,000 cones on a tree
- woody and fall down in autumn
- occur singly or in groups
- upright growth at flowering time
- mature cones hang down
Propagation by the cones
The cones of a sequoia contain the seeds with which it reproduces. In order to better understand how a sequoia cone releases seeds, it makes sense to first look at its structure.
Construction of a sequoia cone
A sequoia cone has about 25 cone scales. These are arranged in a spiral and carry the ovules, which in turn are arranged in two rows. They have the task of forming pollination drops with which Sequoiadendron giganteum reproduces (see below). These pollination drops hide deep inside the cone.
pollination and seed shedding
The sequoia has two natural pollinators:
- the wind
- and the Douglas squirrel
On the one hand, the cones catch pollen carried by the wind. If these meet the pollination drops inside the cone, fertilization takes place.
Likewise, the Douglas squirrel, which uses the cones for food, carries the seeds from tree to tree.
In addition, Sequoiadendron giganteum is one of the monoecious plants. This means that the tree has both male and female flowers, so it can pollinate itself.
At high temperatures, the cones dry out. This causes the ovules to open and release the seeds. Forest fires in particular, which are not uncommon in Western America, the homeland of the sequoia, cause this process. In this case, the unripe, green cones also release their seeds.
Contrary to what you might suspect, the fire is having an extremely positive effect on the development of the sequoia population. While the thick bark protects the trunk, the fires make the soil arable and provide sufficient light through the death of neighboring plants. This creates the best conditions for the germination of the dropped seeds.
Sequoia cones in the focus of research
In order to artificially increase the population of sequoias, scientists harvest their cones from the treetops. The mostly unripe tree fruits are then heated up so that they open and release the seeds. On the one hand, the seeds are used for experimental purposes, in order to obtain more precise information about the giant tree, on the other hand, they are commercially available or sold to tree nurseries, so that you too can soon enjoy your own sequoia in your garden.