The Love Life of Urtica dioica

Urtica dioica is a perennial, flowering plant that blooms from summer into late fall. It produces small green flowers in clusters on strands that are about 3 inches in length.  These strands are attached to the leaf axils between the stem of the plant and the stem of a leaf. The nettle produces both male and female flowers. The male flowers grow in smaller, loose clusters called racemes that are positioned near the top of the plant. The male plant contains four sepals at each leaf axial and the raceme is contained within these sepals during the bud stage. When the plant reaches maturity the racemes uncurl and spring out, exposing the stamen and allowing them to fling their pollen into the wind.

The racemes remain pointed upward for the duration of the plants flowering stage. The female flowers grow in more dense, strand-like clusters off of the leaf axils. Many of these strands grow out of each leaf axial and droop downward. Often there are so many flowers that a portion of the stem is covered. Each flower contains an ovary with a single seeded carpel, a style and a stigma surrounding it. When a grain of pollen is blown into the wind to a female flower, the stigma captures the grain and it travels down to the ovary. The plant is pollinated once the pollen reaches the ovary where it then grows into a small fruit. This fruit contains the only seed produced by each flower of the stinging nettle. The fruit eventually dries and the seed is blown off of the plant to grown into a new individual.

The stinging nettle is a flowering plant that, like all plants, exhibits alteration of generations. The pollen produced by the male flowers is haploid (1n) meaning that it contains one set of chromosomes. Similarly, the ovary within the female flower is haploid (1n). When these two gametes meet, fertilization occurs and the fertilized gametes become one diploid (2n) organism called a zygote. The zygote then undergoes mitosis to create a multicellular diploid (2n) organism called a sporophyte.The sporophyte then undergoes meiosis to produce haploid (1n) spores. These spores will become either the stepal or ovary portion of the plant once it is mature. The mature plant is called a gametophyte and is a result of the spores becoming multicellular haploids (n). This mature plant can then produce haploid (1n) gametes in the form of pollen if it is a male plant and ovaries if it is a female plant. The then cycle continues.

Below is the alternation of generations life cycle that plants, including Urtica dioica, undergo.

Learn how stinging nettles interact with other organisms.