Gymnosperms are plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before and after fertilisation. Consequently, the seeds that develop are naked and not covered. These plants generally include medium-sized trees, tall trees, or shrubs, such as the giant redwood tree Sequoia.

The plant body possesses distinct roots, stems, and leaves. The roots are generally tap roots. Some genera have fungal associations in the form of mycorrhiza (e.g., Pinus), while others like Cycas have specialized coralloid roots associated with N$_2$-fixing cyanobacteria. The stems may be unbranched (Cycas) or branched (Pinus). The leaves are well-adapted to withstand extremes of temperature and wind; in conifers, needle-like leaves with a thick cuticle and sunken stomata help reduce water loss.

Gymnosperms are heterosporous, producing haploid microspores and megaspores within sporangia. These sporangia are borne on sporophylls, which are arranged spirally along an axis to form compact cones or strobili. The microsporophylls form male cones, while megasporophylls form female cones.

Unlike bryophytes and pteridophytes, the male and female gametophytes in gymnosperms do not have an independent free-living existence and are retained within the sporangia on the sporophyte. The pollen grain is released and carried by air currents to the ovule. The pollen tube releases the male gamete into the ovule, where it fuses with the egg cell in the archegonia. Following fertilisation, the zygote develops into an embryo and the ovules develop into naked seeds.