common periwinkle "Bowles"

These plants grow well in sun or in partial shade. Usually they tolerate more sun and heat if given enough moisture; in partial or light shade they need less moisture.

Herbaceous plants are not woody. Their stems are soft, usually remaining green. With some herabceous older stems may harden and look like woody stems (e. g. bamboo).

Leaves or needles remain on the plant for several consecutive years, usually 2 to 5 years. Our descriptions contain the word evergreen.

Plant can in otherwise appropriate environment survive cold down to - 23 °C.

Porous or dry soils are normally light and loose, there is no stagnant water but relatively quickly flows in deeper layers; such ground are more airy and warmer, yet drier and usually contain less humus and for such undergrowth it is often to for drought to appear (e. g. rockgardens, walls, by paths and roads, on gravel, also on gravel surface in towns and close to buildings ...), plants of such undergrowth need well-drained soil, they tolerate drought but cannot tolerate constant moisture or even flooding.

Herbaceous, not woody plant. Stems and leaves may be evergreen or deciduous - thus regrowing every spring. Perennials may blossom consecutively for several years. Some perennials develop special underground organs - bulbs, corms or rootstocks and these species are treated separetelly, not with geophyte and tuberous plants.