Hart's pennyroyal "Alba"

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).

The plant develops new leaves or needles every spring, which dropp off in autumn. Herbaceous plants can die completely in above ground section and grow back in the spring.

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

Wet soils are normally heavier, loamy or even clay, also peat soil and soil rich in humus, soil by watercourses and on swampy terrain. These are mostly less airy or even not airy enoguh for most plants, they are always wet or even saturated with water; water stagnates, only slowly flows away. Plants of such undergrowth do not tolerate drought, in neccessary need of permanent moisture, tolerate inundation, some can grow in shallow water (up to 5 cm in depth) or in garden bed, when watered regularly.

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.