Ornamental bulbous plants, often called ornamental bulbs or just bulbs in gardening and horticulture, are herbaceous perennials grown for ornamental purposes, which have underground or near ground storage organs. Botanists distinguish between true bulbs, corms, rhizomes, tubers and tuberous roots, any of which may be termed "bulbs" in horticulture. Bulb species usually lose their upper parts during adverse conditions such as summer drought and heat or winter cold. The bulb's storage organs contain moisture and nutrients that are used to survive these adverse conditions in a dormant state. When conditions become favourable the reserves sustain a new growth cycle. In addition, bulbs permit vegetative or asexual multiplication in these species. Ornamental bulbs are used in parks and gardens and as cut flowers. The word "bulb" has a somewhat different meaning to botanists than it does to gardeners and horticulturalists. In gardening, a "bulb" is a plant's underground or ground-level storage organ that can be dried, stored and sold in this state, and then planted to grow again. Many bulbs in this sense are produced by geophytes – plants whose growing point is below ground level. However, not all bulbs in the gardening sense are produced by geophytes. For example, rhizomatous irises are included in books on ornamental bulbs, but their growing points are above ground. Many bulbs are produced by lilioid monocots, but not all lilioid monocots have bulbs. Brian Mathew says that "we just have to accept that there is no accurate term which we can use for this group of plants and we are left with 'bulbs' as the snappiest and most convenient." Botanically, gardeners' "bulbs" may be true bulbs, corms, rhizomes or tubers, or combinations of these. Bulb A true bulb (i.e. a bulb in the botanical sense) is an underground vertical shoot that has modified leaves (or thickened leaf bases) that are used as food storage organs by the plant. The bottom of the bulb is made up of a short section of stem forming the basal plate.