UNITED STATESA plant that is an annual lives less than a single year. One that produces vegetative foliar growth one year, and then blooms and produces seed the next year is a biennial. Technically, any other plant that lives any longer is a perennial. That certainly does not narrow down the definition much. Therefore, the term ‘perennial’ used in home gardening typically describes plants that live more than two years, but also lack woody stems like those that trees, shrubs and vines are equipped with.Even this definition is rather vague. Palm trees lack real wood, so are described as perennial trees! Many deciduous perennials die back to the ground and do not seem to be present during part of the year. Some perennials perform only for a few years and then die unexpectedly. Monocarpic perennials that are grown for their distinctive foliage bloom only once, and then promptly die.

Some of the tougher perennials last indefinitely. As they mature, many need to be divided so that they do not get too crowded to bloom. Division to improve performance also makes more copies of the same perennials that can be shared with friends and neighbors until they conquer the neighborhood! Lily-of-the-Nile, African iris (fortnight lily), New Zealand flax and various aloes are the most familiar. Agaves and some clumping yuccas are difficult to work with, but behave almost like less prolific aloes.

Many of the more docile perennials like Shasta daisy, canna, gazania and some ferns are just as easy to propagate by division during their respective dormancy cycles. Others, like geranium (pelargonium), Richmond begonia and all sorts of succulents, are easier to propagate from cuttings. Monocarpic agaves that seem to die after bloom actually develop pups (sideshoots) as their own replacements! Hardy bulbs like daffodil and watsonia are sometimes best if left alone as long as possible, and only divided if they get too crowded to bloom.

Although there are many tender perennials, and many like busy Lizzie and cyclamen that are grown as annuals, many others can be around for a long time. They are generally easier to propagate than trees, shrubs or vines, and are easier to relocate if necessary. As much as I hate to use cliché, perennials are quite sustainable.

Highlight: Hosta

Not every garden can accommodate the luxuriant foliage of hosta. The tender roots and rhizomes need rich soil and regular watering. Even if grown in posh containers, the broad leaves need partial shade. Big plants happen to be striking in pots where their broad leaves can flare back and hang over the edges. In the ground, hostas are distinctive understory plants for Japanese maples and large rhododendrons that lack lower foliage.

Leaves of the largest varieties of hosta can be almost a foot wide and more than a foot long. Yet, miniature types form small clumps of foliage only a few inches wide. Some have glaucous foliage that is quite blue. Some are chartreuse. The most popular varieties have bold yellow or white foliar margins or centers. The small and pendulous flowers that hover in loose trusses above the foliage this time of year are an added bonus. Bloom is almost always white or pale purple, but a few varieties have blue or darker purple flowers.

By Tony Tomeo