What Are Perennials? Identifying Garden Perennials and Why They Fail to Return

This is precisely where the appeal of perennials begins: plants that return year after year, without needing to be replanted each time. But what exactly qualifies as a perennial, how do they differ from annual plants, and why do some supposed “long-flowering plants” fail to come back after all?

What Perennials Really Are – and What They Are Not

In the broadest sense, any plant that lives for more than two years is perennial. By that definition, every tree and shrub would also belong in this category. In everyday gardening, however, the term “perennial” generally means something more specific.

In practical gardening, perennials are plants that die back above ground in autumn and produce fresh growth in spring from roots, tubers or rhizomes.

Common examples include hostas, delphiniums, daylilies, coneflowers and peonies. During winter, they are usually nowhere to be seen above ground, as they wait below the soil for spring to arrive.

Annual, Biennial and Perennial Plants: The Life Cycle Matters

A quick look at the three main groups of garden plants makes it easier to place perennials correctly:

• Annual plants: They germinate, grow, flower, produce seed and die within one growing season. Examples include calendula, zinnia and basil.
• Biennial plants: During their first year, they mainly form leaves; they usually flower in the second year before dying. Examples include foxgloves and hollyhocks.
• Perennial plants (perennials in the broad sense): They survive for several years and often return to flower regularly.

Garden practice makes the distinction less clear-cut. Many gardeners treat certain perennial species as annuals because they become less attractive over time or cannot tolerate frost.

Woody or Herbaceous: An Important Difference

Whether a plant is woody or not is central to deciding whether it is a perennial in the usual garden sense.

Over time, trees and shrubs develop layers of dead, lignified tissue: what we know as wood. Only the youngest layers beneath the bark carry water and nutrients. Since producing wood requires a plant to persist for several years, the following rule applies:

Every woody plant is perennial – but not every perennial plant is woody.

This also includes very small woody plants. Blueberries and certain dwarf shrubs may grow only a few centimetres tall and can look almost like herbaceous perennials, but botanically they are woody plants.

Traditional garden perennials, by contrast, are herbaceous: their shoots do not become permanently woody. In autumn, they usually die back to just above ground level, while their underground parts survive the winter.

Herbaceous Perennials: Hidden Energy Below Ground

Many favourite garden plants fall into this group. They retreat in autumn, but first build up reserves of energy in their roots, tubers or bulbs. These reserves fuel their new growth the following spring.

Bulbs, Tubers and Rhizomes: Small Storage Powerhouses

Understanding how perennials store their energy makes them easier to recognise, particularly when there is still no growth visible above ground.

• Bulbs: Layered storage organs, such as those of tulips, daffodils and ornamental alliums. They hold nutrients for the following year’s growth.
• Tubers: Thickened root or stem sections, as found on dahlias and potatoes.
• Rhizomes: Underground horizontal stems, as found in irises and many grasses.

Where there is a strong bulb, tuber or rhizome, there is almost always a perennial plant behind it.

Annual species, on the other hand, invest chiefly in seed. They must secure the next generation within a single season, so elaborate storage organs offer them little benefit.

Garden Grasses: A Lasting Lawn Rather Than a Disposable Plant

Grasses can be either annual or perennial. For lawns and most ornamental gardens, it is chiefly perennial varieties that are used – a lawn that vanished after one year would be a nightmare for most homeowners.

Some native prairie grasses, such as switchgrass and mosquito grass, are typical perennial species that gradually form dense clumps. Many ornamental grasses can remain in borders throughout the year, with their dry stems giving the winter garden structure.

When Perennials Do Not Return: The Most Common Misunderstandings

Garden forums are full of questions such as, “My tulips have disappeared – weren’t they perennials?” The answer is often more complicated than expected.

Problem	Possible cause
Perennial produces no new growth at all	Waterlogging, rot, voles or exceptionally severe frost
Leaves appear but there are no flowers	The bulb or root is exhausted, nutrients are lacking, or the site is unsuitable
Plant becomes weaker every year	Persistent overfeeding, overcrowding or unsuitable care

Tulips in particular are frequently sold as perennials, yet in gardens they often behave more like annuals. Many modern varieties use so much energy in their first year to produce large, spectacular flowers that there are scarcely enough reserves left for a strong display in the second year.

Anyone who wants to keep tulips for many years needs free-draining soil, restrained watering after flowering and a generous dormant period.

Pansies are another classic example. Botanically, they are perennial plants. By their second year, however, they usually look less appealing, flower less freely and may become partly woody. For this reason, most gardeners treat them as annuals and replace them regularly.

Hidden Perennials: Plants That Are Perennial but Grown as Annuals

Several familiar food crops come as a surprise to many amateur gardeners: in their natural habitat, they are perennial, but here they are usually grown for only one season.

• Tomatoes: In their tropical place of origin, they are perennial plants, but they cannot survive winter outdoors in Central Europe.
• Sweet peppers and chillies: These are also perennial and can be kept growing in winter quarters.
• Potatoes: They produce tubers from which they could sprout again, but in agriculture they are replanted every year.

In a greenhouse or indoors, keen gardeners can genuinely keep tomato plants for several years. Although yields often decline, the plants may continue to produce fruit for a long time.

“Volunteer” Plants: Reliable Returners or Just a Chance Discovery?

Anyone who has gardened for a while will know the sight: a tomato suddenly appears among the carrots, or a sunflower springs up in the middle of a border. These plants grow from seeds that fell into the soil the previous year and then germinate when conditions are favourable.

Such “volunteers” may look like perennials, but they are actually new plants grown from fresh seed.

Typical self-seeding specialists include:

• Tomatoes
• Squash and courgettes
• Melons
• Beans
• Sunflowers

In a vegetable patch, this can be a welcome bonus – who would not be pleased by a free extra tomato? In an ornamental garden, though, these visitors should be kept under control, otherwise they may crowd out planned planting schemes.

A Practical Guide to Recognising Perennials in Your Own Garden

Gardeners new to the hobby often stand in front of bare beds in spring and wonder what, if anything, is still alive. A few rules of thumb can help:

• Mark plants in autumn: Use small canes to identify where perennials are growing when their foliage dies back completely.
• Check the texture: If a shoot feels woody, it is more likely to belong to a shrub or subshrub, such as lavender or rosemary.
• Look below ground: If careful digging reveals bulbs, tubers or thick root sections, this strongly suggests a perennial.
• Keep plant labels: Rather than throwing away labels from the garden centre, save them to keep track of your plants.

One useful tip for impatient gardeners: many perennials are late starters. Coneflowers, cranesbills and some grasses in particular can take their time before producing new shoots. Removing them too early in a panic often means losing well-established plants.

Getting More From Perennials: Medicinal Plants and Lasting Flavour

Many plants commonly called “herbs” are actually perennial plants or subshrubs. Place them well once, and they can be enjoyed for years.

• Echinacea (coneflower): Popular as a medicinal plant and a magnet for bees.
• Yarrow: A tough wild perennial with many uses, including tea and cut flowers.
• Mint: A vigorous perennial that will readily take over an entire bed unless it is regularly contained.

Mint clearly demonstrates just how forceful perennials can be: planted directly into a border, it can soon create a veritable carpet. A large pot or a buried root barrier is the better option.

For beginners, a combination of robust, dependable perennials – such as daylilies, lady’s mantle and purple coneflowers – together with a few more experimental species is worthwhile. Over the years, not only does the border grow; so too does your knowledge of the garden’s quiet, long-term residents.