How to Grow Perennial Plants Care – Perennial Growing Guide

Quick facts

  • Most are easy to grow
  • Plants last for many years
  • There are options for every situation and soil type
  • Best planted in autumn or spring
  • Make new plants by division, cuttings or seeds

All you need to know

What are Perennials that are any plant living for at least three years? The term is also commonly used for herbaceous perennials which grow for many years (To compare: annual = one year, biennial = two years) perennials?

Perennial plants live for many years and come in all shapes and sizes. These versatile and diverse plants fill our gardens with colourful flowers and ornamental foliage and are the mainstay of most borders. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter.

In a gardening context, the term perennial is used to describe long-lived plants without a permanent woody structure, to distinguish them from trees and shrubs (although botanically speaking, trees and shrubs are perennials too). 

There are two main types:

  • Herbaceous perennials – these die back to the ground in late autumn. The roots survive over winter and the plants re-sprout every spring. Examples include delphiniums, hardy geraniums and hostas.
  • Evergreen and semi-evergreen perennials – these keep their leaves for most, or all, of the year. Examples include bergenias, epimediums and hellebores.

Choosing the right perennials

There are perennials to suit any style and size of the garden. There are options for all soil types and growing conditions. As these plants can live for many years, it’s worth choosing the right ones to suit your garden, so they will grow well and look great.

Getting the right look

Consider what you want from your perennials when you consider buying them. For instance, do you want to colour-theme your border, or create an exciting mix of contrasts? Or to create a naturalistic or exotic planting scheme? Here are some pointers to help you choose:

  • Flower colours – you can choose flowers in every imaginable hue, from gentle pastels to vivid, exotic shades.
  • Foliage – is available in wide-ranging forms and colours to provide interest throughout the growing season. Foliage can often last much longer than flowers, so its colour and form is an important consideration when selecting a plant
  • Season of interest – there are perennials for every season, although the majority flower in spring or summer. To keep your garden full of interest all year, including some that flower in autumn and winter too.
  • Style – do you prefer the natural look of native wildflowers, such as primroses and ox-eye daisies, or something more exotic, such as red-hot pokers and arum lilies?
  • Size – perennials come in all sizes, from low ground cover to towering spires, and everything in between. Keep your borders interesting by including a range of heights.
  • Shape – you can choose from low horizontal ground cover to tall verticals or neat compact clumps to vigorous spreaders that will fill gaps quickly.
  • Evergreen or herbaceous – do you want foliage all year round (evergreen) or plants that die down in late autumn and sprout afresh every spring (herbaceous)? A mix of both will keep borders interesting across the season. For ground cover, evergreens are best as their year-round mat of foliage deters weeds.
  • Wildlife-friendliness – many perennials attract wildlife, providing nectar-rich flowers, seeds for birds, and shelter for small creatures.

Perennial borders: choosing plants

When to plant

  • Good-sized hardy Perennials are any plant living for at least three years. The term is also commonly used for herbaceous perennials which grow for many years (To compare: annual = one year, biennial = two years).perennials are best planted outside in autumn or spring. 
  • Bare-root plants, young plants and plug plants are usually only available in spring, and are best potted up straight away into containers.

Where to plant

There are perennials to suit all growing conditions and types of soil – check labels when buying to make sure you put the right plant in the right place. 

Hardy perennials grow well outdoors all year, but some from warmer climates suffer in winter and need the shelter of a warm wall or greenhouse and well-drained conditions.

Most perennials can also be grown in large containers.

Shade planting: annuals, bulbs and perennials

Prepare your soil

Weed the area thoroughly before planting – if weeds are left, they can spread in among your perennials, which makes them trickier to remove.

How to plant

You can also plant perennials in containers, either singly or with other plants. It’s simple and takes little time.

Bare-root plants, young plants and plug plants are best planted into containers initially until they are larger and growing strongly. They should be ready to plant into borders after a few months.

What are plug plants?

These tiny plants, usually just a few centimetres tall, are grown in modules and often sold by mail order. Plant them into slightly larger pots as soon as they arrive – they should grow quickly and soon be ready for planting outside.

Watering

Water newly planted perennials regularly for their first year, until they’re settled in. After that, most only need extra water during long dry spells.

Perennials in containers should be watered regularly during the growing season, and especially in hot weather.

Groundcover perennials in dry soil beneath trees may also benefit from additional watering in summer.


​​Feeding 

Most perennials in borders need no additional feeding, but if the soil is particularly poor, you could add a well-balanced fertiliser, such as Growmore or blood, fish and bone, in spring. Apply a mulch of garden compost or well-rotted manure to the soil surface annually in spring, to enrich the soil. 

Perennials in containers should be given a general fertiliser during the growing season.

Fertilisers


Weeding

It’s best to weed between perennial plants regularly, so weeds can’t get established or scatter their seeds. Mulching the border with garden compost in spring will help to deter the germination of annual weeds. 


Staking

Many tall perennials need staking to hold the stems and flowers upright. Plants with heavy flowers, such as peonies, also benefit from support, as do those in windy sites.

Supports should be put in place in spring, so the plants grow up through them and hide them.

Winter protection

Some perennials from warmer climes aren’t hardy in the UK and can’t cope with winter cold or wet. Check plant labels for hardiness.

Perennials in containers

These need additional watering and feeding and repotting into larger containers as they grow. 

Caring for older plants

To keep perennials growing and flowering well, or to prevent clumps from getting too large, lift and divide them and replant them into fresh compost every few years.

Pruning and training

Perennials need little pruning. However, there are two instances where it is needed:

  • Cutting back – herbaceous perennials die back in late autumn and the dead stems should be cut off at the base before new shoots appear in spring. If you leave them in place over winter, some may look a little untidy but will provide valuable shelter for overwintering beneficial insects.
  • Chelsea chop – perennials that are liable to flop can be reduced in height in late May to produce stockier plants or delay flowering.

Propagating

Perennials are easy to propagate in several ways:

  • by dividing the clump
  • by taking cuttings – either softwood or semi-ripe, or root cuttings
  • by growing from seed, either bought or saved from your plants 

Problems

Perennials, especially hardy ones, are usually robust and trouble-free. However, look out for the following problems:

  • Nibbled young shoots and holey leaves may be caused by slugs, snails, rabbits and mice.
  • Yellow leaves (chlorosis) may be a sign of nutrient deficiency.
  • Tall or top-heavy flower stems may flop over or break – put supports in place in spring.
  • Plants may occasionally go into decline for no apparent reason – this often starts with browning leaves and may be caused by a disease such as phytophthora or pythium root rot.

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