How to grow Perennials

Perennials


Purple globe thistle heads are dotted through salvia in the Dry Garden at Lambley, Victoria. Photo - Lambley Nursery

A perennial primer

 

We have fallen in love all over again with romantic flowery gardens packed with perennials. This group of plants offers the gardener an amazing range of colours, textures and shapes to play with. Here Sandra Ross shares the love, answering the most frequently asked questions about this exciting group of plants, and choosing her must-have favourites.

 

A Perennial Q&A


What does perennial mean?

A plant that lives for more than two years (as distinct from annuals and biennials) is perennial. These plants grow and bloom over spring, summer and autumn, die back in winter and return the following spring with new growth from the rootstock.

 

Why would I use perennials?

Nothing has more diversity of flower, foliage, colour and form than the perennial plant group. They also offer excitement simply because of the way they change over the seasons. Spring’s new growth gives the garden a burst of energy as young stems spear out of the soil from permanent rootstock. Bold and brilliant summer flowers and foliages build to a crescendo in early autumn. Many perennials then age gracefully, lending their natural senescence to the late- autumn and winter garden.

 

Where do they grow?

Perennials are a very diverse plant group. Most of the perennials discussed here love full sun. However, if you have a shady garden you can choose interesting plants with textured and patterned foliage. THe variegated brunnera 'Jack Frost' will carpet the front of a shady border. The fine, pendulous foliage of golden Japanese forest grass (Hakonechloa macra 'Aureola') looks sensational alongside the blue-leafed hosta (Hosta sieboldiana) in a cool climate garden. Some, like the Japanese and Siberian iris, prefer a damp spot so they are ideal along the margin of a pond.

 


Wychwood garden in Tasmania has elegantly mastered the use of perennials to create playful drifts of colour and texture. Photo - Peter Cooper.


What do I need to know to grow them?

You will have fun experimenting with perennials. When making your plan the thing to consider is how big they grow. You don't want them to swamp each other and as a general rule you want to have the taller plants at the back so they don't disguise the front. Some perennials, like the blue Easter Daisy (Aster frikarti), hate being moved, and will sulk and probably die if you try it. So if you get it wrong, change positions.

As far as care goes, simply prune them and the end of winter,when you first start to see the new growth appearing. Remove spent flowers and leaves to allow fresh new growth plenty of room. Some plants, like salvias, need more than just an annual prune. They respond well to a mid-summer prune and will delight you with a fresh flush of flowers. Feed perennials when the new growth arrives in spring. Homemade compost is perfect.

 

Are perennials a good match with roses?

Sure are! Six of my favourite perennial partners for roses:

1. Catmint (nepeta) - silver-grey leaves and small blue flowers.

2. Lamb’s ear (stachys) – a low carpet of soft, felted foliage.

3. Cone Flower (echinacea) - tall stems of cone-shaped pink and cream blooms.


Coneflowers. Photo - Linda Ross

4. Perennial asters/Easter daisies - soft foliage and small daisy flowers.

5. Pokers (knifophia) - not the red-hot variety but the lovely lime, cream and lemon coloured ones that spear through thorny rose stems to great effect.

6. Euphorbia - intriguing foliage colours and chartreuse bracts. ‘Blue Peaks’ has powder-blue leaves and large chartreuse flower heads.

Where can I buy perennials?

It is almost impossible to find perennials in a garden centres these days: go with mail order nurseries selling online.

Lambley Nursery is one of our favourites. It’s set around an old farmhouse in the hot, dry wind swept plains near Creswick in the central Victorian goldfields. www.lambley.com.au

Nutshell Perennial Plant Nursery is located at Wallendbeen, between Cootamundra and Harden in the South West slopes of NSW. www.nutshellnursery.com.au

Perennialle Plants offers a collection of rare, frost and drought tolerant perennials. The nursery is located in Canowindra and is open by appointment. www.perennialle.com.au.

 


An nearly summer morning at Cloudehill reveals a soft tapestry of texture and colour. Photo - Claire Takacs

 

Using perennials

Planting schemes can be designed in layers, in clumps or in swathes. (Read what Michael McCoy has to say about Dutch designer Piet Oudolf’s inspirational way of designing with perennials on page 48.) Groups of complementary perennials can be repeated to give a rhythm to the garden and coherence to a garden border. When making a plan we like to get a good mix of different flower shapes. We aim for a satisfying pattern of feathers, spires, dots, and plates, all filled in with some fluff! Have a close look at the pictures on these pages to see what we mean.

 

Feathers


The foliage of ornamental grasses give lightness to the garden, and the feathery plumes of flower move in the slightest breeze.

 

Stipa gigantea grows to 2m, well above the maximum height of most perennials. In early summer its see-through panicles of oat-like flowers rise high above everything else.


Stipa gigantea grasses in flower catch each ray of light. Photo - Linda Ross

 

Miscanthus transmorrisonensis is another favourite, with arching, almost weeping flower heads. It does need some space to show off its beautiful form though as it grows 150cm x 140cm.

 

Spires


Plants that hold their flowers in spires give energy and elegance to a garden. The flowers reach for the sky, catching light as they go.

 

Russian sage( Perovskia ) has handsome, fern-like, silvery-green foliage topped by clouds of tiny blue flowers. It grows to 1.5m, with strong self-supporting stems if grown in full sunshine.


Perovskia atriplicifolia creates clouds of plumage comprised of thousands of tiny purple flowers wrapped in velvet buds. Photo - Linda Ross

Foxgloves (Digitalis) are actually bi-annuals rather than perennials, but allow them to set seed and you will have them forever. These tall, slender plants and can reach 1.5 m if the soil is moist and rich. The tubular flowers have spotted throats and the foliage is good too!


Foxglove spires reach for the sky. Photo - Robin Powell

 

Agastache was a great favourite at MIFGS this year. Even in drought conditions it continues to produce a succession of tall spikes of dusky pink/apricot flowers that reach 90cms.

 

Agastache 'Sweet Lili' is loved for its long-lived colourful spires. Photo - Linda Ross

Salvia deserves a story all of its own as there are hundreds of them and we’re not counting the annual salvias.The nemorosa group are all good. ‘Caradonna’ has rich violet spikes on black stems, to about 60cms. ‘Blauhugel Blue Hills’ is softer and flowers for 20 weeks! David Glen at Lambley Nursery cuts it to the ground in winter and again after the first flush in midsummer, to encourage another glorious flush of flowers.The greggii group of salvias is good too, and grows a bit shorter but just as flowery.


Salvia. Photo - Linda Ross

 

Fluff


These fillers make a garden border look plump and generous. They have a rather amorphous shape and flower plentifully.

 

Bergenia, once known as saxifrage, looks best in the front row. Rounded glossy evergreen foliage turns crimson in winter. Bright coral pink flower heads arrive late winter and spring. The new variety ‘Dragonfly’ grows 30cms.


Bergenia spires stand tall and straight. Photo - Linda Ross  

Cranesbills are perennial geraniums. They make neat mounds of foliage topped with crinkled blue-lilac flowers. ‘Rozanne’ stays compact, with flushes of violet-blue flowers repeating through spring and summer.


Photo - Linda Ross

 

Easter daisies (aster) have soft fine foliage and small daisy flowers. All the asters make good fillers between taller more robust perennials. ‘Jung Frau’ is one of the best, with large blue daisy flowers with yellow centre. A great partner for roses.


Asters extend the colour through the cooler months. Photo - Linda Ross 

Dots


Flowers that look like dots of colour bring a garden design together. The eye moves to link the dots and create cohesion.

 

Helenium has a characteristic pronounced cone at its centre, a ‘black dot’ that persists even when petals fall. The reflexing petals come in a variety of burnished colours. ‘Moerheim Beauty’ is one of Karl Foerster’s original introductions and is named for his nursery in Potsdam. It’s still one of the best, with rich red flowers that age to ochre brown.


Rocket-shaped Helenium moerheim vie for attention. Photo - Linda Ross

 

Globe flower (Echinops ) has spherical flower heads, steel blue in bud, and opening to balls of powdery mauve-blue when in full flower. The drumstick flower heads, bold silver foliage and stiff stems give this plant great architectural strength. Look for ‘Taplow Blue’

.

Concentric circles of globe thistles dot the garden. Photo - Linda Ross
 

Eryngium (Sea Holly) looks like it’s made of metal. Flowers are blue and spherical and encircled by a metallic blue ruff. Look for ‘Oxford Blue’.


Electric blue sea holly make prickly mounds. Photo - Linda Ross

 

Rudbeckia are free flowering daisies in warm colours from yellow to mahogany, with brown centres. They look good paired with ornamental grasses in big clumps. The seedheads persist as ‘dots’ and look good through autumn and winter. ‘Cappuccino’ is a new variety with huge orange-red flowers.


Happy yellow Rudbeckia flowers are the heart and soul of the autumn garden. Photo - Linda Ross

 

Plates


Plants that hold their flowers horizontally like plates make a good contrast with other flower shapes and also offer good landing zones for bees and butterflies.

 

Achillea has ferny foliage and flattened flower heads. ‘Moonshine’ grows to 50cm with intense lemon flowers and fine silver foliage


Achillea 'Moonshine'. Photo - Linda Ross

Sedum is an indispensable plant for a dry garden. ‘Autumn Joy’ has large flower heads that change colour through the seasons, from green to pale pink to deep pink to deep salmon pink to dark coral pink and finally in winter to a rich mahogany brown. In a cool climate ‘Matrona’ has stiff maroon stems and flower heads of soft pink that slowly age to crimson.


Sedum 'Autumn Joy' attracts butterflies into the garden. Photo - Linda Ross

 

Text: Sandra Ross

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Comments

Helen Fulton commented on 07 Jun 15

Congrats, Linda on your wonderful photography.

Laurie Burridge commented on 06 Jun 15

Congratulations - fantastic, delightful, fascinating, loving every link. Inspirational- can't wait to get some dirt under my finger nails and to order some catalogues

About this article

Author: Sandra Ross