Tough perennials for coastal conditions

Opinion 19/09/2018
Photo: Getty.

By Tony Murrell, Home & Garden host.

Here's my list of recommended plants for a range of coastal conditions in New Zealand, as discussed on RadioLIVE’s Home & Garden.

For those with free-draining sandy soils: generally soils like this have low fertility, Many gardeners think they have to change this and try to feed everything, but in reality there are many plants that do best when they’re not overfed.

Achillea, or yarrow – these guys will flower for months, just trim off any spent flowerheads to keep more coming. There are a range of colours available.

Eryngium planum – not called sea holly for nothing, these plants thrive on poor soils and the violet blue stem colour intensifies in hot weather

Perovskia or Russian Sage is a really tough deciduous perennial, which thrives in free-draining soils in full sun, smothering itself in silver leaves and blue flowers in summer. Silver foliage is usually a good indicator that plants like less water and more sun.

For smaller gardens try Catananche caerulea or Cupids Dart, in blue or white, it has narrow greyish leaves and beautiful papery flowers on upright stems 30-40cm high.

There’s a few tough, hardy Salvia species that are brilliant in coastal situations. These three Salvias all have one thing in common – they all originate from the South African coast, the Cape of Good Hope.

The first is S. aurea or S. africana-lutea as it was previously known. It forms a slow-growing shrub with silvery green leaves and unusually beautiful large rusty-brown flowers. It’s also one I recommend for coping with heavier soils too…as long as it’s not too wet in winter.

Salvia lanceolata is another, slightly smaller growing species, also with unusual coloured flowers; this one has rose-pink tinged warm brown flowers. Sounds weird but is very beautiful in full flower. Again, it has silvery green leaves.

Salvia scabra is the third tough cookie which I recommend for coastal plantings. A wiry, stiff-stemmed but bushy plant with many long-tubed lavender blue flowers all summer long.

We often think of Campanula as being only suitable for traditional perennial borders, but some of them are tougher than they look. Campanula carpatica, C. glomerata and C. rotundifolia are all good choices to try in coastal gardens.

For those gardeners that live in areas with heavier soils but want something bright or pretty, try these beauties...

Asters…you can’t go past them really. Choose tough varieties that multiply well….I grow ‘Calliope’ and 'Hi-Jinx', and A. novi-belgii hybrids in white and lavender, 'Coombe Violet', etc. They do well because they have reasonably shallow root systems that spread out slowly across the soil, so they’re not trying to break their roots through the hard clay pan in order to get nutrients.

The perennial sunflowers or Helianthus are similar. My favourite is 'Lemon Queen', but there are others like 'Golden Pyramid' and 'Table Mountain'

Rudbeckias (not to be confused with Echinacea, which have a woody tuberous root) are another favourite for heavier soils in exposed conditions, try Rudbeckia fulgida and it’s cultivar ‘Goldsturm’, or Rudbeckia laciniata for some height. Some of the annual cultivars like 'Prairie Sun', 'Irish Eyes' and the newer 'Chim Chiminee' are also great fillers for hot sunny areas.

Stokesia laevis or Stoke’s Aster, great for smaller gardens and despite many attempts I’ve failed to kill one yet….they come in white, blue and creamy yellow, form low clumps of evergreen, narrow foliage and they flower for ages.

With Tony I talked about plants for sunny gardens, but what about shade, or damp?

Try out some of these ideas in your own microclimate…

Hellebores….as long as you don’t divide them up and move them about too much they are incredibly tough and once established will do remarkably well provided they get the odd whiff of fresh water. The only thing that really kills them is prolonged dry. Let them self-sow too – they’ll pop up where they are happy.

Heuchera….not the coloured leaf hybrids but some of the original species like H. micrantha, H. americana and H. maxima perform really well in shaded areas and have the vigour that modern hybrids sometimes lack.

Bergenia – these tough plants will thrive on partly shaded banks with little or no maintenance, providing both foliage and flowers.

Clivia, providing you don’t get frosts they are fantastic under trees near the coast! I love mine and have grown some different colours from seed to extend the clumps even further.

For damper places try Persicaria (Polygonum), Lysimachia and Filipendula, these genera are reliable performers that can cope with a bit of damp and neglect.

Tony Murrell is host of Home & Garden on RadioLIVE.