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Gardening guru’s greatest fails: Plants I just can’t grow

In my dry blue garden I can grow oodles of delphiniums, asters, statice, agastache and nigella - so why not English lavender?

Right plant, right place: it’s one of the universal principles of successful gardening. Though some green-fingered optimists take longer than others to learn this lesson, most of us will, eventually, come to realise that there’s no point fighting nature and, more specifically, our local soil type and microclimate.

No sensible southern grower plants subtropical pineapples or peace lilies outdoors, just as no one with any nous in the Far North would waste their money buying paper-petalled meconopsis poppies or azure blue gentians. And although it’s a thrill to occasionally beat the odds – when my poor excuse for a herbaceous paeony sent up a sad, solitary bud last November, for example, I skited on Facebook – ultimately, we learn to accept our garden’s limitations.

When you fail to succeed with something rare, it’s understandable. But what about when you routinely kill bog-standard, run-of-the-mill, common-garden perennials – things like catmint, penstemons and pretty blue Salvia patens? Who, and what, can we blame then?

I’ve long adored English lavender (Lavandula angustifolia) but do you think I can get the jolly stuff to grow? In all my years of gardening, I’ve only ever once grown enough to pick. And even then, I only cut one small bunch.

I know perfectly well that English lavender hates humidity and prefers hot, dry climates because I’ve seen it looking sensational in the stony soils of Central Otago and Marlborough.

Nonetheless, in 2013 I put in my own pint-sized lavender plantation: 25 wee clumps of ‘Hidcote’ in a 2m x 2m, sun-baked bed surrounded with gravel. I didn’t water it or feed it – lavender is tough, after all – but rather than relish the Mediterranean conditions, it simply sulked. Twelve months later, I pulled it out and tried again, this time planting a dozen clumps of ‘Super’ at the feet of  a tangle of thornless boysenberry brambles. But still, no luck.

So it defies logic that, after one of the wettest spring/ summer growing seasons we’ve ever had in Hunua, the trio of English lavenders I’d bunged around a prickly rugosa in my rose border finally saw fit to flower well this year. My bathroom shall smell of dried lavender all winter!

If English lavenders perform poorly in the north, their French cousins can be snippity in the deep south. At Invercargill’s Marshwood Gardens, nurseryman Geoff Genge used to grow masses of French lavender (Lavandula stoechas), with its papery top-knot of purple bracts, but he says the seasons are changing noticeably and now the cold, damp spring weather rots the new growth off the top of the plants.

Russian sage is a shrubby perennial blooms later in the season, producing upright silver stalks topped with lilac spikes.

MARIA DRYFHOUT/123RF

Russian sage is a shrubby perennial blooms later in the season, producing upright silver stalks topped with lilac spikes.

For a violet haze that’s every bit as good as lavender, try Russian sage (Perovskia atriplicifolia). This shrubby perennial blooms later in the season and has upright silver stalks topped with lilac spikes. In the Kings Seeds’ catalogue, Russian sage is described effusively as a “much admired, tall, fragrant, first-year flowering heirloom” but for Geoff, “perovskia remains a puzzle”.

“I’ve never managed to get Russian sage going well,” says Geoff, “so it annoys me immensely when I see it growing beautifully in public parks in Te Anau. Perhaps it’s too damp here at certain times of the year. It must like drier conditions than I can give it.”

Perovskia atriplicifolia ‘Blue Spike’ is favoured by high-falutin’ English landscapers and it’s routinely fêted in international gardening magazines, along with another pale-blue nemesis of mine, the large catmint (Nepeta ‘Six Hills Giant’).

If I see another photograph of this particular variety spilling generously out of English herbaceous borders, I swear I’ll scream. In my garden, ‘Six Hills Giant’ catmint is boring. I have no idea what I’m doing wrong, as I’ve tried it in full sun and part-shade, in both poor and fertile soils, on a dry bank and on a cooler, south-facing slope. In every situation, it ends up flopping in a big grey-green heap.

At Wylde Willow garden in Dunedin, heritage rose lover Fran Rawling has similar issues with perennial penstemons. “I don’t find that any of them do particularly well. They all end up with more foliage than flowers, even when I’m vigilant with deadheading.” For height in her borders, Fran has come to rely instead on Louisiana and Siberian irises, mallows and asters, plus multitudes of reliable cranesbill geraniums around her roses. “They’re such good value and such good fillers.”

I agree, although I’ve lost count of the number of sky-blue Geranium ‘Rozanne’ plants that have met an ignominious end at my place. At the 100th Chelsea Flower Show, the Royal Horticultural Society named it their Plant of the Centenary, but ‘Rozanne’ is a very extravagant annual for me.

Geranium 'Rozanne'.

SALLY TAGG/NZGARDENER

Geranium ‘Rozanne’.

At Wylde Willow, where the winter soil can freeze for a week at a time and summers are rarely blistering, Fran has found that many modern introductions seem to need “a bit more heat and a bit less competition to perform well as garden plants.” Fran, however, has no complaints about colourful catmint: “It’s so easy here and always looks

I’ve now all but given up on ‘Six Hills Giant’ but last spring I decided to have another crack at low-growing Nepeta × faassenii. I mass-planted the plain form with blue and purple delphiniums and cavolo nero, both of which thrived at its expense.

Is it just me with the catmint curse? Possibly, for in Coleen Peri’s New Plymouth garden La Roseleda, two impressive rows of standardised David Austin ‘Sharifa Asma’ roses are made even more eyecatching by the thick floriferous carpet of catmint flanking the path beneath them. What’s Coleen’s secret?

“Nothing,” she shrugs. “It just grows like crazy here but it does get a bit scrappy by autumn. I should probably cut it back twice a year but normally I only get around to it once.” Sensing my keen despair, Coleen charitably pointed out that, even for her, ‘Six Hills Giant’ gets a little lanky in shade and doesn’t flower as profusely as it could.

The lilac blooms of catmint.

The lilac blooms of catmint.

Coleen has her own unrequited loves, including giant frothy-flowered sea kale (Crambe cordifolia). “Having seen its huge white flower clouds in English magazines, I bought some many years ago and it is now well-established in three spots in my garden. Every year it produces the most beautiful, healthy, massive, rhubarb-like leaves but it has never had a single flower. I think it needs colder winters.”

Meanwhile, Geoff Genge blames the chilly Southern winter for claiming his old-fashioned South African stiff twinspurs, Diascia rigescens. “We used to sell lots of it so I was always taking cuttings, then one year we lost it in a heavy frost and I’ve never managed to get it going again, yet at the local crematorium it grows very well,” he laughs.

Sometimes it’s not the plant but its propagation that trips us up. If you’re having trouble germinating perennial heleniums or salvias, says Geoff, don’t cover the seed. “Just throw it on top of the soil and water it in. All the salvias are best done this way.”

Dozens of salvias and diascias have rotted out while winter-dormant in my garden, and I have a similar summer voodoo with verbascums, which despise Auckland’s humidity. But I’m hoping to do better with hostas in the shade between two adolescent oak trees. Having prepped my soil with a truckload of compost and a thick autumn mulch of fallen liquidambar leaves, last spring I put in 100 hostas. The dozen or so at the front will need uprooting and tucking further back, as they’ve caught a touch too much sun, but my fingers are crossed that one day my hosta walk will look as lush and lovely as the metre-high clumps in Pat Stuart’s Wanaka garden.

Pat’s garden was once a peat bog and has its own trout-filled stream, Bullock Creek. “Our soil was very inert when we came here, though, so we feed it twice a year. I use blood and bone, and recently I won a rather nice prize of a big bag of sheep pellets in a raffle.” The garden now boasts all sorts of comely treasures from trilliums to fritillarias and meconopsis. But after “several expensive goes”, she’s declared defeat over the popular purple-leafed tree, Cercis canadensis ‘Forest Pansy’. “It just fizzles out and dies,” she sighs.

Hoping to create a hosta walk, I've planted 100 hostas.

NEIL ROSS

Hoping to create a hosta walk, I’ve planted 100 hostas.

Cercis cause no problems for Trish and John Uffindell at Peppertree Nursery in Thames’ Kauaeranga Valley. Trish is a fan of the new Cercis ‘Ruby Falls’. “It has cascading branches that I’m rather hoping will eventually look like a lovely weeping copper beech.”

When I visited Trish and John’s garden, I was jealous of their gorgeous kalmias, their flowers as perfectly formed as the piped icing on fancy cupcakes. Whereas what Trish longs to grow is comically common in comparison: ‘Iceberg’ roses. “Our soil is too acid. Even with an awful lot of lime, roses just don’t grow well. I had a border with ‘Iceberg’ roses and we replaced them twice before giving up and planting more camellias and rhododendrons.”

If your soil is heavy clay, sandy or acidic, there are obvious clues as to why some plant species don’t prosper. At Wake Robin Nursery in Balclutha in South Otago, Sue Bound knows that her wet, cool climate doesn’t suit heat-loving bulbs such as watsonias and tritonias, but she’s perplexed by the non-performance of her Virginia bluebells (Mertensia virginica).

“I’ve had a few goes,” says Sue, “and whenever I see it self-seeding in other people’s gardens, I take a mental note of the conditions. I’ve seen it thriving in sun and in part-shade, but good dry soil seems to be what it needs most.”

Old-fashioned favourites making a comeback among Sue’s mail-order customers include tall phlox, dusky pink Francoa pendiculata, astrantias and lily-of-the-valley, Convallaria majalis. Even though it “grows like a weed down here”, Sue says she can’t keep up with orders from North Island gardeners desperate to grow it. I wish I could get lily-of-the-valley to colonise my garden like it has in my aunty Kay’s Hamilton backyard. She’s previously dug me two clumps of this moisture-loving rhizomatous perennial but neither lasted the distance here and now she point-blank refuses to give me any more.

As for Astrantia major, I’ve come to truly appreciate the intricacies of its individual flowers, because I’m lucky to get more than a single cluster per plant. I grow both the greenish-white ‘Shaggy’ (also sold as ‘Marjery Fish’) and the pink-red form ‘Rubra’, which Sue says is her most popular variety.

Lily-of-the-valley -- another nemesis.

MAAYKE DE RIDDER/iBulb

Lily-of-the-valley — another nemesis.

When you’ve been raising plants your entire adult life, like Abbie and Mark Jury at Tikorangi in Taranaki, it must be hard not to take it personally when supposedly no-fuss plants such as heucheras and Alchemilla mollis look ordinary at best. “Heucheras are hopeless here,” says Abbie. “Ours get smaller and smaller every year.”

Mark’s theory, according to Abbie, is that in “the quest for the new”, too many plants are trialled in optimum conditions in containers, rather than in garden soil, so we’re getting plants that look great in retail centres, rather than in actual gardens. They’re also dubious about the longevity of some plants propagated by tissue culture.

Coleen Peri has other suspicions: “When I ran The Iris Boutique nursery, I grew all my irises in a bare paddock and while some varieties did better than others, they were all fabulous. Yet when I sold my collection, I kept a few weird and wonderful varieties for my own garden and, when I crammed them in with other plants, they’d die out for no reason.”

Oh dear. Perhaps greediness and a general lack of restraint is to blame. After all, we’re all guilty of coveting too many plants, aren’t we?

 
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