Garden Guru: Potted wisdom

Months of protection from frost helped produce these striking Poor Knights lilies. Photo / Supplied

When the gardeners of Taranaki throw open their gates next week for another fabulous festival, you can bet every property will boast some form of container planting.

Be it a vase, dustbin, baskets, barrels or a humble boot, containers, when you think about it, are strange places to house any living thing. Isolated and prone to drying out, they constitute some of the most hostile environments for plants, yet gardeners just cannot fall out of love with them.

But Jenny Oakley's pots are as creative and varied as the well-stocked borders she tends in her country property near Manaia. Jenny strikes that rare balance between exuberance and simplicity; boldness and delicacy. Her flair has put her in demand with garden centres here and abroad, who regularly call her in to hold demonstrations on "containing with confidence".

Jenny's garden appears effortless but is, of course, the opposite and her use of pots is varied. In places a single pot plant makes a statement while around the parking bay, great chunky repeated containers step out a welcoming rhythm with a note of grand formality.

In softer corners, different sized pots gather in sociable huddles, sometimes with the same plant in several containers to amplify the effect, and the grand finale is a circular pavement studded with an assembly of Poor Knights lilies (Xeronema callistemon).

Jenny has been rushing out since autumn to cover these every time there is a frost warning. She feeds these temperamental giants with a single dose of tomato fertiliser in autumn but otherwise treats them mean. Her reward will be about six scarlet toothbrushes on each plant, which is the horticultural equivalent of reaching the summit of Everest.

With formal horticultural training and a lifetime tending the same plot, Jenny is full of sensible tips based on years of experience. Though her spring bedding only lasts for six months, she still incorporates eight- to nine-month, slow-release fertiliser into the compost because with regular watering she finds nutrients leach out of the soil extra fast.

Another eye-opener is how she fills her pots (mostly terracotta) with common dirt instead of boutique compost (though this "dirt" happens to be rich and volcanic, so is enviably crumbly and free draining). Compost is shunned, except for the top layer, as organic matter tends to break down and compact after a year or two while soil retains its structure and holds moisture well - especially for permanent planting such as shrubs.

While balls and cones of classy box topiary fringed with mondo are the workhorses of her potted menagerie, there are plenty of bold perennials, chosen primarily for their foliage.

Jenny prefers to use hostas in pots than in the ground so plants get watered properly.

Heuchera "Lime Rickey" is great for adding leafy zing to shady verandas while bold-leafed ligularias, such as purple "Britt Marie Crawford", though needing plenty of moisture, do excellent service raised up and shown off.

One of the beauties of containers is the way you can stage them for an ever-changing show. At the Oakley garden particular corners have a changing parade of pots. Foliage predominates in the lee of a decorative wall, with purple aeoniums alongside a family of blue hostas, which do well in full sun. Bowls of rhodohypoxis provide pools of rich colour.

Planters are great for livening up a difficult spot, too. Under the walnut tree, Jenny plays her ace card - displaying her gargantuan hanging baskets dripping blue and white. "You'd think people would have got over doing these," she laughs, "but I still get regular phone calls to run workshops."

Hanging baskets have gone all high-tech and can look more like UFOs than a home for a humble pansy. But Jenny shuns the gimmicks and opts for open wire baskets, lining them with traditional coconut fibre. Birds can notoriously strip this in spring for nest building, but the criss-crossing of black cotton woven between the suspending chains cleverly makes perching near-impossible for would-be thieves.

The Achilles heel of baskets is the amount of watering required. Crystal Rain and "Saturaid" are compost additives that Jenny finds useful. But while some gardeners rig up complicated drip irrigation systems, Jenny reckons they are missing the point.

"Daily hand-watering encourages good husbandry," she explains. "As I water there is time to pick out diseased leaves and, most importantly, to deadhead which keeps the show going for much longer". In November all those hours of work will be ripped out to be replaced with shade-tolerant begonias and impatiens. But for now, the walnut tree is dripping with colour so the crowds who visit next week shouldn't be disappointed.

The Taranaki Rhododendron and Garden Festival, October 30 - November 8. www.rhodo.co.nz

Jenny Oakley's tips

* Rhodohypoxis are bulletproof but re-pot every three years before they become overcrowded. Do it in spring as they are easier to handle then.

* Don't raise pots on feet, put them on saucers instead so excess water and leached nutrients are recycled.

* For hanging baskets build things up in layers putting in some fibre at the base with a sheet of plastic on it to act as a water reservoir. If using a pre-moulded coir or fibre liner, cut it into three strips so you can plant the sides of the basket generously using the two slits between each strip before planting the top.

* For a spring display start planting in July. Hardy old staples such as alyssum and anthirrinums are hard to beat.

* If your garden soil is heavy use a compost that is soil-based to fill pots.