Sea of Purple Hardenbergia

Sea of Purple Hardenbergia (Hardenbergia violacea 'Sea of Purple') does two jobs from one plant: left on flat ground it scrambles into a groundcover about 2m across, and given wires or a trellis it climbs to about 2m instead. Either way, through late winter and early spring it disappears under sprays of small purple pea flowers, at the point in the year when most Australian gardens have nothing going on.

Why you'll love it

• Purple when the garden is empty. Flowering runs through late winter into early spring, weeks ahead of the main spring show.
• Groundcover or climber, your choice. Let it run and it covers ground; give it a support and it climbs to around 2m. Same plant, two different uses.
• Genuinely tough. Frost hardy, drought tolerant, salt tolerant and happy in poor soil, so it holds banks and verges that defeat softer plants.
• Fast cover, and food for bees. It fills its space in a season or two, which matters on a slope, and the late winter pea flowers are a genuine early food source.

Where it works best

Groundcover and mass planting. Plant 1m apart for full groundcover. Ten plants at that spacing cover roughly 10 square metres.

Retaining walls and slopes. Set it along the top of a wall at the same 1m spacing and let it spill over the face. On a bank the scrambling stems and fibrous roots hold surface soil.

Screening, balconies and courtyards. On a fence or trellis it gives a light screen to about 2m, or a small frame in a 400mm pot.

Growing hardenbergia in Australia

Position and climate. Full sun gives the heaviest flowering, and it grows in part shade with a lighter display. It suits subtropical, warm temperate, cool temperate and Mediterranean gardens and is frost hardy once established. The wet tropics are the honest exception.

Soil. Free draining above all else. Poor, sandy and gravelly soils are fine, and a lean site flowers better than a rich one. On clay, mound the bed.

Water and feed. Deep water weekly through the first summer, then it needs very little in most districts. Feed sparingly, and only with a low phosphorus native fertiliser. As a legume it fixes its own nitrogen, so heavy feeding gives leaf and almost no flower.

Pruning. Shear it back by about a third straight after flowering finishes in spring. This is not optional: an unpruned plant goes woody and bare through the middle while the growth runs to the edges.

What to expect when it arrives

It is grown in two sizes, both sold as packs: 140mm in packs of ten and 200mm in packs of six. Ten 140mm plants at 1m spacing cover about 10 square metres of bank or bed, and six 200mm plants cover about 6 square metres.

Plants arrive as young trailing stems rather than a finished mat. Spread the stems out at planting and peg them down for faster ground contact. Expect roots to take hold in four to six weeks in warm weather. Plants are delivered Australia wide, with delivery from $29.95. Every plant is covered by our 30 day healthy plant guarantee.

Plant care guides and related reading

• Compare the full groundcover plant range
• A guide to choosing plants for ground cover
• Browse more Australian native plants
• Plants for retaining walls and slopes

Common questions

How far apart should I plant it for groundcover?

One metre apart. That closes into continuous cover within two seasons on a well watered site. On a dry exposed bank where growth is slower, 80cm is a reasonable adjustment.

Is it a climber or a groundcover?

Both, and what you give it decides. Nothing to climb and it scrambles as a groundcover; wires or a trellis and it twines to around 2m.

How do I stop it going woody in the middle?

Shear it by about a third every year immediately after flowering, while there is still leafy growth on the stems you cut. Skip it for a few years and you get bare woody centres that will not regrow.