Hardenbergia

( har - den - BERJ - ee - uh )

At-A-Glance Information

Hardenbergia, or Lilac Vine, is an evergreen shrubby vine that needs partial shade in the hottest climates and moderate amounts of water. It is a vine that is native to Australia, and has handsome foliage that contrasts nicely against its clusters of purple sweet-pea shaped flowers in late winter or early springtime. These vines grow to about 10 feet tall and need support for their climbing stems to grow well. Grow these vines on trellises or other structures, along walls or fences, or simply as specimen plants in the landscape. They can also do well in containers. Take care when planting these vines in the landscape, as plant parts are toxic to humans and pets, and they can also cause skin irritation in sensitive individuals.

Hardenbergia Species and Varietals

The genus Hardenbergia is a member of the plant family Fabaceae and includes three species. The ideal growing zones for Lilac Vine vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map. 

Hardenbergia comptoniana (Native Wisteria)
Grows best in zones 15-24 and has a light, delicate foliage pattern. Flowers are violet-blue and are held in drooping clusters. Plant beneath an overhang where temperatures will damage the plant (where temperatures drop below 24 degrees Fahrenheit).
Hardenbergia violacea (Hardenbergia monophylla) (False Sarsaparilla, Purple Coral Pea, Caraburra, Purple Twining-Pea, Vine-Lilac, Wild Sarsaparilla)
This prostrate or climbing vine grows best in zones 8-24 and has flowers in lilac or violet, sometimes rose or white. Stems can reach up to 7 feet or more and leaves are leathery and green with pale undersides. Choice garden varieties are outlined below.
'Happy Wanderer'
Vigorous, hardy selection with blooms that are pink-purple.
'Canoelands'
Narrow leaves on a vine that produces pinkish purple flowers over a long blooming period.
'Icicle'
With pure white blooms.
'Rosea'
​Pink-flowering variety.
'Mini-Ha-Ha'
This shrubby-habit dwarf form of Hardenbergia gets to 3 feet tall and wide.

Caring for Hardenbergia

Plant Hardenbergia vines in full sun to partial shade; they will flower most profusely in full sun. Ideally, they should be receiving between 6 and 8 hours of sun each day. In particularly warm climates, they do appreciate some afternoon sun when temperatures reach their maximum. Make sure to plant this vine in a protected area, it will not do well when exposed to drying winds or frost. Soil should be well-draining and moderately fertile. If local soils are compacted, do not drain well, or are particularly poor in nutrients, make sure to amend the planting area with plenty of organic matter or compost before installing. Apply a thick layer of mulch around the base of the plant after installation, ensuring that mulch stays at least a few inches away from the stems. This will increase soil moisture retention, suppress weed growth, and maintain a constant soil temperature. Keep the soil moist while plants establish a strong root system; mature plants are considered somewhat drought-tolerant, but they do appreciate consistent moisture during the growth and flowering season in spring and summertime.

Cut back vines in late winter or early springtime, removing dead, damaged, diseased, or errant stems. These vines tend to become a bit leggy and woody towards their bases, and pruning them back each year in springtime can keep them bushy. Fertilize yearly in springtime with a thick application of organic compost to support growth and flowering for the year. Make sure to remove mulch around the base of the plant before applying the compost, and then replace the mulch after working the compost into the soil.

Propagation

Hardenbergia vines can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your vine, follow the instructions below:

Propagating Hardenbergia by Cutting
  1. Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
  3. Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots. 
  4. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Hardenbergia by Seed
  1. Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
  2. Harvest your seeds. The seed pods on Clianthus plants are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
  3. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
  4. Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Hardenbergia seed pods contain about 10 seeds each.
Hardebergia seeds.

Problems and Pests

Hardenbergia vines are not particularly susceptible to diseases, though they can suffer from issues with the following pests in home gardens:
  • Spider Mites
  • Nemotodes
  • Scale Insects
For more information on these issues, including how to solve them, consult the following pages:
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Gallery

White-flowering Hardenbergia vines are just as eye-catching as their purple-pink flowering relatives.
These vines can be espaliered, creating a wall of color and foliage.
Here, a Hardenbergia vine is planted in the corner of a walled garden, climbing with the help of a trellis.
Hardenbergia flowers are typical of Fabaceae genera.
The bright flowers on these vines will attract pollinators.
These vines can grow to be quite large if left unchecked.

Videos

Learn about these beautiful vines.
All about this great cultivar of Hardenbergia.

Resources

Hardenbergia Growing Guide
Hardenbergia violacea Diseases and How to Treat Them
Wikipedia: Hardenbergia
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 351, Hardenbergia
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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