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Question from Lisa:
I bought a Vine Lilac from Costco maybe 6 months ago (January) and it’s never been the same. I hear they flourish in winter, but I know it hasn’t been happy ever since I brought it home. How can I tell if the soil has too much nitrogen? My neighbor is having the same problem– we live in Santa Monica, the plants are potted and about 5 feet high on a dowel. Help! thank you!

Answer from Pat:
Your winter blooming “lilac vine” is Hardenbergia ‘Happy Wanderer.” I also saw them for sale at Costco so I know that is what you have. It is a good idea to keep plant tags and throw them in an envelope or file designated for this purpose, since then you will always know the correct name. Tags sometimes give care instructions as well, but here are instructions for growing this vine:

Lilac vine (Hardenbergia ‘Happy Wanderer’) is most satisfactory when grown in the ground and supported by a trellis or an arbor. It is easy to grow once established and when well grown and in a spot where it is happy, it blooms throughout winter. Once established it is an easy plant requiring little care, but getting it established may be difficult. Along the coast, such as in Santa Monica where you live, it needs full sun. Inland it can take part shade. Perhaps you are growing it on a patio or porch where it is not in ideal light. It will die or do badly if kept in too much shade in Santa Monica.

Hardenbergia can also be grown in a large tub filled with well-drained, humus-filled potting soil of good quality. When planting a new hardenbergia into a tub, (or any plant for that matter), first place a piece of broken pottery over the drainage hole on the bottom of the tub, then put a layer of potting soil over that, slide the plant carefully out of the nursery container, loosen the roots and lower it gently into the container being careful not to break the crown of the plant. Then fill the sides of the container with more potting soil and press it down with your hands. Water thoroughly after planting. After that, when watering always water enough so that the water drains out the bottom of the pot. (This will prevent a build-up of nitrogen or salts in the soil.) You mentioned nitrogen, this is how to correct any problem with nitrogen build-up in the soil. Before watering again, wait until the plant begins to dry out and then again water adequately until water pours out the bottom of the pot. Never keep a saucer under the pot to catch the drainage water. This is a No-no. When the bottom of a potted plant sits in water that has drained out of the bottom of the container, this can and usually does kill the plant. After watering, wait at least a week or so until the roots are almost but not completely dry, then water again the same way. This plant will die or do badly if overwatered and the ground is soggy. When grown in a container, it will also die or do badly if the roots are allowed to dry all the way.

If grown in the nursery container it arrived in it would be impossible to follow the above instructions and keep the roots of the plant in good condition. If you and your friend have kept your plants in the same containers that they arrived in from the nursery, all your efforts are doomed to failure. The plant cannot live and do well that way. It has to be planted in the ground or else in a large tub. For a 5-Gallon plant, the correct size of tub is at least 18 inches wide and 20 or 22 inches tall. Eventually, it might even need a larger tub. You will also have to provide it with a post or a trellis on which to twine. The stick it came with is not enough.

In addition to the instructions given above, when growing lilac vine in containers you should be fertilizing it every two weeks beginning as soon as the plant stops blooming in spring and continuing throughout summer. This is when the plant is growing. Plants in the ground only need occasional fertilizer in summer to keep them growing, but in containers they need us to feed them since there is nothing in potting soil to keep them going. Fertilize with a high quality liquid fertilizer, such as fish emulsion. Mix according to package directions and feed every two weeks immediately after watering or instead of watering (But if doing the fertilizing this way you must give the plant enough so that the water drains out the bottom of the pot.) Stop fertilizing in summer.

Additionally, this plant needs pruning to keep it from getting entangled. Once the plant has bloomed, that is the time to prune it. Pruning hard after bloom encourages new growth that will flower the following fall into spring. Never prune it in late summer or fall since you will cut off the wood that is going to bloom throughout winter. So don’t prune it now in July. This plant blooms on wood that has grown throughout summer. Pruning after bloom also stimulates fresh growth, but in your case you must wait to prune until next year. If you are keeping the plant in the 5-gallon nursery can, now purchase a big tub and plant as directed above and then follow up by watering correctly and fertilizing with fish emulsion to get it growing again.

I hope by reading these instructions you can see what went wrong in your case. In regard to your question about nitrogen, it sounds as if you think you have over fed it, but having your soil in a pot tested for nitrogen content would cost more than buying a new plant next winter. Better to buy a new plant and start over and grow it correctly. CostCo has had these plants for two years in winter so probably they have a contract with a grower who knows just how to grow them. They most likely will have them again at the same time of year when they are in full bloom, so yes, January. You can also buy them in bloom from good nurseries, usually a better place to purchase a plant since they will be kept outdoors and not in a building where the roots might have dried out. If you plant, prune, fertilize and water a new one correctly and grow it in full sun there should not be a problem with too much nitrogen or anything else.

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6 Responses to “Lilac Vine (Hardenbergia ‘Happy Wanderer’) is not happy”

  1. elaine simmons May 30, 2014

    I want to grow a lilac vine in southern AZ. Would it survive if I planted it in full son?

    Reply
    • If you live in Sunset Climate Zones 8 to 24 you should be able to grow Hardenbergia ‘Happy Wanderer”, but in the hottest climates it needs partial shade or shade at midday. If I were you I would grow it on the east side of your home where it would have shade all afternoon, or place it in the shade of a tree, or arrange a shade cloth structure to provide the appropriate environment. Also a word of caution: Hardenbergia ‘Happy Wanderer’ is an admirable plant giving us delightful color in late winter winter and it looks quite wonderful covering an arbor, but it hates phosphorus more than many other Australian plants. Feed it nitrogen, but never feed it with a “balanced” or complete fertilizer containing phosphorus, or it very likely will die.

      Reply
  2. My vines are getting yellow leafs what is wrong?

    Reply
  3. This is an australian native, which requires a low phosphorous fertilizer – check the NPK rating on the pack and make sure the ‘P’ is low.

    Reply
    • Thanks so much for mentioning the fact that Australian natives detest phosphorus fertilizer. There is little or no phosphorus in Australian soils and as a result none of the Aussie plants need much of it since they can survive with very little. In fact, feeding phosphorus to proteas usually kills them and may kill other Australian native plants also. I think you have put your finger on the problem. I had a hardenbergia die also and now I realize I’d planted it in a spot where a climbing rose had previously grown. Undoubtedly there was phosphorus left l in the ground. Excellent point!

      Reply
  4. Hardenbergia needs full sun or a warm, sheltered or perhaps south-facing location. It does not seem to like cold wind. So yes location could be the problem. Also I think late winter when these plants are usually sold, since they are in bloom, may not be the best time for planting them since so many of them die, but I do not know this for a fact. Star jasmine (Trachelospermum jasminoides) usually grows well in sun or shade but takes off best when planted in warm weather. June is best. Ivy, Boston ivy (Parthenocissus tricuspidata), and Virginia creeper (P.quinquifolia) are other choice for vines that grows well in shade.

    Reply