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Q&A

- Your questions answered.

SEND your gardening questions and photos to mailbox@nzgardener.co.nz.

Will we ever eat our own grapes?

Our grapevine is about eight years old. Every year we’re excited to see it covered with abundant bunches of fruit but by the end of January the grapes wither away. The largest grapes shrivel first and then the smaller ones slowly disappear. Should we give up our dream of homegrown sweet grapes and pull out the vine or can it be cured without the use of chemicals? GEOFF SHORE, AUCKLAND

How disappointing to see your apparently bumper crop disappear before your eyes year after year.

This is likely to be a fungal disease. Grapes can suffer from both powdery and downy mildew plus black spot, botrytis bunch rot and more.

Prevention is better than cure when tackling anything fungal. Prune to open out the canopy and reduce the humid conditions conducive to fungal growth.

Cut off unnecessary leaf growth (about 30cm past the bunches) to open the vine up to more air and light.

Even if you were prepared to use a fungicide, it’s probably too late to spray to prevent the problem this year. But you could consider spraying after the crop has finished to clean up the spores so they don’t overwinter. Make sure you cut off all the mummified fruit too.

Next year pay attention to the leaves as well as the fruit as you may be able to spot early symptoms and take action. Bill Brett (Garden Pest & Disease Control, gardenpestcontrol.co.nz) recommends these sprays:

Yellow or brown leaf spots indicate downy mildew – spray with copper hydoxide, Grosafe Free Flow Copper, from September onwards.

Powdery mildew shows up as a dusting of white on the leaves. Spray at the very first sign with Yates Fungus Fighter but note the withholding period and stop spraying 28 days before harvest. Close to harvest, use Grosafe Enspray 99.

Black spots on the leaves and stems are more likely to occur in cool wet weather. Treat as for powdery mildew.

Botrytis is a mould that develops on the fruit and spreads rapidly. It is more prevalent in wet weather as the fruit ripens. Spray with Kiwicare Thiram (observe the seven-day withholding period) or Yates Natures Way Natrasoap. Barbara Smith

Blooming at last

This air plant sat on my bathroom windowsill for over 20 years but never flowered. Imagine my surprise when I saw this tubular bloom. Please tell me what it is and where it came from. JILL SUTTON, CHRISTCHURCH

You have a lovely example of Tillandsia ionantha in flower.

You have done a wonderful job keeping your little South American air plant happy all these years. It obviously enjoyed your indoor environment where it received the bright filtered light, good air flow and sufficient moisture it needed to grow happily.

Weekly misting is a good way to apply moisture, and try a spray of orchid feed (diluted 1 in 4) once a month from October through to March. It is important that they dry out between waterings.

More information on growing tillandsias and bromeliads is available from the Bromeliad Society of New Zealand (bsnz.org). Our annual Fiesta Show and Sale is in Auckland on February 19-20, 2022.

Diane Timmins, Bromeliad Society of New Zealand

My triffid

This suddenly sprouted from what I thought was a cordyline. It’s been planted for about 10 years but this is the first time it’s done this. Can you please identify it. Will it die after flowering? GAEL EDWARDS, ROTORUA

It is a giant spear lily. Originally from small areas of New South Wales and Queensland, it is now popular with landscapers as it is low maintenance and copes with most soils and is drought resistant.

Ground up roots and the roasted flower stalks were once used as a food source for indigenous Australians.

The scape, or flowering stalk, can reach 5m. If it droops under the weight of the flowers it is Doryanthes palmeri but if it stays erect it’s Doryanthes excelsa.

Each rosette of leaves flowers once then dies, leaving behind several pups (young rosettes) in a ring around the base of the original plant.

It’s got a long way to go before it dies – the flowers last for many months.

Barbara Smith

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2022-01-01T08:00:00.0000000Z

2022-01-01T08:00:00.0000000Z

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