Garden tips: asparagus; frangipani; roses; Phostrogen substitute

My asparagus went to seed and now there are seedlings everywhere. What should I do?

Asparagus take four years to grow to harvestable size.

Last year my asparagus went to seed after several weeks of yummy produce and now many seedlings have developed. Will they crowd the bed? Can I transplant them to a new bed? Will they develop serious crowns?

ALISON CHARLTON, BUNGENDORE, NSW

Each seedling can develop to a full-size crown, so they would crowd the bed. They’ll take four years to grow to harvestable size. Only female plants produce seeds but both sexes are needed for fertile seed; male plants are said to live longer and give better yields. The flowers on male plants are larger and showier. Transplant seedlings in autumn.

A rescued, pot-bound frangipani, planted in my garden in full sun three years ago, has flourished with new growth but never flowered. There are many flowering frangipanis in the area. How can I encourage the supposedly pinky-apricot flowers?

CLARE MCNAMARA, SPRINGWOOD, NSW

It’s common for pot-bound plants to put energy into green growth for the first year or so after release into the ground. Young trees also favour growth over reproduction (flowering). It’s probably older trees you are seeing flowering. Also, the mid-Blue Mountains is getting marginal for frost-tender frangipanis and young trees are more susceptible. Microclimate will affect success. You could try applying a flower-promoting fertiliser, high in potassium and phosphorus.

This year three of our roses, all good named varieties, produced a dull red flower with neither form nor fragrance. Is there anything we can do except pull them out and replace them? May it happen to others?

A HARRIS, ORMISTON, QUEENSLAND

These flowers will be from the common rootstock on to which roses are grafted. Promptly remove any shoots coming from below the graft. If allowed to develop, their stronger growth can kill the desirable, grafted rose. If this hasn’t happened yet, you could save your roses but you’ll need to keep removing such suckers.

Can you help us find Phostrogen? We’ve used it in the past but cannot find it anywhere here.

DIANA DREDGE, BRISBANE

Phostrogen is no longer available in Australia. It had an NPK of 14:4.4:22. The closest substitute would be Thrive Flower and Fruit at 14:2.6:21. Like Phostrogen, it is a soluble powder.

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Send questions to: [e-mail] Helen Young, PO Box 3098, Willoughby North, NSW 2068. Website: helenyoung.com.au. The best question for December wins a signed copy of The Australian Native Garden by Angus Stewart and AB Bishop, worth $50. November’s winner is Chris Hogan of Brisbane, for his question about weed mat.