Ideal pruning for rhododendrons

YOUR questions answered about rhododendrons, tuberoses, cicadas and Mediterranean shallots.

Peter Cundall gardening September 28... Rhododendron ‘Susan’ in full November bloom.

MY rhododendrons have become increasingly leggy. What pruning technique and fertilisers will encourage bushy growth and more flowers?

- Katherine Healy, Aldgate, South Australia

The usual method is cutting just behind the spent flower clusters, or twisting them off by hand. You can rejuvenate leggy plants with harder pruning, even into old wood. If plants are not very vigorous, do this to just half the stems, and the remainder the following year. Rhododendrons like acidic soil enriched with compost but don’t need a lot of fertiliser. An organic-based fertiliser for azaleas and camellias is ideal.

My tuberoses grew long flower stems with myriad big strong buds, but they never opened and then fell off. Why? They had plenty of sun, water and fertiliser. - Helen Sullivan, Brisbane

Deliciously fragrant tuberoses are frost-hardy but not drought-hardy. The bulbs need plenty of water once they start flowering. Extreme heat can stop buds from opening. Double-flowered forms can have problems with buds opening, particularly if flowering later in the season. A shortage of nitrogen in the later stages is blamed; try supplementing nitrogen once the flower spikes develop. Tuberose bulbs only flower once, but side bulbs that develop will continue production.

My cycads get badly eaten by blue moths. What dilution of Yates Success should I use? - Margaret Jennings, by email

Success Ultra treats all types of caterpillars, including those of the cycad blue butterfly, with the same dilution rate of 5ml per litre, as per the label. It has contact and some residual control. Timing is critical with this pest; spray as soon as each flush of new fronds develops, repeating weekly as they unfurl.

Where can I buy some Mediterranean or multiplying shallots? As a child in Griffith, everyone grew them. - Neville Quarello, by email

Australians tend to misname spring onions as shallots, but true shallots form clusters of bulbs. There are several varieties. Allium ascalonicum, called eschalots, are popular in the Mediterranean; A. cepa (Aggregatum group), called potato or multiplier onions, have larger bulbs; and A. cepa (Proliferum group), the tree or walking onion, is a taller plant that forms bulblets on the flower stem. Try greenharvest.com.au and greenpatchseeds.com.au.

Flora

Flanders poppies are a powerful symbol of war remembrance, particularly so for Australians commemorating Anzac Day. These scarlet blooms grew in profusion on the disturbed ground of the battlefields; today they’re common across Europe in ploughed fields and along roadsides. To mark the centenary of the Gallipoli landings, Mr Fothergill’s Seeds has partnered with Legacy Australia, donating 50c of every $2.95 packet of commemorative poppy seeds sold. Legacy volunteers are dedicated to caring for the families of deceased and incapacitated veterans. The centenary seeds are available now at garden centres and leading hardware stores. Sow them from late summer to autumn for spring to summer flowering. Position the seeds where you’d like them to grow, as they don’t like transplanting