This is the section to ask your green thumb questions. If you have a home gardening query please address it to Help @GreenFingers. com. au and we will do our best to help out. Many thanks to Helen Yung, Horticulturist, for her expertise.
Q – What care do I give my new air plants, positioned on an inside wreath?
Tillandsia species are small bromeliads that capture water and nutrients through their leaves, so can grow without soil. They need bright, indirect light. Mist with water – frequency depends on their microclimate but let them dry out between waterings. Add fertiliser to the misting water each month. Soaking in a bowl of water for two hours occasionally is recommended.
Q – What flowers could I grow to attract butterflies and for my grandchildren to pick? (Adelaide Hills)
Butterflies love nectar-rich, bright flowers, particularly clusters of small flowers or ones with open flat petals. Butterfly bush (Buddleia) is the standout: look for sterile, dwarf cultivars that won’t become weedy. Others include daisies, heliotrope, sunflowers, pentas, verbena, cosmos and lavender. More at Butterfly Conservation South Australia
Q – What small plants would add colour and interest to our sunny and windy triangular bed in the dry tropics (North Queensland) ?
Try dwarf ixoras, Barleria ‘Purple Dazzler’, Cuphea ‘Mad Hatter’ in mauve or white, blue Evolvulus pilosus and society garlic (Tulbaghia). Natives include yellow buttons (Chrysocephalum apiculatum), strawflower (Xerochrysum bracteatum), native gardenia (Gardenia psidioides) and white fan-flower (Scaevola albida).
Q – Is it a gardening myth that free ferns (Dicksonia antarctica) benefit from some sugar or golden syrup on the crown and should be watered from the top in a trickle?
Plants manufacture their own sugars (glucose) through photosynthesis. No definitive studies have proven refined sugar solutions will benefit them; in fact they can be detrimental. Sugar water can, however, help cut flowers last longer. Tree fern trunks are essentially a root mass, so watering all over and from the top is beneficial.
Q – What sculptural plant would suit a large pot in part shade to feature in my 6m x 4m courtyard? I live in the Southern Highlands of NSW
For a contemporary edge, try tree aloe (Aloe barberae), Agave ‘El Mirador’ or dragons blood tree (Dracaena draco). For lush foliage, fiddle-leaf fig (Ficus lyrata) or lady finger palm (Rhapis excelsa) are good. You could also try cycads such as Cycas revoluta and native burrawang (Macrozamia communis).
Q – Is applying liquid fertiliser and seaweed to leaves harmful? Do they block the leaves’ stomata and disrupt evapotranspiration?
A – Foliar feeding is not harmful but is not very efficient. Much of the benefit comes from fertiliser running off leaves into the soil anyway. However, it is a beneficial way to rapidly supply major nutrients, or to apply iron, and manganese to plants growing in alkaline soils, or to feed plants where soil nutrients are stolen by aggressive plants nearby. Nutrients enter through the leaf cuticle and stomatal pores without detriment.
Q – My foxgloves are huge. I thought they finished flowering but they keep coming up. What should I do after flowering?
Foxgloves traditionally are biennials that grow a rosette of foliage in their first year and produce 1-1.5m-tall flower spires in spring and summer the second year, before dying. Newer strains can flower within one year. After the first flush, cut the main flower stems just above the basal leaves to encourage several shorter flower stems to follow. Foxgloves readily self-seed so you can have an ongoing supply. The plants are highly poisonous.
Q – What shrubs or climbers would hide a sunny 1.5m-tall brick wall but not make a mess in our pool just 2m away? (Ashmore, Queensland)
As living things, most plants shed something. Clumping palms such as cascade palm (Chamaedorea cataractarum), gingers, elephant’s ears and broad-leafed cordylines are some of the tidiest plants but may burn in hot sun. Consider bird of paradise, cannas, Euphorbia ‘Firesticks’, Nandina ‘Gulf Stream’, Dracaena reflexa, dwarf oleanders, and maybe gardenias. Climbers include bower vine (Pandorea jasminoides), glory bower (Clerodendrum splendens) and stephanotis; these will drop more flowers.
Q – My columnar, spiky cactus has produced several offshoots at the base. Can I propagate them?
Yes. Cut them off with a clean, sharp, sterilised knife, and bevel the cut end towards the central core; allow cuttings to dry until they’re callused over, then plant into coarse sand. Spring is the ideal time. Water sparingly until roots form.