Green With Envy: Sabrina Hahn Answers Readers’ Gardening Queries on Vincas, Natives, and Fruit Trees
Each week, gardening expert Sabrina Hahn delves into the most challenging plant problems faced by West Australian gardeners. In her latest column, she offers detailed solutions for a range of issues, from a wayward tree to a mysterious vinca virus, helping enthusiasts cultivate healthier gardens.
Addressing a Wayward Red-Capped Yellow Gum
Maurice Swanson from Dunsborough sought advice on his red-capped yellow gum, which is growing into the street. Sabrina explains that this Illyarie gum (Eucalyptus erythrocorys) is a mallee, often sold as a single stem but naturally multi-stemmed. Due to heavy leaves and nuts, improper staking can cause it to lean. She recommends pruning it just above the lignotuber at the base now, which will encourage it to resprout as a shrub rather than a tree, improving its shape and stability.
Solving Yellowing Native Plants
Alan Helsby from Victoria Park reported that his native plants, including grevilleas and hakeas, began yellowing after thriving initially. Sabrina identifies this as a trace element deficiency common in Perth's alkaline sandy soils. She advises spraying with a foliar trace element spray and adding pelletised sulphur to the soil. Additionally, hydrophobic mulch might be preventing water penetration, so applying a wetting agent and checking soil moisture to 15cm depth is crucial. Testing the mulch's pH can also help diagnose the issue.
Investigating a Non-Fruiting Grapefruit Tree
Nicole Bertinshaw from Applecross has a 20-year-old grapefruit tree that is producing fruit on only two of its four main stems this year, despite all branches looking healthy. Sabrina suggests the problem may lie in the root system feeding the non-fruiting branches, possibly due to bacterial issues or root knot nematodes. To remedy this, she recommends applying blood and bone and sulphate of potash to the affected side, along with compost and a wetting agent, watered in thoroughly.
Combating Vinca Virus in the Garden
Christa Zimmel from Dianella has struggled with vincas shrivelling and dying after planting, even in purchased potting mix. Sabrina notes that a virus, similar to one that affected vincas five years ago, could be the culprit, transmitted via infected seeds or sap-sucking insects like thrips and aphids. The best solution is to remove affected plants, dig in fresh compost, and purchase healthy, advanced vincas. Spraying new plants with pyrethrum can protect them from insects and prevent further spread.
How to Submit Your Gardening Questions
Readers can submit their own questions to the Green With Envy column by writing to Ask Sabrina, GPO Box D162, Perth, 6001, or emailing home@wanews.com.au. Include your full name and suburb, but note that not all questions will be answered due to volume. Sabrina's insights continue to help gardeners across Western Australia tackle their plant problems with expert guidance.
