Each week The West Australian’s Sabrina Hahn digs into readers’ gardening dilemmas. This week, she’s explaining how to freshen up some frangipani trees, and revealing the potential reason for two readers’ poorly plants — and the culprit may surprise you.
To submit your own question to the Green With Envy column, published inside Saturday’s The West Australian, write to Ask Sabrina, GPO Box D162, Perth 6001, or email home@wanews.com.au. Please include your full name and suburb. Due to the volume of questions, not all of them will be answered.
Princess in peril
Q A couple of years ago, I bought two small, very healthy looking, Silver Princesses from Bunnings and planted them in similar positions — though one gets a little late-arvo shade from a verge tree and the other is a little more exposed to easterly winds and planted (with soil improver etc.) in quite deep builders’ fill (around an elevated new build). They both got a lot of exposure to northern sun, were well watered, took off like rockets, and are now at least 5-6m tall. Some weeks ago, well before all the recent rain, the slightly shaded one began to flower, while the foliage on the other appeared to begin to die. All the leaves are now definitely dead but the smaller side branches still ‘scrape’ green. Is there something I can do to save this tree? Best wishes for your work.
Margaret Tyrer, Claremont
A The tree roots may have encountered builders’ fill and are unable to adjust to the soil type. To remediate the soil, add loam, clay, and compost around the base of both trees. Conduct a soil test to a depth of 30cm and check the pH compared to the top 10cm of soil; these trees typically grow on granite outcrops. The Silver Princess is a resprouter and has a lignotuber, which means it will reshoot from the base if you cut it down to near ground level. This will give it the best chance of survival.
On the fence
Q I’m writing on behalf of my dad John who at 88 is a huge fan. He’s always been a gardener and loved to discuss your columns with our family. He has recently moved house and planted tomatoes along the driveway. With these plants, he’s getting a lot of grey leaves. He normally has great success with his tomatoes and the fact that they are going on to die is confounding. I attach his photos for you to peruse. Please could you advise on what you think the problem may be?
On behalf of John Wilson, Westminster
A The driveway area is often used as an area to dump waste from building sites, including plaster, cement, paint and rubble from tradies cleaning their tools. The planting bed where the tomatoes are growing is very narrow, and the footings of the brick fence may occupy half the space. The tomatoes are displaying signs of nutrient deficiency and may also be infected with a virus. I recommend starting over and conducting a soil pH test to determine if it is very alkaline. If that is the case, you will need to add more compost, trace elements, manure and some clay. Given the limited space, applying liquid fertiliser every fortnight will also help enhance the growth of the tomatoes.
Potted problem
Q I live in the Subiaco area in an apartment complex. Surrounding our swimming pool are six planter boxes measuring 1200 x 1200 x 900D. These planter boxes contain one 10-year-old frangipani tree in each. The trees are 3m high and very healthy. The soil level in the planter boxes had dropped significantly. The three planter boxes on the southern side have dropped by 300-400mm. The three on the northern side have dropped by 200mm. Should we remove the frangipani, take the opportunity to re-waterproof the planter boxes and replant? How do we remove them and not lose them? How much canopy would we be able to remove? How much of a problem to the waterproof layer would the existing root ball be? Could we collar the trunk and simply fill up the planter box with soil and mulch? Should we underplant them with anything?
Kim Bolto, Subiaco
A The best solution is to prune the frangipani back by one-third, then carefully dig them up. Fill the planting boxes with fresh soil, ensuring they are filled to the top, and replant the trees on the same day. Since frangipani have a small root system, they are easy to remove. It is important not to raise the soil level above the trunk, as frangipani are susceptible to rotting. When replanting, ensure that they are positioned at the same trunk level. Great understory plants are perennials such as salvia or the ground cover Evolvulus ‘Blue My Mind’.
