How to save Mandevilla and Syzygium after hot summer?

Rosana1

Hello Bunnings Workshop Community!

After a torrid summer, some of my plants have not survived and others are still fighting, but I want to make sure they go through winter and get to spring looking healthy and ready to grow a bit more!

The first one was a mandevilla that we bought at Bunnings and that looked stunning then. I sent you photos when it started to lose leaves, but it still had new growth, so we kept doing what we were doing. The very hot days, the windy ones and maybe the transferring to another pot took its tole. Now, it looks pretty bad( attaching photos)

My questions is: all the dry stems, should I cut them short? Or is there hope that new growth will come to these branches?

Also, thought of buying more potting mix, filling up the vases, covering with mulch and letting it rest for winter. Should I fertilise before doing that?

My other plant is a Syzygium. Unfortunately, we have 6 of them against a fence and they were all affected by the intense heat that came from the fence. 5 of them are all healthy now, with lots of new growth, but this one has lost all its leaves at the top, branches are looking very dry/dead, but it is pretty healthy at the bottom.(we have added a protection now next to the plant to protect it from the wind and the hot air blow from the air conditioner and will probably try to hang a sail from the fence next summer)

Same question: do I cut the dry stems or will the new growth come on them? As for preparing for winter, can I also add extra soil, fertiliser and mulch?

So, these are my questions. I hope you can help

Thanks in advance,

Rosana

EricL

Hello @Rosana1

Thank you very much for sharing your question about your Mandevilla and Syzygium plants.

Your Mandevilla has definitely taken a hit from the heat, wind and transplant shock, but the good news is it’s still alive and already pushing new growth from lower down, which is exactly what you want to see. The dry stems at the top won’t recover, so it’s best to prune them back. You can lightly scratch the bark with your fingernail first, if it’s brown and brittle it’s dead, if it’s green there’s still life. In your case most of those upper twigs look completely dry, so I would cut them back gradually until you reach green wood. Don’t be afraid to reduce it quite hard; Mandevilla actually responds well to pruning and will regrow from the healthier lower sections in spring.

After pruning, topping up the pot with fresh mix and adding mulch is a great idea. I wouldn’t use a strong fertiliser right now because we’re heading into cooler weather, but a gentle slow-release feed is perfect so it wakes up stronger in spring. Something like https://www.bunnings.com.au/scotts-osmocote-1kg-all-purpose-controlled-release-fertiliser_p2961306 mixed lightly into the top, then topping up with fresh potting mix such as https://www.bunnings.com.au/seasol-25l-advanced-potting-mix_p0274160 and finishing with a layer of https://www.bunnings.com.au/richgro-40l-pine-bark-mulch_p2980119 will help insulate roots and hold moisture over winter.

Your Syzygium is a really common outcome after a brutal summer, especially near fences where heat radiates back onto the plant. The fact that it’s lush and healthy at the bottom is very encouraging and means the root system is still strong. The bare top branches won’t re-leaf if they’re completely dead, so I’d prune those back as well, but try to shape it gradually rather than chopping everything at once. Often new shoots will emerge just below where you cut, and you’ll rebuild a new top over spring and summer. If you leave the dead wood in place, it just wastes energy and slows the recovery.

Adding extra soil, a light slow-release fertiliser and mulch is perfect here too. The mulch is particularly helpful because it keeps roots warmer through winter and cooler next summer, which will make a big difference next time you get those hot northerlies.

Overall, both plants are stressed but very recoverable. A tidy prune, fresh soil, light feed and mulch now will let them rest over winter, and once temperatures lift in spring, you’ll see them push strong new growth again. They won’t look amazing immediately, but they should bounce back nicely over the next growing season.

If you need further assistance, please let us know.

Eric