How to encourage Magnolias to grow?

Mestry1

Attention all green thumbs...

About 2 years ago, I planted 15 Magnolia's approx. 1.5m apart along the back of our property. the intention that these would form a nice looking barrier, blocking our rear neighbours from our view.

Unfortunately, since then 3x have died and the remaining have not grown in height or width. They look exactly the same as the day we purchased and planted.

During the last two years we have tried the following: 

• Daily Soaking - at least 2-5lts of water per tree, this only cleared up signs of dehydration in the leaves
• Liquid fertiliser - a Bunnings rep, recommended Yates - Dynamic Fertiliser and we've been using it nearly every 3-4weeks 
• Horse manure -  after doing a soil test, our PH was quite high (alkaline) we added manure to the base of each tree. 
• Dead growth - over time any branches (twigs) that were looking deadish, were removed.

Lastly, we have 2x Golden Retrievers, who often frequent these areas for 1's and 2's. I initially thought they maybe responsible for the lack of growth, however, 1x area with 5x trees are completely cut off from them and they are still not growing. 

We are a little lost and thinking of just ripping them out and starting again. 

Any help or ideas is greatly appreciated. 

Ryan 

EricL

Hello @Mestry1 

Thank you for sharing your question about your Magnolia's. It sounds like you've been very attentive to your magnolias, and it’s frustrating when they don’t thrive despite your efforts. Based on your description, it’s possible that the soil is still unbalanced or lacking key nutrients. Magnolias prefer slightly acidic to neutral soil (pH 5.5-7), and your initial test showing high alkalinity might still be a factor. High soil alkalinity can limit the availability of essential nutrients, which could explain the lack of growth.

To address this, I recommend testing the soil again using a kit like the Manutec Garden Care Products Soil PH Test Kit available at the store. If it still shows high pH, you could lower it with Manutec 1.5kg Sulphur Fine Granules or Sulphate of Ammonia to create a more favourable environment for magnolias. To ensure the trees are getting the nutrients they need, consider incorporating a slow-release fertilizer designed for acid-loving plants, such as Scotts Osmocote Controlled Release Fertiliser for Roses, Gardenias, and Azaleas, which is also suitable for magnolias.

Additionally, improving the soil's organic matter can make a significant difference. Use a quality compost, like Osmocote 25L Scotts Compost Premium Soil Improver, and apply a thick layer of pine bark mulch, which gradually breaks down and can help maintain a slightly acidic pH. Be sure to keep the mulch a few centimetres away from the trunk to avoid rot.

Given the history of horse manure application, it's also worth ensuring it was well-aged, as fresh manure can sometimes create a nitrogen imbalance or "burn" plants. If you’re unsure, you might opt for a neutral organic option like Dynamic Lifter Soil Improver & Plant Fertiliser to rebuild nutrient levels.

Lastly, your dogs’ activities might contribute to localized issues due to urine’s high nitrogen content, which can disrupt the soil. A barrier or frequent watering of these areas can dilute and minimize the impact.

If after these steps the trees still don’t improve, it might be worth consulting an arborist for a closer look at the soil, roots, and general planting conditions before making the difficult decision to replant. Hopefully, these suggestions will help give your magnolias the boost they need to flourish!

Here is a handy step-by-step guide: Growing, pruning and caring for magnolia trees

If you have any other questions we can help with, please let us know.

Eric