Some of the leaves in the back of tree are turning pale then brown and falling.The tree is about 7ft 3 inc. It sits between 2 tall pine trees on a bed with perrenials. the roots of the pine are all over the flower bed. The trees were doing fine until now. They are south facing and gets adequate sun and are watered every other day. They are
about 18 yrs old.Some of the leaves in back have stared to turn pale yellow. Please help I have 2 trees. Thank you.
Thank you for contacting Toronto Master Gardeners about your Loebner magnolia, Magnolia x loebneri.
This small deciduous tree typically grows 20-30’ tall with a rounded crown. It is often grown in a multi-trunked form. Magnolias have a shallow root system.
Loebner magnolias are best grown in moist, organically rich, well-drained loams. Light requirements are full sun (6 or more hours of direct sunlight a day) to partial shade (direct sunlight only part of the day, 2-6 hours). These trees are intolerant of urban pollution and of soil extremes (dry or wet).
If you haven’t already, inspect the yellowing leaves for signs of any pests or diseases. If you see any signs of either, take a photo and send it to us for identification and recommendations.
If there are no signs of pests or disease, then I suspect that the dying leaves could be due to soil that is too dry. We have had very dry conditions in Toronto this summer. There may just not be enough moisture in the soil, especially given the competition for water from the adjacent pine trees.
You do not say what kind of soil the trees are planted in, or how much water you provide your trees when you water. Here is a simple method to check for soil moisture:
Use a hand trowel or a sharp spade to dig down a foot into the soil part way between the tree trunk and the drip line. Take a handful of soil from the bottom of the hole and squeeze it. If the soil sticks together then it is moist. If you release the soil from your hand and it won’t hold a ball, it is too dry.
Adjust your watering based on your soil moisture test results to ensure that the soil around your trees remains reasonably moist at all times.
Note that magnolias planted in sandy soils need regular watering in smaller amounts, while magnolias in clay soils require deep, infrequent watering.
Also, to reduce moisture loss in the soil, I suggest you place a layer of mulch around the trunk to cover the soil over the tree root zone. Here is a guide to proper mulching .
Loebner magnolias are beautiful trees. I hope your magnolias recover.