‘Significant issue’ causing Japanese maple trees to die – how to avoid

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Japanese maples are a coveted small tree, especially the easily recognisable ones with red, weeping, lacy-leaves. That beauty comes with a price, though. Japanese maples aren’t the easiest tree to grow and keep alive. More have died than usual in the past few years, according to experts, leaving gardeners puzzled about what’s going wrong. Gardening experts have weighed in on what are some of the most common causes for these plants to die.

Mike McGroarty, gardening expert at Mike’s Backyard Nursery shared fertiliser is bad for Japanese maples. He said: “Garden fertilisers are a significant issue as they will kill Japanese maples and other plants.

“It’s true. The typical garden fertiliser that you buy for your veggie garden will take out ornamental plants like nobody’s business.

“If you plan to use regular garden fertiliser on your Japanese maple you might as well write ‘serial killer’ on the bag.”

This is because garden fertilisers are designed to be immediate release. The expert continued: “A bag of 14-14-14 garden fertiliser contains 14 percent nitrogen, 14 percent phosphorus and 14 percent potassium.

“And as soon as you apply it and it gets wet all 14 percent of that nitrogen is released immediately.

“Nitrogen drives top growth, vegetative growth, on plants. Most ornamental plants physically cannot grow fast enough to use that much nitrogen and the overload of nitrogen will kill them almost immediately.”

Mark Bennett, gardening expert at Gardener Report also noted that fertiliser is bad for Japanese maples, especially too much of it.

He said: “Japanese maples are not heavy feeders and they do not require additional fertiliser if they are planted in good soil, amended with compost.

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“Too much fertiliser is also a cause of leaf scorch with brown or yellowing leaves and excess growth with soft stems that can droop.”

Even if gardeners haven’t applied fertiliser to their maple, it is possible excess lawn fertiliser can dilute in rain water and run to the soil around the tree causing the leaves to scorch.

Mark warned: “It should be noted that due to cold weather, additional fertiliser can be a significant problem if it is applied too late in the season or too early as it causes the new growth to be more vulnerable to frost damage.

“The tender new growth turns black when damaged by frost and can be cut back with a pair of pruners without any significant damage to the tree.

“Once there has been too much fertiliser applied then there is not much you can do other than give it time to recover.”

The expert advised the only time fertiliser is necessary when growing Japanese maples is if they are planted in a pot or sandy soil. But if this is the case gardeners should only use half strength multi-purpose fertiliser.

The expert added: “Personally I prefer to use Miracle Gro fertiliser as it is in granule form, contains all the nutrients at the right concentration for your plants and it releases nutrients slowly to prevent problems associated with too much fertiliser.

“In most gardens however the use of a compost or leaf mould mulch adds nutrients to the soil, improves the soil structure and conserves moisture providing the optimal conditions of your Japanese maple.”

Mike agreed organic matter should always be used over regular fertiliser. He said: “What a Japanese maple really needs is good rich soil that contains a significant amount of organic matter. Really good topsoil is just that, organic matter.

“That’s what made it topsoil. For years and years vegetation falls to the earth and rots and becomes topsoil. That’s what all plants, especially Japanese maples, need.”

But not all gardeners have good soil, so what can they do? The expert suggested using fertiliser with something organic like fish emulsion fertiliser, Millorganite, or another organic fertiliser.

Mike added: “Keep in mind, Millorganite is good for your ornamental plants but not your vegetable garden because it’s made from sewage sludge.

“When installing new plants, especially Japanese maples, mix some rotted (bagged) cow manure with the soil as you fill around the plants.”

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