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Mulching Trees- the 411

Most trees in Newburyport are mulched mistakenly. Too often we see what the horticulture industry refers to as “volcano” mulching – the mulch is piled in a cone shape with the highest point around the tree. This is incorrect. The mulch should not touch the bark of your trees or woody plants.

We apply mulch to protect the tree – from the soil drying out too quickly in summer, from lawnmower and weed whacker damage, and to create future nutrients for the tree. Mulch should be applied out to the drip line of the tree – as grass and tree needs are different. The mulch should not touch the based of the tree but should be applied 2-3 inches rising more to the outside edge which creates a slight pool when watering – especially for new trees.

What happens when the mulch is too thick and too close to the tree trunk? The tree cannot ‘breathe’. Every inch of mulch is like applying an electric blanket. As a tree grows, air exchange is conducted in the base roots. When these roots are covered up, the tree begins to grow a secondary root system to reach the air. Eventually the original root system dies out and often the new root system is not secure or mature enough to support the tree. It dies or it falls over.

When you look at the base of a mature tree, you will see the flare and those lovely fat roots coming off the base of the trunk – don’t hide them! When selecting and planting a new tree, look for one where you can see the swelling at the base of the tree and a couple of top roots. If you cannot see them, gently use a fork to pull the soil away from the trunk until you do find the top of the main roots. This becomes the depth you want to plant the tree. It is healthier for the tree to be planted a little high in the soil than too low. Open the soil ball of the tree – loosen it up and help the roots find their way out into the ground. And be patient – it takes three years for the tree to realize it has a new home. Sleep, creep and leap is the horticulturist motto for plants.

If you have mulched incorrectly what can you do to help your tree? Go out and begin pulling the soil away. If you see tiny new roots coming off the trunk, cut them away. Keep exposing the soil as much as you can. Sometimes this means that you have a circle deeper than the lawn around your tree but that is okay. If your tree is still young or new – dig and raise it up to the right level.

The same principles apply to your shrubs – do not let the mulch sit up against the bark.

Typically, if your tree shows decline in its canopy, it means that there is a problem below ground. Look and correct the soil and mulch around the base. If a very major tree with years of build up, call a tree company to come and provide an estimate for air spading to loosen the soil and find the flare of the tree.

The last word on mulch – you do not need to mulch every year, let it break down into soil and feed your trees with a bit of compost instead. If you want the clean aesthetic look of mulch each year, you may need to remove some of the old before applying the new to keep your trees healthy.

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