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How to plant trees which will last

Arborist Mark Roberts tells us how planting a tree requires a lot more than simply sticking it in the ground. Considering the tree’s roots, soil, staking and transport are all essential

I began my career as a horticulturist in the late 1980s. It wasn’t intentional, it just kind of happened. In the 90s, I left the dirt and got into the trees and by the 2000s I moved into education. During that time, I had become involved in an American-based organisation, the International Society of Arboriculture, and started travelling to the USA two or three times a year. One of the many projects they were working on was the development of planting specifications. I had been planting trees and shrubs for more than 20 years and didn’t realise that poor planting was such a problem – but clearly it was then and it seems it still is.

There is no secret to good planting – just find the root flare, plant to the root flare, tease and water. Get it right and life is easy; get it wrong and the problem persists.

Time doesn’t resolve this – three, five, 15 years later, poor planting doesn’t get better. If you get it wrong at the start, you have set a train wreck into motion. There will be only one outcome.

So, how can trees and shrubs be planted right from the get-go? For starters, do less – or more so, don’t do more.

A quality product starts at the nursery, so find a good nursery and use quality plants.

When it comes to plant selection, before you buy or plant it, make sure you:

  1. Remove all stakes or ties*. If the plant can’t support its own weight, then it’s not got much hope in the real world (put it back and get another one).

  2. The root flare (the transition between roots and trunk/stem) should be visible. Gently scrape the potting mix away from the base of the trunk – the first root(s) should be sitting just under the surface (if you can’t see them, something bad or slack has occurred, put it back and get another one).

  3. With the plant on the ground, give it a wiggle – if the bag moves in time with your movement, it’s probably root-bound (put it back and get another one).

  4. Again, with the plant on the ground, give it a wiggle. If half the soil in the bag moves in time with your movement, the plant has probably just been re-potted (this is not necessarily a bad thing, but it will affect how you transport the plant and how you get the plant out of the bag at planting – extra care is required).

When you transport your plants from the nursery to site, don’t chuck them on the back of the ute or on an open trailer. Cover them up to protect them from the wind.

When it comes to planting, make sure you:

  1. Dig a hole wider than deep (roots grow out, not down). The planting hole only needs to be as deep as the bag the plant came in, but it should be two or three times as wide.

  2. Don’t mix in or introduce new soil (your plant has to survive in the soil that is around it – don’t give it false hope).

  3. Don’t sprinkle or incorporate fertiliser into the planting hole (you’ll probably kill the roots).

  4. I don’t recommend slow-release fertiliser tablets either, but if you must, don’t put them in the bottom of the hole (roots grow out, not down).

Once the hole is dug, gently remove the plant from the planter bag (or pot) – do this as close as practical to the hole. Then:

  1. Place the plant in the hole, so it is vertical and orientated correctly. Check that the hole is the correct depth – ie, once the hole is back-filled the root flare will end up at or just above the finished soil level.

  2. With the plant in the hole, tease the roots. Don’t be brutal but don’t be afraid to cut or bend them, separate them and/or move them about so none are circling (dizzy roots kill trees).

  3. Put the original soil back in the hole and firm it down – don’t stomp or force it into the hole.

  4. Check to make sure that the root flare is at or just above the finished soil level – if the plant is sitting too high, replant it. If it is sitting too deep, replant it.

If you have to stake your plant, then do it to keep the root-ball in place. Here’s how:

  1. Stake it low and make sure the top third, if not the top two thirds, of the plant can move about in the wind (it is this movement that causes roots to grow).

  2. Position the stakes outside of the root-ball then drive them in (making sure you don’t damage the foliage in the process).

  3. Only use natural fibre webbing ties (they’ll rot off when you forget to remove them). Consider using three stakes to reduce the chances of mower damage/access.

  4. Mulch it to beyond the edges of the planting hole – or even further if it is not in a garden bed.

  5. Water it. Even if it’s winter, even if it’s raining, water your newly planted plant in.

When it comes to aftercare, remember that the bigger the plant is, the greater its needs will be. Sometimes smaller plants can establish faster and may well grow to fill the gap quicker than larger plantings. Think in terms of growing seasons, at least two and more if you can. The key to aftercare is water – too much and you will kill it, not enough and you will have waste your time and effort. Water is key.

To recap, there is no secret to planting; simply identify the root flare, plant to the root flare, tease the roots (remembering that roots grow out, not down) then water your plant.

* Do not go about removing stakes and/or ties in the nursery without asking permission first.

Mark Roberts is a qualified arborist and tree risk assessor with 25 years’ experience. Mark is also former President of the International Society of Arboriculture, and a past President of the NZ Arboricultural Association. Mark now heads an arboricultural collective based in Dunedin:

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