What the stump killer products actually do
Stump killers sold for gardens are usually one of two things: potassium nitrate, sold as a rot accelerator, or a glyphosate based treatment painted onto a freshly cut surface. Neither removes the stump. The nitrate feeds the fungi that decay wood, so the stump rots a little sooner. Glyphosate kills the living tissue so the stump stops sending up shoots, and it only works if it goes on within minutes of the cut, while the tree is still growing.
Both are a poor choice beside a hedge, a border or a tree you want to keep, because the treatment does not stay inside the stump. Used to get rid of a stump, most of these products do not work, and most gardens that try them are disappointed.
Tree stump regrowth
Some species sucker freely from a cut stump: willow, poplar, sycamore, cherry and lilac are the worst offenders. Cut those flush to the ground and the problem gets worse. The stump holds a store of energy in its roots, and a cut at ground level leaves a ring of live tissue with nowhere to go but up.
Cut a troublesome stump lower, to around 100mm, and keep cutting the regrowth through the growing season, before it hardens, because a stump left to itself only gets stronger. Without leaves, the roots run out of reserves, usually over two or three seasons. A stump you want gone for good is better ground out.
Getting rid of a stump: what drives the price
Grinding is usually the real answer, because it takes the stump out instead of waiting years for it to rot. A machine cuts the stump down below ground level, usually 150mm to 300mm deep, and leaves the roots in place to decay.
The work is priced on the stump and the site: the diameter, how many passes the cutter makes, the species and how hard the wood is, and whether a machine can reach it. Access is often the deciding factor, because a grinder needs a clear route through the garden. A stump in a tight corner or beside a wall may need a smaller machine and more time. Our tree pruning cost page explains what moves a figure on this side of the work, from the size of the stump to the route a machine has to take.
What an old stump leaves in the ground
The stump is only half the story, and what it leaves behind depends on where it stands. In a lawn, a stump is a mowing hazard and a trip hazard, with grass dying back in its shade. In a border it holds the space a shrub or a rose could use, and its roots go on drinking from the soil around it. Along a mowing strip or a fence line it snags the line and turns strimming into slow work. A soft, hollow stump can also give way underfoot.
Roots stay in the ground after any stump comes out, and they affect it for years. As they rot, the soil above them sinks, so a strip of lawn over an old root plate dips and scalps under the mower. Fill the dip with topsoil, firm it and seed it, and expect to top it up for a season or two.
When surface roots have to come out
Old surface roots are worth taking out where they lift paving, catch a blade or leave a border unplantable. A grinder only cuts what it can reach, so roots running away from the stump are a separate job. Roots close to a live tree you want to keep are structural, and cutting them is not garden work: it needs an assessment first, which our tree roots page explains, and the Arboricultural Association covers what a survey looks at.
Once the wood is out and the ground is levelled, the spot is ready to plant again. Replanting and the aftercare that follows are the practice's work, through tree planting and garden maintenance.
Questions about this guide
- Will a stump killer remove a tree stump?
- No. A nitrate product feeds the fungi that rot the wood, which may speed the process up over months or years, and a glyphosate treatment can stop a stump sending up shoots if it is applied to a fresh cut. The wood is still there in both cases.
- Why does my tree stump keep growing back?
- The roots still hold energy and the stump still has live tissue around its edge. Willow, poplar, sycamore, cherry and lilac are the worst for it. Keep cutting the shoots before they harden and the roots will run out of reserves over two or three seasons, or have the stump ground out.
- How long does a tree stump take to rot?
- It depends on the species and the ground. Willow, poplar and sycamore break down in a few years, while oak heartwood can stand for decades. A stump in wet soil rots faster than one in dry, free draining ground. Grinding settles the question in an afternoon.
- Can I plant where a stump was ground out?
- Yes, once the grindings are out and the hole is backfilled and firmed. Wood chips take nitrogen from the soil as they rot, so they are better used as a mulch elsewhere. Give the ground a season to settle before you plant into it.
- Do I need to remove the roots as well as the stump?
- Not always. Roots left in the ground decay and feed the soil, and the dip that follows is easy to top up. Take them out where they lift paving, trip a mower or leave the border unplantable, and leave alone any that are holding up a tree you are keeping.
Need this done in your garden?
The practice prunes fruit trees and garden trees across North Yorkshire and County Durham. Tree surgery, including removal and stump grinding, goes to Ross Webster Tree Services. Their contact details are on their own site.