ChatterBank1 min ago
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It will almost certainly need chemical treatment unless you can afford to get the stump ground out by a profesional.
I'd use any of the SBK (systemic brushwood killers) type weedkillers and mix it with diesel (2 sbk : 1 diesel)
Drill some holes in the top of the stump around 6" deep and pour the mix in. Spring would probably be the best time to do it but be careful, sbk is quite a nasty chemical.
Willow is well known for sending up sucker growth from stumps and roots, cutting them back rejuvenates the even more. Chemical treatments are available if physical removal is impractical. Sodium chlorate is the one most commonly used, you can buy products tailored for this purpose from nurserymen and garden centres- Amicide and Stump-out are two that spring to mind.
Method- drill holes in cut stumps 2"apart and about 1 1/2" deep, fill with the chemical and seal with clay or secure polythene sheeting over the top/s to prevnt rain splashing it out.
Personal Safety-Use suitable protective clothing, rubber gloves and goggles, in case of accidental spillage. Good Luck..