How to divide dahlia 'senior ball'

Dahlia 'Senior Ball' grows from a storage organ, so dividing means splitting that rather than pulling roots apart. The rule is simple: every piece you keep must have at least one healthy bud or growing point, and enough stored tissue to fuel it. Pieces without a bud will never grow, however healthy they look.

At the end of dormancy, just before growth restarts — that is when the buds are visible but not yet fragile.

Lift once the plant is dormant or just waking, brush off the soil, and cut into sections with a clean knife so each has one or more buds. Let the cut surfaces dry for a day before replanting so they seal rather than rot.

Pot each division into fresh compost at the same depth it was growing before, water it in well, and keep it somewhere bright but out of direct sun for two to three weeks while new roots take hold. Do not feed straight away — damaged roots take up fertiliser poorly and it can scorch them.