Overwintering guide
How to overwinter flat sea holly
Winter watering
No winter watering needed in open ground. Containers only need water in long dry, frost-free spells.
The mistake that kills flat sea holly in winter
Cutting flat sea holly hard back in autumn "to tidy up". That removes the growth that shelters the crown, and on some plants removes next season's flower buds entirely.
More flat sea holly care
Overwintering flat sea holly — FAQ
Does flat sea holly need to come indoors for winter?
Flat Sea Holly is hardy to roughly USDA zone 4 — winter lows around -34°C. That means it can stay outside all winter in most temperate gardens. Flat Sea Holly is properly hardy and overwinters outside without fuss. Tidy away anything dead or diseased, apply a mulch over the crown to steady soil temperatures, and otherwise leave it alone — many hardy plants actually need a cold period to flower and grow well the following year. Save hard pruning for the right season rather than doing it in autumn.
When should I move flat sea holly for winter?
Tidy and mulch in late autumn; leave the plant undisturbed until spring.
How often should I water flat sea holly in winter?
No winter watering needed in open ground. Containers only need water in long dry, frost-free spells.
What kills flat sea holly over winter?
Cutting flat sea holly hard back in autumn "to tidy up". That removes the growth that shelters the crown, and on some plants removes next season's flower buds entirely.