At a glance
- Rosemary rarely freezes to death, it drowns and rots. Wet cold at the root ball kills it far more often than pure frost.
- Overwinter it cool and bright at a few degrees above zero, not in the warm home. In a pot it is safer than planted out, because you can protect it from winter wet.
- There are hardy varieties such as 'Arp' or 'Veitshöchheimer Rosmarin' that stay outside in mild regions with protection. Ordinary rosemary is only partly hardy.
- Prune regularly, but never into the old, leafless wood. Rosemary barely re-sprouts from bare wood. Pruning keeps it bushy and young.
Rosemary is considered Mediterranean and touchy, yet it is tougher than thought, just in its own way. Most lose it not in deepest winter but in a cold, wet November quarters or because they prune it wrongly. Both are easy to avoid.
Two things you must understand: how rosemary overwinters and how to prune it without losing it. This article shows both and reveals which varieties may even stay outside here.
Rosemary
Salvia rosmarinus
- Standort
- full sun, poor, free-draining, warm
- Saison
- cool and bright, a few degrees above zero
Wet cold, not frost
The mistake with rosemary is the same as with the olive: you fear the frost and overlook the real danger. Rosemary tolerates dry cold quite well. What kills it is wet cold: a soaked, cold root ball makes the roots rot.
So a potted rosemary is often safer than a planted-out one, because you can protect the pot from constant rain and waterlogging. Overwinter it cool and bright, much like other Mediterranean container plants. How that works in general is in Overwintering herbs.
Pruning against woodiness
Rosemary is a subshrub: over the years it turns woody from the bottom and grows bare and straggly inside. Regular pruning keeps it dense and young. But beware, here lurks the second big mistake.
Never cut into the old, leafless wood. Unlike many shrubs, rosemary barely re-sprouts from bare, old wood. Only ever shorten the leafy, young shoots, then it branches willingly. The best time is spring after overwintering. Sage, a close relative, behaves similarly, by the way.
Hardy varieties and propagation
Not all rosemary is the same. Varieties such as 'Arp' or 'Veitshöchheimer Rosmarin' are considered hardy and survive winter outside in mild regions with a little protection. The usual shop rosemary, by contrast, is only partly hardy and wants to come into quarters.
Propagate rosemary easily
Rosemary is easy to propagate from cuttings. In summer cut non-flowering shoot tips, remove the lower leaves and stick them in poor seed compost. That way you raise free replacements in case a specimen does not survive winter. Rosemary finds a permanently sunny, poor spot on the dry top of a herb spiral.
Not frost but wet cold kills. Overwinter cool and bright, prune only into young wood, and in doubt choose a hardy variety.
The core rule for rosemary
Frequently asked questions
Is rosemary hardy?
Only partly. Ordinary rosemary tolerates dry cold but suffers from wet cold and usually needs a bright, cool winter quarters. There are hardy varieties like 'Arp' that stay outside in mild regions with protection.
Why did my rosemary die over winter?
Usually from wet cold, not frost. A soaked, cold root ball makes the roots rot. Protect the pot from constant rain and waterlogging and overwinter it cool and bright rather than warm and dark.
How do I prune rosemary correctly?
Regularly shorten the young, leafy shoots so it stays bushy. But never cut into the old, leafless wood, because rosemary barely re-sprouts from it. The best time is spring.
Where does rosemary overwinter best?
Cool and bright at a few degrees above zero, for instance in a bright, frost-free stairwell, conservatory or cellar with a window. The warm home is too dark and too dry and weakens the plant.
Can I propagate rosemary myself?
Yes, very easily from cuttings. In summer cut non-flowering shoot tips, strip the lower leaves and stick them in poor soil. Kept moist and bright, they usually root reliably.
Sources
- Bavarian State Institute for Viticulture and Horticulture (LWG): caring for and overwintering rosemary
- Julius Kühn Institute: Mediterranean herbs in the garden
- Related in the magazine: Overwintering herbs and Building a herb spiral
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