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Rosemary is not fully hardy in our latitudes. In very harsh winters, the popular kitchen herb can quickly suffer frost damage. If the rosemary is frozen, it can still be saved with the right measures.
In a nutshell
- put it to the acid test
- cut frozen shoots
- Cut back after flowering
- don't cut into old wood
Moderately hardy
The evergreen Mediterranean shrub should not be missing in any herb bed. Rosemary (Salvia rosmarinus) is not only a popular herb in the kitchen, but is also valued as a medicinal plant. It originally comes from the Mediterranean region. From this it can already be seen that the subshrub cannot tolerate cold temperatures well. In this country, the kitchen herb is very sensitive to frost. However, with the right winter protection, rosemary can normally survive cold periods down to -10 degrees unscathed. After even lower temperatures, it can happen that the shoots of the rosemary are sometimes frozen in spring. The plants only become winter hardy in their third year. This depends on the location and soil.
Rosemary variety 'Arp'
Notice: Breeding has resulted in various particularly hardy varieties such as "Arp", "Veitshöchheim", "Backnang", "Bavaria" or "Heilsberg". In a favorable location, these varieties can withstand temperatures down to at least -20 degrees.
detect frost damage
The full extent of the frost damage only really becomes apparent in April. More or less brown needle leaves are then visible. If there are only a few brown colored needles, there is no need to worry. That is normal. Usually nothing needs to be done here. The new shoot will overgrow this needle. If necessary, however, they can be easily wiped off by hand. However, it becomes more problematic if several shoots are brown. This can be a sign that the rosemary has frozen. If the whole plant is affected, it can usually hardly be saved.
put it to the acid test
With the help of a so-called acid test, it is easy to determine whether the rosemary is really frozen. The implementation is very simple and can also be done without tools:
- Slightly scrape the bark off the shoot with your fingernail
- alternatively use pruning shears or knife
If a slight green color appears, then there is still life in the shoot. Further measures can now be taken to save the plant. However, if a brown coloration of the shoot becomes visible under the bark, then it is frozen. If the whole plant is affected, you can discard it.
Cutting helps
The blue-violet flowers are not only beautiful to look at, but also magically attract insects such as butterflies, bees and bumblebees.
Cutting back the frozen shoots stimulates new growth in the evergreen shrub. However, it should not take place immediately in April, since the rosemary has already started flowering by then. You should therefore wait until after flowering before cutting. The flowering period is usually over at the end of May. Incidentally, late frosts no longer have to be expected. Other reasons for pruning in late May are
- Plant is thriving
- young, green shoots easily recognizable
- Interfaces close faster
- Fungal diseases have no portal of entry
- then grows nice and bushy
Put the scissors on carefully
Clean and sharp pruning shears must be used for pruning. It shouldn't just be cut loose. There are a few things to consider in order not to damage the plant even more:
- don't cut into old wood
- otherwise it will not sprout again
- only remove brown and thin tips
- Shorten the shoot to the first green needle leaves
- Leave 1 cm of the wood that grew last year on the shoot
prevent frost damage
When planting rosemary, you can prevent the plant from freezing in very cold winters. There are also other measures to get the subshrub through the cold season like
- plant hardy varieties
- choose a warm, sunny spot protected from cold north-easterly winds
- pay attention to permeable soil (waterlogging in winter often causes frostbite)
- always plant in spring (enough time for rooting)
- regular pruning after flowering (new shoots offer better winter protection)
- last harvest in October (better maturation of the wood)
- Winter protection important
- Distribute foliage layer around plants
- cover everything with spruce sticks
- remove in spring
- Overwinter potted plants indoors in a bright and frost-free place
Normally, night frosts can still occur until the ice saints in mid-May. Until then, the plants need protection. They should be covered with a fleece at night during this time.
Notice: In an optimal location, the sun does not come out until midday in winter. In this way, the plant can warm up slowly and the plant cells do not burst due to large temperature differences.
frequently asked Questions
Can rosemary still be harvested in winter?If possible, no more shoots should be harvested from outdoor plants. The situation is different with potted plants in the house. If necessary, some shoots can be cut here.
Which soils does the Mediterranean evergreen subshrub prefer?The soil should be well-drained, loose and lean, if possible sandy. The subshrub loves a neutral to alkaline pH value. He is lime tolerant. Heavy, loamy soils are not suitable for cultivation.
What care does Salvia rosmarinus need to grow?Normally, the plant is quite undemanding. A small fertilizer application of compost or horn shavings in the spring is sufficient for garden planting. These only need to be watered on very hot days. Potted plants, on the other hand, need fertilizer every six weeks in the form of liquid fertilizer. Watering is done here when the top layer of soil has dried.