<em>Callistemon</em>, bottlebrush: how to protect it from the cold in winter?

Overwintering Callistemon in pots or planters

In regions north of the Loire, where temperatures frequently fall below 0°C, due to their low to medium hardiness, planting bottlebrush in a large container to be put away for the winter is essential.

If temperatures do not fall below -5°C, you can leave your callistemons in pots outdoors if protected from the cold. Be aware that in a pot, roots are more exposed to frost than in the ground: wrap the container you will leave outside with several layers of bubble wrap or cardboard, then wrap the above-ground part of the plant and the pot with frost protection fleece.

Once winter has passed and risk of significant frosts has gone, remove the protections from potted plants that have remained outside all winter.

In regions with very harsh winters, bring your callistemons indoors before first frosts — into a conservatory, winter garden, unheated greenhouse, or a bright frost-free place where temperature will not drop below 7°C. Ensure good drainage (no saucer filled with water!) and reduce waterings: continue to water very sparingly, about once a month, and allow the potting mix to dry out between waterings.

As soon as the warmer season arrives, when temperatures moderate (around April–May), gradually move pots out into the sun, bring them in at night, and only install them permanently outdoors once there is no longer any risk of frost.

Protecting callistemon planted outdoors

Callistemon is a tender plant; growing it in open ground is really only suitable in regions where frost is neither too prolonged nor too severe.

Genus mainly comprises species of medium hardiness (-10 to -12°C in perfectly drained soil) to low (-5 to -8°C) for the Callistemons most sensitive to frost.

We recommend wrapping it in winter fleece, at least for first winters and especially when severe frosts are forecast. In cooler regions, insulate it from cold as much as possible. It likes to have roots kept warm during cold season. Protection of roots is just as important as protection of foliage: before severe cold arrives, provide it with a natural, insulating blanket bog. Spread a thick layer of at least 8–10 cm of mulch (straw, dry leaves) around the base to protect it from frost, especially during first winters. As soon as temperatures become milder, remove winter fleece.