Are lobelia hardy?

Lobelia are pretty and floriferous perennials with numerous bell-shaped flowers that can be admired throughout the summer. However, the lush splendor is over with the first frost, because the attractive plant is not hardy here. In addition to the blue-violet flowering, annual men's faithful, there are some perennial species of lobelia that can be overwintered in the garden under protected conditions.

Blue lobelia not hardy

Under the name "Männertreu" or "Lobelie" a compact growing and perennial for months with attractive, sold with blue-purple flowers, which are particularly popular in balcony boxes or as plants in the foreground of a perennial border becomes. This is the species Lobelia erinus, which is native to southern Africa, especially in the Cape region. It is warm there all year round due to the subtropical to tropical climate, which is why the plant is not hardy here. The perennial freezes back even at temperatures around zero.

Cultivate Lobelia erinus as an annual

However, the blue lobelia can easily be multiplied by seeds, which you sow in a bowl filled with growing substrate from March. Then grow the seedlings on the windowsill and plant them directly outdoors after the ice saints in May. The numerous cultivars of Lobelia erinus are fast-growing and begin to flower quickly, so overwintering is not necessary. Mannentreu sown in March blooms from the end of May to the beginning of June, depending on the weather.

Which lobelia can be overwintered?

However, the blue lobelia is not the only species in the large genus of lobelia. Around 430 different species belong to the bellflower family (Campanulaceae) counting group. Most of them also come from the subtropical to tropical regions of the world and are therefore not suitable for wintering in the garden. Only the perennial perennial lobelia tolerate frost, but only for a short time. These species, which grow to a height of around 100 centimetres, grow vigorously and under certain conditions can also remain outside during the cold season. Alternatively, hibernation in a cool room is possible if the plants are cultivated in tubs.

These types of perennial lobelia are suitable for overwintering:

• Lobelia cardinalis: "Cardinal's lobelia" or "Shining lobelia" with bright red flowers, from North America, robust and hardy
• Lobelia sessilifolia: tall, violet flowering species for moist locations, from Asia
• Lobelia siphilitica: "Blaue Kardinals-Lobelie", tall, blue-violet flowering species for damp locations, robust and comparatively hardy
• Lobelia splendens: scarlet flowering species
• Lobelia x gerardii (Hybrid): "Gerard-Lobelie", strong violet flowers, very hardy
• Lobelia x speciosa (Hybrid): species with bright red flowers, hardy

Perennial lobelia overwinter

Basically, you have two ways to get perennial lobelia well over the winter. You can leave specimens planted in the garden outside, in pots and others However, plants cultivated in planters must be in a bright room with little or no heating hibernate. The reason lies in the container itself: while perennials planted out, the surrounding soil protects them from frost quite well are protected, the small amount of substrate in the plant pot is not sufficient for adequate winter protection sufficient. The substrate freezes through even after a brief frost, so that the roots are damaged and the plant does not sprout again in spring.

Hibernation outdoors

Even if some plant dealers claim the opposite: Even perennial lobelia that are considered to be hardy only tolerate frost for a short time. If the temperatures in autumn drop to zero or even to minus ten degrees, this does not damage the plants immediately - but after a few days it does. Therefore, you should winterize perennial lobelia that have been planted out by the end of October at the latest:

• from August gradually water less
• do not fertilize from the end of July / beginning of August
• Cut back to a hand's breadth above the ground
• Cover the planting area thickly with brushwood and leaves
• Fir and spruce twigs are particularly well suited
• water little in dry winters

Remove the cover as soon as the first warm days arrive in April. However, protect the tender young shoots from late frosts by continuing to cover them with brushwood or garden fleece overnight. This protective measure should be maintained until mid or late May, depending on the weather.

Hibernation in cold house

If you cultivate your perennial lobelia in pots or live in an area with severe winters and typically heavy snowfall (eg. B. in the Eifel or in the south-east of Germany), you should never overwinter the perennials outdoors. Instead, cultivate them in large planters and overwinter them like this:

• Give into the winter quarters from the zero point
• at the latest by the end of October
• Winter quarters light and cool
• Examples: unheated bedroom, stairwell, little heated greenhouse or conservatory
• Temperatures between five and a maximum of ten degrees Celsius are ideal
• water little, do not fertilize

From the middle to the end of March you gradually increase the amount of water. From approx. In mid-May, move the winterized lobelia back outside and give them the first fertilizer in the form of liquid flowering plant fertilizer.

Learn more about overwintering plants