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Passion flowers, also referred to botanically as Passiflora, convince with a variety of flowers from white to pink to blue and violet. If they entwine trellises, trees or pergolas, they impress with a concise bloom. Correct overwintering is important so that this can also shine unadulterated in the following year. Here you will find out everything you need to know about the question of whether Passiflora is hardy, as well as useful tips for a successful overwintering.
Is the passion flower hardy?
With a total of over 500 species, the genus of passion flowers is extremely diverse. There are also other cultivated subspecies, some of which differ significantly from the natural representatives. Therefore, the question of whether passion flowers are hardy cannot be answered in general.
Since the large number of varieties come from subtropical or even tropical areas, they are unfortunately not adapted to European climatic conditions and quite clearly not as hardy to call.
A few strains, on the other hand, hail from more temperate regions and have indeed tolerated some degree of frost. However, the number of moderately hardy and at the same time generally commercially available specimens is limited to just a handful of Passiflora species:
- violacea - frost hardiness to about -10 °C
- tucumanensis - Hardy to about -15 °C
- lutea - frost hardy to about -15 °C
- caerulea (Blue Passion Flower) - frost-resistant to about -15 °C
- incarnata ("passion flower incarnate") - frost-resistant to about -20 °C
However, even these "hardy" species should not be compared with other plants, which in fact can withstand all the frosts that usually occur in our country. Values of -15 °C or even -20 °C may sound like very low temperatures. But even in the lowlands, a clear night at the peak of winter can produce values that are significantly lower. Even the hardiest passion flower species quickly reach the limits of their resilience and have little chance of surviving without protection.
Flesh colored passion fruit, Passiflora incarnata
Measures when there is a risk of frost
Regardless of whether hardy or non-hardy passion flowers are to overwinter, measures are required to ensure protection from the winter temperature lows. The sensible measures differ depending on whether it is a container plant or a passion flower outdoors.
In the open air
If a conditionally hardy Passiflora is grown outdoors, the following work should be carried out to ensure adequate protection against frost:
- Cut back in autumn
- Above all, cover the root system with brushwood, straw or fleece to protect against the cold
- In deep frosts: cover above-ground parts of the plant with protective fleece
- Do not fertilize in winter
- Do not water during frost to avoid root damage from freezing water
tip: Although the choice of location is not directly related to preparatory measures before hibernation, a suitable location can already set the course for good hibernation chances when planting the passion flower. Ideally, the plants should be placed in a sheltered location, for example near the house or under a protective evergreen shrub.
In the plant pot
When kept in a plant pot, the measures for overwintering look a little different:
- Intensive pruning in autumn
- At temperatures of around 10 °C and below move the plant to its winter quarters
- Frost-free but cool location with about 10 °C to 12 °C
- Bright location without direct sunlight
- Good locations for example cold conservatory or greenhouse
- The more intense the pruning, the darker the room can be
- Reduce the amount of fertilizer greatly, but do not stop completely due to the limited pot volume
danger: One should urgently refrain from overwintering passion flowers planted in pots outdoors. Due to the limited pot volume, the frost penetrates the roots much more than it would in the ground. Under these conditions, even passion flowers, which are actually hardy, can be severely damaged!
The preparatory cut
Both outdoors and as a container plant, pruning is one of the first preparatory measures in autumn. The above-ground parts of the plant can be almost completely eliminated. Depending on the advisor, it is suggested to leave around 10 to 30 centimeters of the above-ground shoots. From these, the passion flower then quickly produces young shoots in spring with rising temperatures, so that they soon enrich the garden again in its usual splendor.
With potted plants, on the other hand, the pruning can be less severe, since winter damage to the shoots is ruled out when choosing the right location. In general, one can say that the intensity of the pruning should be more intense with decreasing temperature and brightness of the winter quarters, since the plant no longer carries out photosynthesis without heat and light.