Some species of Petrocosmea have an annual growth cycle that involves what I have come to term a "semi-dormancy". Right after the autumn and winter flowering period, the plants begin to decline. The outer leaves begin to yellow and will eventually wither. In the center of the plant, the crown of new leaves become thickened and tight...almost as if the plants have an infestation of cyclamen mites. They don't. This cycle repeats every year for some species, and they always burst into rapid, lush growth each spring. The species that exhibit this pattern of growth, for me, are: P. nervosa, P. sp. 'vittatae', P. barbata, P. formosa, P. flaccida, and P. rosettifolia forms #1 and #2. Some hybrids involving these species in their parentage will also show a modified "semi-dormancy". The hybrids exhibiting this modified semi-dormancy are: P. 'Momo', P. 'Asa Blue', P. 'Imperial Butterflies', P. 'Short'nin' Bread', and P. 'Fluffer Nutter'.
One of my two mature plants of P. sp. 'vittatae' after a heavy flowering period. I allow the plant to dry out more between waterings and keep the plant cool. I will groom the dead leaves and flower peduncles off the plant, and will not fertilize it again until I begin to see new growth from the tight silvery center crown of the plant next spring.
The tight, silvery crown of P. sp. 'vittatae' as it retreats into it's annual semi-dormancy. I allow the plant to 'rest' until this center crown begins to expand with lush new growth next spring.
A mature plant of P. barbata 'Keystone'. This plant has been a workhorse of bloom all summer and was the parent of two hybrid crosses when it produced seven full seedpods. It's is deserving of a winter rest. Note how the outer leaves are beginning to yellow. The center crown is taking on the tight, gnarled appearance of it's semi-dormancy. This plant is NOT dying, but resting. Allow it to stay cool, drier, and give it no fertilizer over it's rest. When the new growth begins to emerge next spring, it will make rapid, lush growth. By keeping the roots drier, you avoid rot and root loss. This preserves that large, mature root system, which will support a large, full head of leaves next season. This large rosette of leaves, will nourish a heavy bud and bloom set next season.
The tight, silvery center crown of a P. barbata that is entering it's annual semi-dormancy. The plant is not dying, merely resting.
As the Petrocosmeas wind down from a heavy season of bloom and enter this annual semi-dormancy, it is important to realize that they are not dying. This is a nature response to the changing seasons, shorter days and cooler temperatures of winter. The key to saving these plants is to recognize what is happening and to provide the proper care when this occurs. It is easy to rot the root system if watering is not adjusted. As the plant drops it's leaves, it requires much less water and nutrients to support life. Watering schedules should be adjusted to allow the plants to remain drier, with only enough water to support the very tiny center crown which remains. If done correctly, the mature rootmass will be preserved. This larger mass of roots, next spring, will support a much more lush, and rapid return to full growth. The rosette will be renewed in a shockingly rapid growth spurt. Once growth resumes, I remove any additional offsets or crowns and repot if needed. I DO NOT repot all plants. If a single crown remains and the plant is otherwise happy, I will simply remove the top quarter inch or so of soil and replenish it, add systemic pesticide granules and give the plant a weak fertilizer until new growth is well advanced. Then, I resume my normal care patterns.
Lastly, I will mention that plants grown on reserviors of fertilizer water using the wick watering method, and plants that are kept in a constantly warm environment may not experience this semi-dormancy as markedly as my plants. I attempt to grow my plants as close to what I think their natural habitat provides as possible, so I allow my plants to get quite cool, even cold by some people's standards. I also allow plants to dry out between watering and reduce fertilizers to the point that I am using only plain water for non-blooming plants at this time of year. This is why, I feel, my plants exhibit this pattern.