Leaves of these plants feel greasy, hence the name Pinguicula which is derived from Latin, meaning fat and small. W. Marshall observed that insects became mired on the leaves of these plants. Being aware of Darwin's studies of the carnivorous nature of Drosera, Marshall communicated his observations to Darwin. Darwin subsequently investigated the matter and proved to his satisfaction that plants in the genus Pinguicula are indeed carnivorous plants. The common name for this genus is Butterwort.
Pinguicula are distributed worldwide. They grow in Arctic, temperate, and tropical areas of the world in damp or wet, acid or alkaline, soil in a humid environment.
Pinguicula is a herbaceous perennial. The plant consists of a flattened rosette of prostrate leaves and a fibrous root system. Each species has a characteristic leaf shape which is a variation of a basic elongated oval terminating in a blunt point. The edges of the leaves exhibit varying degrees of rolling in and are green to yellow-green to reddish in color. (Fig. 5-1) Most Pinguicula are homophyllous, meaning the leaves have the same shape and size throughout the entire growing season. The heterophyllous Pinguicula produce leaves after flowering that differ from leaves produced before flowering in size and shape. These are listed in Chart 1. Tentacles and sessile glands cover the leaf surfaces.
Flowers are borne singly on scapes in the spring, with some of the tropical species
flowering a second time later in the growing season. Plants, depending on the species, may have one or more flower scapes which are usually covered with tentacles.
Flower color ranges from shades of yellow, white, blue, and violet to purple. The zygomorphic flowers are sympetalous with the bottom 3 petals forming the lower lip of the flower and the top 2 petals forming the upper lip. The closed, cylindrical end of the corolla narrows to almost a point forming the spur. On the lower lip of the floor of the entrance to the flower is a raised, pubescent structure called the palate, whose degree of exsertion depends upon the species. (Photo 5-1) The flower has 2 curved stamens lying flat on the corolla with the 2 anthers almost touching each other and covered by part of the pistil. (Fig. 5-2)
The fungal odor of Pinguicula is believed to be a prey attractant. Insects are trapped when they light or crawl on the surface of the leaves which are coated with a sticky mucilage. Only the smallest insects can be captured. Usually the struggling of insects attempting to escape results in their being hopelessly entrapped, as well as being suffocated, by the mucilage. The prey is digested and the digestion products absorbed for use by the plant. Pinguicula leaves show little motion during prey capture, as compared to the Sundews. What little motion occurs does not aid in prey capture. The margins of the Pinguicula leaves tend to curl up during and after prey capture to form a shallow bowl which contains the digestive fluids and prevents loss of prey. (Photo 5-2) Often the leaves tend to become distended beneath the spot where larger insects have been trapped.
Fig. 5-2 Flower of Pinguicula. Longitudinal section reveals the relationship of stigma and stamen.
The genus Pinguicula can be divided into 2 groups according to their seasonal growth pattern: plants that form winter buds, or temperate climate species; and plants that do not usually form winter buds, tropical or subtropical species. Chart 1.
Temperate Pinguicula (Form winter buds)
P. algida A P. alpina A,B P. balcanica A,B,C P. corsica A P. grandiflora A,B P. leptoceras A,B P. longifolia B,C P. macroceras A,B P. nevadensis A P. ramosa A P. vallisneriifolia B,C P. variegata A P. villosa A P. vulgaris A,B
A=acid soil B=basic soil C=heterophyllous
Tropical & Subtropical Pinguicula
P. acuminata C P. agnata P. albida P. antarctica P. benedicta P. caerulea A P. calyptrata P. chilensis P. cladophila P. colimensis C P. crenatiloba P. crystallina P. cyclosecta C P. elongata C P. esseriana P. ehlersae P. filifolia P. gypsicola B,C P. heterophylla C P. hirtiflora A P. imitatrix C P. involuta P. ionantha A P. jackii P. kondoi C P. lignicola P. lilacina P. lusitanica P. lutea A
P. macrophylla B,C P. moranensis B,A,C P. oblongiloba B,A,C P. parvifolia C P. planifolia A P. primuliflora A P. pumila A P. zecheri
P. caerulea The yellow-green leaves resemble an elongated oval. They attain lengths of up to 2.4 in. (6 cm). Flower color ranges from violet to blue-violet with dark veins. (Photo 5-3)
P. colimensis Summer leaves are egg-shaped. The winter leaves are similar in outline except thicker. Flower color is pinkish purple. The diameter of the rosette can reach 3 in. (8 cm).
P. gypsicola The distinctively shaped, light green summer leaves are subulate terminating in a rounded point and are about 2.5 in. (6.4 cm) long. In the fall small leaves are produced, forming the winter rosette of spathulate-shaped leaves. Flower color is purple.
P. ionantha The green leaves are oblong with rounded tips and may be up to 3.2 in. (8 cm) long. Flower color ranges from white to violet. P. ionantha is distinguished from P. primuliflora by their floral characteristics. The petals of the former are longer than broad while the petals of P. primuliflora are as broad or broader than long and have a ring of white just above the corolla tube.
P. longifolia The yellow-green leaves are elongated elliptical, taper to the wide petiole and have a wavy margin. Flower color varies from purple to lavender with white areas. (Photo 5-4)
P. moranensis (Former name P. caudata) Summer leaves are long egg-shaped. The diameter of the rosette can reach 7 in. (18 cm). Winter leaves are spathula-shaped and succulent. The large flowers range in color from white to pink to purple. (Photo 5-5)
P. planifolia The elliptical shaped leaves are up to 3.2 in. (8 cm) long. They are green to dark maroon in color which varies with the intensity of sunlight. Flower color ranges from blue-violet to purple to white. Petal shape is distinctive in that the petals are much longer than broad and deeply incised.
P. primuliflora The green elliptical leaves reach lengths of up to 3.5 in. (9 cm). Flowers are violet with a ring of white coloration just along the corolla tube, distinguishing it from the violet flowers of P. ionantha.
P. pumila The egg-shaped, light green leaves terminate in a point. They are about 0.4 in. (1 cm) long. Flowers are violet to white.
The temperate species can be divided into 3 groups, each with similar growth requirements. Chart 2.
Chart 2 Temperate Pinguicula
P. corsica P. grandiflora P. longifolia P. vulgaris
Winter temperatures: 32-34°F (0-1 °C) Summer temperatures: 46-68°F (8-20°C) Growing period: 4-6 months. Dormant period: 6-8 months. Group 2
P. longifolia ssp. reichenbachiana P. macroceras ssp. nortensis P. ramosa P. vallisneriifolia
Summer temperatures: 59-84°F (15-29°C). Growing period: 7-9 months. Dormant period: 3-5 months. Group 3
P. algida P. alpina P. balcanica P. leptoceras P. macroceras P. nevadensis P. variegata P. villosa
Winter temperatures: 26-34°F (-3-1 °C). Summer temperatures: 45-65°F (7-18°C). Growing season: 3-4 months. Dormant season: 8-9 months.
The temperate Pinguicula are divided into 3 groups, those that grow in acid soil, basic soil, or in either. Their soil preference is indicated on Chart 1.
Acid growing media: Sphagnum peat moss; sphagnum (living or dried); 1 part sphagnum peat moss to 1 part perlite to 1 part sand (silica); 1 part sphagnum peat moss to 1 part perlite or silica sand; 1 part chopped sphagnum to 1 part sphagnum peat moss.
Basic or alkaline growing media: Equal parts of sphagnum peat moss, perlite or vermiculite and ground dolomite or limestone (some growers prefer to use less limestone). Various recipes call for a minimum of 1 tablespoon (15 ml) per quart (liter), of growing medium up to V2 of the medium mixture; 1 part perlite to 1 part vermiculite; or 100 percent perlite.
The temperature range required by each group is given in Chart 2. Generally, during the growing season it is best to maintain the temperature around the middle of the range. Night-time temperatures should be several degrees lower than the day temperature. It is vital that a constant temperature be maintained during dormancy, as changing the temperature results in the death of winter buds. In warm parts of the world refrigeration is required during active growth for some of the temperate species of Pinguicula.
The greatest loss of plants in temperate Pinguicula occurs while they are in dormancy. To reduce and/or eliminate loss, winter buds should be sprayed or soaked (about 15 minutes) in a full strength solution of a fungicide such as Benlate. (Photo 5-6). The treated buds should then be loosely wrapped in damp living sphagnum moss and placed in sealed plastic bags for storage.
Group 2 plants can be stored in a refrigerator (not freezer), preferably near or on the bottom shelf where it is cooler. If the winter temperatures in your area are in the 34-39°F (1-4°C) range, plants can be stored outside. If the outside temperature varies very much from these values, other ways for maintaining low temperatures should be utilized.
Some of the species in the temperate group spend more time in dormancy than in active growth and require low temperatures during active growth. To provide dormancy for those Pinguicula species requiring freezing or near freezing temperatures
(group 1 and 3) we use two methods.
The first method involves growing the plants in our cool greenhouse; the winter buds are planted in late February or early March. The plants will grow and flower before the heat of late spring and early summer. After flowering, the plants start going dormant. The progress of dormancy in both flowering and non-flowering plants can be ascertained by checking for development of the winter bud in the crown area. When the winter bud starts to form we remove the plants from the greenhouse benches and place them on the floor in the coolest part of the greenhouse until winter bud formation is complete.
Attempting to keep the plants growing after winter bud formation has started is to court disaster. Once the winter buds have formed treat them with a fungicide as outlined previously and place them in sealed plastic bags. We put the plastic bags in the meat storage tray of our refrigerator until the next growing season.
The second method of providing proper conditions for species requiring freezing temperatures during dormancy is simplified by our new refrigerator. It has a meat tray, the temperature of which can be adjusted to be at or below the freezing point by controlling the opening to a portal which connects the meat tray area to the freezer. Once the portal is adjusted for the correct temperature, the winter buds, which are in moss in a sealed plastic bag, are placed in a styrofoam box or a small thermos bottle and then kept in the meat tray. The reason for putting the buds in the plastic box or thermos bottle is to keep the temperature of the buds constant when the meat tray is opened and items are removed or warm ones added. The styrofoam box should not be sealed too tightly and the thermos too should not be completely tightened because the buds are alive and need oxygen for cellular respiration.
Water & Humidity
This group of plants is particularly sensitive to humidity which should be high, over 75%, for best growth. Medium should be wet during the growing season and much drier during dormancy.
As a group, temperate Pinguicula grow best in indirect or shaded sunlight. In their native habitat they are usually shaded by taller growing plants. If using artificial illumination, start with about 900 foot candles and a 14-18 hour photoperiod during active growth. While dormant they do not need any light.
The flowers are designed to foster cross-pollination between plants. Thus, it is wise to grow 2 plants of each species. The features of the flower are shown in Fig 5-2. Pollen must be transferred from pistil to stigma a few days after the flowers open. The stigma is an elongated flap-like structure that covers the anthers, with its pollen receptive surface on the side away from the anthers. With care, the flap or stigma can be bent to the front, exposing the anthers which may be examined for pollen development. A small brush, or better yet a toothpick, is used to transfer the pollen. The flowers of some species are quite small so it is sometimes easier to tear open the corolla or to remove most of it in order to expose the stigma. The corolla is the tubelike part of the flower that is made up of the fused or joined petals. If pollination has been successful the ovary will start to swell in a week or. two. The mature seed pods will split open to release the seed about 4 weeks after pollination.
Seed to be stored should be dried at room temperature for a few days and then placed in sealed vials or plastic bags and kept under refrigeration. The seeds of the
temperate species of Pinguicula require stratification before they will germinate. For best results, the period of stratification for each of the species should be at least equal to the minimum period of plant dormancy.
1. Brood bodies: Species in groups 1 and 2 except P. vallisneriifolia produce small brood bodies, which are called gemmae. (Fig. 5-3) They are formed in the leaf axils of the outer leaves toward the end of the growing season. Unless they are removed before the mother plant grows in the spring, they will probably be smothered by the leaves of the adult plant. The brood bodies may be left with the mother plant until spring, at which time they are removed and placed, one each, in a small depression in the planting medium so that the top of the brood body is level with the surface.
2. Runners: P. vallisneriifolia produces plantlets at the ends of runners. When the plantlets have rooted they can be severed from the mother plant. Transplanting is most successful when done during the spring before active growth commences.
3. Leaf cuttings: Remove the whole leaf. Dust with fungicide and insert the leaf in sphagnum moss so that the bottom Vs is below the moss. Keep the humidity high, light bright and temperature in the summer range for the particular species. We know this procedure is effective for P. macroceras, P. villosa, and P. vulgaris.
Fig. 5-3 Winter bud of Pinguicula with smaller brood bodies which should be removed and planted separately. They grow into new plants.
Subtropical and Tropical Pinguicula _
About V3 of these species have been successfully cultivated to date. Those for which there is cultural data available have been divided into groups, by the similarity of their cultural requirements.
The Southern United States Species
P. caerulea P. ionantha P. lutea P. planifolia P. primuliflora P. pumila
These plants grow best in acid planting media. The acid media listed for the temperate Pinguicula species are suitable for these also.
While summer temperatures in their native habitats may reach and exceed 95°F (35°C), ground or soil temperatures are usually lower. Summer temperatures 70-90°F (21-32°C), winter temperatures 35-50°F (2-10°C). Some species are subjected to light frost in their native habitats.
Growth stops during the coldest part of the year but the plants remain green. They should be kept drier during the dormant season than during the period of active growth. Treatment with a fungicide will ward off decay. It has been reported that some of these Pinguicula species go dormant during the summer when there is a prolonged drought.
Water & Humidity
These plants enjoy high humidity and wet soils during the growing season, but the medium should be drier during the dormant period.
Indirect or shaded sunlight is generally suitable. Under artificial lighting use 900 foot candles. Photoperiod for the summer 14 hours, for the winter 10 hours.
Many growers have trouble keeping their subtropical and tropical Pinguicula spp. growing from season to season due to rotting. We have found that placing V2 in. (1.3 cm) of washed coarse sand or small pebbles on top of the planting medium in a pot eliminates plant rot or decay. The plants7 roots must extend into the media below the pebble or sand layer. The sand or pebbles are positioned around the crown of the plant. This allows the crown area to remain relatively dry while the roots are in wet or damp soil.
Flowers must be pollinated by an external agent such as insects or artificially in order to set seed. Follow the procedure given for temperate species. Seed can be sown immediately and will germinate. We have found stratifying the seed for about 2 months results in a more uniform and a greater percentage of germination.
Leaf cuttings: Follow the same procedure as given for the temperate Pinguicula spp. except that the temperatures should be higher, 70-85°F (21-29°C). The more succulent the leaves the greater the success rate.
Species such as P. pumila, P. primuliflora, and P. planifolia will develop small plantlets on their leaves while growing under conditions of high humidity, usually in late summer or early fall. (Photo 5-7) These plantlets, if continually removed, can be used to start new plants.
The Mexican Species
P. colimensis P. cyclosecta P. gypsicola P. macrophylla*
P. moranensis—formerly called P. caudata & P. mexicana P. oblongiloba*
"■Produce winter buds.
P. hirtiflora P. lilacina P. lusitanica* P. parvifolia* "Produce winter buds.
The Mexican Pinguicula species grow at high elevations where summers are warm and winters cool and dry. The non-Mexican species grow in Mediterranean areas as well as in other parts of the world with a similar climate. Both of these groups require similar cultural conditions and are the easiest of the Pinguicula species to grow.
The Mexican Pinguicula spp. grow on calcareous or alkaline soils in their native habitat, but they will grow in acid soils also. Both acid and alkaline planting media are used successfully in growing these plants. Any of the planting media listed for the temperate Pinguicula spp. can be used for the Mexican Pinguicula spp. The non-Mexican Pinguicula spp. require an acid medium. Any of acid media listed for the temperate Pinguiculas can be used with these species.
Summer 60-85°F (16-29°C). Winter 40-55°F (4-13°C). Dormancy
The Mexican Pinguicula spp. produce thicker and smaller leaves for the winter or dormant season. Species such as P. macrophylla and P. oblongiloba are described as forming winter buds. Others of the Mexican Pinguicula spp. produce small, tight winter leaves. Thus, it is a matter of semantics as to whether they are winter buds or just small winter leaves.
Indirect or shaded sunlight. If artificial light is used, start with about 1000 foot candles and a summer photoperiod of about 13 hours; 800 foot candles for the winter or dormant season with a photoperiod of 11 hours is suitable.
Water & Humidity
Like most Pinguicula spp. this group enjoys wet soils and very high humidity during the growing season, with drier soils during dormancy.
P. moranesis and P. collimensis tend to grow up and out of their planting medium, exposing their root system. At least once a year the leaves should be lifted to view the base of the crown to see if the plant has grown out of the soil. If roots are visible, the plant should be repotted so that all the roots are in the medium or alternatively position medium around the exposed roots.
Some growers prefer to plant Mexican Pinguicula in pots which have an inch of sphagnum moss over a bottom layer of perlite. The plant is positioned so the base of the leaves is in the moss with the roots extending into the perlite. A suspension of dolomite (available from health food stores) made by mixing Vz teaspoon (2.5 ml) per quart (liter) of water is used to water the leaves and soil once every 2 months. These plants should be fertilized as per directions in Chapter 7.
Flowers must be pollinated by an external agent such as insects or artificially in order for viable seed to be set. Seeds of both of these groups will germinate without any special treatment. Sow seed on the appropriate medium, keep the humidity high, the light bright and within a temperature range of 60-86°F (16-30°C). Seed will germinate within 2-4 weeks.
1. Leaf cuttings: Le>af cuttings should be handled in the same manner as outlined for the southern United States species. The thicker, more succulent leaves produce the best results.
2. Runners: P. oblongiloba and P. macrophylla produce new plants at the end of runners. When plantlets have developed a root system the plants can be severed from the mother plant.
General Information for all Pinguicula Species _
Snails, slugs, aphids and fungus diseases. See Chapter 8 for treatment. Feeding
Pinguicula should be transplanted before active growth starts to reduce losses. Plants can be successfully moved at other times if they are moved with a ball of soil. Some growers claim that those Pinguicula spp. requiring alkaline or sweet soils will benefit from 2-3 waterings during the growing season with a solution of hydrated lime, calcium hydroxide. The usual concentration is 1 tablespoon (15 ml) of hydrated lime per quart (liter) of water. Avoid getting liquid on the leaves when watering the plants.
The Pinguicula species in order of increasing difficulty to cultivate are Mexican, non-Mexican, southern U.S., and temperate. With the temperate species, the longer the dormant period the more difficult it is to grow the plants.
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