Bulbs and tubers
In horticulture, the word bulb includes underground modified stems which are used for propagation e.g. bulb, corm, tuber and rhizome. Plants with tuberous roots are also grouped as bulbous plants. A large number of these plants producing attractive flowers are grown in the hills and are commercially important plants in floriculture. Many types, flower well both in plains and hills but the season of growth and flowering may vary.
A bulbous plant has normally three phases during a yeargrowth, flowering and dormancy. Vegetative growth may precede flowering as in Gladiolus or flowering starts before the leaf emerges, e.g. Amaryllis, Haemanthus. After growth and flowering, the plants in most cases, enter into rest period and the duration of dormancy varies with the type of plants and environmental conditions like temperature and humidity.
Bulbs prefer loam or sandy loam soil. In stiff clay, rooting is delayed and too much moisture often causes rotting. If the soil is not perfectly well-drained, the bulbs may be planted on a bed of sand. Watering is not required after planting as the fleshy underground stems contain sufficient food materials to develop initial growth of root and shoot. Before root formation, watering prove injurious to the bulbs and helps in rotting.
Bulbs, corms, tubers and rhizomes are used for vegetative propagation. Various methods and structures used for propagation are as follows.
Bulbous plants are grown in beds, shrubbery, herbaceous border, grassy land and in pots and bowl. Bulbs, corms, rhizome or tuber are usually planted when they have shown signs of sprouting after dormancy.
The planting materials are normally placed deep in the soil and the soil around it is gently pressed. The depth of planting varies with the type or plants and size of bulbs. For most of the bulbous plants grown in tropical garden, the planting depth is between 3-10 cm.
Most of these plants sunny situation, while Eucharis, Zephyranthes thrive better in semishade; few types, e.g. Pancratium, Haemanthus, Zephyranthes grow and flower well in sun and semishade. Bulbs, corms and tubers should not come in direct contact with fresh organic manure, rhizomes are not usually affected. Time of planting depends on the season of flowering, environmental condition of the region and condition of the planting material. In the plains, Gladiolus is planted from September to November, whereas in the hills, the planting season is normally from April-June. Amaryllis, Hippeastrum, Haemanthus are planted in January-February to obtain flowers in March-April. Caladium and Canna are put in the ground in May.
After the above ground portion dries out the bulbs are lifted out carefully. The root and shoot are cut and the bulbs are cleaned before storage. They should be stored in dark, dry and airy place until the time of next planting. Storage condition is very important for obtaining healthy bulbs. If the humidity is very high, fungus develops on the bulbs and causes rotting. In a very dry atmosphere the bulbs shrived and may lose viability.
It is not necessary to lift all types of bulbous plants every year. Amaryllis, tuberose, Caladium, Pancratium, Zephyranthes may remain in the ground for three years before they are lifted. But water should be withheld when the bulbs are lying in dormant condition in ground or pot. Gladiolus, on the other hand, has to be lifted out every year after drying of leaves.
Some common bulbous plants
Amaryllis belladona is the only species of the genus, a native of South Africa. It is a plant with strap-shaped, glossy, green leaves and producing few large funnel-shaped flowers on a stout stalk, from March-May. Leaves appear at the end of the flowering season and die out before the winter sets in. In warm humid region the plants retain leaves throughout the year and bear flower during the season. Offsets, developed from the original bulb are separated for multiplication. Bulbs are planted 5-8 cm deep in December-January and the plants grow well in rich and porous soil. Amaryllis is not disturbed for several years at one place and the plants continue to produce new bulbs and flowers. It is very suitable for planting in border, shrubbery and in pot. Although rose or rosy pink colour is common, white to purplish colour are also found.
The genus comprises of about 16 herbaceous perennial species with tuberous rhizome. They are a native of tropical America and are widely grown in warm humid climate for the beautiful and attractive foliage produced during the rainy season. Some of the important species are Caladium bicolor, C.humboldtii, C.picturatum, and C.schomburgkii. Numerous varieties have been raised particularly form C.bicolor.
Leaves are usually peltate-segittate, stalks variegated, blades are with very many shades of colour, e.g. variegated green, blue green, dark green, light green, spotted with white, red, transparent white, etc. leaf veins may be red, silvery or green. Leaf margins are coloured with purple, white, yellow or red. In some species, shape of the blade is lanceolate-sagittate. Flowers are unisexual.
The pot compost for planting Caladium should be prepared by mixing loamy soil with leafmould and well-decomposed cow dug manure. It prefers moist but porous soil. Application of liquid manure at frequent intervals enhances growth and improves colour of foliage. Caladium is propagated through division of the tuberous rhizome and rarely by seeds. It is planted in summer and leaves show a fine display of colour in the rainy season.
The leaves start fading in autumn and water is gradually withheld until they have withered. In dormant condition, the rhizome may be allowed to remain in the soil or dug out and stored in a cool and dry place.
The genus is named after Joseph Cooper, an English gardener, comprises about 6 species native of North America, and differing from Zephyranthes by the long perianthtube and erect anthers. They are tender bulbous plants with the habit of Zephyranthes but blooms only at night. Important species are C.drummondii and C.pedunculata. Flowers are fragrant, white, and sometimes tined with red or pink.
Flowers are solitary, the perianth subtended by a bract like spathe. Leaves are long, narrow flat and twisted and appear along with the flower. It is cultivated in a semishady location and in sandy loam soil. Addition of well-rotted compost, sand and charcoal dust in beds or pots is beneficial. Cooperia is propagated by bulbs. It is planted during spring in rock garden, border or in pots and starts blooming during May-June.
This genus is a product of intergeneric hybrid between species of Cooperia and Zephyranthes, first raised in 1900 by Percy Lancaster at the Agri-Horicultural Society, Alipore, Calcutta. Hybrid between Cooperia oberwettii x Zephyranthes robusta is known as Alipore Beauty, is probably the best known Cooperanthes. Flowers are light lilac, rose or white.
It grows well in well-drained sandy loam soil, rich in organic matter and in semishade. Cooperanthes are propagated by bulbs. They are planted in the spring and the plants start flowering by the end of summer. They are grown both in bed or in pot and are good as cut flowers.
The genus Crinum, comprises more than 100 species of large and showy flowering bulbous plants. They are closely allied to Amaryllis and distinguished by the longer perianth tube. The species cross freely and many fine hybrids of Crinum, between Crinum and Amaryllis and Crinum and Hymenocallis are known. Some of he important cultivated species and hybrids are C. longifolium, C. mooriei, C. powellii, C. variabile, C asiaticum, C. augustum, C. careyanum, C. yuccaeflorum, C. giganteum, C.zeylanicum. Flowers are usually white or in shades of red and purple.
The stems arise from the tunicated bulbs with a more or less elongated neck. Leaves are large, about 150 cm long and 12-15 cm wide, evergreen or deciduous, depending on the species. Flowers are regular, often highly scented, tube narrow, with six segments and usually funnel-shaped. In some species flowers are 30 cm long and 15 cm wide.
Most of the species prefer shade or semishady location for planting. Crinums usually have large bulbs, sometimes as much as 60 to 80 cm long with numerous fleshy roots. If planted in beds, the soil should be dug to a depth of two to three feet, mixed up well with sufficient quantity of rotten cow dung and compost. It can also be grown in large pots containing soil rich in organic matter.
Bulbs should be of good size and planting is done to a depth below the ground level, twice the size of the bulbs. The plant will grow and flower for years, if watered in the summer months and top dressed with fresh loamy soil around new vegetative growth. Bulbs are planted in April to get flower during the rainy season.
Eucharis is an important bulbous plant, popularly known as `Amazon Lily. It prefers semi shade and flowers better in plains than on the hills. The bulbs are globular in shape, leaves large lanceolate. The flowers are about 7 cm across, white, sweet, scented, 5-7 blooms appear on a stalk. Eucharis grows better in pots than in the ground and the compost should be rather rich and heavy instead of sandy, but must not be often disturbed. It flowers in the summer and rains and the leaves begin to wither before the winter.
Gladioli are among the most beautiful flowers, blossoming from October to March in plains and during June to September in the Hills. This genus comprises more than 150 species of perennial herbs with base of stem swollen into a corm. Most of them have their origin in South Africa, although a few originated from Europe. The species in cultivation and of considerable importance include : G. cardinalis, G. childsii, G. colvillei, G.gandavensis, G.lemoinei, G.nanceianus, G. nanus, G.primulinus, G. psittacinus, G. purpureoauratus, G.saundersii. The numerous crosses have evolved large number of varieties of varying characters and it is almost impossible to keep up with and enumerate the different varieties of gladioli. Wide range of attractive colour shades may be grouped into white, yellow, cream shaded pink, orange, pale pink on white, pink on cream apricot, salmon, cherry red, orange-scarlet, crimson, purple, mauve and violet, etc.
Gladioli prefer sunny situation with light sandy soil, with pH between 6 to 7. If the soil is heavy, addition of river sand and charcoal improves the soil condition. They grow well both in pot and in beds and the magnificent spikes brighten the garden and room as cut flower. Two parts sandy loam soil mixed with one part of each well-rotted cow dung manure and leafmould and a handful of bone meal is recommended for pot culture. If planted in beds the ground should be dug deep and well-decayed compost at the rate of 4 kg per meter mixed thoroughly and left for sun drying at least for a fortnight. At planting time fresh manure should not be used, but a dressing of bonemeal, superphosphate and wood ash may be given with advantage. In the plants, planting is usually done during September-November and in the hills from April-June, but the flowering season may be extended by early and late planting.
Gladioli are propagated by seeds, corms and cormlets. New varieties are raised from seeds. Seeds germinate freely and the seedlings grown carefully, will flower in the second year. Large flower spikes, however, develop after 3-4 years when the corms attain a good size. Gladioli corms are planted 8 to 10 cm deep into the soil, at a distance of 20-30 cm between the rows and the plants. Application of liquid manure, once at the vegetative stage and again after the formation of flower buds has been found very effective.
The flowering spikes appear in 60-90 days after planting, the flowers continue to open in succession from below upwards and the open flowers remain fresh for a number of days. After flowering, the leaves begin to turn yellow and wither. The plants are then lifted with the corms and cormlets and kept in a dry shady place for a week for drying. The corms are thoroughly cleaned, the cormlets separated and stored on a layer of sand in a dry, cool, airy and shady place until the next planting season. The corms should be examined regularly and those showing sign of rotting or fungus growth should be removed. They are also stored in cold storage but in a dry atmosphere.
As the name implies, the genus Gloriose means `full of glory, popularly known as climbing or creeping lily. They are tall creeping plants, support themselves by means of tendril which arises from leaves. This genus comprises about six species of rhizomatous plants native of Africa and tropical Asia. Important species, commonly grown in the gardens in India are G.superba and G.rothschildiana. Leaves are oblong, lanceolate. Flowers are showy on long pedicels in leaf axils, perianth of 6 distinct long segments ; stamens six with versatile anthers.
Well-drained soil in a sunny location is ideal for planting Gloriosa and the attractive flowers make a fine display of colour when trained on bamboo frame work or low trellis. Gloriosa is vegetatively propagated from rhizome, which may be cut in pieces and planted to a depth of 3-4 cm in April-May.
The plant flowers in July-August. After flowering is over the plant begins to wither and rhizome becomes dormant. If left undisturbed. Gloriosa continues to produce flowers for several years in the same place. Application of liquid manure once at the active phase of vegetative growth and another just before flowering is recommended.
Haemanthus is one of the popular and attractive bulbous plants, commonly known as Football Lily or Bloody Lily. The genus comprises nearly 60 species, native of South and tropical Africa. The flowers are red, crimson, scarlet, pink and some species are white or pale green in colour. Some of the important species are H.multiflorus, H.magnifica, H.lindenii, H.albo-maculaius, H.coccineus, H.tigrinus, and H.candidus.
Bulbs are usually large with thick skin. Stems green, short, thick and fleshy. Leaves are usually large and luxuriant, turn yellow and dry in the winter months, the scape is sometimes curiously coloured. Inflorescence is a dense, many flowered umbel, perianth straight and erect with a short cylindrical tube. Flowers are showy and produced in ball-like heads. Fruits berry like, indehiscent. Flowers often appear before the leaves or sometimes simultaneously.
To plant in beds, the soil is deep dug and mixed with well-rotten compost and planted 40 cm apart. It grows well in pot and small pot is preferred. Application of organic manure in the rains and liquid manure before flowering is beneficial and the plants will continue to flower for several years in the same place.
They are propagated by offsets, which should be detached from the mother plant during spring. The bulbs are planted in pots or in beds during spring season to get bloom in summer and early part of rainy season.
Hedychium consists of 40 species of rhizomatous herbs native of Asia and several species are grown for their beautiful and fragrant flowers in both plains and hills. It prefers semi-shade and moist soil and produces many flowered large spikes during July-October. The leaves die before winter.
Hemerocallis is popularly known as Day Lily as the flowers last for a day and the blossoms fade at night. This genus consists of more than a dozen species and they are mostly native of China and Japan. The plants are very hardy, stout rooted, glabrous, perennial herbaceous plants, admired for their showy blooms.
The leaves are almost grass like, 2 ranked at the base of the scape. Flowers are lily like, large funnel shaped, yellow or reddish orange or brown in colour. Though the individual flower last for a day, but many flowers open successively to keep the lasting beauty for a long period.
Hemerocallis grows in wide variety of soil. While planting, the ground should be dug to a depth of 50 to 60 cm and mixed up with well-rotten compost. They take a year or two to establish properly and should not be disturbed very frequently. Planting is done in February to March and flowering continues from May to August.
Propagation is by division of the clumps and also by seeds. Some of the species are self-sterile and seeds can be obtained easily by crossing two species. Many new-varieties with attractive large flowers of various colours have developed by hybridisation. After 4-5 years, Hemerocallis clumps may be forked out during January-February separated and can be replanted again in the planting season.
Hippeastrum, commonly known as Royal Dutch Amaryllis is one of the finest flowering bulbous plants. The flowers of Royal Dutch Amaryllis are larger, open widely, about 15-20 cm across, tube is shorter and the plant develops larger bulb than Amaryllis belladona. The spectacular flowers have various shade of bright colour and wide range of variation exists in varieties developed by hybridisation. Hippeastrum produced by Ludwig are famous throughout the world. A double flowered variety is also available.
The leaves are broader than Amaryllis and do not dry out in the plains. The bulbs are lifted in November-December, stored in dry cool place for a few weeks and replanted in January-February. Hippeastrums develop flower during March-April and application of liquid organic manure before emergence of flower stalk improves the size and quality of flowers.
This genus comprises about 40 species of bulbous plants native of South America (one in Africa i.e. H.speciosa) cultivated for beautiful fragrant flowers, consisting of narrow green white petals with large coronas and protruding stamens. Some of the important species are H.macrostephana, H.harrisiana, H.speciosa, H.caribaea, H.calathina, H.rotata, H.amancaes, H.tubiflora. Flowers are white, except H.amancaes which is bright yellow.
Well-drained soil in sunny location is good for planting Hymenocallis. The bulbs are planted just below the surface of the soil during February to get the bloom in the month of May. The soil should be prepared by mixing 2 parts of loamy soil, one part of each well-rotten cow dung manure and leafmould. Watering should be given freely during the growing season. So long the plants remain healthy, transplanting or shifting from pot to pot is not recommended. Whenever necessary bulbs are dug out during September October and stored in dry place for planting in February next year. Hymenocallis is propagated by bulbs.
Nelumbo or Nelumbium, popularly known as Lotus is a flower of national importance in India. The genus consists of two species the one bearing yellow flower and the other produces white or pinkish flower.
The plant has rhizomatous stem, large peltate leaves standing well above the ground and it spreads rapidly in shallow water or wet soil. Like Nymphaea, Lotus prefers soil rich in organic matter and flowers profusely in summer and rains. Lotus do not grow well in lily pools and so tank is ideal for it. N.lutea bears scented yellow flowers 15-20 cm across N.nucifera is common in India. The flowers are white or pink, 20-25 cm in diameter. Lotus is propagated by rhizome or seed.
The Water Lily is the most popular flowering plant in water garden. The genus comprises of 40 species of aquatic, rhizomatous plants widely grown in tank, lily pool, streams, lakes and in suitable earthenware containers.
The leaves are oval or round in shape, floating on the water or standing above the water surface. The flowers are very attractive, show various colours: white, yellow, pink, red, blue and shades of colours are found in the varieties developed by hybridisation.
Water Lily prefers clay soil rich in organic matter and sunny location. The rhizomes are planted in soil in the bed of the tank or lily pool or in baskets or pots filled with rich clay soil and then placed in the tank in March-April. In the gardens in cities and towns water lily is often planted in large earthenware container filled with water and a layer of soil. In several species and varieties do not develop in the winter months and the rhizomes remain dormant. Vegetative growth starts in spring and flowers appear during the summer, rains and early winter.
In some species flowers open in day time while in other blooms open at night and close during the day. The species of Nymphaea commonly grown in water garden are as flowers: N. caerulea produces light blue flowers, 7-10 cm across, day blooming. N. lotus, the night blooming water lily, bearing white flower 12-15 cm across. N. odorata, a white flowering and fragrant water lily. The flowers are 8-15 cm across. N. pubescens, has white flowers, 8-12 cm across. N. stellata, a species commonly found in the warm humid region of India. It produces pale blue flowers about 10-16 cm in diameter. Nymphaea is propagated from rhizomes, bulbils and seeds. Most of the species and varieties thrive and flower well at water depth between 50 to 150 cm.
Tuberose (Polianthes tuberosa), a native of Mexico, is widely grown in the plains of India and blooms profusely during the summer and rains, flaunting its fragrance outdoors and indoors. Most artistic garland, floral ornaments, bouquets and buttonholes are made from these flowers. The long spike of flowers is excellent for table decoration. The flowers remain fresh for days together and bathe the atmosphere with their sweet pleasant fragrance.
The tuber is bulb-shaped and the plant is commonly classed among the `Bulbs. The leaves are 70-80 cm long, narrow, linear and radical, bright green in colour. The flowering stalk which emerges from the centre of the cluster of leaves is about 80-120 cm long bearing successively smaller long pointed clasping leaves, uppermost ones are much reduced and bract-like. The flower buds are tubular. Flowers are 5-6 cm long, borne in pairs in an open spike pure wavy white, highly fragrant, tube 2.5 to 3.0 cm long, slightly bent near the base, expanding widely where it meets the oblong obtuse segments.
There are three types of tuberose in cultivation - `single with one row of corolla segments ; `semi-double bearing flowers with two to three rows of segments and `double having more than three rows of corolla segments. Though there is no popular named variety in tuberose. `The Pearl is known to be a variety in the double flowered type. A variety with variegated leaf bearing single flowers is also grown. Single flowered type is more widely cultivated than the other types.
The bulbs remain dormant during the winter months in places where the temperature is low and if early planting is desired, the dormancy can be successfully broken by dipping the bulbs in 4% thiourea solution for one hour. Normally tuberose begins to flower in 90 95 days after planting. It flowers during the summer and rains (April-September) in the plains of eastern part of the country and from May to July on the hills, while in milder climate tuberose flowers well throughout the year.
Bulbs having diameter 2.0 and 2.5 cm show satisfactory growth and flowering. The average life of a flower spike is about 10-15 days in situ, while that of an individual flower varies from 4-6 days. Vase life of a spike varies from 7-10 days, depending on the environment and change of water. The spikes remain fresh for a longer period, if kept in 4% sugar solution.
Tuberose can be successfully grown in pots, beds, borders, shrubberies and rockeries. Propagation is by means of seeds and bulbs. Vegetative propagation is commonly practiced and desirable too, because such plants produce better flowers within a short period after planting.
The land should be thoroughly cultivated until the soil comes to good tilth. A good amount of rotted cow dung or farm yard manure should be incorporated with the soil at least 10-15 days before planting. The bulbs are planted 4-5 cm deep in beds in March-April in the plains and in May-June on the hills. The planting distance between the bulbs is 10-15 cm, while the rows are spaced 25 cm apart. For pot cultivation, 1-2 bulbs are planted in a 20 cm pot.
A fertilizer mixture containing 6 gms of urea, 16 gms each of superphosphate (single) and muriate of potash per square meter has been found to show satisfactory growth and flowering. The above mixture should be applied in two equal doses the first dose before planting and the second one, 4 weeks after sprouting of the bulb. Commercial growers dig out bulbs 3 years after planting. They are stored in a cool, dry and shady place and planted again in the following spring.
Zephyranthes has a fanciful meaning i.e. the `West-wind Flower commonly known as Zephyr Flower or Fairy Lily. The Genus has about 50 species of bulbous flowering plants, native of warmer region of America. It is related to Habranthus, Pyrolirion and Hippeastrum. Some of the popular species are Z.candida, Z.citrina, Z.grandiflora, Z rosea, Z macrosiphon, Z.tubispatha and Z.Verecunda. The flowers are with many colour ranges i.e., white, yellow and various shades of pink.
Zephyranthes is a hardy bulbous herb. Leaves are filiform or linear or may be strap shaped. Flowers solitary, peduncle elongated slender, hollow; perianth funnel-shaped, erect or slightly inclined, stamen 6, stigma 3-fid.
It is commonly propagated by separating the bulbs, sometimes through seeds. Bulbs are planted in spring, 30 to 40 mm deep and 2 to 15 cm apart. They flower during summer and rains and make a very colourful display especially in rains. Top dressing of organic manure once a year in a rainy season will promote flowering and the bulbs may be left undisturbed for many years.