GLADIOLUS AGRONOMY PRACTICE

Introduction

Gladiolus (Gladiolus hortensis L.), the queen of bulbous flowers, belonging to the family Iridaceae and subfamily Ixoideae, is one of the most popular ornamental bulbous plants grown commercially for its fascinating flowers in many parts of the world. It is one of the most important ornamental crops having a pivotal place as cut flower both in the domestic as well as the international market. Gladiolus was introduced into cultivation towards the end of the sixteenth century. Most of the wild species (approximately 300) of gladioli have their centre of origin in Africa, particularly in and around South Africa, but a few species are also from the Mediterranean and adjoining areas of Europe. Ploidy in the genus ranges from diploid (2n = 30) to dedecaploid (2n = 12x = 180). The genus was named by Tournefort and this generic name is derived from the latin word ‘gladius’ meaning ‘sword’ on account of the sword – like shape of its foliage. Popularity of this crop as a cut flower is increasing day by day because of its keeping quality and inexhaustive range of colours of the spikes. This Gladiolus is a slender herbaceous perennial with sword shaped phyllode leaves, grown both for gardens and floral decorations. From the commercial point of view, mainly, it is very important due to its majestic flower spikes having florets of varying shapes, sizes, colours and excellent keeping quality. Gladioli grow from rounded, symmetrical corms that are enveloped in several layers of brownish, fibrous tunics.

Classification

1. 1. Horticultural Classification

There are four types of gladioli based on the size and shape of the flowers. For horticultural purposes, gladioli are grouped as follows

1. 1. • Large flowered (Grandavensis) Hybrids

The large flowered gladiolus is more suited for garden display than floral decorations with triangular overlapping florets. The flower spikes grows to a height of 120 to 150 cm, are strong and erect, with florets of 10 to 15 cm across, closely arranged, triangular and symmetrical flowers and flowers late in the season

1. 1. • Primulinus

Primulinus gladiolus has slender spikes with separate wide florets arranged in a zig-zag pattern. They bear hooded flowers which are smaller in size. The spike grows to a height of 100 cm and bears florets of 5 to 10 cm across. It is a mid- season flowering

1. 1. • Miniatures

Miniature gladiolus, popularly known as ‘Pixiola’, are the daintiest, with upper petal slightly hooded and smaller florets having frilled or ruffled petals These are preferred for forcing under glass or for growing in pots or bowls. Colvillea, Nanus, Byzantinus, Gradis and Tristis are some of the popular cultivars in this category. The spike grows to a height of 60 to 100 cm, with florets of 5 to 7.5 cm across, good for cutting and early flowering type. They include butterfly hybrids which possess spikes up to 36 cm in length. Edges of the petals are often frilled and ruffled with individual florets about 6 cm in diameter, having most distinctive throat markings.

1. 1. • Peacock Hybrids

These are good for cutting, dwarf in height, multi coloured sorts with reflexed petals

1. 1. • Star flowered

These types bear flat star – like flowers, a race raised by Unwins of Cambridge, England

1. 1. Commercial Classification

For commercial purposes, gladiolus are classified on the basis of spike length and floret number. These classifications are given below

Classification of Gladiolus on the Basis of Spike Length and Floret Number

1. 1. Classification of Gladiolus based on the size of the floret

Depending on the size of the floret, gladiolus are classified as follows

1. 1. Classification of Gladiolus on the basis of colour

White, yellow, orange, salmon, pink, red rose, lavender, violet, smokes, tan and brown. In each colour pale, light and medium deep, etc. are also considered.

Soil and Climate:

Gladiolus prefer sunny situation and hence site selected for gladiolus planting should be sunny protected from stormy winds, by wind breaks or hedge. They will not do well if planted close to trees, shrubs, buildings and in low, poorly drained places. Well drained fertile loamy to sandy loam soil with the pH of 6.5-7 is highly preferred for gladiolus cultivation. Highly acidic and alkaline soils should be avoided. Clay soil is not suitable for gladiolus cultivation. Adding sand to make it porous can amend light clay soil. Water logged, heavy sticky soil will result in decaying of corms as well as delay in growth of plants. Therefore heavy soil should be supplied with sand, decomposed leaves and organic manure. Thorough incorporation of these materials into the soil and judicious cultural practices will improve the physical texture of the soil. Organic matter should be incorporated into sandy soils by heavy application of manure. The added organic matter will help in retention of moisture and prevent leaching of fertilisers. It produces bigger size flowers in areas with moderate humidity.Favourable temperature range for growing gladiolus is between 27°C and 30°C.

Planting

To prepare the soil for planting, it should be spaded or ploughed to a depth of 30 cm to obtain the best flowers. Land is prepared during September – October and the corms are planted up to November. Even December planting is also recommended. To encourage sprouting, the brown dry scales or the tunics are removed. The corms should be disinfected properly before planting to reduce the chances of disease infestation. For prolonging the blooming period, (a) planting of corms of different grades, (b) planting of corms at 15 to 30 days interval, (c) planting of corms at different depths (7.5, 10 and 15 cm), and (d) use of early, mid-season and late varieties, etc., are helpful. Gladiolus corms which are healthy, disease free with diameter of 4 to 5 cm should be selected and planted at a spacing of 30 x 20 cm. Shallow planting of corms is essential. The depth of planting of the corms should range from 5 to 10 cm. Deep planting of corms will result into poor production of cormels and also cause decaying of corms. Generally, the performance of high crowned corms is better than large flat corms.

Nutritional Requirements

FYM is mixed thoroughly in the soil while preparing the field for planting corms @ 20 tonnes/ ha of FYM. 120 kg N, 150 kg P2O5 and 150 kg K2O per hectare is recommended, of which 60 kg N and entire dose of P2O5 and K2O is applied as basal dose. The remaining N is given in two split doses, 30 and 60 days after planting. i.e. first dose at 4-6 leaf stage and second at earthing up stage i.e. 6-8 weeks after planting.

Irrigation:

Judicious use of water is possibly the most important single factor in the production of the best gladiolus spikes. A gladiolus crop must not be allowed to suffer from water stress especially when spikes are emerging. Regular irrigation at an interval of 7 to 10 days depending upon the weather is necessary. Over watering should be avoided. Irrigation should be withheld at least 4-6 weeks before lifting of corms.

Cultural Practices:

After the corms have sprouted well, watering should be done, if necessary. When the shoots are about 20 cm high they are covered by heaping the soil up to a height of 10 to 15 cm. Earthing up is essential after 6-8 weeks of planting corms, or before the emergence of spike. This enables the plants to grow erect despite high winds and rains, and suppresses weed growth. Earthing up the soil is a must in case of light soils. These plants need staking for its satisfactory growth and if not staked may fall or break by high wind velocity. In cases where the spikes grow longer or stems are not strong enough to bear the lodging or mild stroke of wind, they are supported with about 1.5 meters strong stakes. Strings instead of stakes may be used at the time of the appearance of the spikes. Strings are stretched between the stakes along the row to provide easy and adequate support. Staking is done when the plant attains the height of 15 cm in order to provide shelter from the wind.

Curing of Spike (Harvesting):

After planting the corms, gladioli comes into bloom in two to three months, depending upon the species and variety. Early flowering varieties start flowering within 80 – 90 days, while late varieties start flowering within 100-145 days after planting. The flower spike should be cut as close to the base as possible with a sharp knife or a scissors after the first floret on the spike has opened. Later on, the other flower buds i.e. florets on the same spike will open in a sequence, slowly starting from 14 below and continuing upward when placed in water. While harvesting or cutting of the spike, care should be taken that at least four to six basal leaves should be retained on the plant to ensure proper development of corms and cormels. This is vital for the new corms to have good flowers in the following year. For the internal market, flower spikes are cut when 1-2 lower most florets on the spike have opened and for the external market, when the colour has fully developed in mature unopened buds. Immediately after cutting, the spike should be immersed (upto 15 cm from base) in a bucket containing water.

Vase life

The various aspects of quality parameters of gladiolus cut flowers are their keeping quality, straight strong stems free from side shoots, uniformly spread florets with a specified number per spike, turgid florets facing in one direction, colour, freshness, foliage with proper length and free from damage, dust and spray residues, absence of insects, disease and bruising injury. Gladiolus spikes are generally harvested with relatively few florets showing colour. Vase-life of gladiolus spikes varies from 5-10 days, depending upon the cultivar and room temperature. About 2.5 cm long basal ends of the spikes should be cut off and the spikes placed in acidic solution having pH between 3-3.5 to increase the shelf life.

Harvesting and Storage of Corms:.

• • Lifting of Corms and Cormels

After harvesting of flowers or spikes , plants are twisted down to ground level for allowing the corms to mature. Once the spikes are cut out, the leaves begin to turn yellow. Plenty of moisture, followed by a dry period, before lifting ensure the formation of large corms. Gradually the water supply is reduced till the leaves get dried naturally. After 3 – 4 weeks corms and cormels are lifted from the ground. Corms are matured when 25% cormels have become brown which generally take 30 to 45 days from flowering when the leaves also start yellowing. Corms and cormels should be dug out with the help of a spade. Soil should be dug deep in order to take out all the cormels. The corms are checked for any disease infection and the affected corms are discarded.

• • Curing

Curing is one of the essential post harvest operations for successful storage of corms. After lifting and removing the adhering soil, the corms and cormels of each cultivar are kept in trays in a shady but well ventilated place for about a fortnight. For curing, the layers of corms should not exceed three, which may be cured for five weeks at 21°C.

• • Cleaning, Grading and Storage

After the corms are fully cured, these are cleaned and diseased ones discarded. The old withered corms are taken out and cleaned. Treating the corms with 0.2% Captan 15 days before storage or dusting with 5% Cythione dust and Dithane M-45 protects them from insects, pests and diseases during storage. After cleaning, the corms and cormels are graded in different grade-sizes. The corms are stored in perforated trays in a well-ventilated cool and dark room with temperatures not exceeding 27OC. Being smaller in size, the cormels are stored in plastic trays having fine perforations. It is advisable to keep on turning corms and cormels periodically, for preventing their rotting due to poor aeration. The corms are periodically checked during storage and the decaying ones are removed. The cormels of exotic cultivar vary considerably in respect of hardiness, depending upon their size. The small sized cormels (<0.5cm diameter) are fairly hardy and may be stored at room temperature, without decay. However, the large ones (>0.5cm dia.) of exotic cultivar require low temperature during storage and should be kept in cold storage. To avoid chances of mixing, the cormels are packed in hessian cloth bags before putting them in perforated trays for keeping them in the cold storage. Like corms, the cormels should also be taken out of the cold storage in the first week of October and kept at room temperature for a week before planting them in the ground.

Yield:

The yield of flower spikes and corms in gladiolus depends on variety, corm size, planting density and management practices. Gladiolus planted at a spacing of 30 x 20 cm yields approximately 1,50,000 marketable spikes per hectare. Additional income can be obtained from the sale of corms.