How to Grow and care for Gladiolus

How to Grow and care for Gladiolus

How to Grow and care for Gladiolus

Introduction

in this article, I’m going to show you how to How to Grow and care for Gladiolus. Gladiolus is a genus of important perennial bulbous flower belonging to the family Iridaceae and is grown throughout the world as a major cut flower. The genus consists of 260 species mainly native to South Africa. The inflorescence of gladiolus is a spike. Each flower bud is encased separately within its own spathe. which consists of two green bracts. Stems are unbranched producing  1-9 narrow, sword-shaped, longitudinal grooved leaves, enclosed in a sheath and grow from rounded, symmetrical corms.

Cultivation

How to Grow and care for Gladiolus

Climatic conditions

They are preferably grown in the highlands. A temperature range of 18-23 °C  is conducive for optimum growth and flowering with night temperatures being lower than day time temperatures. A site 2500 ft above sea level and protected from strong winds would be most suited for their cultivation

Growing Media and Planting System

Commercially, gladioli are grown from corms and cormlets. Generally, inflorescence initiation takes place after the initiation of 6-8 leaves. However, all of these leaves will not be seen outside and they may be in the process of elongation.

Planting under full sunlight in sandy-loam soil is the most preferable for gladioli cultivation. However, a pH of 5.8 to 6.5 is recommended and planting in all types of soil is suitable for growing gladioli, provided the soil has good structure, rich in organic matter and is well-drained. If the planting area has clay soil it is recommended that the soil is dug up to 1-1.5 ft depth and river sand is mixed to improve soil texture prior to planting

Spacing of 15×25cm or 20×20cm is maintained for high-density planting in raised beds: mainly for production of cut flowers at commercial scale. A number of corms required is about 28 t0 42 per square meter. Corms may be placed 3×6 inches apart for garden landscaping. Small size corms are planted at a depth of 7cm and larger ones at 10cm. Deeper plating adversely affects the production of the number of flower buds and will reduce the number of cormlets however the daughter corms produced in deep planting are healthy.

Irrigation

Soil should have sufficient while planting to enable easy rooting and sprouting. Watering may be done once a week sufficiently to wet the roots. Very early during the growth stage when flower initiation takes place, as well as from the fourth leaf stage through to flower stem elongation are important stages of growth-sensitive to water stress

Nutrition

Fertilizers may be applied at various stages of growth as well as depending on soil types. However, the following amounts and types of fertilizers may be applied for an area of 100 sq. m when grown in local soils:

  • Initial basal mixture: 650g Urea, 475g MOP and 2980g TSP
  • At 2/3 leaf stage:  Urea 650g, 475g MOP
  • When buds show colour and are seen on the inflorescence: Urea 650g, 475g MOP
  • 2 weeks after flowers have open: Urea 650g, 475g MOP
  • It is also possible to improve flower colour in gladiolus by application of balanced fertilizers in the form of pellets or show-release granules
  • As a general rule varieties showing rapid growth, large plants and large flowers respond more to fertilizers
  • Deficiencies of elements in soil or fertilizer pattern are easily noticeable in these plants
  • Nitrogen – paling of foliage and reduction in the number of florets
  • Phosphorus – leads to dark green foliage and purple colouration in the lower leaves
  • Calcium – results ain the disorder ‘topple’ which causes breaking over of gladiolus in the vase after most of the flower have opened
  • Magnesium – yellowing between veins which appears first in the older leaves and causes delayed flowering
  • Iron – causes interveinal
  • Boron – horizontal cracking of the leaves starting from the margin of the leaves and extending towards the midrib

Gladiolus is highly sensitive to fluoride toxicity. Zinc is also an important nutrient and it improves plant growth and leaf size. Iron deficiency causes interveinal chlorosis

It has been reported that treatment with Ga3 at 100ppm, IAA at 100ppm, CCC, B – Nine and Ethrel was effective in increasing the vegetative growth, improving corm size and number of flowers per spike. Lengthening the life of the spike to a significant extent, improvement in flowering and cormel formation as well as an increase in floret size.

Weeding

Weeds have to be removed regularly when they appear in the fields. Since they compete with the crop and result in the production of the low-quality spikes and unhealthy, small corms. Manual weeding can be practised carefully although there are maybe chances of mechanical damage. Resorting to chemical control will also help and is best done prior to planting of corms. Perennial weeds can be generally controlled by applying Glyphosate during field preparation.

Aftercare

Loosening the soil may be practised up to a depth of 10cm when plants reach a height of 20cm. mulching is important to prevent excessive evaporation and also protect the soil from temperature fluctuations and weed growth, sawdust, grass shavings, chopped straw, etc. can be used for mulching. Improvement of flower and corn production through plastic sheeting has been reported with increase corm production by more than 50 per cent. Staking of plants is important to prevent them from falling over when blooming or due to winds. Taller varieties may be supported with a strong stake of 1.5m.

Propagation

Gladiolus can be propagated through corm, cormlets and seeds. Propagation through seed is carried out only for breeding new varieties. Gladiolus produces only one to three corms per plant. Number of plants depends on the number of aerial shots. Cormel production per mother plant varies according to variety. Climatic conditions and management practices. The quality of flower produced depends on the size and weight of the corms. The size should be at least 5cm in diameter for minimum quality spike production. Cormels take at least 2-3 seasons to become full-sized corms.

Lifting of corms

Generally corms mature six weeks after harvest of flower spikes. At least two and preferably four leaves should be left on the plant after cutting spikes to help corms mature properly. Thus plants need to be watered and fertilizers also need to be applied until leaves dry out after harvest of flowers, corms are lifted as soon as they mature. Lifting is done manually, which may be time – consuming. however, care should be taken to avoid damage to the corms. Corms should be cleaned and dipped in a fungicide solution within 2 days after lifting. Washed corms and cormels may be subjected to air circulation for quick drying these corms and cormels are subsequently kept in trays variety-wise.

Separately and dusted with a small amount of Carbaryl 85% WP. Thiram or Captan 80% WP to prevent infection of corms. Trays are then placed in a shady but well-ventilated place until they are to be replanted in soil.

In certain instances gladioli are cultivated purely for the production of corms in such cases fertilizer applications also need to be changed to suit formation of corms as follows:

Basal dressing – 670g Urea, 440g MOP and 1180g TSP

One month later – 670g Urea, 440g MOP

02 months later – 670g Urea, 440g MOP

03 months later – 670g Urea, 440g MOP

Dormancy of corms is an important problem faced in the year-round cultivation of gladiolus Low-temperature storage (3-7 Celcius for 3 months) followed by treatment at high temperatures as well as the application of chemicals such as Ethrel (1000 ppm), GA3 (100ppm) and Benzyl adenine (20ppm solution for 24 hours soaking) are generally employed for dormancy breaking.

Disease and Pests

Diseases

The disease commonly known as Yellows or Fusarium rot is caused by Fusarium oxysoprum. Symptoms including curving, bending, stunting of stems and premature yellowing of leaves and paling and drying of plants in general in the field and corm rot in storage. Corm rot, not always visible externally, is often restricted to the corm base. When the corm is split in half, there may be dark coloured streaks that extend from the centre of the corm base through the flesh and rot is seen extending from the centre outside. In storage, corms develop dark brown spots on the surface; in severe cases, the entire centre may be black and decayed. Pre-planted or post-harvest dipping of corms in captan 50% WP, 80%WP or Thiram 80% WP is effective in disease control. Growing medium/soil pH should be maintained at 6.6-7 and corms should be stored under dry conditions and examined intermittently for indications of disease onset. To obtain perfect control of this disease, it is important to develop varieties with resistance/tolerance to the fusarium.

Scab or bacterial blight is caused by the bacterium Pseudomonas marginata. Disease symptoms include soft, brown patches on leaves as well as pale yellow, water-soaked spots on corms. As the disease progresses, circular lesions on corms turn brown and sunken with distinct raised margins. Infected corms should not be planted but burnt and destroyed for diseased control. Proper cultural practices including high field sanitary as well as use of clean tools also help in preventing disease spread when watering, wetting of leaves and flower spikes should be avoided as much as possible only watering at the base.

Corm rot or Stromatinia dry rot is caused by the fungus Stromatinia gladioli. Frequency of disease occurrence is high during cool, wet weather. Initially leaves turn yellow prematurely and die. Small, red-brown, sunken lesions may b seen on corms. When an infected corm is cut in half, dark streaks can be seen radiating out from the core to the surface of the corm. Often plants are infected in groups as the fungus spreads from the original infected plant.

To manage the disease, infected corms should be removed and discarded; only healthy corms have to be planted in well-drained soils and corms should be harvested during dry weather. Treating the soil and corms with a fungicide prior to planting may be beneficial. Replanting gladiolus corms in infected soils should also be avoided

Botrytis leaf spot and blight is caused by the fungus Botrytis gladiolus leads to brown spots or lesions with red streaks seen on the leaf and stem. The leaf lesions vary in size and shape and often have brown or grey centres covered with grey masses of spores. As the disease progresses, the tips of the leaves or the stem may turn yellow and die.

Infection of the flowers usually begins near the edges of the petals and appears as water-soaked spots. The spots enlarge rapidly and the flowers become slimy. Turning a brown colour, and begin to droop. Under moist conditions, the flower soon covered with a mass grey spores.

The fungus may produce small, black, hard structures on bed plant tissue and corms. These sclerotia serve as survival structures for the fungus and can remain in the soil for many years.

Symptoms on infected corms include sunken, round, green-brown lesions. The lesions may vary in size from pin-point to ½ inch in diameter. The inside of the corm may be partially rotted with brown strands radiating from the centre or have a spongy decay.

The best form of control for botrytis is prevention. Which involves sanitation, air circulation and proper water management. Affected flowers and plant parts need to be removed and discarded appropriately. A 10% Clorox solution may be used to disinfect the nursery and storage area of corms. Wetting of flowers and foliage should be avoided as much as possible when watering early in the day helps ensure the plants and flowers will be dry by nightfall, corms, flowers or foliage should not be allowed to stay wet overnight. Application of Mancozeb 80% WP, Manabe, 80% Wp or Chlorothalonil  75% WP, 500g/l SC according to labelled instructions, following required safety precautions would also assist in its control

Pests

Aphids suck the sap from young plants while thrips feed on flowers, floral sheaths and leaves. Both are winged insects and may spread easily. They cause damage to leaves and flowers making them unmarketable. Careful regular inspection of plants and flowers followed by the application of imidacloprid 200g/l SL, 70% WG, thiamethoxam 25% WG in keeping with labelled instructions, is helpful in the control of these insect pests

Slugs and snail may feed on young leaves and new shoots entirely destroying young plants. It is best to manually remove pests by hand or apply a bait containing Metaldehyde 4% or 6% RB

Harvest, Post-Harvest and Packaging

How to Grow and care for Gladiolus

Harvesting of flowers is carried out at tight bud stage with at least four flowers on the plant intact and t least one to five buds showing colour and or when first two buds begin to open. Buds may easily open one by one. Spikes should be placed in a bucket of water immediately after harvest and the stalk re-cut underwater by removing 2-3cm basal parts. This is to prevent stems being blocked with air bubbles. Spikes should always be kept in a vertical position to prevent geotropic bending. If markets are far away, after pre-cooling at 5-6 °C spikes are kept under refrigerated condition at 2.3 °C to 2.8 °C, at this condition spikes can be kept for one week before transport.

Gladiolus spikes are generally packed in 3-5 ply cardboard boxes 1.2 meters in length. 60cm in width and 30cm in height as well as perforated at several places for circulation of air. The spikes are arranged head to tail alternately and tried to make bundles of 10-25 spikes which are subsequently packed in boxes.

It has been reported that vase life solutions such as 8HQC, STS (Silver thiosulphate). Citric acid combined with sucrose (20% solution) increases the vase life of gladiolus

check out my other article:How to Grow and Care for Gerbera

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