Gladiolus advice
Simple advice for the beginner
The first step that most beginners take on the long and happy road of growing gladioli is to either see them waving gracefully in a neighbouring garden or showing themselves off to perfection on the show bench, bolt upright and ready for inspection like ranks of well-turned out soldiers.
Having had the corms planted they start to prepare to grow some themselves but often find themselves struggling for advice through lack of literature on the subject or the absence of local growers who can offer advice.
That is why you should join the British Gladiolus Society.
The South African species were originally pollinated by long tongued anthrophorine bees, but some changes in the pollination system have occurred, allowing pollination by sunbirds, noctuid and Hawk-moths, long-tongued flies and several others. In the temperate zones of Europe many of the hybrid large flowering sorts of gladiolus can be pollinated by small well known wasps. Actually, they are not very good pollinators because of the large flowers of the plants and the small size of the wasps. Another insect in this zone which can try some of the nectar of the gladioli is the best known European Hawk-moth Macroglossum stellatarum which usually pollinates many popular garden flowers like Petunia, Zinnia, Dianthus and others.
Many of the approximately 300 species of flowering plants of the genus Gladiolus, (part of the iris family) native to Europe, Africa and the Mediterranean are widely cultivated for cut flowers. The flowering spike, which springs from a corm, reaches 2 to 3 ft (60 to 90 cm) in height and has many funnel shaped flowers, all clustered on one side of the stem. There are six petal like floral parts and sword like leaves. Cultivated gladioli, which come in all colours, have been developed mostly from southern and eastern African species.
Gardeners tend to have a love/hate relationship with gladioli; very few people sit on the fence.
If you're reading this, you probably appreciate the intricate beauty of these dramatic flowers and enjoy the vast colour selection. Gladiolus hybridising is a hot area in the horticulture world right now, with breathtaking results. The outstanding choices are popping up so fast that we’re having trouble keeping up with good selection of photographs but can't wait to grow dozens of cultivars in the near future for just that purpose. No longer the predictable flowers your grandmother grew, glads have morphed into stylish contributors for both gardens and bouquets. Here's to experimenting with zippy new choices!
All about Classification of Gladiolus
For anyone interested in the Gladiolus, and particularly for those of you interested in attending and competing in Gladiolus classes in shows, you should try and acquaint yourself with the world-wide classification codes.
All codes consist of 3 digits, the first of which specifies the diameter of the fully developed bottom floret of the spike:
The second digit denotes colour (i.e. green, yellow, orange etc, 0-9) and the third digit denotes the "strength" or hue of that colour. Second digits may be (0) = Pale, (2) = Light, (4) = Medium, (6) = Deep and (8) = Very Deep.
Notice that the third digits are all even numbers: even numbers indicate that the colour is without any conspicuous markings present, whereas by increasing the number by 1 to make it an odd number signifies that conspicuous markings are present.
For example, Doris Darling 442 is a large flowered pale Pink bloom without distinctive markings whereas Pink Elegance 443 is a large flowered pale pink with a distinctive mark, in this case a white throat.
The table below indicates how the second and third digits in the classification are used.
So to summarise, all you need to do to become reasonably proficient at recognising Gladiolus codes is to learn the floret width codes (1-5, narrowest to widest) denoted by the first digit (see table above), and below, the second digit colour codes (0-9) and the third digit colour strength code (0-8). Don't forget that if the third code digit is an odd number it means that the floret has distinctive markings.
Any cultivar that has a prefix ‘P’ is a Primulinus type and should have florets of no more than 3½" in diameter. These are very specific type and in modern times have been maintained almost exclusively by amateur enthusiasts.
Propagation from corms, cormlets and seed
Gladioli produce a new corm each year as the old one shrivels and die. They multiply by the production of cormlets, that is to say mini corms that are produced during the growing season and can be found around the base of the new corm as it is lifted in the autumn. These cormlets will, if grown on, grow to a size where they are capable of producing a flower and this flower will be identical to its parent, i.e., cormlets taken from a red flower will always flower as red. This is the main way of increasing stock of a particular cultivar.
Gladioli can also be propagated by division which involves sectioning a corm and planting it as one would a normal corm, however a growing point ‘eye’ and a section of the basal root plate must be present on each section for it to grow.
Gladioli can also be grown from seed and it is by this method that new cultivars are created. Pollen can be harvested from the male reproductive organs of one spike and applied to the female parts of a ‘mother’ plant and if all goes to plan a seed pod will eventually be formed that will contain many seeds. These should be harvested when ripe and can be sown the following spring into a greenhouse. Here they will germinate and may even produce a flower in the first season but more probably it will be the second season before a ‘new’ creation will be seen.
Alternatively if one lets mother nature do the work seed pod from spikes that have been left in the garden to be pollinated by insects can also be used.
Gladioli can also be propagated by division which involves sectioning a corm and planting it as one would a normal corm, however a growing point ‘eye’ and a section of the basal root plate must be present on each section for it to grow
Growing corms from cormlets
Propagation from cormlets is the major way of increasing stock of a particular cultivar to give plants identical to the parent. Cormlets are found around the base of the parent corm when it is harvested in the Autumn and will carry all of the characteristics of the parents.
Cormlets can withstand colder conditions than corms and can therefore be planted earlier in the year. As they don’t need heat they can be planted in large pots from late February if protection can be given such as a greenhouse or frame, then moved outdoors when conditions allow. Any potting compost will do the job, a little sharp sand and or grit added to the medium will make sure that good aeriation and drainage is acquired.
They can also be planted outdoors from April onwards, preferably where Gladioli have never been grown before. The soil should be prepared in the Autumn by incorporating some humus material such as peat or well rotted manure, however high Nitrogen Fertilisers should be avoided as these can cause fungal diseases.
Gladioli have a dormant period which can be broken by storing the cormlets in cold conditions followed by somewhere warm for around ten days, the door of a refrigerator is ideal for the cold phase with a temperature of 18 degrees centigrade for the warm period. It is also helpful to prepare the cormlets for planting after the refrigerating by removing the hard outer husk or shell as germination is considerably hindered by this protective layer. If difficulty is encountered doing this then soaking overnight in warm water will help.
The prepared cormlets are now ready to be planted, the pots should be filled up to about 5cm from the top, a layer of sharp sand can be added to add extra drainage and this gives you a nice clean corm at harvest time, then the cormlets can be planted on top 4 cm either way, another thin layer of sharp sand is added then the pot is filled up to within 1 cm of the top. Give the pot a good watering and if possible cover with a sheet of glass or polythene to help germination.
If you are growing the cormlets outdoors it is advantageous to cover the area with a sheet of polythene to warm the soil up before planting. The same planting system can be used as for the pots, if grown in rows allow a little room between them to be earthed up during the growing period.
Watering should be carried out regularly throughout the growing season and should be sufficient to get to the roots not just the surface of the soil. Cormlets can withstand a greater level of feeding than mature corms and should be fed on a regular basis with either liquid feeds, or dry fertiliser worked into the top few centimetres of the growing medium. The pots will need to have a little more than the soil grown ones as the fertilisers tend to leach out through the extra water they have, a feed every 7 to 10 days will suffice. All feeding and watering should cease by the end of August to give the new corms a chance to ripen before harvest. It is at this stage that the pots should be put back in the greenhouse or frame to grow on, remember the longer the cormlets grow the bigger the corm will be at harvest time.
During the growing period the plants should be kept weed free as these will compete for the nutrients which are available, they should also be sprayed periodically to protect them from aphids etc. Any plants that do not look healthy should be discarded and burnt, if not infections will quickly spread to other healthy stock. It is advisable to take any flowers off the plant if they attempt to flower as all the plants energies should be directed towards the corm. As soon as the foliage starts to turn brown the plants should be harvested, even if not brown the plants should be lifted by early October unless protection of a greenhouse is available, they should all be lifted by mid November so they can have a period of dormancy.
To lift the corms gently ease the whole plant up with a fork and shake of any excess soil, twist or cut off the foliage as close to the corm as possible and trim back any roots. The corms should then be put into trays to dry in a well ventilated area, after about two weeks the roots should just twist off if not leave another week then try again. Discard the old roots but keep all the cormlets which were around the new corm. The dried and cleaned corms can then be put into storage in a cool frost free area. Whilst in storage they should be regularly checked and any showing signs of disease should be destroyed. Once spring arrives the corms can be planted out into their flowering position, any corm larger than 20p piece will give a flower although it may need another season before it reaches its full potential. Any smaller than a 20p piece should be treated as cormlets and be grown on for another season.
Pests and diseases
The gladiolus is relatively free of pests and diseases of epidemic proportions: however, as with all subjects it is vulnerable to certain fungi, virus and insect damage. Below is a summary of some of those that are more likely to be encountered in no particular order of their threat. The common prevention message as far as all are concerned is to destroy all infected or suspect tissue whether leaf or corm - do not compost.
Storage rot penicillium spp.
Corms may become soft during storage or appear to be covered with bluish-green masses of fungal growth. Control involves careful selection of clean, well-ripened corms for storage during digging. These corms should be cured for three weeks at 80 F, with artificial heat if necessary. It is also helpful to carefully inspect the corms after storage and to destroy any corms that don't appear healthy.
Caterpillars
Caterpillars can also be a pest and when present will often attack flower buds hewing a hole through the entire bud and thus the petals held inside. In addition they may also emerge from the tips of a spike in tight buds generating further holes which will detract from the beauty of the plant.
The first symptom of infection is the appearance of tiny, reddish-brown, raised dots on the basal part of the leaves. These spots enlarge and coalesce to form longitudinal lesions or streaks. Under favourable weather conditions, large, brown, dried areas develop on the leaves. These are followed by a rot of the stem at or just below ground level. Lesions on the corms are light-coloured, watery spots at first and become darkened with a raised margin, the centre of which shows a hard, gummy exudate which is shiny and reddish. The most effective method for control of this disease is selection of a site with well-drained soil. It is also very important to discard any corms that show disease symptoms.
Stromatinia rot
This corm disease is caused by a fungus called Stromatinia gladioli and is most prevalent during periods of cool wet weather and as such can be a particular problem in northern European climates.
The first signs of disease are usually on the growing plant and are evident by the yellowing of leaves which eventually shrivel and die. Evidence of the disease on the corms is the appearance of reddish brown markings which are sunken and if the corm is dissected, dark markings are seen as a marbling emanating from the centre. A particular problem with this disease is that the fungus produces an over wintering particles called Sclerotia. As a result diseased corms should never be planted and as a precaution corms should always be harvested in dry conditions. If Stromatinia is suspected in growing plants that soil should not be replanted in subsequent years as the disease is capable of passing from soil to plant.
Fusarium yellows and corm rot
This disease is caused by the fungus Fusarium oxysporum, var. gladioli and is often referred to as Fusarium yellows or Fusarium Wilt. The symptoms are a yellowing of the leaves starting with the older outside ones first and this is accompanied by the apparent stunting of newer leaves. In addition the spike itself will often be stunted and faded in colour. The plant may also have blackened areas at the base which spread onto the corm. Eventually, if left, the whole plant will wilt and when lifted for destruction, (for this is the only course of treatment), the interior of the corm when opened will appear marbled with a brown colour.
Where Fusarium occurs, fertilise sparingly: nitrogen should be applied in the nitrate form rather than as ammonia or urea. Soil pH 6.6 - 7.0 preferred. Harvest corms in dry weather if possible and cure them rapidly using forced air at 80 - 100"F if available. Inspect stored corms and rogue out suspects.
