The manual for growing gladioli includes my many years of experience and is of course updated annually with new preparations for the protection and nutrition of gladioli. However, I want to remind you that I also use several professional preparations that I do not mention here, they are not normally available in stores.

During 45 years of growing and crossing gladioli, I have experienced a lot. I have eliminated complicated and even unnecessary and time-consuming procedures. I want to spend as much time as possible with gladioli, improving them – crossing them, i.e. breeding new varieties.

Of course, I am not stating anything revolutionary here, I am just reminding you of the principles of growing gladioli, summarized in 15 points.

Suitable location

The sun must not be missing and the wind as little as possible, because gladioli really do not like wind. If you have no other option, grow them in the same place every year, but it is best to rotate the beds in a three- or multi-year cycle. If you must plant in the same place, make sure that the soil is free of wireworms and other pests that could pierce the tuber and thus open the door to fungal diseases, especially Fusarium, Botrytis and Bacteriosis.

Soil preparation

The plants are suitable for almost any type of soil, because it can usually be adjusted as needed, for example, more acidic (pH 3-5.5) limed to the ideal pH of 6.5. The exception is heavily waterlogged soil, which is at risk of fungal diseases. Before planting the tubers, the soil must be loosened to a depth of +- 30 cm. To suppress the influence of unwanted fungi in the soil and especially for proper nutrition of gladioli, you can use the ecological preparation Azoter, which is available from the manufacturer and for gardeners. Just before processing the soil, use it according to the instructions on the product packaging. I have good experience with it and not only for gladioli but also for useful crops.

Do you have experience with wireworms on your plot?. In gardens near grassy areas or fields, you will probably never completely get rid of them, but you can significantly suppress their occurrence to an acceptable level. If you have more acidic soil and wireworms occur, 2 weeks before planting the tubers, spread nitrogenous lime on the area (about 75 g per 1 m2) and work it into the soil. Be careful, do not plant before the lime has reacted in the soil, you can burn your seedlings and even destroy them! , which unfortunately happened to me. It is safer and more effective to spray FORCE 1.5 G on the affected area before tilling the soil and also in the rows when planting. The product is not the cheapest (available only online, not available in retail stores), but the guarantee of pest eradication is 98%, according to my experience. It is not necessary to add any granular fertilizer to humus-rich soil before planting, especially if well-matured manure was used the previous year.

Planting material

A high-quality one-year-old tuber is almost round in shape, but a 2-year-old tuber is often the best. Namely, in the first year, a tuber grown from a rootstock with poor nutrition and care (or from a small rootstock) will not „make“ the maximum possible size of the tubers and thus the parameters of the flower! In a 2-year-old well-nourished tuber, the shape of the tuber is less round to almost flat. Such a tuber has a larger diameter than a 1-year-old tuber, has an almost smooth circumference and the root crown has a smaller diameter. If the same tuber is planted in the 3rd or 4th year, although the diameter of the tuber is approximately the same as in a 2-year-old, the tuber is usually flat with more pronounced protrusions around the circumference and has a large diameter of the root crown. It is typical for such a tuber that many dormant buds wake up in the spring, i.e. many sprouts sprout. It is advisable to break off all the sprouts and leave only one dominant one. If you leave 2-3 sprouts, the stems will grow obliquely with a tendency to roll out and curve and the flowers will be of lower quality.

In case of emergency, an old tuber can be used to save the variety by removing the brute and renewing quality seedlings. If we are saving the variety, it is necessary to break off the forming flower spike in order to grow as much quality brute as possible for propagating the variety.

The choice of variety is up to each of you. The composition of the gladiolus assortment in the offer of retail chains from Dutch suppliers has not changed for many years. The offer includes very old, mostly simple, smooth-skinned and dull-colored varieties. Visitors to exhibitions organized by the Gladiola Martin and Gladiris associations are surprised by how beautiful gladioli exist in shape and color. Newly bred gladioli are modern also in that they last a long time in a vase, can hold 10 or more open flowers at the same time, have a high number of buds up to 30, are strongly waxy and the flower petals are beautifully ruffled. Recently, full-flowered, variegated and most recently needle-shaped flowers have been bred. So it is not surprising that the largest Dutch producer of gladiolus seedlings has expressed interest in supplying Slovak-bred varieties for their commercial needs.

It should be noted that individual varieties have different vegetation periods (from 60 to 110 days). In more northern areas, therefore, grow earlier varieties. A reputable supplier will state this in the offer. Let’s not forget that after flowering, the tubers must mature in the soil for at least a month.

Preparing seedlings

2-3 weeks before planting, if no sprouts of at least 0.5 cm or more in size are visible on the tubers (due to low storage temperature) and waiting roots, increase the storage temperature to 18°C or more so that the tuber wakes up from winter sleep – dormancy. In older tubers, there is a possibility of several sprouts waking up at once. Leave only one dominant one, a maximum of two, and let the wounds dry. . By increasing the temperature and thus the formation of sprouts, you will significantly shorten the time to flowering and there will be more time for the tubers to mature after the flowers are harvested. Especially suitable for northern regions and late-flowering varieties.

Proper planting

We plant as soon as possible, as the soil can be worked, so that in the fall after the flowers have bloomed, there is at least a month for the new tubers to mature. Before planting, fertilize lightly in reserve, preferably with Osmocote Pro 3-4 directly into the beds for seedlings. This will ensure a gradual and regular supply of all nutrients, including trace elements, during the important period of growth and flowering, i.e. 3-4 months after planting.

Plant large tubers to a depth of 10 cm, in drier soils you can also plant deeper. Small tubers or brutes shallower to a depth of approximately 5 cm. Plant only the largest brutes with a spacing of 5 cm and before planting, for some varieties with a very hard shell, soften them for about 15 minutes in Savo (non-concentrated). Maintain a spacing between tubers about the width of the tuber diameter (5-7 cm), which you will appreciate when flowering. The plants will support each other, there is no risk of them breaking out. However, due to the density of planting, it is necessary to think about a sufficient supply of nutrition. If there is enough space, you can plant the tubers with a spacing of 10 cm or more. Then it is advisable to use support sticks during flowering.

Row spacing

The proven row spacing is 40-50 cm, and they should be oriented north-south, but this is not a strict requirement. Currently, I plant in three rows with a spacing of 40 cm and a path of 50 cm, which allows me to comfortably care for the gladiolus from both sides and the gladiolus shade each other less. In front gardens, you can plant in different shapes, but pay attention to the height of the varieties so that they do not overlap each other, and so that they harmonize nicely in color.

Watering

After planting the tubers and brut, water them well. The water requirement for gladioli increases as flowering approaches, while it decreases with flowering until the end of the vegetation. Do not overwater the soil, but do not let it dry out completely either. Highly mineralized water is not very suitable for gladiolus, so it is ideal to collect and use rainwater. The soil should always be moist in order to start the germination process.

One good-tested piece of advice! The last few summers have been extremely hot and dry, when the growth of gladioli stagnates during the hottest periods of heat, or rather, the flowers dry out and do not open well, the colors lose their saturation. At such times, I connect the hose directly to the cold water pump from the well and set the sprayer rose to fine drops or mist and spray high above the gladioli. A fine, partially heated water mist falls, which will greatly please the gladioli and they will come to life right before your eyes. In this case, there is no need to be afraid of cold water. It has a similar effect as when we pass through fog gates.

If you have drip irrigation, you will make gladioluses very happy if you start it during the hottest time of the year, provided that you do not soak the soil near the tubers more than 2-4 cm, and 1-2 cm for the tubers!!!. The root system of the tubers (and of course the leaves) must not be affected by cold water to avoid heat shock.

Be careful, I came across a case where the drying leaves were very similar to the Fusarium disease, i.e. they dried up from the tip down and the leaves turned pale. In the end, it was just insufficient watering during high temperatures at the roots of the gladiolus. Check mechanically whether there is enough moisture at the roots! .

Fertilization

The soil in gardens has a different nutrient status or pH value, so I recommend doing an analysis at least for basic nutrients (nitrogen, phosphorus, potassium) once every three to five years. If you fertilize your flower beds with manure, only use well-matured manure, preferably in the form of biohumus, otherwise you risk an increased incidence of fungal diseases. The fertilization interval varies from garden to garden, as it depends on the quality of the soil, its permeability, old nutrient reserves, etc.

However, in practice, you will encounter undernourished gladioli rather than overfertilized ones, mainly due to dense planting and the associated lack of nutrition or incorrect fertilizer application. If there is overfertilization, you will recognize it by the fact that the entire stem, including the flower head, will be unnaturally stretched, and the spacing between the flowers will be atypical for the given variety. Gladioli tubers, especially those fertilized with nitrogen, are susceptible to fungal diseases not only during storage, but especially during cultivation in the next season.

After the formation of 4-5 leaves, when the newly formed tuber has already taken root and the entire root system is fully developed, fertilize with a smaller dose of Cererit and work it into the soil!! so that the unstable nitrogen from the fertilizer is not lost. In the next period, especially when the flower spike appears until flowering, fertilize again with Cererit. I use Cererit from the 4th leaf 2 x until flowering but in small quantities!. I also spray Kristalon 2-3 times on the leaves to provide the fruit and flower with trace elements. After flowering, fertilize with a fertilizer with a minimum nitrogen content and a higher potassium and phosphorus content (potassium sulfate, Kristalon autumn, etc.).

It is necessary to use a wetting agent with all sprayings to create perfectly and continuously wetted leaf surfaces. It is not enough to use the recommended amount of wetting agent from the manufacturer for gladiolus leaves, e.g. Silwet Star 0.1 ml per 10 l of water. I have tried adding 0.3 ml of wetting agent per 10 l of water to the sprays, because otherwise small droplets would form on the leaves and the entire spray would have a significantly reduced effectiveness. Of course, it also depends on the pressure and distance when spraying, you need to try it. A simple test of proper leaf wetting is to dip a gladiolus leaf into the spray. The leaf should be continuously covered.

It may seem that the fertilization that I carry out throughout the vegetation is too intensive. In my case, this is not the case. It is only adjusted to the planting density of the tubers, between which there is only about 4-5 cm of space, and the quality of the soil. With a different planting density and soil nutrition, you can significantly reduce the intensity of fertilization.

Protection against fungal diseases

Remember that when mushrooms start to grow in the nearby forest, the conditions for their occurrence have also arisen in the garden. Carry out a preventive spraying with some of the preparations such as Kuprikol 50, Champion 50 WG, Teldor 500 SC (against botrytis), etc., but do not forget about the aforementioned wetting agent, otherwise the effectiveness will be 70 percent lower. However, if you use any of the biological fungicides against fungi, find out if the tolerance to the organic product is good. For example, the bacterial product Azoter tolerates several fungicides well (verified in laboratories). Protection against thrips is also important, which can completely destroy developing flowers at favorable temperatures and humidity and participate in the transmission of viruses and fungal diseases along with aphids.

Protection against thrips

In autumn (if you did not have time to do so in spring, but this period is less suitable) gladiolus tubers should be treated as protection against the occurrence of thrips under the scales, with one of the products: Decis AL, Decis Protech, Karate Zeon 5 CS, etc. During the season, use blue sticky plates to signal, attract and catch thrips, as well as other sucking insects. When first found on the plate, especially during warm and dry weather, spray with Decis AL or Decis Protech. When using Karate Zeon 5 CS, be careful and mix the lowest recommended spray concentration, otherwise you may burn the leaves. Repeat the spray as needed, usually at 10 to 14 day intervals, basically also during flowering, since the flowering time span is approximately +-50 days depending on the variety and size of the tuber. Sprays can (unless prohibited by the manufacturer) be combined with fungicides and foliar nutrition.

Sucking insects, but especially thrips, are carriers of viral diseases. Virosis on flowers is manifested by pale spots compared to the original color and light white-yellow stripes on the leaves. Virosis is incurable and is also transmitted through brutes to new tubers. Viruses are present in most gladioli, but individual varieties are resistant to different degrees. A good prevention against thrips is autumn pickling of tubers. The occurrence of thrips during the season can be limited by the aforementioned spraying.

Caution!

Leaves and flowers damaged by thrips can easily be mistaken for virus disease! , so that you do not accidentally throw away otherwise healthy plants. The spots on leaves and flowers damaged by thrips are visibly thinner from the bite,

weakened (almost translucent) and run intermittently more or less straight along the sloughed cells separated by the veins, unlike virus disease, which is more in the form of spots scattered throughout the leaf and flower and

especially the thickness of virus leaves and flowers is the same everywhere!

Soil care

The bed with gladioli should be loosened as needed during the growing season. If the soil is not loosened sufficiently, the roots of the plants will partially die, which increases their susceptibility to bacterial and fungal diseases. Before flowering, mulch the soil around the plants on both sides so that they do not lie down after rain and in the wind.

Harvesting flowers

The flower stalk should be broken as low as possible by tilting it sharply to the sides and pulling the flower out of the leaf axil. Save the leaf area, it will be needed for good tuber maturation. I do not recommend cutting with a knife, due to the possibility of transmitting botrytis or viral diseases (?). If you encounter shape or color deviations when harvesting flowers – deficiencies in a given variety, do not propagate such plants further. Mark the highest quality individuals of a given variety and use only this brut for further propagation (so-called positive selection).

Harvesting and treating tubers

Remove the tubers from the soil at least a month after flowering, but feel free to do so later, but not after the fungal diseases on the leaves have fully spread. After removing the tuber from the soil, the stem should be broken off, not cut or cut off, because that way the product used later against thrips and fungi will get better under the tuber scales. It is also a good idea to remove the entire old tuber and its root ball immediately, especially on older and larger tubers, although it will not be the easiest. It is not advisable to clean them of scales or roots at the storage location, because you will breathe chemical fumes and dust. If you have the conditions and protective equipment to do so, leave the tubers with the root ball at a temperature above 20° C for 15-20 days. Then they can be easily separated from the dried root ball. I do not recommend removing all the scales from the surface of the tuber, only the first or second layer. The tuber dries out unnecessarily and in the event of a fungal disease during storage, fewer tubers will become infected if they are at least partially separated by scales.

If the tubers are slightly damaged by punctures and subsequent infection with bacteria (bacteriosis) after harvest, do not remove the shiny dents. The tuber would dry out and the peeled wounds could be a place of repeated infection. Healthy plants can grow from such tubers. Discard those that are severely damaged, especially at the root crown and dormant buds.

Pickling against thrips and fungi

We can combine them into one operation, the miscibility of the preparations is usually good and is indicated. Against thrips, we use one of the preparations: Decis AL, Decis Protech, Karate Zeon 5 CS and add e.g. to the solution Teldor 500 SC semi-systemic against Botrytis, Champion 50 wg against the fungal disease Fusarium and bacteria. They are mostly miscible together. We pickle for about 15 minutes, while moving the tubers.

Storing tubers

After treating the tubers, dry them in a ventilated place or somewhere else warm and dry for about 10-15 days. Preferably not in the sun. Burns – dark spots (only an appearance defect) form on under-ripe tubers. Store at a temperature of 2 to 12 °C and a humidity of about 60 to 80 percent. Occasionally move them, ventilate and check their health. Frequent losses during storage are caused by the appearance of the fungus Fusarium, which causes soft rot with a white fungal coating. The usual cause is insufficiently treated and poorly dried tubers or high storage humidity combined with higher room temperature, especially in tubers over-fertilized with nitrogen or otherwise weakened.