Gladiolus – Planting and Handling, Harvesting and Storing

The classical and majestic gladiolus is one of the best-loved decorations in the gardens anywhere in the world. Due to its spike alike image it's also called a sword lily.

A long time ago, around the year 300 BC, it used to grow as weed in the wheatlands of Ancient Greece. Later in history, in Ancient Rome, gladioli already were known as the flowers of patrician gardens.

Nowadays, the interest for cultivating gladioli in private gardens is high, and today we're going to acquaint you with the specifics of the handling and cultivation of the gorgeous gladiolus.

Content

11 tips for gladioli cultivation
Preparing a gladiolus for planting
Planting gladioli
Handling & care
When to dig up gladiolus bulbs?
How to store the corms over winter?

11 Tips for Gladioli Cultivation

There are 11 must knows about how to grow gladioli successfully. This knowledge will surely help you to cultivate and handle the plants easier and more productively.

1. Do not grow gladioli on the same spot of your garden for more than 2 years. When transplanting gladioli to a different place, follow the golden rule of flower gardeners – remember about crop rotation.
2. For transplanting a gladiolus, choose a spot in your garden that has a different soil composition. For example, if first your plants have been growing in the loamy sand, transplant them after 2 years into a soil that contains a small amount of aluminium oxide.
3. For planting gladioli, choose the corms that are adapted to your climatic zone. A gladiolus is an easy to stress plant. It doesn't like being moved from a warm climate to rainy and cold zones. When ordering gladioli from the Netherlands, you can be sure it will be a truly glorious flowering, even if they are going to decorate your garden with their beautiful blooming only once.
4. Do not plant whole and splitted corms next to each other. The big ones are going to suppress the smaller corms. Plant them in order: from smallest to biggest. It's better to plant the largest ones separately, in the different spot of your garden.
5. It's important to maintain the correct depth of a trench that you are going to plant your gladiolus in. For light soils the ideal depth will be the diameter of a bulb x 4; for hard soils count 3 times the diameter of a bulb. If your gladiolus isn't planted deep enough, you will have to support the stalk. If the corm has been put too deep, it might not bloom at all.
6. 3 to 5 days before the planting, peel off the tough top skin layer of a divided corm. Otherwise your gladiolus might not germinate. After planting, water the plant every second day.
7. Gladioli love light! Better don't choose a shady place for your plants. Late bloomers probably won't even start flowering. The early species you may plant in a shaded or semi-shaded spot, but don't expect early flowerage.
8. The lot where you locate gladioli needs to be aerated, or there will be danger of fungal diseases
9. If your plants are growing in the loamy sand soil, use a foliar application method to provide extra nutrition.
10. In the average summer, water your plants once a week royally. When the summer is dry, and temperatures are higher than usual, avoid overheating of the soil by watering your plants in the evening and afterwords loosening the soil by earthing-up the ground and removing weeds.
11. Very accurately follow the requirements for harvesting and sprouting corms.

Preparing a Gladiolus for Planting

3 to 4 weeks before the planting you need to start with peeling off the tough corms' skin.Be careful not to damage the sprouts, and remove all the sick or locally affected parts. You can leave the corms that were slightly touched with sclerotinia or scab, in this case cut out the affected area and cure the spot with a disinfectant. After the peeling and treating, place the corms into a light and warm room, evenly spread in one layer, sprouts up. In this way you assure that sprouts will be growing well.

Before planting, cure the corms against thrips and fungus by dousing them with Actinovate fungicide for organic gardening or Previcur. You may also use alternative fungicides, available in your local stores, or a 0.3% solution of Fundasol.

Splitted corms also need to be prepared for planting. 10 to 15 days before planting choose the splits that are about 7 to 8 mm in diameter with noticeable root bumps (for smaller varieties of gladiolus you can use smaller splits). Peel off the tough skin. Place them into a box in one layer, and put the box in the diffused light. To disinfect sprouted splits douse them with a solution of potassium permanganate (1 g for 1 l of water) for 9 hours, or use other available disinfectants.

Planting Gladioli

Planting gladioli requires accurate following of the guidelines, written with consideration of their biological specifics. When choosing a spot in your garden for growing gladioli, keep in mind that they are light-demanding and warm-requiring plants.

Find a sunny, wind-protected and well-drained lot. The more to the north you live, the more light gladioli need to have on their spot. Even a little shade can affect your gladioli and delay flowering. In the more southern regions gladioli beds can have a little shade around the noon.

Never plant your gladioli into soil with a high groundwater level. Choose a flat horizontal lot, or one with alittle (5°) slope to the south, so the excess water can run down.

For effective cultivation it's also important to consider soil acidity. The slightly acidic soil, with pH 6.5 to 6.8 is optimal for a gladiolus. When being put in the soil with a higher pH value, a gladiolus can experience such problems as darkening and wilting of foliage, flower opening issues and getting a fusarium disease. In an alkaline medium, the iron in the soil becomes indissoluble, so the roots are unable to use it. As a result, the chlorophyll formation in the foliage slows down, and the leaves turn yellowish.

To neutralize acidic soil you can use chalk (limestone), powdered dolomite or eggshell. Apply 150 to 200 g per 1 m² when trenching the soil.

Black earth is ideal soil for gladioli, but you can also use clay loam or loamy sand. To make them more suitable for your plants mix sand with heavy clay loam or other way around, and also add humus and compost. When the lot is well-warmed, you only need to loosen the ground right before planting corms.

In arid regions, spade the soil in the Fall, so the ground will keep its moisture. Then softly loosen it again right before planting the bulbs.

It's good for your gladioli to grow on the lot where you have been growing vegetables,beans or perennial herbs before. But do not plant gladioli on the place where you have been growing root crops or asters earlier.

When you during the Fall already know the location of your future gladioli, you can start preparing the soil for planting in the Spring. Treat the ground with superphosphate (100 g for 1 m²) and potassium chloride (30 to 40 g for 1 m²). Non-chlorinated potassium fertilizers are better to use after winter, right before you trench the ground.

Note, that a Fall digging needs to be about 10 cm deeper than in the Spring.

You can plant gladioli continuously from mid April to mid May, but always considering the weather and local climate. As mentioned earlier above, you should plant big corms about 10 to 15 cm deep, while small corms are to be put in the trench at the depth of 8 to 10 cm. Space the big bulbs 15 cm, and the small ones 7 to 8 cm apart. Also keep 20 to 25 cm space between trenches.

Moisten a trench with water or a light fungicide solution. Fill the bottom of the trench with a 2 cm layer of sand. It's even better to place a layer of peat moss into the trench, then put the corms on top and cover them with soil. Peat moss avoids mold formation, and keeps the ground moistened even when the weather stays hot for a long time.

Handling Care

You need to take a good care of your gladioli. When the sprouts are around 10 cm high,nicely mulch the gladioli bed with a 5 cm layer of humus. It will protect the soil from dehydration and overwarming, and provide corms with nutrition when watering.

The watering rules for gladioli are very clear. Moisten the soil once a week richly (10 to 12 l per 1 m²). Do so early in the morning or in the late afternoon, when the sun is down.Avoid water drops on the foliage. For that create watering trenches (3 to 5 cm deep) inbetween your rows of plants. Pour water into the trenches, then loosen (5 to 6 cm deep) the moistened ground, and hill up the soil around your plants.

Also loosen the soil once in 10 days, no matter if it rains or not. During the hot summer water the plants every 3 to 4 days, otherwise flower stalks become withered, and flowers will dry before they even open up.

When you see there first flower buds appeared, support the stalks with stakes if needed.

Don't forget to remove dead flowers, so the plants won't spend nutrition on ripening seeds.

Weed Control

Of course, handling of gladioli includes a weed control. Do it regularly, but whenever necessary: normally 3 to 4 times during the Summer. Watch out that weed doesn't attack sprouts, otherwise there might be issues with blooming. On top of that, the plants that growing in the soil full of weed have a higher risk of being damaged by slugs or getting diseases.

Fertilization and Nutrition

It's recommended to fertilize gladioli with mineral manures several times, each on a different stage of growing.

The first time you apply nitrogenous fertilizers is when a plant gets its first 2 to 3 leaves. On every 1 m² of soil apply 25 g of ammonium sulfate, or 25 to 35 g of ammonium nitrate, or 25 g of urea, all in dry state. When plants that have a lack of nitrogen their foliage becomes inconspicuous. Plants that get too much nitrogen grow faster, look stronger, but slow down in flowering and become low resistant to fungal diseases.

For the second fertilization (when your plant gets 5 to 6 leaves) you use a nitrogen-potash-phosphate fertilizer. For 1 m² of soil use 15 to 20 g of superphosphate, 10 to 20 g of ammonium sulfate and 10 to 20 g of potassium sulfate.

The third time you fertilize your gladioli is right after they get flower stalks and right before the first flower buds appear. For each 1 m² of soil apply 30 to 40 g of superphosphate and 15 to 20 g of potassium chloride.

You gladioli also need organic fertilizers. These you need to apply in liquid state, so the nutrition can be easily delivered directly to the roots.

In the beginning you can use chicken manure. Mix 3 buckets of chicken manure with 4 to 5 buckets of water, and let it infuse for 10 to 12 days. Mix a liter of the obtained infusion in 10 liters of water, and apply the mixture inbetween the rows of plants. Loosen and hill up the soil. Use liquid fertilizers every 2 to 3 weeks, but completely stop applying them around mid August.

Never use horse manure for fertilizing gladioli.

Another effective way to fertilize your gladioli is a spray application, when you spray mineral fertilizers onto the foliage. It gives your plants a flowering boost and increases their decorative effect. When following this method, use a water solution of boracic acid (0.15 g for a liter of water), or copper sulfate (0.2 g for a liter of water), or 0.15% of potassium permanganate. Add a little bit of soap in the solution and assure you spray it on both sides of the leaves.

Like this nourish the foliage 2 to 3 times during the Summer at the start of the growing process and during the budding period.

Another important thing about handling gladioli is to cut the flowers in the correct way.

Do it with a sharp knife in the early morning or in the evening. Be sure to keep at least 4 leaves on the stem, and the remaining part of a cut stalk stays hidden between these leaves. Then they will assure the further growth of the gladiolus and the development of its corm.

When to Dig Up Gladiolus Bulbs?

Digging up corms also needs to be well-timed. Do it in the Fall, starting mid September, when your gladioli have stopped flowering. More precisely, 35 to 45 days after the last blooming. The corms that are ready to be dug up can be recognized by their root cover, the offshoots are also covered by tough skin and easily get splitted from the main corms. Wait for dry weather to start digging, first take out the early species, then the late ones. As last, dig out the smallest corms and splits. If you notice that some bulbs are affected by black or brown spots, dig them up earlier to avoid other diseases.

You can mow down the stems before digging, or just cut them off with a pruner shear after you've dug up the bulbs. The roots also need to be cut off. Softly dust the bulbs, split all the offshoots from their main corms.

Put all corms and splits into a screen tray and rinse them with water. Then douse them with a fungicide solution for 20 to 30 mins to disinfect and rinse again. Next, cure the corms with a 3% solution of potassium permanganate or different disinfecting solution,and lay them to dry for 3 days.

Cover the bottom of a box with paper and place there the disinfected and dry corms. Store them at 25 to 30 °C and turn them once in a while. After 10 to 15 days reduce the temperature to 18 to 22 °C. 30 to 40 days later you can peel and sort the corms.

When cleaning the corms peel of only the top (dirty) skin. Split the offshoots.

What to do with the splits of gladioli?

First sort them by species and size. Big splits have a diameter of 0.8 cm or more. Medium ones will be about 0.6 cm. The rest is being categorized as small. Store them in paper bags at a temperature of 5 to 6 °C. Higher temperatures are dangerous for splits: they might loose their sprouting ability. It's handy to use the fridge to store the splits.

How to Store Gladioli Corms Over Winter?

A dormant period of gladioli normally lasts from 35 to 40 days. During this time corms are unable to sprout even when in ideal sprouting conditions.

But keep in mind that right after the dormant period there is a risk of premature sprouting.

How to save your gladioli until the Spring comes?

Remember that the ideal temperature for storing the corms is 5 to 10 °C with a 60 to 70% humidity.

To make the conditions even better put a few peeled cloves of garlic into the box where you store the corms. At least once a month check if your corms didn't get damaged. Also replace old garlic cloves with new ones.

The optimal place for storing gladioli corms is a cold, aired cellar. The best is to put your corms in is a screen tray, to improve ventilation. To keep the trays on shelves is handy and saves you space. Another nice way to store the corms is to put them into cloth sacks.

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