Gladioli – Planting and Growing

What to look for when buying

Good quality corms are “high crowned” or plump, with plenty of energy to put into producing a good flower.  The corms should have the skin peeled back to show the waxy surface of the corm, which should be free of any black marks or spots.

Any white powder on the corms is just talcum powder which is sometimes used to help keep them dry and to prevent damage to their waxy surfaces; it’s not a chemical to be concerned about.

Storage

If you’re not going to plant them right away, be sure to store the corms at home in a cool, dry, airy place to keep them in top condition.  Warm conditions or lack of air movement may cause early sprouting and root growth.  A mesh bag or plastic bulb basket is ideal to use for storage.

Planting

You can plant any time from July to December.  Gladioli flower around 100 days after planting in July, reducing to 90 days for December planting.  By planting corms every month, you can have flowers from November to April.

Large groups look magnificent at the back of a perennial display.  Plant mixed colours in groups of 25 or more for best effect; single colours may be planted as few as 10 in a group for striking displays.

Gladioli prefer a position in full sun, and tolerate a wide range of soils as long as drainage is reasonable.  A sheltered position is a good idea, or a location where the plants may be tied back to a fence or building for support in the wind.

Prepare the ground well, loosening it to a depth of 25 cm to allow a free root run and good drainage.  While some fertiliser may be added at this stage, use a minimum and work it in well or it may burn the soft new roots.  Never use any manure-based fertiliser or fresh animal manure as the high ammonia levels encourage disease and rotting.

Plant corms 15 cm deep and 12 cm apart, in groups for the best effect.  Plant the corms with the scar from last year’s roots facing downwards.

Care while growing

Gladioli are relatively easy care subjects, needing some attention only if conditions become hot and dry

To ensure good flower development in dry conditions, water well once a week, keeping the ground moist but not wet.

Thrips (small sap-sucking insects) become more active on gladioli in hot dry conditions.  They target soft new growth on the plant such as developing flower buds, and remove so much sap that the buds may fail to open.  They are fortunately very easy to control with a fortnightly spray.  A general-purpose rose spray is ideal, or you can use alternatives such as soapy water or garlic preparations, but good coverage is essential.  Wetting the plant well when watering also discourages thrips.

Flowering

You may leave the flowers to enjoy in the garden, or pick them for indoor use as soon as the bottom floret shows colour.  Try not to remove too many leaves when cutting the flowers, as the corm needs these to grow and prepare for next season.  Slip a sharp knife between the second and third leaves down on one side of the plant, cutting into the stem 20-30 cm from the ground.  Grasp the stem firmly and give it a quick twist to remove the flower spike cleanly from within the plant.

To maximise vase life you should remove any spent florets, trim the stem and change the vase water every two days.

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