Growing Gladioli
This guide is based on more than 45 years of experience in growing and breeding gladioli. It is regularly updated to reflect proven cultivation practices, nutrition, and plant protection.
Some professional products I use are not mentioned here, as they are not commonly available to home growers. The aim of this guide is to present clear, practical principles without unnecessary or time-consuming procedures.
Below are the key foundations of successful gladiolus cultivation.
Suitable Location
Gladioli require full sun and as much protection from wind as possible. Strong winds weaken stems, reduce flower quality and increase the risk of lodging.
Ideally, planting beds should be rotated every three to four years. If this is not possible, ensure the soil is free of wireworms and other pests that may damage tubers and allow fungal diseases such as Fusarium, Botrytis or bacteriosis to develop.
Soil Preparation
Gladioli grow well in most soil types if properly prepared.
The ideal soil pH is around 6.5. Acidic soils should be limed in advance.
Avoid waterlogged soils, which significantly increase the risk of fungal diseases. Before planting, loosen the soil to a depth of approximately 30 cm.
Ecological microbial preparations may be used to support soil health and nutrition. When applied according to the manufacturer’s instructions, they can noticeably improve plant vitality.
Wireworms
Wireworms are common near grassland and arable fields. Complete elimination is unrealistic, but their population can be significantly reduced.
In acidic soils, nitrogen lime may be applied approximately two weeks before planting. Never plant before the lime has fully reacted in the soil.
In cases of severe infestation, soil insecticides applied before planting are highly effective.
Planting Material
The best flowering results are usually achieved with healthy two-year-old tubers.
One-year-old tubers are often underdeveloped
Older tubers tend to produce multiple shoots – keep one dominant shoot only
Older tubers may be used to preserve valuable varieties, but flower spikes should be removed to support tuber regeneration.
Variety Selection
Retail chains generally offer older, simple varieties with limited flower quality.
Modern gladioli bred in recent decades offer:
long vase life
a high number of flowers open at the same time
up to 30 buds per spike
a strong waxy finish
ruffled, full, variegated or needle-shaped flowers
Exhibitions best demonstrate the true potential of modern gladiolus breeding.
Preparing Tubers Before Planting
If tubers show no signs of sprouting, increase the storage temperature to around 18 °C
two to three weeks before planting.
This shortens the time to flowering and improves tuber maturation, particularly in cooler regions. Leave one dominant shoot only.
Planting
Plant as early as soil conditions allow.
Large tubers: 10 cm deep
Small tubers or bulblets: about 5 cm deep
Spacing of 5–7 cm allows plants to support each other but requires adequate nutrition. Wider spacing may require support during flowering.
Row Spacing
Recommended row spacing is 40–50 cm.
A north–south orientation is beneficial but not essential. Proper spacing improves air circulation and reduces disease pressure.
Watering
Water thoroughly after planting. Water demand increases before flowering and decreases afterwards.
Avoid both drought and waterlogging. Rainwater is ideal.
During periods of extreme heat, fine overhead misting can significantly reduce stress and protect flower quality.
Fertilisation
Under-fertilisation is more common than over-fertilisation.
Basic principles:
soil analysis every three to five years
use only well-matured organic matter
avoid excessive nitrogen
Balanced fertilisation during leaf growth and flowering is essential. After flowering, use fertilisers with low nitrogen and higher potassium.
Disease and Pest Protection
Preventive protection against fungal diseases is essential, especially in humid conditions. Always use a wetting agent to ensure effective coverage.
Thrips are among the most serious pests, damaging flowers and spreading viruses. Regular monitoring and early intervention are crucial.
Harvesting and Storage
Harvest flowers carefully without cutting tools to reduce the risk of disease transmission.
Lift tubers at least one month after flowering, dry them thoroughly, treat against pests and fungi, and store at 2–12 °C in a well-ventilated environment.