Plant your bulbous irises in the fall!

The Iris genus includes herbaceous perennial rhizomatous and bulbous plants. The bulbous irises are the first to open the horticultural season’s iridaceae flowering ball, flowering early in April. The date varies according to the winter and the regions. Nowadays, garden centers offer us more and more varieties of these irises in the fall. In the past, they had to be sent by mail.

These irises thrive in sandy or gravelly soil and are planted in the fall. They should be installed in groups of 5 to 10 bulbs to achieve a mass effect. In the spring, when they flower, they must be exposed to full sun.

After the first season, many of these irises produce small bulbils that do not flower the following year. Some gardeners grow them as annuals, putting bulbs in the same place every year. Finally, a very floriferous colony settles over the years giving a show when several plants have not even come out of the ground.

Here are varieties to prioritize:

Bukhara Iris – Iris bucharica

  • Height: 25cm to 50cm (10 to 20 inches)
  • Width: 30 cm (1 ft.)
  • Exposure: sun
  • Soil: well drained
  • Color of flowering: white and yellow
  • Diameter of the flower: 5 cm (2 in)
  • Flowering time: May
  • Hardiness zone: 4
  • Use: rock garden

Dwarf Iris – Iris danfordiae

  • Height: 10 to 15 cm (4 to 6 inches)
  • Width: 10 cm (4 in)
  • Exposure: sun
  • Soil: well drained
  • Flowering color: shiny canary yellow spotted with brown
  • Diameter of the flower: 5 cm (2 in)
  • Flowering time: April
  • Hardiness zone: 5 (3 and 4 with good mulch)
  • Use: border of a flowerbed, undergrowth

Iris HistrioidesIris histrioides

  • Height: 10 cm (4 in)
  • Width: 7 to 12 cm (3 to 5 inches)
  • Exposure: full sun Soil: tolerates several types of soil if it is well drained
  • Color of flowering: blue
  • Diameter of the flower: 10 cm (4 in)
  • Flowering time: April
  • Hardiness zone: 3
  • Use: border of a flowerbed

Reticulated Iris – Iris reticulata

  • Height: 15 to 20 cm (6 to 8 inches)
  • Width: 7 cm (3 in)
  • Exposure: full sun
  • Soil: well drained
  • Color of bloom: bluish to dark purple with golden stripes in the center
  • Diameter of the flower: 5 cm (2 in)
  • Flowering time: April
  • Hardiness zone: 3
  • Use: rock garden, border of flowerbeds

Although the next plant is not strictly an iris according to botanists, this plant is very close to the Iris genus. It is the only species of its kind: it seems that the name of iris tuberosus would now be the correct name.

Tuberous IrisHermodactylus tuberous

  • Common names: snake iris, tuberous hermodactyl, tuberous iris, snake’s head
  • Height: 30 to 38 cm (12 to 15 inches)
  • Width: 7 to 15 cm (3 to 6 inches)
  • Exposure: full sun
  • Soil: well drained, poor and alkaline
  • Color of flowering: beige-green tinged with purple black
  • Diameter of the flower: 5 cm (2 in)
  • Flowering time: end of May
  • Hardiness zone: 7, 3b with good early snow cover
  • Use: rock garden, border of a flowerbed

7 Tips for maintaining irises

  1. Most Irises are cultivated in the sun
  2. Rhizomes of rhizomatous irises should be planted generally close to the soil surface while bulbous iris bulbs are planted deep down.
  3. Bulbous irises are planted in the fall at a depth of 10 to 20 cm (4 to 8 inches).
  4. Irises are worth being planted in a group to give their spectacular effect.
  5. Fertilize in the spring with compost or low nitrogen fertilizer.
  6. The dried flowers must be removed.
  7. Irises are therefore not very demanding plants if their preferred soil is respected.