How to Fertilize Iris Flowers in Minnesota

For a second season of blooms, it is important to remove spent iris flowers, leaving as much of the stem and foliage as possible. This will allow the remaining foliage to continue to grow until it wilts and turns yellow. During the summer months, when the bulbs are dormant, it is best to keep the soil fairly dry and irrigate every two weeks to keep the soil moist and prevent plants from going dormant. However, too much water can cause normal irises to rot, so it is recommended to keep reblooming lilies separate from standard irises.

Schreiner's Gardens offers a food for irises specially formulated to provide balanced nutrition in the flower garden.Resistant bulbs or bulbs that bloom in spring require a cold period to break their dormancy and begin the development of spring flowers. An advantage over the bearded iris, the English iris blooms later in the year and blooms in June and July. It is grown from a rhizome and is a mostly carefree garden staple, except for the dreaded iris borer caterpillar.

Types of Irises

The large bearded iris (from a rhizome, often called German iris), the bulbous iris (correctly, the Spanish or Dutch iris), the English iris, found in the Pyrenees; the beautiful and thin Siberian iris, and the Japanese iris, which looks similar to the Siberian iris, but has different requirements.

The Dutch iris (Iris Hollandica) has orchid-like flowers with silky petals and blooms later than the bearded iris. The Siberian iris is still one of the easiest iris plants to grow; some flowerbeds continue to bloom for decades without any division or insecticide, forming a large stripe of blue, lavender, white or one of the new multicolored colors.

Fertilizing Irises

If you are planting new lilies in summer or dividing older clumps in summer, it is also a good time to add some low-nitrogen fertilizer to the newly planted iris. BlomsBulbs sells a mix of what they call English iris bulbs (iris latifolia) that includes purple, white, blue and mottled irises. Or, if you are preparing a large area for planting lilies, add ½ pound of a low-nitrogen fertilizer, such as 6-10-10 per 50 ft2 (or 1 ½ ounce by 10 feet) to your garden bed.Unlike other types of irises that grow from thickened roots called rhizomes, Dutch irises grow from teardrop shaped bulbs that are planted in the fall.