What Type of Fertilizer is Best for Iris Flowers in Minnesota?

NPK stands for the ratio of nitrogen, phosphorus and potassium. Generally, irises need 3 pounds of nitrogen per 1000 square feet. The best fertilizers for lilies are those with an NPK ratio of 10-10-10 or 5-10-10, which are high in potassium (K) and phosphorus (P) but low in nitrogen (N). NPK values such as 5-10-10 or 10-20-20 are optimal for iris plants.

If the plants are properly installed, have well-draining soil and good exposure to light, it may be a soil fertility issue. To check if pH and fertility are suitable for good iris growth, do a soil test. The ideal pH of the iris soil is 6.8 and the soil should have average levels of nitrogen, as well as sufficient amounts of phosphorus, which helps plants to form flowers. A superphosphate, colloidal phosphate or bone meal modification applied in early spring can help plants develop their flowers.

Iris plants generally do not require as much nitrogen as other leafy plants and, as such, specific fertilizers for irises have a composition of 4-10-10 or 6-10-10, which means they are fertilizers with a low nitrogen content. To increase the health and vigour of your plants, fertilize the first year and any year after that. This improves the buds of flowering plants and, as a result, the iris will produce larger and more abundant flowers. If you're not fertilizing your iris plants, you may be missing out on one of the easiest gardening tasks to create the most beautiful flowers for your perennial garden.

The spotted or striped leaves of an iris plant may indicate the presence of iris borers, which is more common in the eastern U. S. UU. Bone meal is often applied below the mass of the iris at the time of planting (usually in late spring) because the phosphorous in bone meal is ideal for the new iris rhizomes that are creating the bulbs.

Schreiner's Gardens offers a food for irises specially formulated to help you provide balanced nutrition in the flower garden. Or, if you're 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.If you're planting new lilies in summer or dividing older clumps in summer, it's also a good time to add some low-nitrogen fertilizer to the newly planted iris. I mainly grow bearded irises and Siberian irises, but these fertilization methods would work well with Dutch irises, bearded irises, Japanese irises and any other type of irises you might have in your garden. If you suspect the presence of the iris borer, dig up an entire group of iris bulbs, divide it with a sharp knife and examine the roots and rhizomes.

Siberian irises are less susceptible to the iris borer, so if you have problems with this pest, you may consider switching to more Siberian irises in the future.