Fertilizer helps your irises bloom better and grow into stronger and healthier plants.

Early Spring (The Wake-Up Call)

• When: Apply fertilizer about a month to 6 weeks before your irises bloom. A perfect local indicator is when tulips are blooming in your neighborhood.

• Why: This provides a vital nutrient boost just as the plants break winter dormancy and begin pushing out new growth and flower stalks.

2. Early Summer / Post-Bloom (The Recharge)

• When: Apply a second round roughly one month after the blooms have completely faded.

• Why: The plants use up an immense amount of energy to flower. This feeding replenishes their nutrient stores, helping them build strong rhizomes and root systems over the summer so they can survive winter and bloom again next year.

3.  At Planting

• When you plant an iris rhizome, it is essentially in a race against the upcoming winter. It needs to establish a robust, healthy root system before the ground freezes or goes dormant so it can anchor itself and absorb nutrients for the following spring’s bloom.

  Fertilizing at planting gives the rhizome the exact fuel it needs for that initial root push, but the type of fertilizer you use matters immensely.

• A Quick Reminder on Planting Depth: When you finish planting, make sure the top of the iris rhizome is exposed to the sun (just barely peeking out of the soil). Burying them too deep is the number one reason irises fail to bloom!

Purchase Schreiner's Fertilizer

Specific fertilizer recommendations depend on your soil type, but low-nitrogen fertilizers (6-10-10), bone meal, and superphosphate are all effective. A light application in the early spring when tulips are blooming in your neighborhood, and a second light application about a month after bloom will reward you with good growth and bloom. Avoid using anything high in nitrogen. 

Watch Ben Schreiner advise us on how to fertilize our iris: