For the Love of Iris

Articles, Tips and Notes from Schreiner's Iris Gardens

The “Scoop” on Fertilizing Iris

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OSchreiner’s 6-10-10 Controlled Release Iris Foodur general rule of thumb on the subject of fertilizing Iris is as follows: one month before bloom season, while the tulips are blooming, apply a low-nitrogen, well-balanced fertilizer, such as Schreiner’s 6-10-10 Controlled Release Iris Food. Keep the fertilizer several inches away from the rhizomes. In late September, fertilize again. That sums it up nicely, but perhaps you would like a bit more to chew on about the “what” and “when” of feeding your Iris. Read on for a more substantial serving of info on nurturing both your soil and your Iris.

There are four main nutrients that we must maintain in the soil: nitrogen, phosphorus, potassium, and calcium. The first three nutrients are found in most mixed fertilizers, and calcium can be purchased separately in the form of limestone. Nitrogen is necessary for new cell formation in all parts of a plant. Compared to other nutrients, nitrogen is typically the most lacking. A symptom of a shortage of nitrogen is yellow-green stunted growth. Potassium (potash) is necessary for strong roots and stems as well as deep flower color. A symptom of potash deficiency is weak stems and yellowing or browning leaf tips and edges. Phosphorus is necessary for development of roots and stems. This nutrient also stimulates fruit and seed production. A symptom of Phosphorus deficiency is red or purple discoloration of leaves.

Before applying any fertilizer to your garden, do a soil test to discover what your plants actually need. The best way to know how much, and at what proportion, to add nutrients to the soil is with a soil test. Simple soil tests can be purchased at garden supply centers. Once you determine what nutrients are lacking or are in abundance, you can amend the soil to correct most problems. Your soil test may also reveal a need to correct pH or add trace minerals, for example. Taking and following the results of a soil test is the preferred method to determine fertilizer amounts.

Fertilization of Iris is important to obtain best results, but must be done in moderation. The only thing Iris may resent more than underfeeding is overfeeding. Nitrogen, potash, and phosphorus are essential for Iris, but excessive nitrogen promotes lush growth that is more susceptible to rot diseases. If applied in concentrated form, do not allow the fertilizer to come in direct contact with foliage and roots, as the plant may be damaged or killed. Low-nitrogen fertilizers, such as 6-10-10, are ideal for the needs of Iris.

When to apply fertilizer to Iris:

1)   In the spring, about a month before bloom, apply a light application of fertilizer around the Iris clumps.

2)  At planting, incorporate ½ lb of a low-nitrogen fertilizer such as 6-10-10 per 50 ft2 (or 1 ½ oz per 10 ft2).

3)  After your Iris bloom is another time you should fertilize them. Doing so keeps them healthy and in tiptop shape for better growth for the next year. Wait a month or so after blooms have finished, or in the fall, with enough time before winter so the Iris have the proper nutrition they need going into their winter dormancy.

Now that you’ve got the scoop on Iris nourishment, you can take the necessary action to feed your hungry Iris. Schreiner’s Gardens now offers a specially formulated Iris food to help you provide balanced nutrition in the flower garden. Order now for summer and fall shipment.

Happy gardening!

The above information was compiled from the following sources: www.ces.ncsu.edu, www.homeandgardenideas.com, www.lewisgardens.com

Author: Schreiner's Iris Gardens

Dedicated to growing and selling the finest Iris in the world.

8 thoughts on “The “Scoop” on Fertilizing Iris

  1. Excellent web site yyou have here.. It’s difficulkt to find quality writing like yours these days.
    I seriously appreciate people like you! Take care!!

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  2. How much area will a bag of the fertilizer cover? How is it applied? The article says IF applied in concentrated form – does that mean that it can be dissolved in water and applied generally over the iris bed, without fear of damaging the rhizomes? If so, in what concentration? How much dry product to how much water? How about a hose-end sprayer? I would greatly appreciate another article with more in-depth information regarding the actual application of the fertilizer, and I suspect many others might feel the same.

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    • Thank you for the great questions. By “concentrated form”, we are referring to a granular type that is not designed to be diluted. If you choose to use the type of fertilizer that is to be diluted, we suggest you follow the manufacturer’s recommendations for ratio and method of application. The fertilizer that we sell is granular and should not make direct contact with the rhizomes. Sprinkle one tablespoon per rhizome onto the soil surrounding the plant and gently work into the soil. Water after applying. We will post more information about applying our Iris food soon. All the best!

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      • Well, as much as I’d prefer to use your product, I think I’ll have to use something that can be diluted. I have three very large iris beds, with a total of nearly two hundred plants. At my age, and arthritic state, I don’t think I can do the “work into the soil” routine too well. Thanks for the reply, and happy gardening!

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      • Although we do recommend to work the fertilizer into the soil, the fertilizer can still be effective if simply sprinkled on the soil around the plants and then watered in. Perhaps give a package of our product a try. Regardless, we wish you all the best and great happiness in your gardening. We welcome you to share a photo of your amazing collection in bloom next May!

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      • A little more on the topic of dry vs. liquid fertilizer: A fellow local Iris breeder had the following to add to the conversation. Because of the waxy leaf surface [of Iris], not sure how efficient foliar feed would be [e.g., a liquid sprayed on through a hose attachment], but any fertilizer taken up by the roots would have to be in liquid form, such as the dry granules which become available when we water and the plant dines on fertilizer soup. Hope that helps!

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  3. Thanks for the article about fertilizing iris. I knew about low nitrogen fertilizer and not using too much, but your information about the timing of the two feedings really helped!

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  4. How about potasium capsels, crushed? I have lots of them and they are hard to swallow.

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