Iris

Family: Iridaceae

Genus : Iris L.

Introduction

The Iris, genus Iris, is an herbacious perennial of which there are about 170 species. The Iris flower belongs to the natural order Iridaceae of the class Monocotyledons. They have a petaloid six-parted perianth, an inferior ovary and only three stamens (the outer series). True irises grow from thick underground stems called rhizomes.

The Bearded Iris is one of the loveliest plants that you can grow in your garden - whether they be one of the early, short, early bearded types, the medium sized, or the tall, huge flowered and later blooming bearded.

When is the right time to divide?

The preferred time is from August to September. If division is left too late into the fall, you may not get bloom the following spring, however, the plant will probably survive the division.

You can also lift and divide in the early spring, before extensive new growth has occurred.

Lifting and Dividing

Lift and divide Iris roughly every two to three years. If not done, the flowers will become more and more sparse, eventually not flowering at all, and the rhizomes will push up above the soil.

1. Using a garden fork, carefully loosen the soil around the outer edge of the clump. The small, (easily damaged)juicy roots descend from the rhizomes.

2. Gently wriggle clump free of the soil. A large, entwined mass of rhizomes and white roots will be seen.

3. With a hose-end sprayer, wash off remaining dirt. Once cleaned, the Iris can easily be disentangled.

4. Separate rhizomes and carefully inspect each. Discard any that are unhealthy looking or dried up. Search for holes which indicate the presence of borers; search also for any signs of rot (which may follow grub damage) The rhizome will feel soft and squishy.

5. Using a clean, sharp knife, carefully remove any portions with borer damage or any signs of rot. Discard the bad portions in a sealed garbage bag - do not add to the compost.

6. Disinfect knife with 70% denatured alcohol to avoid contamination of healthy plant tissue.

7. The division of rhizome should have at least three healthy, fleshy roots growing from it. Make your cut.

8. Remove any dried up or damaged foliage. Add this to your sealed garbage.

9. Shear off the top half of the leaf fan with sharp scissors. This helps to reduce water loss from the plant while the roots are re-establishing.) Prior to planting, as a precaution against disease, soak the divided rhizomes in a solution of Benomyl (2 tablespoons to 1 gallon of warm (80° to 85°F) water) for 15 minutes. Alternatively, dust rhizomes with garden sulphur.

Planting

Plant your newly divided rhizomes with leaf fans pointed in the same direction.

Iris should be planted in the full sun, or in a location where they get 5 hours minimum of sunlight.

1. For each Iris division, dig two slanting holes, 5 inches deep and 2 inches apart.

2. Set the rhizome firmly on the two inch 'saddle' and place the trailing roots into the holes on either side, dividing them equally.

3. Fill in the holes containing the roots, and gently firm the soil over them.

4. Add soil to cover the tops of the rhizomes to no more than 2 inches.

5. Water the new planting thoroughly. Then add transplanter solution. Water once a week until new growth appears.

Soil

Loam, or clay loam soil to a depth of about 10 inches (Iris tolerate a wide range of soil types and growing conditions, but will produce really well in the right soil). The mix should contain between 20 to 30 percent clay and as much as 50 percent of sand. Add well rotted manure or compost to the Iris bed. (Iris are heavy feeders and deplete the soil of nutrients; replenishing the soil regularly is a wise cultivation habit.)

Spacing

Plant your new divisions 12 inches apart for best results.

Note: Do NOT plant rhizomes too deeply; they may not bloom. Clean up ALL debris around Iris bed to ensure that pests and disease are controlled. Use black tree netting over your new planting to keep away squirrels.

Diseases

Bacterial Soft Rot of Iris (Erwinia carotovora), Bacterial Leaf Spot of Iris (Xanthomonas tardicrescens), Fungal Leaf Spot of Iris (Didymellina macrospora), Rust of Iris (Puccinia iridis).

Pests

Borer of Iris (Macronoctua onusta)

References

The Iris Book, by Molly Price, Dover Publications. New York. 1973

Pirone, Pascale P., Diseases and Pests of Ornamental Plants, 5th Ed. John Wiley and Sons, Inc. 1978. Canada.