July Iris Care from Gary & Sharon Petterson3401 E. Baseline Rd, Phoenix, Az 85042 (602) 437-0700 FAX (602) 437-8660
Water in summer:
We have SRP flood irrigation. We water the bearded every 2 weeks and spuria once a month. If you have drip, tape or hose deep water bearded every 10 to 14 days and spuria once a month. If your iris are inmixed beds, water to keep least drought tolerant healthy. Do not overhead water as this could get water in the fans and cause rot. Too much water will cause steam in the humidity that causes rot.
Broadleaf weeds can be killed with Grassgetter. Or hand weed and then apply Amaze or XL2G pre-emergent weed control to avoid further summer weeds. Both are granular and control the broadest spectrum of weeds and grasses. They can be sprinkled around the irises according to the label without hurting the rhizomes. This gives about 6 months control of weeds if you do not disturb the soil. Carefully pull the few weeds that appear. Nutgrass: control with Sedgehammer. This herbicide translocates to kill the nut and is the safest, most economical herbicide. It kills only nutgrass. Hand weeding only spreads the nuts and solarization is not effective on established nutgrass.
Rotting from fungus:
Apply Agri-fos on Tall Bearded iris. It is available in pints and quarts. Great Big plants also helps control fungus. Spuriarotting is better controlled with Terrachlor. Call 602-769-7020 to Sharonto order some.
Use Merit to control mealy bugs at the same time you treatfor fungus since mealy bugs transport fungus.
The basic iris handbook recommends pH of 6.1 to 7.2. As we water, we continue to add salts. To keep the pH lower, Gary recommends applying FirstStep Soil Acidifier (DisperSul) 3 times a year. We remember when by thinking of these holidays: Valentines Day, Memorial Day and Labor Day. Sprinkle around the plants and water in. This also keeps water from standing and attracting mosquitoes. It also helps water go deeper that establishes better rhizomes. The other advantage of a correct pH is that fertilizers can be taken up by the plant instead of being locked up by the caliche. If you dont know what your pH is, bring a soil sample to the meeting to be tested.
Sterilize with solution of 1 Tbs /gal water. Then soak in superthrive and plant, being careful not to cover the top of the rhizome with soil. Willard and Betty Schroeder said they plant the bloom stalks and they usually grow for them.