January
Spread triple phosphate (like 0-30-0 or higher) fertilizer lightly around irises and carefully scratch it in around the rhizome. Water thoroughly.
February
In the last week of the month, fertilize with a balanced 15-15-15 fertilizer, scratch in if you’re using granules, and water it in. Plant chilled rhizomes when overnight temperatures are consistently 50-60 degrees.
March
Remove dead outer leaves. Spray for aphids as soon as you see them. Look for natural beneficial predators like ladybugs or use natural pesticides or wash well with high pressure water. Start looking for buds.
For more information about home gardening, please get in touch with the Master Gardener Help Desk (702) 257-5556 or extensionClarkMG@unr.edu (great for sending photos with your questions)
April
If it’s windy, support flower stems with bamboo stakes and guide side stalks. Newly planted rhizomes may not
bloom the first year.
May
Deadhead flowers and cut back fully-bloomed stalks low to the ground. Feed after blooming is done, with
balanced 15-15-15 or 7-7-7 fertilizer. Add compost and mulch but don’t cover the rhizome.
June
Don’t over water. Irises don’t like “wet feet.” Too much moisture can cause root rot.
July
Supplement drip irrigation with hand-watering if needed, depending on summer heat and rain.
Dig and divide through this month (every 3-5 years or when the bed gets crowded or less productive).
August
Prepare new beds and amend soil with compost and mulch in old ones. Continue to groom existing plants for
debris and pests. Adjust watering based on heat and rainfall.
September
Replant divided rhizomes when the temperature stays consistently below 100 degrees.
October
Feed with 15-15-15 or 7-7-7 fertilizer.
November
Apply a slow-release fertilizer.
December
Shared rhizomes can be chilled in the refrigerator if not already planted. Wrap loosely in newspaper.