You might notice that the bloom of your prized irises begins to decrease in vigor and quality. Irises are heavy feeders of the soil's nutrients and are competing for what little nutrients remain. Digging and dividing irises are the solutions to poor bloom problems.
July and early to mid August are the months to transplant and/or divide iris in the Prescott area. For the best bloom, it is recommended that iris clumps be divided every 3 years. Dig up the clumps with a shovel or other similar tool. When dividing, break off rhizomes from each other and replant only the largest fans. Throw out rhizomes with old blooms stalks. If you want, trim the fans (leaves) to 4-6 inches to prevent them from blowing over.
Make the holes at least 12-14 inches around and no closer than 18” apart. Closer planting will result in dividing clumps more often than every 3 years. If replanting a large clump, dig a hole the size of a tire rim.
Remove the dirt and the rocks. Rock removal is easily accomplished with a box screen made of hardware cloth (wire mesh). Then mix the dirt with 50% Forest Compost (available at Mortimer’s Nursery, Lowe’s Garden or Ace Hardware). Place the mixture back into the hole and fill hole with water; this will settle all air pockets.
In a day or so when the soil can be packed down without getting your hands muddy then plant the irises. Remember not to plant if the soil is still real muddy; as the iris will settle too low. You should be able to pick up the moist but not soggy soil and have it fall through your hands.
Add a tablespoon of bone meal, and a tablespoon of cottonseed meal; mix well with the soil. Do not use any more than that. Plant the rhizome with the top exposed to the sun, roots face down in the hole. Pack the soil firmly around the roots. After planting, use all purpose balanced fertilizer such as 10-10-10 with nitrogen 10 or less. Applying a root stimulator is also beneficial.
Water well and let the soil dry out between each watering. Water 2-3 times a week unless we get a good rain. The goal is to encourage growth as indicated by new leaf production. This may take 2-3 weeks. Once new growth is well established, water 1 to 2 times per week. The rhizome needs time to root before the first freeze which could be as early as September 15th in the Prescott area and it takes a minimum of 3 weeks to root. Frost occurs a few weeks later in the Verde Valley or Yarnell area.
Potting iris from the PAIS Rhizome Sale or received through commercial growers in the mail. The only common bulb iris is dutch iris, which this site will not address.
Potting rhizomes which have been out of the ground for a while will help insure that they root faster and grow vigorously once planted in ground.
Alfalfa, like many other forms of compost, adds humus to the soil which enhances plant growth in almost any type of soil from the acidic rain leached soils to the sandy, granular, alkaline soils of the arid desert. What makes alfalfa special is a chemical called Triacontanol which is a growth stimulant. When any form of raw vegetative matter is added to the soil, decomposition occurs which generates heat. Warmer soils, relatively speaking, would stimulate root growth. Also fermentation of vegetative material generates alcohol, another growth stimulant. Alfalfa is readily available from local feed stores in several forms. Meal is a finely ground powder form. Rabbit alfalfa food is a compressed palletized form expands dramatically when wet. Horse cubes are coarsely compressed into 2” squares. The meal or pellets are easiest to work with. They come in fifty pound bags.
Consider adding alfalfa to soils annually at transplant time and rototill it 6-8 inches down into the root zone. The plants seem to establish a new root system very quickly and do not put up top growth. Since the value of most compost is used up within the year, an annual application is important. It can be added as top dressing or applied as a soil drench as “alfalfa tea”. You can apply a handful of alfalfa meal around the base of reluctant spring starters which seems to be a benefit before bloom time.
You can then apply the liquid to your iris beds once every couple of weeks. The left over alfalfa mush at the bottom of the container can be worked into the soil as organic matter.
It happens once in awhile to everyone who grows irises. A fan will fall over; its base has turned mush and stinks. Left unchecked, this bacterial rot will destroy the entire clump. It requires immediate action. Here are two recommended courses of action.
So, bloom is over and what happens to your iris plants during this transition period before July? Actually, this is an interesting question and the answer helps explain why irises are transplanted during July and August in the Prescott area. Bloom in the Prescott is just about finished by the end of May and all that energy in the form of starch that was stored in the rhizome has been used to form bloom stalks as well as causing an overall increase in leaf growth and enlargement.
Do irises go through a period of dormancy after bloom? A number of irises writers say this is so. Actually, irises are not “dormant” but rather changing the growth pattern from one of bloom (May) to that of plant enlargement and the beginning of new fan development from the rhizomes. The larger the rhizomes and leaves, the more successful this new fan development will be. Smaller, less vigorous plants will produce smaller new fans. Last years new fans developed during this period begin to grow as these fans are the ‘chosen ones” and possibly will bloom next year. In our environment you have to water the plants regularly and add fertilizer around each clump.
Reprinted from March 2007 PAIS Newsletter, by Barry Golden
Composting depends on having something to break down, adequate water to wet the mass, and a plastic cover to cover your pile. You don’t need fancy/schmanzy compost starters. Find an area of your garden that is fairly level and start piling leaves, grasses, weeds (omit those weeds that have gone to seed) and kitchen scraps like vegetables (no meat). As one adds materials, just sprinkle the mass lightly with water. Try not to soak the pile, but if you do, nothing bad will happen. Just do it!
Add some form of manure, like horse manure, to get the pile composting faster. This is all about bacteria, fungi, yeasts, worms and other insects that will use the pile of material for their nutrients to grow and reproduce. Your pile should get hot from the energy released from bacterial growth and reproduction. Never underestimate the power of microbes like bacteria. The bacteria need water and adequate nutrients to grow. Turning the pile with a shovel every month or so will help the bacteria grow. Many of these composting bacteria need oxygen and that is why you turn the pile every so often to aerate the pile. Cover the pile with a plastic tarp to retard water loss, but you can cover the pile with anything available, like plywood.