Planting Irises

I will be planting a bunch of tall bearded iris from Zebra Gardens in two weeks.

Some will be planted in an exsisting flower bed in which I am going to be adding three inches of acidified cotton boll compost on the surface. The other bed is brand new dirt in which I will be adding 25% by volume cotton boll mulch & peat moss to the soil after removing the rocks.

Should I add my three inches of compost/mulch on the surface before or after planting the iris rhizomes?

I live in western Colorado and the soil has a fairly high pH.

Any and all comments about Iris planting and culture are greatly appreciated!!!

iris prefer a slightly alkaline soil. It is a must that they have perfect drainage and never stand in wet soil for any length of time. No shade. Bury the rhizones only 2/3 of the rhiz deep with 1/3 top left exposed to the sun. Do not mulch over the top of iris.

Sharon,

I had buried the rhiz 100% with just leaving the leaves showing. All 24 I planted are all growing just fine. There was even one tiny rhiz of 2 I planted side by side of 'World Primier', which within a day, the very small leaves died and turned brown completely. I had just pulled off the brown and dried up leaves which left nothing for the rhiz to grow by way of the sun. Within a week there were 3 brand new leaves peaking out from the soil. they are now about 6" tall...very cool!
I've grown Cannas, Daylilies and Crocosmia. I just don't understand why it's not good to completely cover the rhiz when planting...

This message was edited Aug 20, 2009 12:29 PM

If you completely cover your rhiz, it is more suseptible to rot! Your humidity is very low in CO, so you might not have as big a problem. You should check with one of the commercial gardens in CO. When I was at Greenhorn Valley Iris, he had some mulch in his beds, but not right up to the iris. Good luck! I planted a few iris at our place in Rye CO. They really grow slow, so it seems watering would be helpful there.

The other problem with plainting the rhizome completely under is you will have beautiful foliage but no blossom, as the sun on the rhizome is what stimulates bud growth, so you really need to expose at least the tops of the rhizomes to the sun!

The rhizome is a food storage STEM--so it needs the sun, covering the lower part maks sure that the roots are not exposed. Many people equate the rhizome with a bulb--not so.

I always pull my compost/mulch away from the stems. The soil I am making from dirt will have excellent drainage.

Any thoughts on fertilization? I am thinking of 0-4-4 liquid kelp & superthrive root stimulant to get things started this fall until the ground freezes and I start throwing the snow on top of them until it melts in Spring.

Yes, No, Maybe?

Have not tried that ,We usually just stick to the compost in the fall.

Pewjumper,
I would definitely add bone meal to your beds if you are planning to use that much cotton boll which tends to acidify your soil. Besides iris thrive on phosphate which is the chief nutrient in bone meal. The fertilizer you are proposing sounds like it would be good. They just don't need any nitrogen until after they have bloomed next summer. And not too much even then. I personally use compost, alfalfa pellets and bone meal when planting mine.

MT.......I always use bone meal in the soil. I have alkaline sandy soil, with very little nutrient value. Do you mix compost and alfalfa pellets (not too much Nitrogen?) in the soil when planting? or on top?

I mix them in the soil. Alfalfa pellets do contain nitrogen, but according to my county agent, they break down so slowly they don't produce very much nitrogen at any given time but a little bid over a long period of time. They also provide lots of minerals and help free up nutrients in alkaline soil by making it more acid. Bone meal is, of course, very alkaline and it sounds as if you could use something like compost or alfalfa pellets to balance it out. Compost, generally doesn't have that much nitrogen either. It mainly conditions the soil and slowly reduces nutrients. But compost does have a remarkable effect on most plants, causing them to green and grow, rather quickly around my yard.

good info....thanks