Iris Doctor

By M. D. Faith

 

 

The people visiting the Central Arkansas Iris Society booth at the recent annual Arkansas Flower and Garden Show in February asked several basic questions on growing bearded iris. The following questions were among those most frequently asked.

 

“When moving bearded Iris to a new place in the garden, or to a new garden, how do I prepare the iris for setting?”

 

Trim tall bearded iris fans to about eight inches in length, and the roots to a length of about six inches, if you are setting them in July or August. Setting in September and October leave the roots a little longer, if you can, say two to three inches longer, and it should go without saying you trim all dead roots away.

 

Break or preferably cut the new rhizomes into single fans at the point where the rhizomes join each other. You must also cut as far away as you can from any active rot, being sure that the rot does not contaminate the garden, discarding it along with the old spent rhizomes in the trash destined for the city dump or incinerator. The spent rhizomes being those that have no green fans attached.

 

Thoroughly wash all soil and debris off of the fans and rhizomes, in a place where the waste and water cannot get into your garden soil, and thereby possibly introducing an unwanted disease or pest.

 

If you plan to set the iris within one or two days, then mix one part household bleach to ten parts water, and then completely submerge fans, rhizomes, and roots in the solution, all for at least thirty minutes by the clock. You will probably need to use a lightweight on top to keep them submerged.  Then rinse with water thoroughly, hosing them with a strong stream of water is preferred, then submerge again in clean tap water, and soak for thirty more minutes. I usually repeat the soak and rinse two or more times, because I feel the solution is a little hard on the plants.

 

Set Immediately, or you can hold them in a shallow container of water with roots fully covered, rhizomes partially covered, and with the base of the fans well out of the water for one or two days.

 

“I have a large area I would like to plant bearded iris in. How do you prepare this area, which has not been amended or planted before, for growing bearded iris?”

 

Divide it into strips of about three feet in width the length of the area to be planted. If you have a tiller available, pulverize the soil with the tiller as deep as possible, six to eight inches in depth is preferred. Remove the pulverized topsoil to one side using a hoe and shovel. A square point shovel is the most efficient.

 

In the bottom of this strip you have now created, begin tilling to pulverize the bottom of the strip again to a depth of six to eight inches. Remove this mixture of topsoil and possibly some subsoil to the other side of the strip. The results of these efforts is a flat-bottomed strip, three feet wide by 12 to 16 inches deep, depending upon the natural or normal depth of the top soil in your area.

 

Now using the shovel and garden hoe rake into the strip the topsoil, which you first removed, leveling and spreading it evenly across the strip being prepared. If the soil is fairly porous, spread three inches of sphagnum moss (this is the best), or composted cow manure (the kind you buy in the bags), or composted shredded leaves, or shredded leaf mold on top of the topsoil. Sprinkle a tablespoonful of 10-20-10 plus 10% sulfur per two liner feet of bed space. It is all ways best to use the homogenized fertilizer, which has been mixed wet and then pelletized, since this insures that each portion has the same identical ratio of plant food.

 

Mix all together with the garden tiller until this topsoil, sphagnum moss or other organic matter, and fertilizer are all well blended together. It is important that all is pulverized and evenly mixed.

 

If you have a heavy clay based topsoil with a clay subsoil which does not have much sand or gravel in its composition, mix a three inch layer of builder’s sand in addition to the above soil amendments. You are fortunate, indeed, if you have a sandy loam soil and don’t need this additional sand.

 

After leveling and firming the soil in the strip, shovel and rake the topsoil-subsoil, which was last removed from the strip on to the top of the strip and level. If this is sandy loam, work in with the garden tiller a three inch layer of sphagnum moss, or other organic soil amendment, or in the case of clay soil, add an additional two inch layer of builders sand also. Mix and pulverize this well. This gives us a raised bed three feet wide the length of the area to be planted, that after leveling and firming, is ready for the iris.

 

Preferably this bed would be prepared one to two month before needed for planting or setting of iris. It would be great if prepared in early spring for July or August planting time, or in April and May for a September and October planting time.

 

If we were careful handling our soils in the above operations, most of the weed seed are now buried too deep to germinate, and we will gain back some of the hard labor of preparation, in relatively little effort in weeding and tending the bed

 

Immediate planting can be done by watering the first layer after firming well, and allowing it to stay open for a few hours, or over night, before mixing and firming the final layer. The final Layer should be sprayed lightly with water hose every hour or so until thoroughly moist. If immediate setting of the iris is planned then it is best to do this after setting the iris.

 

“How do you set the iris? How deep should the rhizome be in the soil?”

 

Using beds, as described in the previous question, to set these beds, we strike a line down the top center of each bed. Set three rhizomes toe to toe in a triangle shape, centered every two feet down, the centerline of the bed. Where you have three of each variety, this works well giving you a good clump quickly that can stay two or three years.

 

Where you have only one rhizome of each variety you can set in the same manner with compatible varieties placed together.  That is varieties with compatible colors and height, and with the same growth habits, can be planted toe to toe in a triangle. Just be sure and tag each rhizome so you can tell the varieties apart when not in bloom, and mark them on a diagram of the bed.

 

Using a gardener’s trowel scoop out the hole for setting the three rhizomes. Leave a ridge from the center of the triangle for each rhizome to be set on, and then spread the roots equally right and left of the ridge, and push down slightly and then back-fill around the roots of each rhizome. Smooth and firm the soil around each rhizome. If this is done properly the rhizomes, after watering in lightly with the garden hose several times, should be seen slightly above or flush with the soil level.

 

Here in Arkansas, I have never seen a case of sunscald, that is where the sun actually burns and destroys part of the rhizomes, but I have heard it said by some that you had better bury the rhizome so that the Oklahoma sun can not scald the rhizome. I think the summer sun on the rhizome is a great help in controlling soft rot, and other pathogens that tend to cause rot in bearded iris.

 

“My lawn and garden is small. How do I prepare my iris beds for planting?”

 

All of the above instructions can be applied to small beds in the form of circles, ovals, squares, rectangles, and triangles scattered around the garden and lawn. You can’t very well use the tiller on the smaller ones thought. You must use the round pointed shovel and the spading fork.

 

Outline the bed with the round pointed shovel by overlapping the cuts and shoving to full depth if possible. Loosen by prying up all the way around the bed. Then loosen the center with the spading fork as well as the outline cuts. Remove all green vegetation and any perennial roots that can cause future problems.

 

Shovel the top six to eight inches into a wheelbarrow, large shallow wooden or metal box, or even on to a sheet of plywood. A screen, two by three feet, composed of a 2” by 4” wood frame covered on one side with 1/2” hardware cloth is a very helpful tool in preparing the small bed. Working this top eight inches through this screen helps to get out unwanted vegetation as well as larger debris. It is now ready to mix with equal portions of well-rotted organic matter as described above, and builder’s sand, adding one tablespoon of 10-20-10 to each four square feet of bed space.

 

Shovel out the next layer of six to eight inches to a different container for screening, mixing, and

amending as above.

 

You proceed to build these beds in the same manner as above with the first out being the first back into the beds. A collar of plastic or metal, brick or stone will allow you to have a raised bed that is ideal for bearded iris, while controlling the lawn from growing in to the beds.