Do Iris Rhizomes Bury Themselves?

10 years ago

Sorry if this is a duplicate. I just posted, and can't find the original so I think I did something wrong.

This Spring I planted heritage variety rhizomes from a supplier that sends them in April, for Spring blooming. I was careful to plant them with the tops of the rhizomes uncovered.

During the Spring and Summer, they rhizomes seemed to bury themselves, The tops are no longer visible.

This Summer, I moved some established clumps to a new location in a raised bed. Again, I was careful to have them slightly above the ground level. Those also seems to have buried themselves.

I am wondering if the roots somehow pull the rhizomes deeper into the ground? It's a soil mix that is 1/2 native topsoil, lots of clay, and 1/2 yard debris compost from a local recycling center. The bearded irises seem to thrive in this soil but I'm wondering if they will rot in the winter if the rhizomes are not exposed. The local climate is rain all winter, with occasional freeze. The irises are in raised beds.

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Comments (5)

iris_gal
10 years ago
When I plant rhizomes in a newly dug soil they will sink as the soil settles. So I plant very high in those situations. Actually I walk on freshly dug soil to compact it somewha before planting.l

To my knowledge iris roots do not pull the beardeds to certain deepths. What happens is soil settles, heaves, washes over, etc. Lilies are the only bulb I know of that have roots with the ability to pull the bulb deeper if needed. Rhizomes not.

Contrary to published blurbs, beardeds frequently do not bloom the first spring after planting.

In raised beds drainage should not be a problem even in the PNW. Good luck.
chadinlg Zone 9b Los Gatos CA
10 years ago
I think this all started with advice to leave the rhizomes exposed so they would ripen in the sun - which is quite the urban legend...
The plant knows whats best and will grow accordingly depending on the soil type and climate.
The roots which pull bulbs downward are called contractile roots, and Iris do not have them, however new offsets will grow where they will...
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sherry Austin
10 years ago
I've had the same problem in my garden.. Part of it is due to the slope of the land.. mulch moves downhill and gathers around the fans.. I also have a serious problem with voles. By excavating under and around the plants, the rhizomes sink down. I really hate the voles...They are so much harder to kill than gophers, and they go right through gopher baskets.
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Original Author
10 years ago
Thanks for the helpful responses.

Iris gal, on the Spring-planted rhizomes - this spring I planted quite a few varieties. All but one or two of them bloomed. I think the flowers were smaller, and shorter, than if they were planted the previous fall, but that's a guess. If they bloom next year, I'll have a comparison. One variety, Flavescens, sent up several flowers, but almost died out, leaving only one small fan. The ones that bloomed were: Florentina, Sans Souci, Quaker Lady, Iris germanica, Pallida Dalmatica, Shah Jehan, and Flavescens. The one that didn't bloom was Shannopin, which is interesting because that one has the strongest growth now. Maybe because it didn't bloom. Oh I forgot, also Mme Chereau and Mrs. Horace Darwin also bloomed. Mrs. H. Darwin developed rot but I trimmed off the rotted part and it recovered completely. I guess that makes 9 that bloomed. Memory not working so well :-)

Chadining, I didn't know that was an urban legend! Most of my readings have recommended keeping the rhizomes exposed! I have had a couple of rhizomes that rotted out, all from new plantings. I speculated they were infected at their origin, because none of my established varieties rotted. It might have been injuries during planting, leading to infection. But I have been trying to plant them all with the rhizome tops fully exposed to the sun. It will be a relief if I don't have to worry about that

Sherryaustin, I have mine in raised beds. Originally, when constructing the raised beds, I stapled chicken wire in place so the bottoms were completely lined with chicken wire. Something tunneled through anyway, or climbed over the sides and then tunneled from there. My newer raised beds have 1/2" mesh hardware cloth. We'll see if that helps.
iris_gal
10 years ago
Congrats on the good show! The old heritage cultivars often outperform newer super-hybridized ones.

I tried the 4-inch pot idea this year. Planted 3 of the new 6 in the ground and the others in pots. Of the ground ones, only 1 put out new growth earlier (obviously a vigorous grower). Since they are not all the same, no conclusions. But at least I know the potted ones didn't show a head start in this zone.

One pot had 'Orlaya' seedings appear. OMG. Need to save those babies. Gently pulled out the iris ('Bollywood') and saw its new roots were about 1/2 inch after 2 1/2 months. Off topic, sorry.