Okay, me again. I found squishy rhizomes in another clump - Summer Olympics. I noticed only the older, rhizomes were exhibiting this so it might just be the older rhizomes rotting off and possibly traveling to the newer ones. Just a guess.

Ok..does the rot smell really bad?? If so.. you have bacterial soft rot. If its not smelly then you have another issue on your hands. I cant be much help when it comes to borers..We dont have them here. (W TN).. But i know borers start in the leaves and eat their way down the fans and into the rhizomes . Mother rhizomes do rot away..but they shouldn't cause their babies to rot. Have you had lots of rain and heat?

Hi, thanks for answering. I should have the best sense of smell, so unfortunately, to say I didn't get a whiff doesn't say much. There were dried discolored areas and then really yucky areas that just were shells of rhizomes with orange goo.

I'm thinking/hoping it's just the mother rhizomes. This is my third year with iris, so I guess it's about time for this to happen?

It has rained a bit and we have had a bit of a heat wave recently. We need more rain as the ground dries up fast.

I have no experience with boreres either. Mother rhizomes on mine generally just tend to shrivel & dry up rather than rot as such. The one area I had a problem with rot where water was standing a bit, I didn't need to dig to smell the rot, it was very obvious. Still, if I remember, when I dug up a couple, it looked & sounded similar to yours. I went ahead, dug & cleaned up the rhizomes & they were fine.

I was cleaning my iris bed out the other afternoon.. (still got lots left to do.) I found some rot that looked like this.. My thoughts on it .. it was an iris that had bloomed this yr. you could see a little of the stalk that didn't get snapped off completely. All of the rain had set in and caused the rot into the rhizome. Everything around it was ok.. Of course the weeds that have taken over this bed probably didnt help anything either..

I almost shudder hearing the word borer , since they were the major source of root rot with my collection of tall beardeds , since their holes do allow bacteria and other kinds of rot easy access to the insides of the rhizomes. Haven't checked mine in their new home , since they have outpaced the rot in growth and grown replacement new ones faster than rot has killed the older rhizomes.

Thank you both. I'm hoping it was just old rhizomes doing their thing. I only found one that had anything resembling a tunnel in it.

I will be super careful to remove any debris around them this year and trash it just in case.

Ok, I think I have borers. I was using a razor blade to cut out old rhizomes just incase old rhizomes cause rot to spread into newer rhizomes. I found this fat guy under one that had a tunnel underneath (not through)

He was super energetic and moving fast on the sidewalk to find new food. I've seen similar types of grubs in my soil far away from Iris, but what cinched the deal was I started digging up everything and one squeezed itself out of a rhizome to check out what had moved its home.

I now have all the tall bearded in the front yard Iris soaking in bleach solution. In the next few days I will take out the mini Iris and then the Iris from the backyard.

I've been reading borer threads and it seems I might be able to dig out soil a few inches, add in new and replace back where they were. Otherwise, I will need to find a holding area and there's not really a good place. Does that sound good?

I went by the Iris bed and saw an earthworm on top. I went to put some soil on it (keep that guy moist!) and two fat borers were just sitting there acting like annoyed patrons at a restaurant waiting for their meal! I threw them in the road (ew to squishing).

I have never seen a borer that was brown like that, but the shape and appearance is very similar. I also have never seen one outside of a rhizome. It would seem to me to be too early in the season for them to be that large, but they could have been busy a while depending on your climate. The eggs are laid on the leaves from the previous year. The number one preventative measure is garden hygiene over the winter. In early spring you may see what looks like water marks on the leaves or sap coming from the leaves like somebody stuck them with a pin. This is the entry damage. They then chew their way down the leaf and when they get to the top of the rhizome they go bananas. Usually they eat a large portion of the base of the leaf away at the soft and juicy meristem. This typically causes the leaf to flop over and expose a bunch of mush. The borer then works it's way through the rhizome. In moist cool climates like New England this rapidly translates into bacterial soft rot in addition to the damage the borer is doing. For an already existing infestation, you need to use a systemic pesticide. The only alternative is to go nuts digging up your prized plants and soaking them in a dilute bleach solution, but in my experience, the already weakened plants don't survive the shock of being dug up and soaked in bleach solution. If you have a lot of iris, the best plan is to get a roofers torch and singe the tops of the plants in January while the ground is very cold/frozen. This wipes out the next generation of borers. You don't want to keep the heat on long enough to actually warm up or burn the rhizomes. The goal is just to burn away the dried dead material and any eggs sitting on the surface.

Cheers,

Werner

Thank you both for your guidance.

There's an alternative hypothesis that these live in my soil and simply act like borers. There were baby ones clustered at the bottom of the leaves, big ones making furrows under the rhizomes and a few were inside the rhizomes.

Since last year I lost a great deal of rhizomes to rot and little tiny worms, I was very cautious in the Fall to cut leaf tips and even remove all fall leaves. I removed the Fall leaves multiple times. I don't see entrance wounds or flopping although the tiny flanking leaves on the side were a bit withered and wrinkled. Last year I saw leaves yellowing at a fast pace and in the wrong order (inside leaves before outside).

The inside leaves turning yellow before the outside leaves is a strong indicator that the meristem has died. This is frequently a sign that borers have been at work. The little tiny worms you see in the rotten rhizomes are not the cause of the rot, they are opportunist larvae of a fly of some sort that feed on the already rotting tissue, and typically make it worse. If you live in a moist climate, the best defense against rot is to ensure you have loose well drained soil, and then to elevate your planting beds by building the soil up so that the garden is somewhat mounded and higher than the surrounding lawn/etc. Much like what they did here:

https://www.confessionsofaserialdiyer.com/front-yard-makeover-one-year-later/

Do not use mulch on or around your iris. Mulch dramatically increases Rhizome rot.

Cheers,

Werner

Werner, I appreciate the advice. I don't mulch the Iris although they like to collect leaves when it's windy. I remove the leaves down to bare soil.

My native soil is clay based although not like pottery clay. I'm thinking of taking out a few inches and making a mix of the native soil (for nutrition) and sand. I would make sand the main component. Maybe the texture of sand plus the drier conditions might help deter whatever is considering the Iris as a snack? The fence bed is slightly higher than the sidewalk, but I can mound it a bit more.

The garden link is amazing! If they DIY'd it all, I'm in awe. However, I bet they are sweeping that mulch off the pavers constantly (speaking from experience). ;)

I have not had luck with adding sand to clay soils. The area in Baltimore where I am located is entirely clay. Adding sand did not help with drainage, it just made compact sandy clay which doesn't drain well either. What has worked for me is to add perlite which functions like sand, but is itself porous and able to transfer moisture through it as well as around it. Iris are also heavy feeders, so sandy clay soil is not going to give you big healthy plants. Find a nearby horse farm and ask if they have any aged horse manure. You want stuff that is a couple of years old and no longer has any decomposition going on. You will need to add preen to the mix because horse manure is super high in seeds from weeds (unless you enjoy constantly pulling weeds). I recommend horse manure over cow manure because cow manure is much more acidic (which does mean less seeds). If you don't have any horse farms in your area you can use cow manure and add lime, or if you can afford bagged soil amendments, that works too. It can take years of turning and mixing to transform soil into a sustainable base for gardening. Unfortunately, this is also the reason why bad farming practices can leave land barren and useless for generations if it is not tended properly. Synthetic fertilizers have certainly been a game changer, but do not provide everything a plant needs. Majestic historic gardens did not get the way they are overnight. Good luck. I hope this helps.

Perlite:

https://www.epicgardening.com/perlite/

Cheers,

Werner

Also as a side note, historic iris are MUCH more resistant to rot and poor soils. Some of the older varieties will grow pretty much anywhere.

Cheers,

Werner