Help - Too much rain??

There has been sooooo much rain here in southeastern PA the siberians and ensatas love it - they never looked better, but the beardeds are beginning to rot where the foliage emerges from the rhizome. I sure could some input.

Mine too here in SW PA and more flooded roads tonight

You could try sending some rain to California. ;-) It's been so long, I can't even remember when it rained last, but I think it was around March 5.

I found a clump sitting in an inch of water! Wet, wet time here in Iowa. Nights are cool & heavy dew in the mornings when it hasn't rained. Maybe if I complain enough, God will send us a nice hot drought for August. Then, I can complain about the heat!

You aren't the only ones with rotting iris. The month of June was a terribly rainy one here and for the first time I did not have to water at all for over 4 weeks. Now my irises are rotting. They have been in this bed for 4 years with no problems. I pulled off all leaves that were loose and tomorrow I intend to dig them all up, cut off the rot, dip in a bleach solution, put sulphur powder on them, and after a few days replant in a different spot. It will be work but maybe I can salvage a few. I don't know if this is the right method, but I'm flying by the seat of my pants. If anyone has other suggestion please LMK. Thanks, Jenny

It has gotten alot warmer here now, but still raining. We got soaked TWICE last night with several thousand other people at the fireworks. Humid & hot today. Sure makes the weeds grow fast & the daylilies are blooming like there is no tommorrow. I cut many of the iris down to 8 inches to open them up to the sun. They look alot better this week.

sh1025 I also just dug up a lot. Many borers this year. What proportion bleach?
I've been unable to find sulphur powder here. Suggestions?

They tell me 9 parts water, one part bleach. Soak for 20 minutes, then rinse & dry.

Well, didn't get them dug yesterday and probably won't today. We are baling hay while the sun is shining. Rain is supposed to set in again possibly late this evening. If it doesn't maybe I can find time early Wed. morning to dig and treat the irises. I am disgusted with them! Yes, the 9 to 1 proportion is what I use too. I am replanting them in another spot but where that is I haven't a clue right now. Jenny

Try just cutting them down first & letting them air out. I cut back any other perennials leaning on them too. It's alot less work than replanting! That has worked on most of my clumps in the past.

I cut back some things around them, but didn't cut them back. I'll get out there now before it gets hotter and cut them back. Thanks wandasflowers Jenny

Most years my iris take little care other than cutting off scapes. This is just one of those years we have to do a bit more. Kind of like raising with teenagers....

So you think it would be okay to leave them in the ground but cut the leaves (that look terrible) back?

Most of the time that works for me. We have plenty of time for new leaves to grow. Dig one up & see if it's just too much rain or root borers doing the damage.

WF - thanks for advice - will do. I'm planning on working on them this evenin' after it cools down.....way hot right now.

I'm interested in knowing more about how to treat irises with root borers. I dug some irises today to move them because they didn't look like they were doing too well. Was I shocked to see huge borers nearly the size of my thumb coming out of them! And boy, are they ugly! Now, are you saying I should put them in a bucket with 9 parts water and 1 part bleach? Or did you mean to water them with it? I don't want to move them near any other irises for fear of infecting them all. But then again, I might dig some others to see if they, too, are infested. Thanks for any input.

Rosemallow,

I'm afraid there's not much you can do about borers at this point in the season short of digging your irises, cutting the borers out of the rhizomes, and squishing the buggers. The bleach solution soak is generally performed as a means of treating/preventing bacterial soft rot infections that sometimes occur as a result of the wounds inflicted on the rhizomes by borers. If you choose to do so, soak the rzs for 20 mins in the bleach solution, then rinse in clear water and allow to dry for several days before replanting.

Soon, the borer larvae that are currently feeding on your rzs will leave the rzs to pupate in the surrounding soil. This fall, they will emerge as dull gray moths that are active at night. The moths will lay eggs on old iris foliage and perhaps other plant debris around your garden. The eggs will remain dormant until temps warm up to 70 degrees next spring, at which time they will hatch and begin the feeding cycle all over again.

The fact that you are only noticing borers in one part of your garden right now doesn't necessarily mean they aren't present in your other irises as well, so check them all carefully. Of course, once the moths emerge this fall, they can easily fly to any other part of your garden to deposit their eggs.

The best way to deal with borers is to do an extremely thorough garden clean-up, removing all dead and dying iris foliage and other plant debris (and all the borer eggs attached to them), in late fall and again in early spring before temps warm to 70 degrees. Burn or trash the cleanings. Do NOT compost.

There are also systemic insecticides that can be applied to irises in early spring to kill hatchling borers as soon as they begin to feed. I have found a safe and highly effective product to be Merit (marketed as Bayer Advanced Lawn Season-long Grub Control). Unfortunately, systemics are not effective against borers that have been feeding long enough to enter the rzs and get big like yours are now.

Iris borers are icky and harmful to irises, but they're certainly not indestructible.

Good luck!

Laurie

Laurie, Thank you for your detailed answer. I usually cut back my iris in November of each year, but leave foliage on the rest of my garden for winter cover. (The dry foliage helps keep the plants insulated. ) I usually remove the dead foliage in late April, but I'll try moving it earlier next spring as a preventative. Thanks for your good advice.

Thank you, too, Laurie. I couldn't find my post and did it twice. I feel badly about these pests because I had been buying different irises from the internet over the last three years and they were expensive purchases. Is it okay to cut them all back now?

Rosemallow,

In terms of borer control, I doubt if cutting the irises back now would do you any good. Your borers have obviously already reached the rhizomes, and any foliage you cut now will probably be replaced by the plants in time for the adult moths to still have plenty of places to lay their eggs this fall.

It's generally not a good idea to cut back healthy, green foliage. The plants need their foliage to continue to feed themselves for next year's bloom. If you cut foliage now, the irises will expend precious energy replacing those leaves instead of storing that energy for next year's bloom. I'd leave the foliage alone for now and cut it back in early winter or early next spring. I usually do my big foliage clean-up in early spring while temps are still nice and cool (50s).

Laurie

Laurie

Laurie,
After I read your reply, I went out in my yard to check out the other irises. I started to clean up the dead leaves and noticed that the green ones don't look so good, either. There is some sort of grainy substance near their base. It looks like the borers have already infested them, too. I noticed when I dug out the first batch that the rhizomes were hollow from the borers. Certainly, those won't grow again. I'd like to try to save the ones that still look healthy. If nurseries can dig theirs out and keep them over winter, can't I try this on the rest of them and re-plant them in the spring? Do you think that would work?

Rosemallow,

It's my understanding that commercial iris growers replant their irises in the summer-fall. They don't overwinter them out of the ground. Some of the "marts" may, but that explains why their rhizomes often look so wretched and perform poorly or die.

If you want to dig your irises and remove them from the borer-infested soil, I suggest you pot them up or place them in large planters for a month, then replant them in your garden, hopefully after the borers have started to pupate. That way your irises won't be stressed and set back by being kept out of soil, but they'll be safe from further borer attack this season. Just be sure to cut out and destroy any borers you find in the rzs when you dig them and allow the wounds several days to dry and scab over before potting or replanting.

You might be truly amazed at the resiliency of bearded irises after borer attack. I've seen rzs that were almost entirely hollowed out start to sprout tiny increases from their sides and continue growing. Truly amazing! Try potting up the hollowed out ones, too, and see what happens. They might just make it.

Good luck!

Laurie