Fall and Winter questions for new Iris gardener

I am brand new to growing German Iris. I live in the St. Louis County suburb Olivette in MO (Zone 5B). This past spring I started my first bed. The grew well, bloomed well, and now we are quickly approaching the Fall Season. I read somewhere on someones blog that Iris should be fertilized twice a year...does that mean the Spring and the Fall? What would they like to be fed with and when should I do it? Also, should I be making a plan on how to Winterize them. It feels like their partially exposed bulbs would get cold this Winter without putting mulch over them or am I supposed to pull them up and store them for next years planting. I have never cared for these plants in this climate before so I really don't know what to do.

Thanks in advance
Susan :-)

The rhizomes are a food storage stem & will be fine if the roots don't get exposed. They are the tender parts. The main thing is to prevent heaving. Put a rock or a brick on top. Fertilize in the spring & after bloom.

Thank you for helping. Can you explain what heaving is.
Susan

you won't have a heaving problem. In really cold climates when it gets super cold the soil itself freezes and then it thaws on warm days and then it freezes again........Not in St Louis

Actually, your zone could experience heaving -- everyone can have the freeze-thaw-freeze cycle depending on the winter! For the first year, it is a good idea to put something on them, like a brick or stone as suggested, or cover them loosely, like with pine boughs. My siblings live just outside Chicago, and they had heaving with the iris I planted for them, and they are zone 4. It is always better to be safe than sorry when you are first starting! :)

I am in zone 5a just SW of Chicago. Heaving is the big challenge here with newly-planted iris. That's why I try to get them in the ground before Sept.1. And yes, bricks and stones really do save the day. (I also follow a suggestion I learned here -- and that is to have a small amount of unfrozen garden or potting soil on hand to place around roots in the event they should become exposed from heaving.) Usually the rhizomes can simply be pushed back into the ground. But if the ground re-freezes before you catch it -- there you are with a heaved iris that can't be pushed down. This is where the extra soil comes in handy.

Heaving is an issue here about 80 miles due East of St Louis, especially for irises planted
late. I used metal tent pegs to hold timbers and stone walls in position. They are driven
into the ground about 8 inches and each spring they are raised out of the ground about
2 or 3 inches.

Just cover the irises with an additional 2 or 3 inches of soil when they pop to the surface and
remove it after the freeze/thaw cycles are over.

Thank you all for the help, I will use the heavy stone method and keep a bag of soil handy. Being from Florida, I had never heard of heaving before. I've only been through one Winter here so I don't have enough info to go on. It was fairly mild but I do remember the ground being frozen enough that I could not dig. I do get some relief by being in St. Louis County and fairly close to the city heat.

Another question...why do people cut the top half of the fans off? Is that about where the new growth pops up next year? I really do need to read up.

Susan :-)

I had never heard of the rock or brick on top of the rhizome trick. I thought of it myself, but figured that it might lead to rot? I suppose if you took it off at the right time it would be ok, but we have had the freeze, thaw, heat, cold, erratic weather in late winter. Hard to know when winter is over.

I thought about that to Caitlin. It would be great if they would not rot as we have the freeze thaw problem here too.

I've never had problems with rotting when using rocks to hold down the rhizome. The rocks don't usually trap moisture that could lead to rotting. Mulch -- now that's a different story.

The top part of the fans are cut after transplanting to prevent loss of moisture in the leaves. Otherwise it does not have to be done, just remove leaves as they brown & die to keep the area clean. Some people cut others because it looks 'neat'. Not really a good idea.

Well I have lots of rocks and I am going to use them. Thanks for the great idea.

As far as new growth, it usually is the center leaf in a fan whether is is a mature plant
or one of the new babies. That is the leaf the iris borers go for since it is smaller and
tender in the spring when they become active.

Bricks work also for those who are rockless. We have rocks thanks to being in N.England.

susan, if you contact Comanche Acres in MO, you will find they have a specialty fertilizer for irises. they sell it mail order in 5 lb bags.

bonjon
Thanks for the insight on the fertilizer. I will get some as I plan to expand the iris bed this year. Last year I just bought some pretty fans already started at the nursery in the Spring. Someone told me that if I wanted to plant my own bulbs this Fall that I should do it at least 4 weeks before the first freeze in order to establish. Is that true? Around here that would be (I think) before the end of September.

Susan

in the future, for purchases, a local nursery is usually not a great way to go unless they specialize in iris

check online at www.irises.org, find the link to the Regions, locate which one your state is in, then check for local iris societies. they often have sales. MO is very active, and y'all have more than one commercial grower in MO, too. there's a link on there for commercial growers nationwide as well, who almost all do online sales during the summer harvest season. and all kinds of culture info.

GREAT TIP...thanks!! :-)

You can use a low nitrigen fertilizer. I like to use a time release and then in the spring some Super Triple Phosphate when it warms up before they bloom.

susan, just about every avid iris grower I know has a "special" way of fertilizing that seems, with trial and error, to work for them. a lot depends on your soil, and getting it tested is the best way to start. any good decent garden soil is better than great for irises. they can tolerate some pretty poor soils, but do best in average garden soils with great drainage. fertilizing should just add back to the soil that which is missing or frequently used up.

there are two main classes of irises, for me. the ones that thrive in lots of water (beardless), and the ones with deserts in their heritage that must have good drainage. I believe "German" iris is one of the species desert irises whose genetics are in our Bearded Irises on the market today. Haven't heard that term used for them in a long time, but it's commonly used by non-irisarians. seems I heard a lecture once that the modern hybridized Bearded irises have 4 species parents altogether.

Someone with more background in the history of irises can probably correct me.

'German' is used because of being I. germanica. Even that designation was a misnomer. Yes, it is used by people who don't know the plants are bearded irises.

thanks irisMA. sometimes my brain can't retrieve... I drew a blank on the species when I wrote this.

As a matter of fact, the bearded irises did came from species. I. pallida & smaller version I.cengealti, I.variegata for the main species. I. lutesens is a smaller dwarf iris, but when I. pumila was crossed with the tall bearded the modern SDBs resulted. Beardless siberian irises are crosses with I. siberica & I. sanquinia. Later I. typifolia was added to that mix to produce earlier bloom. Not sure if everything is spelled correctly, especially the last species. But aren't hybridizers grand to produce our modern garden plants?

This is all so fascinating!

Exactly when do I place a rock or brick on top of Iris rhizomes and exactly when do I take the rocks or brick off the rhizomes? Is it only done with newly planted Irises?

I plant the Tall Bearded Irises.

Thanks!

Marilyn

I'm not sure about the answer to your question, but I put rocks or bricks on each of the new rhizomes I planted this year, just to keep them in place until they root. Some years I have had the plants pushed out of place by worms or whatevers before they got their roots dug in. When they felt resistant to a pull I set the rock to the side to save for later.
This year, I requested and got earliest delivery on the irises I ordered. The ones from Schreiner's are big and healthy, some from another grower were small and without anchoring roots; we will see how they do. My feeling is that the bigger ones have more reserves for the plant to draw on as it grows its' new roots.

Check the plants before winter & if they are not solidly in the ground, place the rock etc. Remove in spring if it feels solidly in the ground.

I haven't ever used rocks, and have only had a few fall over or need replanting. but maybe using the rocks at planting time would help keep the deer out. last year they must have uprooted 20 or so - and once out of the ground, their ID is lost.

I learn more and more just standing on the sidelines of this forum...thank you. I will get the soil tested soon, I believe that will be a big benefit to all of my gardening. Currently my Iris are in a very slight sloping area of primarily clay soil that had been amended with mature finely shredded leaf mulch and a little bit of organic material. The drainage is good. I've managed to find several large landscaping bricks and plan to used them for the techniques mentioned above.

Back in Florida I grew a number of iris in my yard but none like the tall bearded iris I see here. I had a nice patch of Japanese Iris, a very prolific bed of what we called walking iris, and a very beautiful delicate iris that at first I thought was some kind of orchid and looked like a Oncidium. All of these varieties were virtually trouble free and very rewarding. Hopefully I can do these plants justice!

I am a quick learner and thank everyone for their input. Every time I look at my garden I feel happy :-)

depending on where you were in FL, you probably didn't grow the bearded irises. didn't know JIs went that far south. LA irises probably loved FL.

mine are grown in nearly the same conditions you have. with our dense red clay (unbaked brick), we also use old decayed bark mulch which is locally called "soil conditioner". I also add builder's sand and compost. it's a ton of work doing all that, but I've had fun "playing in the dirt. my only problem has been the slope pitch. it tends to wash dirt down a bit too much over the rhizomes. and the compost washed out a bit, too. I'm trying to terrace it now.

A few more questions........

Do I place the rock on top of the rhizomes when I plant the Irises?

How big and heavy should the rocks be?

What about if the rhizomes are planted on a slope?

Do I use more than one rock on each rhizomes?

Are rocks used on existing rhizomes (that have been planted last year or longer)?

When in the Spring do I take off the rocks?

Thanks for all the help!

Marilyn

They are just used on newly planted irises to hold them down tp prevent heaving. After the first yr. they usually are not neccessary. It is the alternate freeing & thawing which causes trouble. Irises planted in July should be set & not have a problem. Yes, on top of the rhizome, that is where the weight is needed.

As irisMA pointed out, irises planted during July should not have a lot of problems with
spring heaving unless they are in the colder regions. Pic of a pair of irises potted in a
4 gal+ pot in early July. Dug for a special trade. Note the roots--new roots nearly a
foot long and the original roots decayed. That is why I fertilize the bottom 1/3 of a pot
so as to force new root growth.

This is a temp plot for some oldies planted about July 15. The early increases are nearly
as tall as the mother rhizome's leaves. They still have until early December before any
hard freezes sufficient to freeze the soil. I would not expect to have any problem with
heaving.

Thanks for the information.

I'm planting the Tall Bearded Irises in August and September. One of the rhizomes I just planted in August was out of the ground and on it's side the other day. I'm going to place a rock on it tomorrow.

I'm waiting on an order from Schreiner's that's getting shipped tomorrow and should be here in a week, then I'll plant those in the ground. I'll need to add rocks on top of them.

When in the Spring do I need to get the rocks off of the rhizomes?

Marilyn

Marilyn, it sounds to me like the squirrels are at work in your iris bed. They are notorious for pulling newly-planted rhizomes out of the ground.

There are few dug out here as well. Will keep an eye on them & if they are solidly in the ground I won't bother with rocks. Some places further north than we are, don't have the freeze & thaw problem, so don't mulch after the first year of planting & replanting.

The point of mentioning July was early July is the best time to plant irises in this area.
Each week's loss in time is a week's loss in growth. You reach a time when little
growth will take place and heaving is almost guaranteed. You need the good root
system to anchor the plants. With late September plantings, I would consider waiting
until January and a good hard freeze then applying a good layer of loose mulch such
as straw. The usual purpose of mulch is to keep the ground cold, not warm. Check
with the experts but I would think there is little chance of rot while the ground and
the rhizome are below freezing. There is a major iris gardener in your general area,
I think going by the DG name of 1913cat or something like that, who could give you
the very best advice.

I pot mine the minute I receive them so they can get a head start growing roots while I'm trying to figure out where I'm going to plant them.