When time of year is best to divide plants???

Remember, I'm VERY much a beginner gardener...
My husband and I just finished our backyard with sod, redid the sprinkler system, and marked out the flower beds, and don't have a whole lot of money left over for planting in our beds. I have a bunch of perennials out front that I could divide and use in the backyard (Phlox, Ostrich Fern, hostas, day lillies, larkspur, varigated iris, heuchera, monarda, incarvillea, jolly bee geranium). When is the best time of year to divide? Should I wait til fall? And which of these plants can be divided?
Also, I live in Utah and the soil here is pretty much a clay consistency. What is the best thing to do to prepare my beds for planting? Manure?
I'm so new at this, it's almost embarassing....
Thanks everyone,
Lisa

If you are in a Zone where the ground freezes solid in winter, it would be better to divide your perennials in spring or summer rather than in fall, so that they have time to grow more roots before winter arrives.

Perennials that originated from Mediterranean-type climates have a "rest period" in summer when it is easy to divide them. Bearded Iris, for example, right after flowering, can be dug up and the rhizomes pulled apart. Re-plant iris rhizomes shallowly, with the top of the rhizome at ground level.

Plants with tangled masses of root, such as hosta, can just be sliced apart with a spade. Others can be gently pulled apart or levered apart with two forks.

I usually prune the foliage back by half when re-planting, so as to not put too much stress on the roots. Keep divided plants well-watered (but not swamped).

Your clay soil will benefit from the addition of vegetable matter such as compost and peatmoss. Peatmoss is a great "soil conditioner," but does not contain any nutrients.

Hi Lisa, good that you have made a start on your garden, thats the hardest bit, the lawn and the care for during the summer, if you want to split up your plants, you have a really nice colection, then you could start this after all have finnished flowering, but before the soil is too cold, or early spring, just as you see the new shoots come through the ground, if you have storage or room indoors, you could divide them up end of flowering and put them into pots to care for till the foliage dies down then just water enough to stop the pot soil from drying out, but only just, then come spring, add some compost and food to the soil to give them a real good start to the new season and their new situation in your back yard, June above is right that if you have clay soil, you need to add stuff to it to break it up, so that the plants get air, neutrients and feed at their roots, in clay soil it is difficult for plant to get that as the soil stays wet a long time, no air gets around the roots and it holds onto any neutrients so the plant dont get any, maybe the end of summer start of spring will give you the time to prepare your soil ready for your new plant to get the right start, good luck with your gardening, dont try do too much all at the one go or you will get too disheartened if you find it hard to look after a huge amount of ground and your not used to all the plants care and need, so good luck, Happy gardening, you will love it. WeeNel.

Lisa,

With so many different plants to be divided you might want to post your questions on the Forums that deal with each plant. Those folks can give you many details. Also a good gardening book, by a local expert if possible, will be priceless.

For example: bearded iris are divided in Aug, all across the USA. Huechera in fall, usually, but, spring is OK too. And on and on.

If you have heavy clay (the stuff we call adobe) in addition to compost you can add sand in modest amounts. Usually a bulk building supply place, like a brick yard or landscape supply, can deliver it in bulk for a reasonable cost. You can spread it on new and established flowerbeds in a thin layer, let gravity and the earthworms work it into the existing soil for you. Compost and mulch are going to be your best amendments.

Yes sand and clay is great....we use washed river sand and cow poo (aged).....and as already stated let the dear little earth worms work it all down for you.

Thanks SO MUCH to everyone who has posted in response to my question. You have no idea how much help you've been to a COMPLETELY lost mind ;-)
Again, thank you...
Lisa