as you remove the hosta, you can create pathways so you have access to the areas in the back of the bed...either leave them mulch-covered or you can put in little stepping stones. something as small/unobtrusive as a brick (just to have something other than a
plant to step on and it won't be too noticable) or you can go more dramatic and get some real pavers and make actual little pathways.
i've seen some nice stepping stones in home depot and lowes...they're round or square and they're made to look like stone embedded in concrete - it's some kind of recycled tires or other rubber material. pretty cool! and they look real too!!
for spacing on the hosta's, i'd use the leaf length as a general guide - space them far enough apart so that the leaf tips are just overlapping. should give them plenty of room for new growth. definitely mulch the areas in between to keep stray
weeds in check.
if you put them a little closer together, you'll get better coverage over the soil and that will help keep the
weeds down (with or without mulch - i'd still put some down, tho). and they'll still have room to grow out a bit.
you might want to just trim back the over-growth and let the
rose get more air circulation (they DO need that) and see how it does over the season. you might be surprised! there are some
roses that do better in part shade (my neighbor has a couple). and it definitely sounds like it's choked right now (i transplanted some
roses from a neighbors yard a couple of years ago - the bed was totally overgrown by
weeds...kept finding more
roses as i was going through the
weeds to see what else was under there!! they've all done tremendously well since i moved them!)
the bright red mulch (probably cedar) can be moved aside so that you can add the compost. you can replace the mulch after you get the soil amended. is the red stuff around the
roses? that might be why they aren't
growing too well. personally, i like licorice root mulch. it keeps it's color and doesn't block the water too much from getting into the soil. and it does compost nicely (i don't think that red stuff breaks down at all - not sure tho).
if the iris looks like this, then it's the bearded type:
if it looks like this one, then it's the siberian type:
http://home.pacbell.net/kenww/bbg_iris/bbg_siberian/BBG_I_sanguinea-lrg.jpg regardless, if they're overcrowded they're not going to bloom as well or have as nice a
flower as they normally would.
splitting them out will help. the bearded are rhizomes - very easy to break apart and then just replant at the same depth. the siberian are bulbs - i don't have that kind, so i don't know if you can break the bulbs apart or if they just propogate from
seeds. regardless of the type, if they're over crowded they need to be split.
for all the bulbs/rhizomes i'd put in some bulb food (i use a pellet type) to give them a boost. you can do that when replanting - just put a teaspoonful in the hole and gently mix with the soil and then cover with a layer of soil and then put the bulb in. i also put another little bit around the area at the top of the soil level, too.
if you have bulbs you aren't going to be moving, just work the pellets into the soil over the general area where the bulbs are - watering/rain will get the nutrients down through the soil to the bulbs.
the poison ivy will be difficult to remove if you can't/don't want to use something to kill it.
i'm not allergic to it. even so, i take precautions when dealing with it (it's in my neighbors yard and does grow through every now and again).
i wear long sleeves and gloves and long pants unless i have something to kneel on. as much as i hate to do it, i use gasoline to kill it. just a couple (or a few if it's a larger
plant) of tablespoons applied directly to the roots. that's important!! you must get it on the roots if you want to kill the
plant.
after treating, i let it sit for a couple of days - until the gas is taken up into the
plant and it dies - depending on the size of the
plant that can take up to about 5 days.
then i put on the long sleeves and gloves again and carefully pull the stuff up...even with the gloves on, i still use a plastic bag to actually handle the
plant and then i put it right into a trashbag and seal it up when i'm done.
the thing with poison ivy is that the
plant gives off an oil and that can transfer to anything - clothing, animals, other
plants. all you need to do is brush against it to release the oils. and it doesn't dry up...so it's very, very easy to spread the oil and not even know it. anything that i am wearing when dealing with the p-ivy gets taken off as soon as i'm done and is cleaned seperately from my other clothing.
other than gasoline/diesel i don't know of anything that actually will kill the p-ivy.
the grapvine thing may be wild grapes or it may be an invasive vine that looks similar. either way, that one should be easy enough to pull up. it does grow underground, so use the same technique as with the regular ivy - moisten the soil beforehand to make it easier.