I have won a few battles in the past with bamboo grass as it has blitzed half of my front yard and kreiged into the garden year after year. I've spent many foolhardy summer days ripping the rhizomes out from around the plants, digging my fingers delicately 8 inches into the soil to root them out from between other roots. Of course the rye grass folded like Ben Ken-obi in the first year, and now at last it has thoroughly destroyed the liriope garden border and found refuge in the dirt under the porch. As spring approaches, I anticipate the green shoots from rhizomes nestled deep in the root balls of the rhododendron, the hosta, the columbine, the cleyera... The tulips and white star plants have likely sprouted for the last time, for in the coming seasons they will surely be strangled, drowned and run through by its cloud of ugly green leaves, its fat, pasty and pointy root system, the evil plague that is bamboo grass.
There is hope though. So far the concrete walkway from the street to the front steps has held the invader force at bay. The rhizomes pummel and squeeze the concrete, slowly pulverizing it, like an orcish horde of Mordor besieging the ramparts of a dwarfish stronghold, determined to strike west in the name of lebensraum. A vigilant anti-air campaign has prevented bamboo grass from gaining a foot hold through seed bombardment. A plan has been laid, a new garden to the west has been prepared. When appropriate the plants that can be transplanted will be transplanted to this safe haven, leaving only the cleyera or the rhododendron ( or maybe those can be transplanted as well, I'm not sure, I think I would need to clean them down to bare root). After the exodus, an assault will begin on this unwelcome weed the likes of which has never before been seen. I'm just not sure what that is...
1)how to best get rid of bamboo grass, once any saveable plants have been transplanted? It now covers approximately a 25'x25' area...
2)bamboo grass bad. do not remove half-heartedly. kill it with fire. the horror.. etc
Compare the price of new plants with the work involved in saving them. Most common perennials grow fast enough when you plant new ones that it is probably acceptable to toss the infested ones when you are clearing the whole area. Rare or sentimental plants are worth saving, so put your efforts into digging and cleaning them of all possible weed parts when you transplant them to the other (cleared) space.
Herbicides can be applied VERY carefully around good plants, even if it means getting in there with a paint brush and painting it on the leaves of the weeds. I think this is preferable to bare rooting a Rhody, though bare rooting can be done, it is risky. Rhodys do not have a strong recovery potential. Be sure to use all recommended protective gear!
On some tough weeds (this one sure qualifies!) be sure to read the instructions about diluting the herbicide, and applying a second dose. You will probably be using a strong solution, and highly likely applying 2 or more applications as more and more of the weeds sprout. It will take time.
In the large area, once the good plants are gone, I would allow the weeds to grow to the optimum size based on the weed killer you are using. Then spray. If the instructions specify a second application, or you want to try a different herbicide go for it.
Some herbicides work best when the plants are actively growing. So time the sprays for this season, and water, perhaps even fertilize the weeds to best circulate the herbicide.
When it seems the weeds are not going to come back, then deep till the soil and remove the remnants. This will take time and patience.
Then wait and see if there is any recovery, and repeat.
Other option (very expensive): Haul away the infested soil. For an area of about 25 x 25 this involves a tractor and big truck. Even then you are not sure you got it deep enough!