Question
I have a flower garden that I plant annuals in and a rose garden.  The problem is that nut grass grows in it.  I can pick it all out and in just a matter of days it is growing back.  How can I get rid of it permanently without killing my flowers and roses?

Answer
Nutgrass (aka 'Purple Nutsedge' or 'Cyperus rotundus' to botanists) is famous in certain parts of the country for being one of the scariest Weeds on earth.

Folks at the Mississippi State University Agriculture Extension consider Nutgrass akin to agricultural terrorism.  Specialist Roy Kuykendall tells us that 'In the South, coco or Nutgrass is one of the worst Weeds in golf course turf':

turf.lib.msu.edu/1920s/1929/2912225.pdf#search='nut%20grass%20organic

Mr Kuykendall goes on to explain what makes this Weed 'so pernicious'.  As many as FIFTY (50) more plants can emerge from a single Nutgrass tuber, growing malignantly underground, building more tubers along the way.  'At the Delta Branch experiment station, Stoneville, Miss., one nut planted in a 2-foot tile PRODUCED MORE THAN 1,100 NUTS IN A SINGLE GROWING SEASON.'  He also reports that 'one nut buried 6 feet deep in the soil germinated, sent a long slender thread upward, reached the surface after 18 months, and produced a strong, vigorous plant.'

This is The Weed From Hell.  It grows up through pool liners, into asphalt, through building basements.

There is NO chemical treatment known to eradicate Nutgrass.  There is, however, one treatment that has possibilities: ordinary Table Salt and some other Chlorides, applied at certain rates.  This is NOT unfortunately an option for flower gardens.  Only for Lawns.

To prepare for battle, let me recommend a good posting on "Nutgrass Control in the Lawn, Landscape and Garden" by the University of Hawaii Cooperative Extension Service. (Yes, even in Paradise, gardeners have problems):

One of the Hawaiian WMDs involves dehydrating the Nutgrass tubers.  They say that 'if tubers are brought to the soil surface for about one week under sunny conditions, they dry out and die.'  Soil solarization, an organic foolproof method of killing vegetation that is better than RoundUp, will do the same thing. Combined with VERY careful hand-weeding (you know what happens when you miss one!), this will kill your Nutgrass, and you will live to tell it.

www2.ctahr.hawaii.edu/oc/freepubs/pdf/L-9.pdf#search='nutgrass%20organic'

This is an important step toward eradicating Nutsedge.  Before you get desperate, try Soil solarization, which was recently described in another answer to a gardener who was not sure what kind of weeds were growing in their garden.

Like I've siad before: Pray it isn't Nutgrass.  And Pray if it is.

Then read up on those treatments and make a decision.  In the meantime, rest assured, the best botanical minds in the country are actually working on this Weed as we speak, calculating ways to remove it from our lives, testing and theorizing furiously.  There's money to be made in those Nutgrass Removers.  I apologizing for not being more optimistic about your immediately choices.  But who knows what the future holds?  In times like these, this problem could be solved tomorrow.

L.I.G.