Ask Mr. Smarty Plants

First of all, my suggestions will be plants native to your area since our focus and expertise are with plants native to North America.  Your plant may not be a native.   In which case, you will need to consult another source for possible identification.   You can visit our Plant Identification page to find several sources that will accept photographs of plants for identification purposes.  They can identify both native plants and cultivated non-native plants.

To try to identify your plant I did several searches in our Native Plant Database.  Since your description of the flower sounded like those of the Family Asteraceae (Aster Family) I first selected that family name from the list of families under the FAMILY search slot.  When the list of over 1100 plants came up I used the NARROW YOUR SEARCH options in the sidebar and picked "Arkansas" from Select State or Province, "Shrub" from General Appearance and "White" from Bloom Color.  

Your description sounds a lot like Baccharis halimifolia (Groundseltree); however, the groundsel tree doesn't bloom until late summer/early fall in August through October.  I assume you mean that it is blooming right now.  This plant would have a woody stem and be classified as a shrub.  It does grow rapidly so it could have only started to grow a couple of years ago and you might not have noticed it until last fall.

I did a similar search but substitued "Herb" for "Shrub" since I don't know if the stems on your plants are woody or not.  I found three possibilities—Achillea millefolium (Common yarrow), Hymenopappus artemisiifolius (Old plainsman), and Hymenopappus scabiosaeus var. corymbosus (Carolina woollywhite).    None of these are listed as growing to 6 or 7 feet, however.

Just in case your plant wasn't a member of the Family Asteraceae, I tried another search using the COMBINATION SEARCH option on our Native Plant Database.  I chose "Arkansas" from Select State or Province, "Shrub" from General Appearance, "White" from Bloom Color and "April" for Bloom Time.  Also, I did the same search but substituted "Herb" for "Shrub" and added "3-6" and "6-12" under Height (in Feet).  I didn't really see anything that matched your description, but you should do these searches yourself to see if you find anything that looks like your plant.

If none of these is your plant, I suggest you photograph it and send photos to one or more of the plant identification forums listed on our Plant Identification page.  You might also contact your Van Buren County Extension Agent to see if they know your plant.  Also, they have a Plant ID Database that has both native and cultivated plants for use in home landscaping that you might look through.