According to Flower Essence Services, flower essences are "dilute, potentized herbal infusions or decoctions" which are prepared from plants that are either wildflowers or pristine garden blossoms.  We can say from our personal experience, and from the many research studies (below), that they are safe and gentle, yet powerful tools to restore emotional and mental harmony and balance. 

There are a plethora of case studies showing the effectiveness of flower essences in the literature. However there has also been a few randomized clinical trials to determine their effectiveness and I've tried to highlight examples from this research below with links to the full text, when applicable.  There are lists of additional research available for your review through the Bach Centre, the Bach Flower Research Program and through Bach Flower Education.  Lastly, this is an extremely interesting study by two geologists who used the remedies to enhance the inherent properties of rocks:  Rossi, M. & Setti, M.  The Bach flowers: between adaptation and activation.  La Medicina Biologica. March 1999. 

Campanili (1997) took 115 patients with a diagnosis of depression and anxiety and treated them with the remedies. He reported improvement in 89% of the cases and noted that the remedies were observed to be completely safe with no indication of even the slightest side effect.

Halberstein et. al. (2007) wrote that "the results suggest that Bach Flower Essence Rescue Remedy may be effective in reducing high levels of situational anxiety."

Cram (2004) reviewed 5 clinical studies on the use of flower essences in treating depression and came to the conclusion that "the convergence of findings from these five outcome studies strongly supports the concept that flower essences may be used adjunctively to facilitate the resolution of mild to moderate depression."

Cram (2001) also underwent a quasi-experimental study where flower therapy produced a 50% decrease in depression on both the Beck depressive inventory and Hamilton depressive scale at one month and three months.

Toyota (2005) completed a randomized comparative test and double blind study of 40 patients and came to the conclusion that Rescue Remedy "can alleviate anxiety and tension prior to operations, and that it should be considered to have potential as a pre-anesthetic medication."  

Cram (2000) performed a small double-blind placebo study that demonstrated the effectiveness of the remedies in alleviating situational stress.    

Yang and Wang (2012) completed double-blind randomized crossover design to evaluate the effect of Bach Rescue remedy on heart rate variability in healthy women. They reported that "increased parasympathetic activity and decreased sympathetic activity were observed in individuals receiving Bach Rescue remedy. These changes may explain the stress relieving effect of Bach Rescue remedy."

Mehta (2002) did a pilot study on the use of flower essences in children with a diagnosis of attention-deficit/hyperactivity disorder (ADHD) which "showed them to be efficacious in reducing inattention and hyperactivity as measured by the Childhood Attention Profile (CAP) (p = .02). It also found almost a doubling of improvement in global functioning over control subjects as measured by the Columbia Impairment Scale (CIS)." 

Howard (2007) completed a retrospective case study analysis and came to the conclusion that  "the majority of clients derived an overall improved sense of well-being. Of 384 cases studied, 88% felt better emotionally, and of 41 clients whose primary concern was pain; nearly 50% experienced relief. Only two reported feeling no improvement, and whilst there is no feedback as to relief of pain for the remainder, all but one experienced an improvement in emotional outlook."

Ruhle (1995) completed a randomized control group design with pregnant women who were 14 days overdue.  A lot of variables were at play but effects for the group given Bach remedies were regarded as desirable. This group had a shorter time until delivery, fewer complications in giving birth, less need for analgesics, more positive states of mind and reduced anxiety.

Weisglas (1979) performed a double blind placebo test and stated "when compared with the placebo group, there were improvements in well-being and enhancement of creativity. These changes were more prominent in the group receiving a mix of four Bach Flower Remedies. Of particular interest in the finding that the remedies acted independently of the user's belief system - evidence that militates against a hypothesis that the effectiveness of the remedies is merely that of placebo."  

Campanini. M. Bach Flower Therapy: Results of a Monitored Study of 115 Patients. La Medicina Biologica. 1997; 15(2): 1-13.

Cram, J.  (2004). Five clinical studies on flower essences in the treatment of depression. A convergence of evidence: flower essence therapy in the treatment of major depression. Calix, Volume 1, page 89-106. 

Cram. JR. (2000). A Psychological and Metaphysiological Study of Dr. Edward Bach's Flower Essence Stress Formula. Subtle Energies and Energy Medicine 11(1) 1-22.

Cram J.R. (2001).Flower essence therapy in the treatment of major depression: Preliminary findings. International Journal of Healing and Caring 2001;1.

Halberstein, R., Desantis, L., Sirkin, A., Padron-Fajardo, V., & Ojeda-Vaz, M. (2007). Healing with Bach Flower Essences: Testing a Complementary Therapy. Complementary Health Practice Review, 12(1), 3-14. 

Howard, J. (2007) Do Bach flower remedies have a role to play in pain control? Complementary Therapies in Clinical Practice. 13, 174-183.  

Masi, M. P. (2003). Bach flower therapy in the treatment of chronic major depressive disorder. Alternative Therapies in Health and Medicine, 9(6).

Mehta SK: (2002). Oral flower essences for ADHD. J American Academy of Child and Adolescent Psychiatry. 2002, 41: 895-10.

Rühle, Gudrun. Pilot study of Bach Flower Essences administered to first-time mothers in prolonged pregnancy. Erfahrungsheilkunde. 5;44(12):854–60.

Toyota, S. (2005). Study into Bach as a pre-anesthetic medicine. Department of Anaesthesiology, Tsudanuma Chuoh General Hospital, Japan.   

Weisglas, M.  Personal growth and conscious evolution through Bach flower essences [dissertation]. San Francisco, CA: California Institute of Asian Studies; 1979 (as cited in bachcentre.com)

Yang, S & Wang, Y.  Effects of Bach Rescue remedy on cardiac autonomic balance in healthy women. International Research Congress on Integrative Medicine and Health 2012 Portland, Oregon, USA. 15-18 May 2012.