  Although only a handful of organic materials have shown polariton
condensation, their study is rapidly becoming more accessible. The spontaneous
appearance of long-range spatial coherence is often recognized as a defining
feature of such condensates. In this work, we study the emergence of spatial
coherence in an organic microcavity and demonstrate a number of unique features
stemming from the peculiarities of this material set. Despite its disordered
nature, we find that correlations extend over the entire spot size and we
measure $g^{(1)}(r,r')$ values of nearly unity at short distances and of 50%
for points separated by nearly 10 $\mu$m. We show that for large spots, strong
shot to shot fluctuations emerge as varying phase gradients and defects,
including the spontaneous formation of vortices. These are consistent with the
presence of modulation instabilities. Furthermore, we find that measurements
with flat-top spots are significantly influenced by disorder and can, in some
cases, lead to the formation of mutually incoherent localized condensates.
