This is the information I found regarding orthoboric acid's solubility:
Textbook (NCERT India): Sparingly soluble in water (didn't say what temperature - presumably cold) and highly soluble in hot water.
Wikipedia: "Boric acid is soluble in boiling water."
My question: why is it only sparingly soluble in cold water even though it has polar $\ce{B-OH}$ bonds? Also, what happens on increasing the temperature that increases the solubility?