Managing moisture is a major consideration in perennial seed germination. Too little or too much can seriously affect germination percentages.
Initially, it is advisable to begin with pre-moistened seed flats. Then, when the seeds are sowed, the first watering should not require heavy flooding. A heavy watering may dislodge seeds. Adequate moisture will provide for germination but not completely saturate the soil which can ceate dangerously low levels of oxygen.
Irrigation booms have helped watering routines. Still this has not eliminated the periodic need for hand watering dry spots which requires someone skillful with a good eye and attention to detail. On hot days, shading and fog can reduce greenhouse temperatures, and water evaporation from the seed trays.