Last year we got caught out - the spring was so cool we decided not to chalk the glasshouses. This caused all sorts of mischief because we couldn't regulate the temperature in the glasshouses and had to continually shuffle plants around due to the heat of high summer.
This year we chalked all the glasshouses in early May. It certainly benefits the internal temperature of the glasshouses to be more constant, which is a better environment to establish the plugs - as the season goes on there is a need to look at the individual requirements of plants. The sun lovers - Gaura, Phlox, Verbena, Helenium are some examples. The ground ferns, the Brunnera, Aguia, Oulmonaria, were removed to shade tunnels. So far this season the Nursery has managed to have a more favourable watering regime - periods of rain certainly helped!