In the interior valleys, you can plant seed in July or August. Transplants may be planted in early spring. Lettuce should be started in partial shade, as it is very sensitive to heat. My boxwood shrubs are declining color is fading, leaves bending inward . Boxwood psyllids are the problem.
Damage is mainly aesthetic and can be tolerated to a certain degree.
Chemical spraying will not reduce damage. Nymphs are responsible for most damage that is usually apparent in the spring. No treatment will restore foliage, but you can reduce attacks by discouraging new growth, which promotes greater numbers of psyllids. Minimize plant shearing, closely monitor water and nutrients. My apricots and peaches have brown rot.