The propagator must balance the need for photosynthetically active radiation and the heat that accompanies light. Shading is used to reduce the radiant heat load during propagation.
It is commonly used to protect emerging seedlings, unrooted cuttings, and initial grafts.
Shade can be provided by thermal curtains, greenhouse whitewash, plastic shade cloth or wooden lath.
Thermal curtains
Field-grown seedlings, such as conifers, need shade over first year plants. Traditionally, this has been done using wooden lath fencing.
More recently, plastic shade cloth has become more cost effective and has the advantage of coming in different densities of shading.
After side-veneer grafting of these conifers and Japanese maples, the propagator covers them with a white polypropylene cloth that reflects light and helps retain moisture under the cover.
An additional black shade cloth is placed on top for additional shading to help prevent excessive heat buildup. Both cloths will be removed once the grafts have taken.
