The base consists of an 18-inch-deep layer of sand to ensure drainage. The wood-and-wire-mesh rooting beds are placed directly on top of the sand and filled with pine bark or other rooting media, and the sand does a nice job of "wicking" away any excess water that might otherwise cause waterlogging.
Beds are constructed of 2 x 8 or 2 x 6 treated lumber, with 1/4-inch galvanized hardware cloth nailed to the bottom to contain the rooting medium (usually milled pine bark).
The structure has a plastic roof that is replaced as needed (every 2-3 yr) and we usually cover this with an additional layer of shade cloth. Rooting under a covered structure excludes rain and gives us better control of moisture and humidity.
Separate time clocks allow us to use half of the house for hardwood propagation of dormant cuttings and half of the house for leafy softwood cuttings. Each clock system consists of a 24 hr clock and a minute clock, wired in sequence so that the mist comes on intermittently during the day, but does not run at night.
Click these links for a description blueberry propagation techniques or images.
This house is used for both hardwood (winter) and softwood (summer) cuttings. The image above shows rooted hardwood cuttings in late July. These were dormant (winter) cuttings that were stuck in the beds in April on a 1.5 x 1.5-inch spacing. Cuttings were hand watered until they began producing leaves in late April, then intermittent mist was used from late April through mid-July. You can see that these cuttings are producing a second flush of pale green leafy growth, indicating that they are rooted and watering can thus be reduced. By late summer, hardwood cuttings are watered only as needed. This is quite different from softwood cuttings for blueberry (and muscadine grape) that are collected in summer and rooted under mist in August and September.