Potential Need for Hardening Off Float Produced Hemp Transplants

— Written By and last updated by

6/4/2019 – One of the first things many growers producing hemp for floral production noticed was that float systems for producing clones, common in tobacco, did not work so well with hemp. Hemp seems to be especially sensitive to excess moisture and hemp does not appear to have the same potential for root recovery that tobacco has. N.C. Department of Agriculture & Consumer Services Regional Agronomist Brandon Poole has come up with a possible solution for growers who would like to use a greenhouse float system. You can see a plant from an overhead watered system versus one from a float system at the bottom of the page.

Potential need for hardening off float produced hemp transplants

Brandon Poole – Regional Agronomist – NCDA&CS Agronomic Division

After spending significant time in various hemp clone and plants from seed production facilities last week I become aware of an issue that could pose significant risk to growers going to the field with float system produced transplants from seed. Currently, there are four methods of supplying water and nutrients to hemp transplants – over-head watering, ebb and flow watering, flood tables, and float bed production. The first three methods of production allow for media drying that promotes root growth within the media. However, the float production system constantly has water available and the root system quickly moves below the media into the float water.

After observing root systems of all production methods (see below picture), I feel there is a need to harden off plants produced from seed in float systems before going to the field. If plants produced in float systems are not hardened off there is potential for devastating root damage from handling as well as moisture stress to the plants. As for hardening off the plants I would suggest that growers remove trays from the float system and water overhead for 1 to 2 weeks before they plan to go to the field. This will allow minimal stress to the plant while promoting root development within the plug. This additional root development in the plug should reduce water stress on the plants when transplanted as well as aid in removing the plug for planting.

Good root development on overhead watered seedling versus poor root development on float watered seedling.