Efficacy of Wetting Agents on Mature Poinsettias, 2011
Pell Greenhouses / Perennial Solutions Consulting
Hudsonville, MI
Objective: Evaluate the increased water holding efficacy and drought tolerance of Essential 1-0-1 and other wetting agent on mature Poinsettias through drench applications.
Treatment Rate Rate Per Gallon Solution Treatment Method
Untreated Water Control -- Drench
2 oz
2 oz / gallon 59.2 ml Drench
4 oz
4 oz / gallon 118.3 ml Drench
AquaGro L 7.6 oz / 100 gallons 2.3 ml Drench

Method: A Poinsettia study was conducted at Pell Greenhouses in Hudsonville, MI starting on December 16, 2011 on 'Prestige Red' (Euphorbia pulcherrima) Poinsettia; 8 replications with a total of 32 plots. Prior to treatment they were placed through an initial wet-dry cycle, followed by a drought cycle. Solutions, eight ounces each, containing various treatments of Essential 1-0-1 and AquaGro L, along with an untreated water application, were applied to the 1.5 L containers which were set down on the greenhouse floor in a randomized pattern. A mixture of Sunshine #4 (Canadian Sphagnum peat moss, perlite) was used as the growing mix and was slightly dry at the time of treatments. Many of the plants were displaying drought symptoms (including damaged bracts, wilted/flagged leaves, upward curling and yellowing, chlorosis, of the lower leaves) prior to the treatment application. The plants were still marketable subsequent to the injury experienced.

The plants were watered at various intervals after the product application and weight of each was taken both before watering and then roughly 30 minutes after, establishing initial holding ability. The starting value of each replication represents the container capacity.

On December 18, approximately 238 grams of water by weight (approximately 8.0 fluid ounces) was administered to each replication. Time was recorded both before and after watering and the plants were allowed to dry down to a minimum of 20% of post irrigation weight.

Figure AOn December 20, the replications had reached the targeted amount of water consumption (loss or use). Each reached the minimum of 20% at slightly different time, and once an individual replication reached the minimum target rate, it was then watered again using 310 grams (10.5 fluid ounces).

Following the watering on December 20, the plants were then allowed to dry out until slight to moderate drought symptoms were present. The plants were not allowed to reach extreme drought stress as this typically does not allow the plants to fully recover and be marketable – flowering. Each replication was then observed twice per day and evaluated for physical signs water stress and drought over the next 3 days. The weight of each replication, in grams, was recorded and tracked over this time. Each plant was evaluated independently at the end of the drought cycle for each replication and was based primarily on the symptoms present, not on the replication reaching a particular weight.

At the end of the drought cycle, each replication was assigned a drought rating based on plant appearance and displayed drought symptoms. Average drought ratings ranged between 1.0 & 1.4. The plants were intentionally not allowed to reach the point of severe drought symptoms so that permeant injury did not persist after re-watering. (See Figure A)
The final watering occurred on December 23, and signs of injury and weights were taken December 24-27. (See Figure B)

Figure BResults: Use of wetting agents during production can significantly reduce the amount of water required to grow crops (about 20 – 40%). This means less water is required at irrigation because the growing mix re-wets faster and reduces the amount of irrigation needed over time, due to the ability of the treated plants to hold onto water longer. This can be useful to growers when applied at the end of production cycles, just before placing plants for sale at retail locations (where plants may not get the same level of care they would in a production scenario), building the water stress tolerance and improving appearance to the consumer and raising the likelihood of a sale.

Both rates of Essential, 2 oz. and 4 oz. increased the water holding of the containers by 4% and 6.3% respectfully in comparison to the untreated replications at the beginning of the drought cycle. This was slightly better than the increase of AquaGro L which increased the water holding ability by 2.3%. (See Figure C)

The initial water holding ability for both Essential treatments (2 oz. & 4 oz.) increased, while AquaGro L barely had any effect on the initial holding ability of the growing mix (0.8%). Two of the treatments, (Essential 4 oz. and AquaGro L) took slightly longer to reach the 20% minimum weight loss target in the initial wet-dry cycle. AquaGro L took 2.8 hours (5.7%) and Essential 4 oz. took 4.0 (8.2%) hours longer than the untreated.

The amount of time until injury symptoms were observed was also increased by both application rates of Essential as well as the application of AquaGro L.

The treatment of Essential 4 oz. held the most water at the beginning of the drought cycle. Overall, Essential applied at a 4 oz. treatment had 5.2% more water holding ability than the untreated plants and lasted 23.9% longer before the plants expressed drought symptoms.