Teach Your Staff To Avoid Overwatering

By |

Why does something as simple as watering a plant become an issue for growers each year? We growers know our crops and read all the culture guides, but when the time comes to turn our people loose with hoses each season, problems arise.

I’ve come to the conclusion that far more plants are lost each year to overwatering than to underwatering. I truly believe the people we all hire each year are good people who want to do a good job caring for our crops. But human nature puts such a fear of drying down a plant and killing it into their heads that they overwater and kill the plants with kindness (instead of through neglect). This excess care can cause issues, including little or no root growth, high or low fertility levels, various fungal or bacterial diseases and undesirable plant habit.

The Yin/Yang Of Plant Care

There are occasions when a plant care person will severely dry a plant to a damaging level. This situation usually occurs in one of two scenarios: 1) The person has been told to grow drier and pushes the plant too far in the other watering direction (welcome to the land of yin/yang watering care), or; 2) due to a rapid improvement in outdoor weather conditions, light and/or temperature levels change faster in the greenhouse than the plant care person can react to the plants’ response.

As a producer of both young and finished plants, our biggest issue is with watering our liner production–especially from December through mid- or late March. Not only are day lengths the shortest of the year, but the weather and light levels are also at lower-than-desired levels. We have corrected this situation by supplementing light levels with 400- and 1,000-watt high-pressure sodium lights used both in the propagation and growing-on areas.

But watering is still a point of concern. Be it on benches or flood floors, plants that are watered before they need it–or watered too heavily when they do get watered–can cause the plant growth or disease issues I’ve described.

Training & Info Are Key

So what’s a grower to do? What we’ve been the most successful with is “shadowing” new watering staff for one to two weeks, using experienced plant care people. These staff members share all the “do’s and don’ts” with the new employee and also point out their personal tricks of the trade.

What has also worked well for us is developing a printed “growers protocol” booklet that all plant care providers are given. There is a large section devoted to watering in this booklet. All new watering staff are instructed in the watering protocols, and they are also reviewed yearly with existing staff. New growing staff members are shadowed when they start and trained for one to two weeks by experienced staff members as described earlier.

We have also learned that it’s much better to water “lighter” and more frequently, if needed, in the early growing months than to water heavily and possibly too early.

Judging When To Water

The primary factor we use to determine watering decisions is usually visual. Our peat-based soil is “black and shiny” when wet, “dark brown to black” when moist, “brown to dark brown” when moderate, and “paper bag brown to light tan” when dry. Over time, we have developed crop action plans that show the stage of soil moisture at which each crop should be watered. The grower then visually “grades” the current soil moisture level and weather conditions to make his or her watering decision.

Other tools suggested to our staff are physically picking up representative plants to judge them by weight, and while doing so, removing a few from their container to observe the entire soil/root ball. Often, the uppermost layer of a container can appear dry while the largest percentage of the soil mass can be quite moist. Based on time of day and environmental conditions, delaying watering may be the best action to take in this situation.

Summer vs. Winter Conditions

We have successfully used other types of information to help fine-tune our watering staff’s accuracy. One that has worked well is to show historical graphs of day length, sunlight levels (especially for the months of December through March) and average day/night temperatures both in the greenhouse and outdoors. These graphs clearly illustrate that even when the sun is shining in the early growing season, for many growers, the quality and duration of this sunshine does not persist for long enough periods to warrant early waterings.

Finally, we take this a step further and encourage our staff to understand how summer and winter conditions vary, as do watering requirements. For instance, in the late spring/early summer, final waterings are done between 4 and 5 p.m., before going home. Typically, the outdoor temperatures are in the 80s or 90s, darkness doesn’t occur for four or five hours, and night temperatures are in the 70 to 80-degree range. In these conditions, range crops are fine in the morning.

Winter conditions are very different: The sun shines for a short period of time, especially when the greenhouse temperatures are cooler; darkness comes three or more hours earlier than late spring/early summer; and night temperatures are dramatically lower–both outdoors and in the greenhouse. So why do we as growers automatically feel the need to water as much in the winter? We train our staff to understand these different conditions and change their watering practices accordingly.

These practices have been helpful to our watering staff and I hope will be helpful to yours. Try them and fine-tune as needed. Good luck, and here’s wishing everyone a great spring!

Dennis Crum is the director of growing at Four Star Greenhouse in Carleton, Mich. You can reach him at dcrum@pwfourstar.com.

Leave a Reply

One comment on “Teach Your Staff To Avoid Overwatering

  1. Norm

    You said “The primary factor we use to determine watering decisions is usually visual. Our peat-based soil is “black and shiny” when wet, “dark brown to black” when moist, “brown to dark brown” when moderate, and “paper bag brown to light tan” when dry. Over time, we have developed crop action plans that show the stage of soil moisture at which each crop should be watered. The grower then visually “grades” the current soil moisture level and weather conditions to make his or her watering decision.”

    The problem I have (and I have killed more plants due to over watering than I care to admit) is that when you are looking at 2 to 3 gallon containers, while the top of the soil looks dry, and may even feel dry with a finger probe several inches into the pot, deeper in the pot the soil is wet.

    We have tried poking fingers into the bottom slits of the pots to see if they are wet. Not a very effective method and difficult for plants on deep shelves or tables unless you pull them off to reach them.

    We tried using moisture probes, but found that the results were not trustworthy and at times were more a reflection of how dense or compact the soil was than how wet.

    We are a very small neighborhood operation, and cannot afford to lose plants like this. We do fine from Nov until about late Feb, and then the dying starts.

    Isn’t there some other trustworthy method of telling whether to water or not? A reliable moisture meter that actually works? A litmus type stick that changes color that can be stuck into a pot? Grasping, I know. But so frustrated!!