The In’s and Out’s of Watering and How to Best Handle that Pressure by Mike H.

Thursday, April 15, 2021
I hope this finds all of you settled in and preparing for the upcoming spring season with your greenhouses and fundraisers. The challenges this year have been incredible in so many ways, especially with all of us still dealing with Covid issues and policies. With the increased demand for horticultural products and plants, there are a lot of growing pains that have reared their heads in trying to accommodate the demand. With shortages of plants and delayed production of horticultural supplies,  the stress levels have been quite high. This was indeed the year to get your orders in early for both plants and supplies.
I hope this finds all of you settled in and preparing for the  upcoming spring season with your greenhouses and fundraisers. The  challenges this year have been incredible in so many ways, especially  with all of us still dealing with Covid issues and policies. With the  increased demand for horticultural products and plants, there are a lot  of growing pains that have reared their heads in trying to accommodate  the demand. With shortages of plants and delayed production of  horticultural supplies, the stress levels have been quite high. This was  indeed the year to get your orders in early for both plants and  supplies. Please make notes for next year.

Compounding  these issues was that nasty cold snap and blizzard that held up plant  orders (both incoming bare root material and outgoing rooted plants) and  froze many shipments while delaying many others. Growers are still  struggling to catch up. FedEx fell behind and is still not yet back to  their A-game. If they were shipping auto parts all would be good but  with plants, there is little room for delay or miscalculation.

 This should really be a wake-up call to our country… just how brittle  our day-to-day operations are, and vulnerable to weather, computer  hacking, and in general lack of security to the point where our World-Wide network  can be shut down. This should be a wake-up call for all to be cautious  and do more to have regional and local controls of sources, energy and  food.

It will feel good to have everything finally in the  greenhouse and on its way to spring! Now that we’re actively growing our  plants, I’m once again getting questions regarding irrigation and  associated fertilization that is so crucial to the successful  cultivation of fast-growing annuals.

My first “part-time” job in a   production greenhouse took place when I was in college and working  about 60 hours a week with a full course load. The range was an old  cut-flower range that dated back to the early 19th century where roses,  gladiolas, and snapdragons were the primary crops. We were in the  process of converting it to potted plant production at the  time. Watering was almost all manual at that time so constantly wet feet  were part of my daily routine. There was an old-timer on staff,  Charlie, who watched me, with amusement, water on my first day for about  10 minutes, before stepping in to show me the proper techniques and  impress on me that “the man with the hose grows the rose”. I heard this  phrase several times again since then and it is indeed so true how  proper watering can make or break a crop.
 More decisions regarding irrigation are made each day throughout the  crop cycle, more than any other which must be made correctly to make a  uniform crop as well as stronger and healthier plants. Healthy plants  are more resistant to diseases, insect pests, and the occasional dry  spell. You can also control plant height with disciplined watering. As  most of you know, with too much water and too little space tomatoes can  rocket up and become spindly almost overnight.
 Watering is difficult to monitor for an AG Teacher with multiple  responsibilities, going in so many different directions simultaneously.  When to water is based on many criteria. And what works this week may  not work next week with the crops maturing and daytime temperatures  increasing, watering schedules will evolve as well.
 Then there is the variety of plant material being grown with each  asking for their own preferred schedules and moisture needs. In most  cases, you cannot meet the exact needs of each and every plant in a  school-type setting, but you can arrive at a compromise that works for  most. Some are “water hogs” that need much more water than most others  that seem to require much less. Verbena and geraniums can require much  more water than New Guinea Impatiens and other less robust varieties.
 To grow any crop successfully, you must observe your plans as much as  possible. If you see a thirsty plant you should feel thirsty, too. “Be  one with the plant” is the mantra I always followed. Try to observe both  in the morning and afternoon as a lot goes on between the two. Proper  irrigation decisions target a balance between too dry and too wet which  is not always easy to accomplish especially while, as most of you are,  on the run.
 What affects a watering schedule?
  • Maturity of a plant (newly planted cutting compared or mature and “ready for sale”)
  • Type of plant (New Guinea Impatiens requiring less water vs Verbena requiring more)
  • Time of year which affects greenhouse temperatures, sun intensity and length of day all affect transpiration
  • Soil  type: peat-based mix which holds more water longer vs a bark-based mix  that is more porous, thus requiring more frequent watering.
  • Container  size and dimension both affect watering needs. Taller standard pots  will dry quicker than shallower, pan-type containers. To illustrate  this, take a regular sponge, soak with water and hold horizontally. Not a  whole lot of drainage….? Now move the sponge to a vertical position and  watch what happens….!
  • Location in the greenhouse, amount of air  movement as well as exposure to light or shade are all going to affect  the amount of water that your plants require.
 So, when should I water?
  • The answer here is always changing and is a balance, influenced  by all the above. The goal is constant moisture (much different than  “constant wet”), not unlike the Goldilocks principle where the porridge  is “not too hot nor too cold but just right.” This is not always an easy  goal but there are clear indicators.
  • The weight of the  container before and after watering says a lot. In a small greenhouse  setting, this is probably the easiest way to determine watering  needs. Most soil mixes will hold seven to ten times their dry weight in  water. Container weight is an easy means by which to tell whether water  is needed.
  • Color of the soil medium indicates the same. Soils are much lighter in color when dry and shift to a dark brown when hydrated.
  • Wilting  leaves are probably the most obvious symptom of thirsty plants but  please keep in mind this may not always be the case. While they will  wilt when dry, some will also wilt on the first sunny day following a  prolonged cloudy period. It takes a while for the vascular system of  some plants to wake up after becoming lazy in overcast weather where  they didn’t have to work as hard. Watering here may prove  detrimental. Also, wilting leaves may be indicative of bad  roots. Popping the plant out of the pot and observing the root system  will quickly confirm this or rule it out.
  • Leaf “shine” indicates  hydrated plants. This is hard to fully understand without observing  them with that dull, non-gloss finish when becoming thirsty.  Hydrated  leaves have a shiny “glow”. When dry or just about dry, many lose that  luster which is the last step before wilting. This is their way of  conserving water by not bringing moisture to the surface of the  leaves. Again, to perceive this one does need to be observant.
  • In  summation, when to water becomes a compromise in many cases especially  with a lot of different plants treated as one. Some get a bit more water  than needed and some a bit less, which is fine with a good quality soil  mix providing air to the roots. It is the long-term effects that will  cause damage to your crops if consistently watering too much or too  little. Fortunately, most plants are very resilient and with relatively  short-term crops such as spring annuals, this compromise usually works  quite well.
 General rules for watering are surprisingly few and relatively easy to adhere to.
  • Try to water in the morning, especially in cloudy weather or  winter months. This allows all day for plants to take up the water and  make the most of the day’s sunshine.
  • When you do water, water  thoroughly, letting water drain from the bottom of the container. This  can be difficult to do if untrained students are watering, or if one is  in a hurry or distracted. Water must get to all roots which means at the  very bottom as well. This also allows some of the fertilizer salts to  be leached out thus avoiding salt damage to the roots.
  • Ideally,  fertigation with each watering is best for overall plant health. Like  people, plants need to eat. Their meals should be provided consistently  for best results, rather than being rationed out once a week or on an  arbitrary schedule which too often reflects convenience on our part  rather than the well-being of the plant.
I understand the above would be much easier for a grower to  accomplish due to the focus of plant health and a profitable crop being  pretty much the extent of a grower’s job description. As AG Teachers,  you have this obligation as well as a plethora of other duties  throughout the day, nights, and even weekends. Proper watering is indeed  a developed skill that requires constant observation and  focus. Students, while meaning well, can be either helpful or  detrimental depending on their training and “focus” while handling the  watering wand.

Hand watering and manually turning on valves is  good as you can “inspect” plants as you water. Dry spots, diseases,  insects, and other growth issues are easily found as you make your way  through the crop. But watering by hand is also time-consuming and  difficult to account for during busy weeks or on weekends. These time  constraints set the stage for stressed thirsty plants if too many  compromises are made.
 An irrigation system in place with a controller and various zones for  automatic watering can be very helpful in ensuring the thorough,  uniform watering of each plant, both during the week and over the  weekends. I’m sure that those of you that have an automatic system in  place would not trade it for the world. These systems provide proper  watering when needed and allow for more free time that was once spent  holding a watering wand on Sunday afternoons. Chances are that those  Sunday waterings are more of a “keeping things alive” routine than a  disciplined focus for the well-being of the plants.
 These systems are cost-effective in so many ways. If set up  correctly, fertilizer can be dosed with each watering to best meet the  crops’ nutritional requirements. This will in turn produce a better end  crop with less incidence of disease which is often the result of  compromised growing practices. All this while your weekends are spent at  home rather than in the greenhouse.
 These systems do require a bit of thought to set up and schedule  which will have to be tweaked week by week as weather and plant maturity  change over the course of the crop. One must still monitor the plants,  especially making sure each morning that no dry spots exist which would  indicate a clogged sprinkler or even a failed solenoid. Other than  cleaning the filters, watching for clogged sprinklers or drip tubes, and  just making sure someone doesn’t accidentally unplug the controller,  these systems are relatively care-free. As with anything “automatic”,  some oversight is necessary to make sure all is as it should be.
 If you have any questions or concerns about an existing system or are  interested in setting one up for your greenhouse, please do not  hesitate to reach out as I would be glad to help you design as system  that would work exactly as needed for your greenhouse. Growing better  crops with less time in the greenhouse will be the end-result.
Superdial Indoor/Outdoor Controller
If you’re doing something different  in your greenhouse than is shared above and all is going well, please  don’t change. Perhaps modify, experiment and consider but be cautious  before changing a good thing. Successful growing is the result of many,  many variables. Some we have control over and some we don’t. The above  is only meant as a guide or checklist prior to the upcoming growing  season.
If you need help or elaboration on any of the above topics, please feel free to contact us.  If you need a source for or advice on annuals, perennials, pH or EC  meters, soil or anything else, I can help you with that as well.

Happy Growing!

 Mike Hellmann
Plants and Cuttings Manager
 P.S. Curious about my background and how I got to Hummert? You can find out more here.

Find the original blog and other helpful hints, click here!