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Subject:  "Foamers" explanation (update)

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Joze (Joe Ailts)

Deer Park, WI

Im back, this time with a plant physiology text book. And it appears as though the logically based theories about excessive water pressure as a primary contributor to "foamers" may be true. According to the text, plants exhibit a phenomena know as "root pressure".

You can observe the effects of root pressure when you cut a vine. Ever notice the sap that leaks out the ends of a cut vine? A positive pressure force must generate that flow.

Positive pressure is generated when roots concentrate ions (minerals). Lord knows we have high concentrations of ions in our soils (sodium, potassium, calcium, etc.) The high concentration of ions attract water, subsequently generating positive pressure in the root system.

A direct quote from the text: "Root pressure is most likely to occur when soil water potential is high and transpiration rates are low (high humidity). When transpiration rates are high, water is taken up so rapidly into the leaves and lost to the atmosphere that a positive pressure resulting from ion uptake never develops in the (roots)."

"Plants that develop root pressure frequently produce liquid droplets on the edges of their leaves, a phenomenon known as guttation".

Curiosity- Those that have routinely experienced foamers, have you also observed guttation?

12/26/2010 10:13:36 PM

Brooks B


awesome Joze!,, FINALLY! a scientific answer to this after all these years,

12/27/2010 5:17:19 AM

Joze (Joe Ailts)

Deer Park, WI

Thanks, Brooks. This book is fascinating reading...in fact i spent about 16 hours on the pot the other day, so engrossed in the content the time just flew by. :) sorry, i couldnt resist.

I want to ensure my words are not taken out of context...while the text supports the idea of positive pressure in the plant vasculature system, it is not a definitive explanation of why foamers occur. The smoking gun may be when evidence documents that positive pressures can lead to rupture of vasculature. That evidence may or may not exist in print, I'll continue my search.

Interestingly, there is good documentation of the opposite scenario, where negative pressure (vacuum) due to excessive transpiration actually leads to a collapse of the internal vasculature. When you think about the "sucking" force necessary to pull water to the upper reaches of a 100 meter tall Redwood, you can visualize how these mechanics strain the vasculature system and why, subsequently, wood is so damn hard in very tall trees. Fascinating!

12/27/2010 10:08:11 AM

Smallmouth (Team Ozark)


Joze, very interesting. As for negative pressure you mentioned, just another thought on that is conifers or softwoods generally transpire less than broad leafed or hardwood species of trees.

12/27/2010 11:29:31 AM

Don Crews


We had a ridiculous amount of moisture this year. My greenhouse faired better but since it received its cover during the summer it did little to limit excess water from accumulating. My 1579 grew very fast and ..blossom split. I set two more on secondary vines for genetic crosses and left until the end of season. About a week after pulling the plant I went in to get some equipment and noticed wet spots that were better than a foot in diameter. These spots were not just wet it was muck. A closer inspection revealed a piece of root pumping out water. With my peat soil it would have taken five gallons of water to create a spot that wet. Root pressure over the whole plant when the soil was wetter would have been unbelievable. Perhaps foaming stump is not the only symptom of extra "root" pressure.

12/27/2010 12:26:36 PM

Brooks B



now the question is, how do you think we/I can prevent this from happening?,, let more or all side vines continue to grow out untill after the 30 to 40 day mark of the pumpkins growth, then terminate all vines? You would have to have a pretty big area to do that, but Im sure it would help alot to prevent the foamers, but then again, you might be taking alot away from the pumpkin also, there's got to be a fine line to where we can let so much plant grow to where it will help in preventing these foamers but yet not take alot away from the pumpkins growth ether.

More to come on this Topic Joze, But for now I gotta get off the puter and relive some of my own pressure, just hope it doesnt take another 16 hr's ha!.

12/27/2010 10:12:37 PM

Joze (Joe Ailts)

Deer Park, WI

The million dollar answer of foamer prevention can go a bunch of different ways. In the previous thread on this topic, a number of experienced growers suggested minimizing moisture/watering around the crown area.

Indeed, in the absence of copious water levels around the crown, hypothetical root pressure may not develop. This could contribute to minimizing the development of a foamer. A drawback of this tactic may be include compromising water availability through the taproot, thereby limiting fruit growth. Although the extent to which this occurs is variable and nearly impossible to measure.

I am an advocate of increasing leaf surface area, which has a number of inherent benefits built into it in addition to contributing to minimizing foamers. More leaf area equates to more transpiriation. More transpiriation creates a larger net negative pressure in the main vine vasculature.

Some may counter than high humidity is causal factor in foamer development, and that more leaves do not resolve a high humidity scenario. To that, I state that water vapor concentration in leaf tissues is between 95-99%. Rarely is the relative humidity, even on summer's hottest days, greater than 70%. As such, there is still a differential gradient between the leaf and the atmosphere. Recognize that the greater the differential, the greater the rate of transpiration.

12/28/2010 9:03:26 AM

Joze (Joe Ailts)

Deer Park, WI

Sooo...plants need CO2. And so long as there is ample moisture (which is the case when foamers occur), the stoma remain open and transpiration hums along, albeit at a slower rate due to less differential between tissue & atmospheric water vapor concentrations.

Back to leaf surface area argument- In addition to increasing net transpiration, an obvious benefit to more leaf surface area is more photosynthesis. Photosynthesis is the obvious driver of growth in the plant system.

For years, growers have minimized the value of vegetative growth at and beyond the pumpkin set. Some have even falsely claimed that vegetation beyond the pumpkin does not contribute to the pumpkin's growth. These myths need to be dispelled and a new appreciation for factual plant physiology must be gained, as these insights are sure to enhance our collective march towards 2K.

For starters, I also advocate for allowing the main vine tip to grow indefinately. Yes yes yes, Im aware of the countless reports of growers who chop the main vine and grow big pumpkins. Anecdotal evidence aside, recognize that the main vine tip is the primary source of production for a very important plant growth hormone. Science shows us that the hormone is manufactured in the vine tip and transported BACKWARDS through the plant, all the way into the root system, where it promotes the growth of new root tips.

My point here is that new growth, specifically within vine tips, is a screaming beacon to the rest of the plant that the system as a whole is still in a growth stage. As a result, the root system will continue to do its job. And so long as the pumpkin itself remains the most potent "sink" in the system, the fruit will grow.

12/28/2010 9:16:03 AM

Joze (Joe Ailts)

Deer Park, WI

Chopping vine tips to "funnel" plant nutrients in the pumpkin is, at the surface, solid logic. Unfortunately, biology is never quite so black and white. Chopping vine tips ultimately removes the signalling source described above. This essentially forces the pumpkin to operate in isolation, in terms of drawing nutrients in its general direction.

With vine tips intact, specifically those beyond the fruit set, hormonal signalling will continually encourage nutrient flow from the established vegetative material in front of the pumpkin, past the pumpkin, through main vine vasculature.

This is important, because the sink that screams the loudest (pumpkin) AND the sink IN CLOSEST PROXIMITY TO the source, gets the goodies.

The above proposed sets the stage for a prepetual "tidal wave" of sorts stemming from established material in front of the pumpkin, pushing towards the pumpkin and new growth beyond.

I've deviated away from foamers, but in a larger context, these thoughts are intended to minimize foamer onset as well as enhance nutrient allocation and signaling in the plant.

12/28/2010 9:24:12 AM


Western PA

So at night, when the leaves are full of dew, and very little wind, transpiration slows way down ?

It sounds like if any growers out there live in a breezy area, especially at night, their plants may benefit.

Your last 2 paragraphs are VERY interesting.Great info Joze !!

12/28/2010 9:54:40 AM

Joze (Joe Ailts)

Deer Park, WI

Transpiration does indeed slow down during the night. This is a function of photosynthesis shutting down. In the absence of light, there's no need for CO2. As such, the stoma (pores in the leaf surface that release water vapor and take in CO2) close up.

Considering day/night flucuations in rates of transpiriation, it is concievable that foamers "erupt" as a consequence of positive pressure built up in overnight conditions, coupled with excessive moisture and high humidity.

12/28/2010 10:58:36 AM

Joze (Joe Ailts)

Deer Park, WI

To give you a taste of how significant this process called transpiration is, consider the following fact: 97% of the water taken up by the root system is evaporated through transpiration. The remaining 3% is divided up as follows: 2% fuel metabolic processes that require water in their reactions. 1% fuels growth.

You read that correctly. 1% of the water absorbed by roots fuels growth of new tissues.

12/28/2010 11:03:43 AM

Tom B


perhaps this is one thing that makes giant pumpkins what they are. increased efficiency in this process moving that to 2-3%????

Just throwing an idea and a number at you.

12/28/2010 11:14:05 AM


Western PA

Wow !! , only 1% goes to tissue growth. That is mind boggling to think that a fruit can gain 40 pounds or more and yet the root system is taking in and transpiring MUCH, MUCH more water than 40 pounds !!
I would love to know just how much water a 1000 sq. ft. plant can take in, in a 24 hour period.

Joze, I thought the stomata are open at night ?, or do they only open for a few hours at dusk, then close, then open briefly in the first daylight hours ?

12/28/2010 11:16:19 AM

Joze (Joe Ailts)

Deer Park, WI

Tom- Your suggestion may be so. I've too wondered if AG's are an exception, as the percentages are a standardized average of all plants.

If we run some backwards math, the numbers get a little crazy: If 40lbs/day pumpkin growth= 1% of total daily water uptake, then these figures suggest the plant is absorbing and transpirating ~4000lbs of water (500 gallons) per day. Outlandish, and giving merit to Tom's suggestion that AG's allocate a larger percentage to fruit growth.

Stoma, in principle, need to be open during the day to allow for CO2 uptake. They will close during the hottest part of the day and in dry conditions to conserve water, however the need for CO2 often trumps water conditions. Maximal opening would be around times of dusk and dawn, when light is ambient and temps are cool.

12/28/2010 11:27:35 AM


Western PA

Thanks Joze, that clears it up for me.

12/28/2010 11:40:15 AM



Now I am really confused. "Transpiration does indeed slow down during the night. This is a function of photosynthesis shutting down"
Everything I have read about photosynthesis is that it occurs more at night because of at least a 10 degree temp change( cooling down at night) and the leafs open up the most for photosynthesis during the night.

12/28/2010 2:04:53 PM

Nana Rea

Massillon, Ohio

Joze, I like the sounds of what you're saying. I can remember standing over a plant that had the main and secondaries terminated, and the tertiaries all nipped off, and instead of thinking I was all set for big pumpkin growth, I thought....I've got a stagnant plant here! Three cheers for Mother Nature!

Also...if excess water in the vascular system might contribute to a foaming stump...and transpiration slows down at night....would it follow that one should not water in the late evening or during the night?

Thanks for another great thread.

12/28/2010 2:16:53 PM

Joze (Joe Ailts)

Deer Park, WI

Thomas- your logic partially applies to plants like Cacti, who, because of their extreme environmental conditions, need special circumstances to deal with the transpiration/photosynthesis dichotomy.

The plants in our gardens are called "C3". This is simply more scientific jargon for plants that follow the typical day/night photosynthesis scheme.

Fact: photosynthesis occurs during the day. photo=light. The sun needs to be up for this process to occur.

To add confusion to the mix, there are "dark reactions", a poorly named process has nothing to do with day/night timing but rather the fact that these reactions do not require light to occur.

12/28/2010 2:45:17 PM

Joze (Joe Ailts)

Deer Park, WI

Nana- Watering timing is a debatable topic with many considerations. If one's primary consideration is avoidance of foamers, then yes, AM watering would intuitively make sense given that root pressure peaks during the night and assuming this is a contributing factor.

12/28/2010 3:28:01 PM


Joliet, IL



here are a couple nice reads that may help some understand better what joze is on to. is there any way cavitation or a rupture of the xylem wall is possible due to a fluctuation in root pressure due to changes in temperature and more important humidity. and also could a quick hot spell with the plant thirsting too much and maybe deprived for a day or 2 and not adequately watered followed by a rain storm and high humidity blow the system out so to speak at the weakest links, maybe like small growth fissures around the massively growing stumps? it is a very fine line between watering too much and not enough with these beasts. and i know many of my leaves will burn on a windless 75 degree clear northeast wind day with very low humidity before they will burn on a 90 degree day with high humidity if i do not mist. i can imagine some cloudy days with high humidity right after some very hot dry air spells puts some internal pressures on the plant we can't see. very interesting stuff to roll around the brain joze.

the key is for us all to narrow it down....and then all think of the best solutions. i like it joey!!!

12/28/2010 6:21:12 PM

Big Kahuna 21

Ontario, Canada.

Joe, very interesting discussion and highly informative as you are very well versed in AGP physiology. This is a bookmark post for sure. Not sure if this is what your looking for but here is my comments.

After your prior postings a couple of weeks ago I came across a term called Anoxia (lack of Oxygen). I believe this maybe the correct terminology you seek for Mr. Foamy. PUMPKIN VINE ANOXIA. AGP's require oxygen for respiration and it appears as if this hypoxic (low Oxygen)condition can arise in vine sections under certain circumstances.

Sink source relationship is most definitely at play here. Plants with stronger sinks appear to have a better ability to govern resource distribution and therefore are thought to be less problematic. These sinks as you stated can be either the primary fruit, shoots or roots. You are most definitely on to something here.

Oxygation of water and the soil could boost yields in patches that have wet soil conditions with high transpiration days. I have been working to provide much more air to roots than in past years.

Adding amendments that increase the macro pore size of the soils structure enhance the root zone. Sub soiling for better drainage and incorporating tile systems all help too. Quick transition from heavy rainfall events is a very important factor.

Co2 foliar spray products conserve moisture in the plant on low humid high temp days. They also allow the plant to respire at more constant levels when faced with environmental extremes.

12/28/2010 7:23:35 PM


South Bloomfield, Ohio

Your second to last sentence brings me back to a question I raised earlier this growing season Russ and never received a response: are CO2 products adding to the problem of foamers? I lost five out of six stumps this past season due to this very topic of discussion and it was the first season I ever used CO2 foliar products. I hypothesized that transpiration was restricted(the very reason we use CO2 products?) and excess water built up in the plant.

12/28/2010 8:23:44 PM


South Bloomfield, Ohio

Perhaps we should be mindful to use CO2 products only during periods of prolonged drought. I know some growers swear by its use and had very successful seasons, attributing that to the use of CO2. Perhaps these growers experienced less-than-normal rainfall seasons?

My season was one of average rainfall and my soil is well-drained and I irrigated enough to equal 1" of rainfall per week(including rainfall).

12/28/2010 8:29:36 PM

Brooks B


Joze , GREAT post so far!

Alot of new stuff here that I would have never gave thought to.

12/28/2010 9:05:03 PM

Frank and Tina

South East

Maybe even the use of myccorhizea on highly fertile soil could be a bad thing? As the fungus increases water and mineral absorbtion for the plant.

12/28/2010 9:24:27 PM

Joze (Joe Ailts)

Deer Park, WI

Shazzy- great links, very informative stuff. I've considered cavitation as a possibility as well. Until we can get the right tools to make the appropriate measurements, will be hard to say conclusively what phenomena is causal. Cavitation is pretty extreme, but then again so are AGPs.

Russ- Im familiar with anoxia in root zones saturated by water...have not given consideration to whether this could apply to vine tissue and/or this could be related to foamers. Regardless, increasing oxygenation to the root zone provides many benefits as you alluded to. Nice contribution-

12/28/2010 9:31:17 PM

Big Kahuna 21

Ontario, Canada.

Thanks Joe. I believe that too much of a good thing may in some situations be harmful too. I would suggest that yes you are correct. Water balance within the the plant is extremely important. Any types of stress that affect transpiration hinder the ability of the leaf to moderate its local climate. This all plays havoc inside the plants vascular system.

Yes, the plants compensation point needs to be regulated with greater skill when using C02. Balancing the plants demand with uptake is a battle for a lot of growers.

High canopy transpiration rates on low humidity days play a huge role in the function of the Fruit Sink (FS). The FS under such conditions becomes a store for sudden increased transpiration and begins to build peduncle resistance. This weekens the future FS capability to import from the plants two rivers, setting the stage for the foamy hypoxic event.

Secondary sinks such as Adventitious root growth leading up to the time of termination and beyond to late August can be stimulated with Foliar phos with IBA or NAA. Secondary root sinks during this phase of the plants growth cycle could moderate Mr. Foamy.

12/29/2010 5:27:18 AM

Big Kahuna 21

Ontario, Canada.

Plants I have observed with a weak primary FS that are also terminated often bolt with spurts of shoot growth along the vine nodes. This maybe and an indication of building hydraulics within the plant.

Drying the crown area as stated early on resolves the condition but can also ultimately hinder yield of the primary FS. This lends us the oppoutunity to explore the soils condition in the the root zone. Lowering moisture levels increases oxygen uptake thereby reducing anoxia.

The lesson here is finding balance. Determining the right combination of soil and moisture ratio for a particular soil in a particular condition. All patches are different and all conditions are different. The most accurate answer depends on each local unique condition both psychical and environmental.

12/29/2010 5:57:56 AM

Big Kahuna 21

Ontario, Canada.

In some patches this is all pretty much a mug's game. Until we learn to balance all the factors our patches present us with the effort can often be futile.

My struggles with BES and under weights had been overcome in using Co2 and now I too was faced with MR. Foamy in 2010... The challenge never ends does it....

I am amazed at what has been accomplished. In my few years here on BP we have managed to add nearly 50% to the total weight of these monsters. These foamy issues are mere growing pains we will resolve and Y2K will soon arrive.

Joze, great topic. Looking forward to seeing you at the convention.

12/29/2010 6:20:59 AM

Joze (Joe Ailts)

Deer Park, WI

Here's a practical solution that I'd encourage those with Foamers to try-

Many are aware that calcium strengthens plants. On a molecular level, calicum creates bonds between consituents of the plant cell wall, literally "cementing" the wall together, and thereby conferring strength upon the structure.

Many have used calcium in various forms and delivery mechanisms to minimize splitting in pumpkins. The same principle can be applied to foamers, and again with potentially far-reaching benefit.

Assuming that external vine tissue has the capacity to absorb exogenous nutrients, I suggest weekly application of a calcium solution to the length of the main vine.

If indeed these tissues absorb calcium, not only will there be an increase in local calcium content, which conceivably confers enhanced foamer resistance, it may also jump into the xylem sap flow and be transported to other areas of the plant, where it serves its multitude of functions within the plant system.

Skeptical? Exogenous calcium applications have been used in commercial fruit and crop programs, validated by scientific study, to enhance tissue durability and minimize disease.

12/29/2010 11:38:45 AM

Joze (Joe Ailts)

Deer Park, WI

For a very digestable primer on the role of calcium, this is a must-read: http://www.simplyhydro.com/calcium.htm


12/29/2010 12:01:40 PM



hey joe, now that you mentioned it, i had one plant in the field with irrigation and it had evenly weekly foliar applications of calcium and glucose spray. The glucose spray i made by mixing water with corn starch and heating it to 120 degrees for 15 minutes, once i converted the starch to sucrose i added 2 ounces of spray to one gallon water and sprayed the plant weekly. It was the only plant out of 6 that did not have a foamer. I think this is a great coincidence and calcium should be tested further to prevent foaming stumps.

12/29/2010 3:11:42 PM


Pocatello (cliffwarren@yahoo.com)

Wow, I get away from the computer for a few days and miss all this great conversation! Thanks for this thread! Now for that eye massage...

12/29/2010 4:56:32 PM


Midway, UT

This may not add a lot to the discussion but it has been my observation that in low humidity areas like Colorado you don't see Mr. Foamy issues. There has never been a confirmed case of a true foaming stump that I'm aware of in Colorado. We also typically have dry summers with very low humidity, which may confirm some of the hypothisys put out earlier in regards to transporation.

12/29/2010 6:52:08 PM


Pocatello (cliffwarren@yahoo.com)

Exactly... here in Idaho we are very dry and I have never seen this phenomena. We typically might see one rain storm between late May and early September.

12/30/2010 12:25:29 AM

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