What's your definition of 'over water'?

I guess I should add. Last season I had a 2 ft. Acer saccharum in a gallon pot with 511 for media and in the hot weather, I watered it every day, sometimes twice a day. That was with keeping the pot protected from the sun. Otherwise full sun on the top.

511 drains very fast and hold only so much perched water so an actively growing plant in the heat of summer has to be kept watered frequently or it will dry out the root zone and bad things can happen.

Technically you can over water in any medium. Environment and plant vigor will play a major role too. It depends on what is the water demand of the plant under those conditions. If it is cool and the plant is not growing much water demand is low. First year in 511 the mix will drain fast. As it gets populated with roots and the medium breaks down it will hold more water. So second season it may remain more wet. Third season it will be even worse.

i seem to recall.. that your garden is a bit of a jungle ... i like it ... [if im thinking of the right one]

a black pot in sun ... can heat and require constant watering ... think bigbox/nursery blacktop.... etc ...

a pot itself not in sun .. in a yard with reduced wind.. due to surrounding vegetation ... might not require any water other than ma nature ...

of course .... it depends on the pot size.. and the tree .. a babe in a 5 gal pot would be very different than a 5 foot tree in the same pot ...

ken

I almost offed a JM in gritty mix! Thanks to Al's advice, I didn't

I should have been a little more precise: instead of saying it will hold more water I should have said it will hold more perched water. That may or may not translate to overall water holding capacity of the mix but I suspect it is logical to think it will hold more water. Here is the reasoning.

As the bark starts breaking down it will start occupying more of the air spaces between the larger particles. More roots in the mix will also start contributing to space between particles. As the size of the spaces decrease the perched water height will also increase. That means more of the soil will be saturated right after watering.

It is quite possible that for a healthy plant when it is actively growing it will use up most of the water and effects of saturation may not be that evident. If water demand is less then the roots will be sitting in saturated medium for a longer period of time.

My observations with my plants supports the above description. I see it takes longer to drain as the medium ages. Happens with gritty too as the bark breaks down.

When repotting after too long in a mix I have frequently observed that there is a very dense root mass circling the outside - a very good indication that the mix is anorexic at that point.

I also have many plants in gritty mix. Often same type of plant some in gritty and some in 511. After 3 years or so, very often 511 will have many circling roots while the gritty will have very little - for similarly sized and of similar age plants. To me it suggests that griity being made of mostly durable components remains porous longer.

Okay Stuart, Let's have it, why are you asking? :-)

It's been 90 degrees here for 3 days in a row and the leaves are curling on one of my Acers which is in the 5 1 1 mix. The tree is in full sun and I've been watering it almost every day. Maybe I'm not watering it enough? It's a purple leafed Acer that can handle full sun.

Move it out of full sun. It is quite possible the container soil and therefore the roots are heating up too much in your hot weather. Full sun in the ground and full sun in a container are two very different circumstances.

So do I water when the potting mix is completely dry or moist?

Completely dry? no.

I usually dig around the outside with my finger on my flowers in 5-1-1. But to tell you the truth, 5-1-1 drains so well, I just water until it comes out the bottom a little. Water and air go down through so it's not the same as soil where you can drown out the roots but you still don't want it to be completely saturated all the time.

That sugar maple I talked about thrived all summer until I gave it away and built a good set of roots in the process.

Keeping the tree year after year may require more attention than doing it for just one season like I did.

With difficulty, assuming it’s outdoors.

My bigger issue is it gets hydrophobic if someone breathes on it too hard.

NEVER let 5-1-1 get completely dry. You’ll about never get it re-wetted. At least that has been my experience.

Stuart, I believe you are mainly growing Japanese maples in containers, right? If so, the soil should never be allowed to dry completely. "Evenly moist" is the watchword :-)

I have never had an issue with the 5-1-1 becoming hydrophobic, even when stored long term in a lidded plastic tub indoors. YMMV

'My bigger issue is it gets hydrophobic if someone breathes on it too hard.'

Hairmetal4ever,

What kind of bark are you using?

I've never had that problem using pine bark.

Pine bark! Unless it’s the particular type I am using.

Okay, thanks!

I've heard of using Fir bark and didn't know if that would be different in some way. I'm not sure exactly what type of pine I'm using either, just says 'pine bark' on the bag. The only difference I can see is if the bark is partially composted or not composted, that could make a possible difference, I suppose there could be other variables too.

Fresh pine (and fir) bark have high suberin content that gives its water repelling properties. Initially it takes a while to soak up water if it is dry. As it ages it loses suberin (slowly) and becomes less hydrophobic. If you take fresh bark and soak it well you find it floats on water. Aged pine bark once soaked tends to sink suggesting that water holding capacity of fresh bark is less.

Along with suberin, high lignin content also prevents it from decomposing quickly. Fungus which is usually the first colonizer of dead material find it hard too. It takes a while before fungus can start colonizing pine/fir bark. Essentially pine/bark is quite durable compared to other hardwood bark such as oak, maple, etc.

Fir bark tends to be thicker and rounder whereas pine bark tends to be like flat discs. That is why pure pine bark will tend to stratify (lay flat in a stack). This kills the air spaces quickly. Perlite or other roundish component is added to prevent stratification.

So basically, mine isn’t aged enough?

It‘s funny then, that even my three year old 5-1-1 is still pretty hydrophobic.

Some parts of my pine bark gets kind of soggy and a small percent doesn't soak up much water at all. I soak and stir it frequently a few weeks before using. Once peat & perlite is added and soaked, works great.

My main source of pine bark is Agway and it is very fresh bark. For the last few years I have been storing about 2-3 bags worth in a 55 gallon plastic drum with open top. It is open to rain/snow. Over several months it ages a bit. I also add a bit of urea to speed up the process. I do one batch in fall to use in early spring for my deciduous and conifers. I start a batch in spring again to use it through summer. It works out a lot better than using the Agway bark straight out of the bag.

Stuart: You may also try putting a layer of sphagnum moss on top - it will reduce evaporation loss. Weigh it down with a few rocks otherwise it can fly way when dry. In our area Robins will steal them though for building their nests in spring/early summer.

In our local bonsai club field, we use shade cloth to cut off some of the afternoon Sun. It is slightly tilted towards the SW sky so the plants get direct morning to early afternoon Sun.

Most containerized trees want protection from direct midday sun when it's in the 80s or warmer .... and I'm not just talking about its effect on root/soil temps. New growth of most trees can suffer significantly from over-exposure to direct sun, and all maples should be considered sensitive.

Al

I guess my concern is whether an Acer can get root rot if it's watered very frequently in the 5 1 1 mix. Thoughts?

Absolutely. But it's not easy to 'catch a disease'.

Here they call the graphic a disease triangle, but it really should be a disease tetrahedron (a pyramid with 4 triangular sides). If you have a active virulent pathogen that is genetically capable of recognizing a host and can produce enough inoculum to infect a host, and an environment conducive to development of the pathogen (or said pathogen is harmful/stressful to the host) and the host is susceptible to the pathogen, plus the time (the 4th facet of the tetrahedron I mentioned) it takes for the pathogen to multiply, root rot and/or other biotic diseases can occur.

Al

Stuart, I should correct my description on my little maple. When I said it was 'full sun', It was partially protected by the deck rails all morning, with direct sun a few hours in the afternoon, then again shaded by the house after 6:30 PM, so basically what I forgot was it was broken sun at times. The board was to keep sun off the pot even in the afternoon. I see too it was a 3 gal pot.

I mainly would water in the morning and just depending on the heat, sun and wind, if the top of the media looked like it was drying out pretty good, I'd water in the evening too but not necessarily every evening.

Al, you said Most containerized trees want protection from direct midday sun when it's in the 80s or warmer ..

Does that include figs, citrus and bananas?

Never had an issue with hydrophobic pine bark either. I concur with TOC, and I do the same. I like to buy next years bags at the end of the summer (you might catch a sale in the fall) I put a hole in each end of the bag and run the hose through it so it's good and saturated and leave it till spring. I guess I do the "partially decomposed" part myself.

When pine bark is composted commercially, it's stacked in windrows and turned occasionally with machines with augers (much like a auger-type snow-blower that would pile snow in neat rows instead of blowing it far and wide) designed to move rows of composted products; this, because anaerobic composting creates organic acids that quickly reach critical levels under airless conditions. If you're doing your own composting inside the bag, even on a very small scale, it wouldn't hurt to leach the bark before using it, and to make sure the lime has opportunity to go through its reactive phase before using media that utilizes the bark as its base.

Al

Gardengal, do you water your Acers when the potting mix is completely dry, moist or wet?

I'm not sure I can answer that very accurately as it is for me now after many years a very experiential thing. I know my trees, know how my containers function and know when I should be watering so don't really pay much attention to the soil itself. Not very helpful, I'm sure :-)) The best I can say is I never wait until the soil is completely dry, as that puts the trees under too much stress.

I agree with the above. All maple species are telling you they want water several hours ago or it's too hot to suit them and they want protection from the sun/heat when you see the newest foliage wilting. To tell which adversity they're complaining about, check the soil moisture conditions with a tell. If the soil is still amply moist, don't water - move them to shade. If the soil is too dry - water. Always wait for water that's been on simmer in the garden hose all day long to run until it's cool before watering potted plants.

Since I use the gritty mix for all my maples, I often give them an extra watering at the hottest part of the day when it's in the upper 80s or warmer. I don't check moisture levels first, I just do it because I can, w/o worry of over-watering. A little more care is a good policy with 5:1:1 and pretty much a requirement with all bagged media based on fine particulates (peat, coir, compost, .....).

Al

I’m up to 50 varieties of JM in containers with a variation of the 511. I use forest humus in place of pine bark fines. I’ve been in the 90’s to low 100’s and I’m watering them every morning and sometimes even in the evening. My JMs are happy with their new shade cloth.

Nick, is your potting mix dry or moist before you water?

It is always moist when I water them.

This is a response to a post on the Trees Forum.

I use a mix similar to 511 and have some of my containers in full sun. Most of them in morning - early afernoon sun. I cover the top with ~ 1 inch of large pine barks to reduce water evaporation. This is very important for me to have a reasonable water schedule due to my frequent travels. For trees of medium size (faster growth), I water them once every 2-3 days if it is hot, sunny and dry (over 90F). otherwise I water once every ~5 days. For small and dwarf(slower growth), I water once every 5-7 days or even longer. I don't let them completely go dry. If I am not sure, I check with my finger under the mulch. If it feels dry, I water. If moist, I don't water. Most of my trees are in ceramic (mostly 2 and 3-5 gallon size, a few are 7 gallons). Gradually I found a routine/schedule that works well

Over watering can happen in my zone during the long and rainy spring. So I cover a few more sensitive pots with plastic cover on the soil. It never happens in the summer.

My potting mix: half composed pine barks (sold as soil conditioner), half regular store bought potting soil, sometime I added a little bit of Perlite if I have it hardy. All my JM trees and a few conifers (over 40 in containers) are all doing very well for the last few year. So far the only time I need to repot is when I need to up pot or root prune to control the tree size.