Something to consider is that the water in the hose, if it's exposed to the sun, will be hot until the hose water is flushed and ground water is running out. In other words you may not do much to reduce temps if you are putting hot water into the container (other than evaporative cooling near the surface).

As far as evidence pertaining to which approach will cool the potting mix better I don't have any ;) I would think high volume would do it better as it would have the water moving throughout the container faster and less opportunity for the water to be warmed at the surface, but the difference probably isn't great either way.

Of course the timing of applications is a consideration. Timers set for mid-afternoon can go a long way toward slowing the effects of solar gain when it's at its peak.

Al

Water the plants with ice, early afternoon.

During the summer the water is a steady 75F (I used to be an avid B&W photographer and know these things from my darkroom work). I plan on running the hose under ground and in the shade to keep the water from getting much warmer than this. Also, I will have a couple of pressure release valves which will drain the above ground portion of the hose once the system shuts down.

Al, you bring up a good point. My initial thought was to set the timer a little later in the afternoon to speed up heat loss. In TX not only does it get hotter, but it stays hotter for a larger portion of the day. For example, tomorrow the weather forecast indicates it will reach 80F by 10am, 84F by 11am, peak at 86F from noon until 6pm, and not fall below 80F until 9pm. These temps are still pretty mild. Realistically, in a couple of weeks the first digit of those temps will be '9's, and it will stay like that into September.

Does my thought to give up control of the root zone temperature during the heat of the day and bring it back down quickly when it is possible to do so make sense? Any input is greatly appreciated.

~james

p.s. if it makes a difference, all of the containers in question contain deciduous fruit trees.

James - I want to do some reading for you before I reply, but I know that even those short exposures to temperature extremes have significant impact on root function and viability.

I know you have a lot of trees, but have you considered shading the containers? You could use the white fabric that the fine mesh outdoor furniture is made of. If you cut circles a little larger than the containers, then cut a slit to a center that was relieved to fit around the trunk, they will rest on top of the soil or container walls and shade the entire container while still allowing water and air permeability. When I get the gardens situated and can take a breath, I plan on doing this with many of my bonsai - especially those in dark pots & the material I have growing on in (black) nursery containers. I was touring the Frederik Meijer Gardens & Sculpture Park collection a couple of weeks ago & they are using this technique with noticeable success for their trees not accessible for public viewing.

BTW - nice to see you. You don't come around enough. ;o)

Al

What are you using for your containers? I am using mostly black pots so I have been using old white plastic bags that the pine bark or mulch has come in, cut it a little and wrapped around the pots to keep the sun off.

Hi Al,

Sorry, I have been so busy, I have not had much time to check in. My trees have also been neglected. Not so good while temps are approaching 100F. It is always good to come in and see old friends.

I understand high temps have an impact on root function. I guess the question is if the impact worsens as temperatures rise (e.g. is 100F worse than 90F?) Or is the impact on function the same at all temps above a given threshold?

lruett,

I use Air-Pots elevated off the ground. I grow off the ground due to the presence of RKN in my back yard and in Air-Pots to increase the interval between root pruning.

This is a pic of my set up from early 2008:
{{gwi:32566}}

I can attach something (i.e. pink insulation board, aluminum flashing, etc.) to the side of the trays which face the sun. At this time of summer, the sun is high in the sky, which makes it difficult to effectively shade the container. Since I am setting up the sprinkler system, and can set it to water at any time during the day, this is a bit of a bonus.

~james

I use sunscreen fabric that I buy in a roll from big box stores and cut them up for whatever the length of rows of trees I have and just simply attach the end of fabric strip to both ends of the rows with cloth pins. Cheap and easy.

James,

Impressive set up. Very nice and organized unlike mine. Lol. Where did you get air pots? I use Rootmaker, Smart pots and Roottrapper (great for keeping mix cooler). I read somewhere that once it reaches 95*F, root growth or top growth (?) slows down. Of course pot in ground is best as I have smart pots filled with garden soil and trees are growing like weeds. I wish I had more space and better soil for that. My soil is all rocks...

Most deciduous trees put on the best root growth when soil temps are between 60-75*. Reductions in up to 40% of the potential root growth are seen in most species at 80* and growth declines as temperatures climb. Even if we allow carica an extra 5* to be generous, it's reasonable to assume that trees will suffer at soil temps exceeding 85-90*. These high temperatures also affect photosynthesis because they force stomatal closing, so they should be avoided. soil temperatures of 115-120* are usually high enough to kill most deciduous trees.

James - there are white, uv-resistant poly slip-covers you could use for your trees' containers that help prevent heat build-up considerably in soils in containers exposed to the sun. They breathe and reflect light/shade the container. Would that help you?

Al

Hi Al,

At this point it is a bit of a moot point. I have been traveling for the past five weeks, during which time I was planning and ordering components for the sprinkler system. Also during this time, the people who were suppose to water my trees did not. Between figs and pomegranate I lost about 120 trees. I only have seven left to worry about.

Since the winters here aren't so harsh, I'll rebuild in the fall.

As for the slip covers, I remember some slip covers being available from RootMaker. I'll look into those.

thank you for your input.

~james

Awww, man! I'm SOO sorry about your trees. That's a total bummer! I bet you feel like throttling an irresponsible someone. I wish there was something I could do ....?

Fare well, James.

Al

That sucks, James. I played with drip irrigation for awhile myself and the primary impetus was leaving for a few days and hiring a neighbor girl who has her own containers and is quite responsible (I let her babysit my kids) to water.

She didn't. The day I left her family was notified of a death in the extended family and left town immediately. Not her fault at all, but my plants didn't understand that.

My losses were nowhere near as extensive as yours though.

Thanks for the sentiment guys. I'll just use this as motivation to do things differently next time. A for throttling someone, it should probably be me. I let being busy get in the way of taking care of my trees. Whereas I don't mind getting the hose out and watering the trees when it's ~100F, I suppose not everyone feels the same enthusiasm for figs and pomegranates.

~james

I really do understand your attachment to your trees, James. I have a couple of hundred trees & woody plants growing on for bonsai. Most, I've attended to for so long they're more like my kids than trees.

For example: I really need to reduce the number of plants I tend so I have more time to devote to the really good bonsai. A lady that had attended a garden walk at my home a few years ago remembered that I did bonsai & showed up knocking at my door at noon Sat, wanting to buy a bonsai tree for her college-age daughter, who was with her. Wouldn't you think that out of a collection that size, that you wanted to reduce, that you could find at least one tree you'd be willing to sell off? NOPE. I ended up giving her a lollipop-shaped Eugenia that was left over from our club's last workshop in the name of promoting bonsai. I'm telling you - it's like selling your kids ..... so I really do feel your pain.

Al

Sorry to hear about your loss. I learned a couple years ago that I can't rely on anyone to do anything right so I did everything i could to set up irrigation system to keep my plants alive while I'm away. Not perfect but still much better than having others water them for me while I'm away.While I'm a cheapskate, I'm forced to spend a quite bit of money on irrigation system to ensure that every plant get watered. I have a week to set it up before I go out of town so hopefully I can get it done early enough to do early trial run to see if it works.

Have you considered growing them in the ground using knitted bag or smart pots using topsoil? That's what I'm doing in a tiny section of my lawn and apparently they need much less water AND growing like weeds ( in a former plant bed that has been extensively ammended). Too bad, I can't do large numbers in the ground as my soil is not very ideal because I live on limestone rubbles and that means removing rocks that are in the way. If I ever started a tree farm, I would be using exclusively knitted bags and roottrapper bags to cut back on watering in hot weather...