soil warming

[Axel]

That's most interesting Greville, the chamaerops not really responding to warm water.
I figured the butia would like this treatment since they come from a hot and wet summerclimate. Chamaerops obviously comes from a different climate but the fact that it seems indifferent to warm water to some extend surprises me. Warm water seems really suitable for some palms while others seem to react only slightly different.

Beautiful chamaerops, nice long petioles, there is no difference between this one and the ones growing in the south of france/italy/spain.

[GREVILLE]

Axel, I think my Chamaerops has grown so well because the soil heats up readily without the addition of warm water. The rocks on the raised bed get hot on sunny days and at the back of the rockery which is banked up against a 30cm thick loading wall is another brick structure trapping and radiating heat.The Chammy stays hot from head to toe

The Butia now has impaired light gathering capacity with older leaves damaged by fungal spots necessitating their subsequent removal. In addition to soil warming I'm convinced you need to keep as many leaves on the plant to maximise photosynthesis. I cut off far fewer leaves off the Chamaerops so there is greater light gathering capacity to encourage growth. Rooting also runs deep to get plenty of moisture.

I'm sure the Butia would be bigger if I could have kept more clean and healthy leaves.

[Axel]

Yes, stones and structures do the trick for most of the palms in our country. It seems wise to always plant palms in and between stones. The extra degrees are more than welcome in our summerclimate.
Greville, I still would love the see a picture of the Phoenix canariensis_CIDP.

[GREVILLE]

At last, I'm able to post an update on my rising soil temperatures now that I can use a new laptop which has a keypad that works!!

Attempts to revive my Washingtonia through doses of warm water have failed a bit like trying to repair our old computer - so this will be replaced and I'm looking forward to starting again and comparing growth rates with the old one.

Apart from a twenty year old Puya chilensis I have no other casualties and unusually high soil temperatures have already boosted everything to mid-summer growth rates.

After an extended holiday the plants have gone without their customary doses of warm water but it seems after the incredible April just gone it wasn't necessary. I've now started giving them hot water at my summer rate (40c) - not so much to keep the growth rate going - more to prevent a scrub fire Everything is so dry!

Examples: The Livistona Australis spear opened fully in my absence with a big spear cluster following. This is growing in my shaded NW facing bed and is last to warm up. A result more likely had in July. What a contrast to losing my Puya and Washy in the hottest and most sheltered part of the garden!
The Phoenix canariensis_CIDP spear cluster has almost opened fully if to reveal more damage than at first thought. However, fresh green growth can't be far behind.
Brahea armata is already opening its second leaf.

I'll continue with my soil warming results when I can reorganise my photos in to a new file.

[jimhardy]

I guess part of the problem with trying to revive a Washy with warm water
in early spring is that they really should be kept dry coming out of cold winter sol temps.

[Daniel]

To generalise, it seems that a healthy palm coming out of Winter will benefit from having warm water, but I have also observed that a weak plant will not benefit at all and can even suffer having excess water of any temperature during Spring.

I have also observed that different palms can tolerate higher water temperatures than others and some palms benefit from having warm water every day and others such as Washingtonia prefer a weekly watering. Sabal Minor and Butia Yatay can handle water at very high temperatures, I discovered this last Spring before I was able to mix the temperature of the water coming out of my hosepipe. I found that I could water certain plants with water at 60c (please do not try this at home) and once the water started to cool off as the tank ran out I could then water all of my other palms.

Other observations are that Brahea Edulis loves huge volumes of water and the temperature is fairly irrelevant to them.

[Dave Brown]

To generalise, it seems that a healthy palm coming out of Winter will benefit from having warm water, but I have also observed that a weak plant will not benefit at all and can even suffer having excess water of any temperature during Spring.

I have also observed that different palms can tolerate higher water temperatures than others and some palms benefit from having warm water every day and others such as Washingtonia prefer a weekly watering.

I am firmly of the belief that real growth cannot cannot be sustained without root atcivity. My experiments last year with soil temp measuring showed that Washingtonia growth was not triggered by a rise in soil temp, it seemed to be sun and air temp..... BUT, that growth was a small amount, and that the same air temp gave a lot more growth mm when the soil was warmer. In Washingtonia robusta at least, maximum growth rate seems to be driven by a combination of: high air temp; high sun temp on leaves and trunk; and warm soil. I guess without warm soil it is just draining it's reserves.

Without going too off subject, my W robusta suffered extensive damage last winter with temps around -10C and 6 ice days in December (not consecutive). Most leaves were damaged, and the conveyor belt of spears were also damaged at their tip. This means that the first 4 leaves of new growth are also damaged.

In April 2010 the average 30cm soil temp (Next to the Washingtonia Trunk) was 11.2C. This year (2011) with 15 ltr 40C watering almost daily it has been 15.6C

There are lots of complications as my soil is 100% modeling clay so the 7.5 ltr watering can when poured on covers about 4 sqm area before is soaks in. In fact a major factor in how much heat you can get into the soil is determined by how well the water drains through. If it doesn't, you are heating the surface and radiating the heat down. If it drains very well you have the problem of needing far more water to cover the area, but could overheat some areas

The soil is covered with slate chips, but this year I covered the slate with black weed fabric and the plastic parasol cover used in the winter. I can only do this as the soil does not absorb the water readily as I can pour in at one point and it distributes under the fabric.

It may not seem much rise in temp but it has been far more stable and does not fall much in colder weather.

The difference in growth this year to last is astonishing, although warm water will only be a factor, as exceptional warm temps, and high sun and UV levels will also play a part, April 2010 saw 140mm petiole growth where as April 2011 has had 590mm, and 4 new fans opening.

Bottom line is the soil permeability makes all the difference in how much warm water affects your plants.

[GREVILLE]

Dave is absolutely right in showing that the more permeable the soil the better effect adding warm water will have to raise soil temperatures. Although I'm on sticky clay all my beds are raised with augmented material that drains freely.

This year I noticed that the weather was warming things up well even before April began to cook everything. The very early start and end to winter seems to have made February the real start to Spring. The bed where my washy grew was bursting into life by Valentines day so I had no compunction about resuming my love affair with warm water on my exotics so early in the year, instead of starting in April when the beds are already warming up.

However, I have just discovered that too much COLD water may have contributed to the death of my dearly departed Washy. I saw a stream of water coming out of a gap in my guttering during a thundery downpour this weekend. It was landing from a great height right on top of the dead Washy's trunk Being at the side of the house I wouldn't normally notice this so was the crown of leaves being battered by a waterfall before the freeze took its toll? Perhaps Dave's parasol arrangement may have spared it!
Jimhardy's point about keeping the plants dry may well apply here. I certainly wouldn't start this treatment when the soil is still cold and wet. Much better to do it when growth shows that things are warming up, especially when high temperatures and high UV sun levels have triggered it off

Daniel makes a very valid point when some plants respond more to hotter water being applied. The frost hardy heat lovers among the palms bear this out.