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Saturday, September 10, 2011

Zimbabwe and the Baobob Tree

Hosted at the Bradshaw's house in Harare. Geoffrey
was a fantastic guide in helping me work with local farmers
 I went to Zimabwe in August of 2011 to work with some local farmers on some irrigation schemes. They call them irrigation schemes if a group of farmers all use the same source for watering their fields. So for instance if the source of water is a river and there is a diversion from the river (can be a canal or a pump) then everyone getting water from that diversion would be on the same scheme.

Sometimes this is a very large main canal and if this main canal is split into two canals and the water can be diverted (forced to go into one or the other but not both at the same time) then each of these would be an irrigation scheme.

Using siphon eight siphon tubes to bring water from the
lined canal to flood their onions
So I worked with about 17 of these schemes with an average number of farmers of about 200 or so. I primarily worked with issues of "governance" surrounding these schemes (how is the water going to be managed and shared so that they all get an equal share?). But if you have never been to this part of the world then it is a treat.

The fields are irrigated on a rotational basis determined by when water is released to them by the government agency that controls water deliveries from surface sources such as rivers.
Baobob tree reaching estimated ages of 3,000 years old
or more
In southern Africa there is a tree that is quite remarkable called the Baobab or Baobob. I prefer to call it Baobob because it reminds me of me. Locals use it for as a food source by opeing the fruit (kind of dry on the inside) and sucking on the seeds. Kind of a citrusy flavor if you suck on the semi-dry pulp surrounding the seed.

It is normally found in the drier regions of the country, regions such as IV and V. The outer bark can be removed multiple times from the trees without apparent damge to them and this is then woven into mats and used in the homes or the mats are sold along the roads to people passing by, usually tourists.

Fruits of the baobob which has a pretty dry pulp on
the inside but sucking on the seeds and the surrounding
pulp of the seeds reveals kind of a pleasand citrusy taste
The outer bark is removed from baobob, woven and used for
making mats for flooring and sold along the roads

The Problem With Pruning Pine Trees So They Don't Blow Over

A fairly recent trend in pruning in Las Vegas has been pruning pine trees so they don't blow over. We have some wind gusts that periodically get pretty nasty when they reach speeds of up around 70 mph (112 kph) or more. The trend was to remove some of the canopy so that there is not so much leverage on the root systems. This leverage, or sail effect, by the wind can pop the trees over when gusts come up quickly and our trees can be pretty shallow rooted which does not help to anchor them.
This Mondale pine was pruned probably
 in an attempt o reduce with wind load (sail effect)
 on its canopyand help reduce the potential
for blowing over

You can see that removing the inner small
branches concentrates the weight of the new
growth all on the ends of the branches causing
 them to bend and in some cases to break

I have some concerns about thinning pine trees to allow more wind to blow through their canopies. Not that it is done but really more about HOW it is done. Take a look at this picture of a pruned pine tree just for that purpose.

Most pine trees will not regenerate new growth on older branches once this growth is removed. Once the wood is older than about three years old most pines will not cause new growth to come from this older wood. Once this young wood is totally removed, it is gone for good.

By removing these small limbs in the interior it prevents pines like Mondale from renewing the removed growth. The juvenile part of the limb is now concentrated
only in the growing tips which are all at the ends of the branches.

This might be good in theory (the tree trimmers don't have to come back as often). But this can create a problem.Think of a fishing pole. Why is the pole diameter tapered and not all the same diameter along its length?

Poles or branches which are tapered help spread the stresses of bending along its length. If a pole or branch has no taper, then the stress of bending is concentrated in a very small area of the pole or branch which will increase its chances of snapping or breaking. By removing this small wood deep on the inside it also causes these "thinned" older limbs to no longer increase in girth (caliper or diameter).They bend more and more as the weight of the new growth is added to the ends of the branches.

Pine tree with a canopy thinned a bit better so
that limbs are less likely to bend and split
A better approach would be to selectively leave some juvenile wood on the interior of these larger diameter branches so that these branches will increase in caliper and taper. So instead of removing ALL the small juvenile from branches deep in the inside, remove some but leave some as well. This still results in thinning and allows for wind to move throught the canopy easier and also results in distributing this increased load along the branches rather than concentrating the load in a small area of the branch which increases its likelihood of failure (snapping or bending).

Just a thought.

Sap Oozing from Plum Tree Trunk

Sap oozing from the trunk of plum
Q. Last week I noticed sap bubbles 6 to 8 inches off the ground on the trunk of my year old Santa Rosa plum. I removed the bubbles and reapplied the whitewash. I checked again today and they are back. I've had plums before and the boars always win. I had hoped the Santa Rosa would do better. What can I do to save this tree?

Roses in the Hot Desert Do Well But Different From Growing in New Jersey

Garden rose not doing well in our
desert soils. They can do VERY well
if you just follow some simple advice
Q. This past spring I cleared a large "L" shaped area in my yard and planted 8 various rosebushes. They have sun from about 9 a.m. to about 5 p.m. They are watered in the evening and fed regularly. They are well planted with planting medium in large holes, and then mulched. All flowered during the spring and early summer.

Now, however, they are very spindly looking. The leaves left on them are brown and the stems are turning brown. There are no bugs that I can see. I tugged on them and they are still firm in the ground. Have they died and should I replace them, or wait until spring and see what comes back? Should I cut them back, and if so, how much? I do not want to cut too much off.

Palo Verde Dont Like Butch Hair Cuts

Q. Attached are pics of a Palo Verde which has some unusual black growths on the upper sides of the limbs. I'm wondering if it has something to do with pruning, since it appears to be only in areas that have been pruned, although other pruned areas are unaffected.

Damage to upper surface of palo verde limbs from reader

Palo verde pruned too high, in my opinio, allowing for
potential sunburn on upper surface of limbs

Palo verde with sunburn damage, borer damage and
limb and trunk damage

A. My first reaction to the pictures was sunburn damage. But I would have to see if this damage was sunken like a canker.
Next I would take a sterilized knife and cut around the edge of the damage and through the damage to see if the wood below the damage was dead or not. If it was dead below the damage and the damage was sunken then it is most likely sunburn damage to the limbs.

The pics you sent had damage all on the upper side of the limbs which is consistent with sunburn damage. You wondered if it might be associated with pruning which it is. The big mistake people make on Palo Verde with the photosynthetic green bark like is pruning so much that too much light gets inside the canopy and burns these photosynthetic limbs. Even though the are designed to absorb light there is such a thing as too much light.

These trees don’t make a lot of shade and when we remove too much canopy we will get sunburn on the limbs. Once we get these limbs sunburned then we have to look for possible borer damage. They go hand in hand and several borers are general feeders and are not really particular what they lay their eggs on.

The adults focus on damaged trees for egg laying. So cut into the damage and look for football shaped exit holes about 3/8 to ½ inch long and ¼ inch wide under the damaged, sunburned bark. If this is the case, don’t prune so heavily next time and leave enough cover to prevent sunburn.

Ornamental or flowering plum leaves
with wind damage
Q. I put in a desert landscape with 2" of rock in the front yard with various bushes and 2 flowering plum trees. This probably was a mistake, as I read one of your articles which said that this type of tree is not suited for rock mulch. Anyway, my question is about watering the trees. I have a 28" diameter by 5" deep watering reservoir around each tree. There is a layer of bark mulch in the reservoir. Right now I water the trees twice a week filling the reservoir up twice at each watering.

This is purple leaf plum in a desert or rock landscape.
It will look good for about five years without much
attention. But after about five years it usually starts
with leaf scorch and may begin getting iron chlorosis
So far every summer around August some of the leaves partially dry out and turn brown. Is this caused by too much water or not enough? I water the bushes 3 times a week by drip system for 30 min per watering. They are all healthy and green. Also the bark on the trees are splitting in places and falling off. Do you think I will loose the trees at some point? Any advice will be greatly appreciated. I read all your colums in the RJ that you write. Lots of excellent advice there.

A. Flowering plums can handle the rock better because you aren’t really worried about a crop of fruit to eat. But the rock on top of the soil will aid in the depletion of organic matter and over time it will most likely turn the pinkish color that accompanies iron chlorosis in red leaved trees like the purple leaf plum. If not corrected that can lead to more of a decline in the tree opening it for dieback and insect/disease problems.

This is the purple leaf flowering plum when it has iron
chlorosis. Plants with green leaves will have their
leaves yellowing with green veins. In plants with purple
leaves the leaves will turn pink instead of yellow but
the veins will still be a darker color than the leaf blade
Bark mulch is not nearly as effective as plain old ugly mulch made from chipped landscape trees. Not many nutrients in bark, it decomposes slowly, and is all just about the same size so it doesn’t decompose as effectively as chipped wood mulch. Plus 28 inch diameter irrigation basin is not very big. As these trees get bigger they will need more water. Increase the basin to about six feet in diameter (three feet from the trunk) all the way around the tree and fill this basin which should be about three to four inches deep. Fill it twice with each irrigation.

Hard to say why the bark is splitting and falling off but I would pull the loose bark off and look for damage to the trunk such as holes for borers. The bark should be removed anyway of the trunk is dead under the bark and it is pulling away from the trunk. Often this type of situation turns into a long lingering death spiral for the tree over the next few years when it will decline more.

Fall Lawn Replacement in the Hot Desert

Upper surfaces of grass blades can help identify
which type of grass it is: L to R, Kentucky bluegrass,
perennial ryegrass and tall fescue
 Q. I need advice. We planted about 100 square feet of sod a couple of years ago. It had been doing quite well. I believe it was over fertilized 5-6 weeks back.. It is now very brown and not responding to watering. I plan on replacing it with new sod once it cools down. My question is, can I put the new sod over the old or pull out the old and re-prep the sub base? Any advice would be appreciated.

Sod removal using a sod cutter
A. You didn’t say what kind of sod it is but I am assuming it is tall fescue. Tall fescue represents about 98% of all lawn grasses in the Las Vegas area due to its tolerance, for a cool season grass, to our high summer temperatures. Before you do anything make sure it is dead. Tall fescue can appear dead but if you see any green at all at the base of the dead grass then it may just have died back.

Tall fescue is very drought resistant even though it uses a lot of water. It can dieback when water is not available and sit there for quite awhile appearing dead and then re-emerge from grass that looks dead and start growing again. This might take a couple of weeks of applying water after it turned brown. It might then be a bit sparse and you may have to seed into the grass again to get it to fill in those bare areas that didn’t make it.

Power rake, aka dethatcher aka verical mower used for
removing thatch, slicing stolons and improving
water penetration to turfgrass or lawn.
However, if it did turn brown due to a heavy fertilizer application then that is salt damage and tall fescue is not all that good in its tolerance to salt and then it is very probable you are right. You have two alternatives in replacing the sod. One is to rent a sod cutter and cut the old sod out leaving behind a ready made surface for resodding. Or you can try digging it out by hand and leveling the surface in preparation for the new sod. A lot of work. You will not be able to put new sod on top of the old sod. The old sod will leave an “interface” that will cause all sorts of problems for the new sod.

There is still yet another alternative worth considering. The dead grass is a perfect seedbed for seeding a new lawn. In about late September to mid October mow your dead lawn as short as you can and use your bag on the mower. Don’t mulch the dead grass back into the dead lawn. Next rent a power rake, sometimes called a dethatcher, and dethatch the dead lawn deep enough (you can adjust it) so that when you make a pass or two you can see soil between the dead grass blades. It is important to see bare soil throughout the dead lawn.

Patchy look to a lawn when a coarse textured grass is seeded
into a finer textured grass. An example would be seeding
K31 or Kentucky 31 tall fescue (a pasture grass) into bluegrass or
even a turf-type tall fescure with a finer texture
Purchase good quality tall fescue grass seed, 100% tall improved tall fescue and not Kentucky or K31 tall fescue, the cheap stuff. Apply a starter fertilizer such as 16-20-0 or any fertilizer high in the middle number(in this case 20) but having some of the first number (in this case 16). Seed at about 10 to 12 lbs of seed per 1000 square feet and topdress it with topdressing or steer manure with NO MORE than about 1/8 inch of topdressing. It is best to do this with a roller for applying this stuff. You can rent one from most rental places. Irrigate about three times a day for a few minutes each cycle. Irrigate long enough to wet the topdressing but not long enough to cause it to run off of slopes or puddle. Do this about 8 am, 1 pm and 6 pm. Your biggest challenge will be keeping the pigeons and other birds off of your seeding. Reduce your watering to once a day when you see grass emerging usually in 7 days or less.

A wild idea would be to not use tall fescue but a different grass seed that has high tolerance to heat in our area and a much softer feel to it. These are the heat tolerant perennial ryegrasses. They are superior to tall fescue in feel and water use but you have to get the right kind of perennial ryegrass. Some perennial ryegrasses are very heat tolerant and others are not at all and will burn up when it gets hot in the summer.

One of the best of the perennial ryegrasses is a combination of Palmer and Prelude perennial ryegrasses. It has been used on golf courses for nearly 30 years now here and does very well in the heat. You can mow it short as close as ½ inch or less (if you seed at the right rate for this kind of cut) or even up to two inches. It is soft to the touch, unlike tall fescue which has tiny hooks on the edges of the leaf blades that can cause “itchiness” some people think is an allergy which it is not. The problem is that it is only available in 50lb bags. This seed blend is available in Las Vegas from Helena Chemical Company but it will be pricey in that quantity. I could not find it on the internet in smaller quantities.