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Don’t Panic, It’s Organic: How and when to water trees

Andy Lopez, Contributing Columnist/Invisible Gardener
8:40 am PDT March 15, 2017

Trees naturally take care of themselves. They have a deep root system that actively looks for sources of water and minerals. Look at the trees in nature, and you will see how they manage to survive months and sometimes even years without any apparent source of water. Trees have deep roots that go down four times as deep as the tree is tall!

After a good rain, your trees will not need to get any water from you for at least a month and, in many cases, a few months can go by before you should turn on their drip. 

Your trees will need three drip heads each, at two gallons per hour. They should be placed 3 or 4 feet away from the trunk; the best spot is midway out to the drip line, with space evenly around the tree. Tree vents, clay drain pipes or as we call them here in Malibu, wine bottle holders, are buried 1-3 feet down. They get a green grate cover which fits into the tree vents which you then attach to the drip head.

You should set your drips to water your trees for one hour once a month at most during hot times. The amount of time depends on your soil and its ability to hold water. This is the training part since you are also training your soil to hold more water. Your soil’s ability to hold water depends on how alive it is. Your soil has living microorganisms, and if they are not present, your soil will not be functioning, and it will not have the proper organic matter and bacteria that is needed for trees to be able to hold more water. 

Your tree’s root system (and the whole tree itself) also holds a great deal of water in storage for later use. By watering them only as they need it, you are encouraging the trees to develop deep root systems, needing very little water from you. Conditions caused by recent rains show how bad it is to water your trees several times a week, and not very deeply. The tree’s roots will stay close to the surface with very few roots going down deep. When the wind and rain comes, the trees with shallow roots fall over because they have nothing to hold on to.

By placing four tree vents midway between the trunk and drip line, and by placing a drip head to allow slow watering deep into the soil, you allow the trees to keep deep root systems.

Feeding your trees organically will ensure that they are healthy and disease and pest free. Thus, an important part of feeding your trees and indeed your entire property is to provide rock dust, compost and a nice acid mulch several times per year. Never place anything directly up against the bark, try at least 2 feet out and about 10 feet past the drip line. I also suggest vertical composting. Place tree vents about 10 feet out from the tree about 3 feet down. 

Place the drip head on top and water deeply once a month. Replace the mixture once or twice per year. What you are doing with the tree vents is establishing a micrological colony. It is this colony that helps the root system grow and establishes a connection with the mycelium that lives beneath the soil.

The mycelium is constantly under attack by human pollution and weird ways of living. The farmers, homeowners and gardeners are constantly destroying the topsoil, realizing CO2 and damaging the soil’s ability to capture CO2 and hold it.

This year, temperatures will be higher than ever before here in Malibu, and I suppose many other places will be having the same problem. You must protect your soil and thus your trees from this heat. Mulching will help, but you need to start a native ground cover. The ground cover will naturally keep the temperatures down and keep the soil from baking and becoming hard. 

Planting natives will also help. There are many natural ground covers that will love Malibu’s mellow climate but will not be too crazy about high temperatures, so they will die off during the summer months but will do fine the rest of the time.

A good ground cover that has deep roots and doesn’t mind the high heat is called Kurapia; it is available locally as ready-to-plant sod. It requires very little watering other than at first to get it established. It is excellent for tree root protection, as well as for lawn replacement and slope cover.

If you want to see how well your trees are doing, get a refractometer and do a reading on the leaves. A high Brix reading is what you want. Remember trees with high Brix readings will not get attacked by pests and will not be getting diseases. It also shows you that the tree in question is either doing fine or needs help. 

Many folks have been overwatering their trees as it gets hotter, thinking that water is all it needs. This is not the case. Remember, city water is full of chemicals which destroy the microbial life in the soil and damage the tree’s root systems and in turn damages the tree. Whenever mineral intake is reduced, then the plants get stressed and the pests and diseases come. Never fertilize your trees with a chemical fertilizer. Never damage the trunk of the tree, as it will stop the flow of nutrients to the tree.

Any questions? Email me at andylopez@invisiblegardener.com.