Drought- Supplemental Watering for Mature Trees

Replies to This Discussion

Permalink Reply by John Hanika on July 19, 2012 at 10:51am

Because the soil is so dry even at 4' depths, we have been telling customers on trees planted in the last few years to double or triple the amount of water they are applying. Suggest 10 to 15 gallons at the trunk on new trees. We are finding the surrounding soil is stealing a considerable amount of the moisture away from the root ball.

Key to successful watering on recently transplanted trees is to apply it as slow as possible to get a thorough drench on the root ball where most of the roots lie on a transplanted tree.

Permalink Reply by Laura Wagner on July 20, 2012 at 9:59am

 Hi John - What frequency are you recommending watering? Could you do a blog post about your recommendations?

John Hanika said:

Because the soil is so dry even at 4' depths, we have been telling customers on trees planted in the last few years to double or triple the amount of water they are applying. Suggest 10 to 15 gallons at the trunk on new trees. We are finding the surrounding soil is stealing a considerable amount of the moisture away from the root ball.

Key to successful watering on recently transplanted trees is to apply it as slow as possible to get a thorough drench on the root ball where most of the roots lie on a transplanted tree.

Permalink Reply by John Hanika on July 27, 2012 at 11:31am

There are a few variables in deciding the frequency because you can also drown a tree, particularly conifers.

First, don't get mislead by looking or feeling the soil around the tree. The top soil may well be saturated but the soil moisture down 6-24 inches is what counts. We have people with lawn sprinkler systems tell us 'we water every day'. What they don't realize is the moisture is only going down about 6 inches. That is why the system is called a 'lawn sprinkler', great for grass but never satisfies a tree.

Second, Emma's suggestion on frequency was on the mark. Under normal conditions, a through watering weekly is the routine if mother nature does not supply it. In drought conditions watering twice a week would be sufficient, in general, if you water properly (slow,slow,slow). Here we look specifically at species. A maple would be happy with twice a week, A Birch might be left thirsty under these conditions and 3 or 4 times might be appropriate. A conifer doesn't like wet feet, so watering twice a week might be too often and watering every 5-7 days would be our recommendation. So you need to look at the species of the tree and it's water requirements in order to make minor adjustments.

Third, wind is a very important variable. As we all probably know, trees loose water through their leaves. This is called transpiration. In May of this year we did not have 100 degree temperatures but we had strong hot winds that caused a tremendous amount of water loss in the trees. The temperatures were in the 80's but the wind did the damage as the trees could not replace lost water fast enough. This is when leaf scorch occurred and some trees went into shock. Wasn't all that hot but the wind did a number on a lot of trees throughout Iowa.

Worst situation occurred the last few days when we had 100 degrees and gusty winds. I have noticed mature trees that are now dead due to the heat, drought and winds. These conditions forces us to increase even further the amount and frequency of the 20,000 trees we have to water here at the farm.

Another trick you can use to reduce transpiration is spray the foiliage with Wilt Pruf. We have done this on many trees here at the nursery. We also spray trees that are going to be transported. This is normally a once a season application but if a lot of new growth is occurring we may repeat it. Good for both deciduous and conifers as well as shrubs.

Fourth is humidity. Usually never a problem here in Iowa with all the corn but this is an issue this year. The last several days have seen humidity in 20% level. Don't know if our equipment was off but we had a heat index 2 points lower than the temperature. Not sure that is possible. But low humidity levels determine an increase frequency in watering.

One final comment. Many older and mature trees, particularly trees that have been in place 5- 25 years, are struggling also. We have mad recommendations to customers to water very heavily using a lawn sprinkler over the entire area from the trunk to 10-15' outside of the drip line. Once every couple weeks as long as drought conditions remain. Let that sprinkler run for several hours or overnight.

Good luck, hope this helps and no apparent end in sight.

Laura Wagner said:

 Hi John - What frequency are you recommending watering? Could you do a blog post about your recommendations?

John Hanika said:

Because the soil is so dry even at 4' depths, we have been telling customers on trees planted in the last few years to double or triple the amount of water they are applying. Suggest 10 to 15 gallons at the trunk on new trees. We are finding the surrounding soil is stealing a considerable amount of the moisture away from the root ball.

Key to successful watering on recently transplanted trees is to apply it as slow as possible to get a thorough drench on the root ball where most of the roots lie on a transplanted tree.

Permalink Reply by Jim Mitchell on August 16, 2012 at 3:04pm

Thanks for the great information I will definately pass this along! This is certainly a "hot" topic here in MO, at least people are asking questions and paying attention. One thing I have to stress on newly planted stock(1-4yrs) is don't love it to death. We are blessed with some wonderful clay soil and in the newer developments I'm not sure if you can even classify it as clay soil. Overwatering is a problem, irrigation systems are the scurge.... trying to explain this, is at the very least challenging