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Sunday, November 26, 2017

Pine Tree Recovery from the Heat

Q. I have fifteen-year-old, 20 to 30 foot pines on a half-acre. They suffered during the heat this past summer. After your advice, I am doubling the amount of water and hosing off the needles once a week. How long is the recovery time using vitamins? 
Too much water? Probably not. But they don't need it as often as a lawn does. When you look at the amount of water that pine trees need, the total amount of water is not far from what an efficient lawn would need. The difference is in frequency of application. Trees, this includes pine trees, should be watered much less often than a shallow rooted lawn.
A. I am not a big fan of applying vitamins like Super Thrive. Some people swear by them, It can be cheap insurance though if you're not sure. Your call on that one.
Who can argue with success? The research doesn't support it but the use of products like these (and other "me too" products) are not supported by research. However, some landscape professionals and homeowners disagree. In the long run, it's cheap insurance to use it.
            Washing the needles of pines is not necessary. It is true of Italian cypress because they tend to get spider mites. Pines do not.
            They might need more water than 15 gallons. Play that by ear by watching the new growth next spring and early summer. You should get at least 12 inches of new growth every year and not experience severe needle drop during the hot months. Those are indicators the tree is not getting enough water.
When you see this in a pine tree growing in the desert, it usually means a lack of water. The amount of water pine trees need is grossly underestimated by most homeowners and landscape professionals. They need a lot of water all at once but they don't need it that often.
            Once you find the right amount of water (minutes and gallons), keep it consistent through the year. The amount of water they are given should not change much throughout the year. It's like filling a gas tank. Instead, change how often they receive the water. Summer months water more often. Winter months, water less often.
One of the best ways to irrigate large trees is to "basin irrigate". This is a modification of an irrigation technique called "flooding". Rather than drip irrigation, a landscape bubbler (not a drip bubbler) is used to fill a flat basin. The basin around the tree, doughnut if you will or moat, must be flat! This basin is increased in size every few years to accommodate a larger tree. The bubbler emits water at one or 2 gallons per minute. The basin is full in 10 to 15 minutes.
            As plants get bigger, they require more applied water, not watering more often. Watering frequently with small amounts of water produces shallow roots and trees that blow over in strong winds.
            You should see an improvement in the first half of next year. Nothing this year.

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