Dying of Thirst

July 20, 2011

What killed your shrub or tree?

Nursery people and landscapers are hearing it every day.  "This tree (or shrub) died.  What disease or insect got it?"  Some ask, "What can you do for me?"  Many still ask, "What can I spray?"  Often they do not want to hear the truth:  The cultural or site conditions--your care--is what kills 95 percent of plants.

They Were Thirsty

Most of the time when a tree or shrub dies within two or three years since planting, it has nothing to do with a disease or insect (even if you see an insect, it's usually secondary or incidental).  Usually the problem is all about the water and soil.  Usually the roots dried up before the plant could get established.  Woody plants start out with small root systems.  Balled-and-burlapped specimens may have had 95 percent of the roots cut off before getting to your house!  It takes a steady contact with good, moist soil, for those little root hairs to start taking in water.  The shrub might need 5 to 10 gallons of water per week.  Did it really get it?

We will see a lot more dead plants after weeks of extreme dryness like recent ones.  If you planted a tree or shrub this spring, you need to have watered it deeply twice a week if there wasn't rain.  And mostly, there wasn't!  If you planted it last season, there were several dry periods when the roots might have dried up.  Even in winter, conifers and broad-leaved evergreens (like Rhododendrons), continue to lose moisture through the leaves.  The frozen roots can't take up water to replace it.  The plant slowly dies.

Smarter Watering

Water deeply if you water at all.  It takes longer than you'd think.  Check with a shovel to see if you got the soil wet 15 inches down.  You might have to lay the hose down for an hour or longer, over a root area or stand there with the water wand pointed downward while you sing the entire Hallelujah Chorus (to each plant!).  Or use a dripper hose or sprayer for hours.  Shallow daily watering just trains tree roots to remain at the soil surface (too much daily water and poor drainage kills too).  If there is no rain for a week, water anything planted during the last two years twice that week, deeply.  If plants have been established longer, they can wait longer--but if there is no rain for two weeks, get going.  Irrigation systems, a dripper or soaker hose, are more efficient than sprinklers (that lose lots to the air).  Morning watering is better than in the heat of the day when it evaporates faster.  Evening watering encourages fungus diseases and slugs.  If you put lots of compost in the soil when you plant, the soil will hold more water.  Finally, mulch the soil surface (up to three inches, not touching trunks) to keep moisture in.

You Are Human

It's human nature to want to believe it isn't our fault when a plant dies, and it's hard to believe how much water it takes to get to those plant roots--when we can't see them.  But believe it:  most of the plants are dying of thirst!