When I was working with homeowners over the decades, one of the most difficult things to figure out was why two trees out of a group of eight would die after transplant while the other six looked just fine. It would be highly unusual for 5 year old pines to die of disease or insect problems. Usually within the first several years after transplanting, trees that die have not been able to re-establish their root systems at the new site. The most common cause for this is under-watering…however, over-watering can also be the problem.

The roots of plants need to have oxygen around them in order to grow and thrive. When there is poor drainage (common in clay soil) or over-application of water, the roots are totally surrounded by water and the oxygen is lacking. This will cause two things. First, the roots will just not expand and move out into the soil adjacent to the planting hole. Second, root rot fungi may get started and kill roots.

If roots are inhibited from growing or lost due to rot, the top part of the plant must suffer. Plants must have a balance between the amount of roots and the amount of foliage. So, if the roots are killed or don’t grow, the foliage must also pull back proportionally because there will not be enough water to support needles or leaves. Twigs will die, needles will turn brown from top to bottom and there will be an overall unhealthy look to the plant. In extreme cases, the whole plant will die.

Although over watering can cause this problem, sometimes the condition of the tree’s root system at the time of transplant may be the cause. Circling roots, damaged root systems and miss-handling of the root ball at the time of planting can set a tree back and some of them will never recover from it. Including large amounts of granular fertilizer or fresh manures in the transplant hole can cause the roots to “burn” (rapid dehydration as the water moves out of the roots and into the salts in the fertilizer or manure).

Hope this gives you some ideas about what may have caused your problem. Unfortunately, figuring out what to do about it is more difficult. If you think you may be over-watering, dig a small hole about the depth of the root ball of the trees and fill it with water. It should drain away over night if your drainage is good. If it doesn’t, you may need to adjust your irrigation system to provide smaller amounts of water so that any excess drains away in between watering.

Good luck,
Mr PGC