Improper planting of a tree or shrub is the number one reason they die! Improper watering, and improper mulching are close seconds and thirds! Today, along with providing you a link to our Fall Tree and Shrub Planting Guide, we’re going to explain why planting a tree and shrub at the correct depth and width is so important (plus we’ll give you a few other helpful tips).

How Deep to Dig a Hole when Planting a Tree

When you planting a tree, dig a hole only as deep as the rootball of your tree. The top of the rootball should be level with the surrounding soil when the tree is placed into the hole. 

Here’s the reason: A tree will settle into the soil over the years. The deeper you dig, the looser the soil is in the hole. The looser the soil, the more a tree gets settled down into the soil. The deeper a tree settles into the soil, the more likely it’s root collar will get buried. When a tree’s root collar gets buried, roots struggle to get adequate oxygen. When the roots don’t get oxygen, the entire tree starts to struggle, and the struggle can end in death. Follow? So basically, you should plant your tree at the exact same depth it has been growing in the container.

Using a level or straight board like the one pictured can help make sure your rootball of your newly planted tree is level with the surrounding soil

How Wide to Dig a Hole when Planting a Tree

When planting a tree, plan on digging a hole at least twice the width of the tree’s rootball.

Here’s the reason: Contrary to what you may think, most tree roots run more horizontal than vertical and they are somewhat shallow as opposed to deep. As a matter of fact, about 80% of a tree’s root system lies within the top 18 inches of soil. So by digging a hole twice as wide when planting a tree, you loosen the soil in the area that the roots will be growing into, allowing for faster and easier access to get established.

Mulching and Watering Newly Planted Trees

As mentioned at the beginning of the blog, planting a tree improperly is the number one cause of tree death, but mulching improperly and watering improperly are number 2 and 3. So here are a few extra tips to remember this fall when planting a tree.

1. Mulching. While mulching your newly planted tree is highly recommend, you should NEVER place mulch up against the trunk of a tree. Apply your mulch around your tree in a doughnut shaped berm rather than up against the tree in a volcano form. This mulch berm will also help with watering your newly planted tree correctly. 

Mulch piled up against the side of the trunk can:

  • cause moisture to get trapped against the trunk. The tissue of a trunk is not designed to be exposed to constant moisture. This could result in root rot and the possible demise of the entire tree.
  • cause secondary roots to grow upwards where they can get damaged by sun, frost, and even start to strangle your tree, again, ending in your tree’s demise.

See the doughnut shape here with the mulch? No volcanoes! In this picture, you can see how the berm can easily be filled with water for a good root soak.

2. Watering. Newly planted trees will definitely need regular watering to get established. Lucky for us, planting trees in fall (the best time to plant in San Antonio) offers more chances of natural water from rainfall along with less evaporation due to cooler temperatures.

  • Plan to water your newly planted tree once a week with a slow, trickling flow of water for about an hour. Adjust this schedule around weather: less water when adequate rain is available, and more water during times of extended drought.
  • The doughnut-shaped mulch berm allows for easy, deep, efficient watering without losing water to runoff.

For our full tree and shrub planting guide with illustration, see the link.

~The Happy Gardener, Lisa Mulroy