Too Deep in Love: Two Common Killers of Freshly Planted Trees
Trees are the cornerstones of our landscapes. No other kind of plant impacts the local ecosystem as broadly and effectively as trees; they create shady, cool microclimates, provide erosion control with their expansive roots, and supply habitat and food for many creatures. Planting trees is not difficult, but with their slow growth and considerable price, it pays to get it right the first time. Here are two common problems we see with freshly planted trees at Rick’s Nursery.
The most common and fatal error in planting trees is burying the root ball too deep. It only takes a few inches of soil on top of the root ball to smother it. When you plant your tree, take it out of the pot, then lightly brush off the loose soil on top-assume that the tree was never planted at the correct depth in the pot by the nursery that grew it. Then, after you finish planting the tree, you should still be able to see the top of the potting soil. In areas of poor soil drainage, it may be appropriate to leave the “shoulders” of the root ball as much as 2 inches above grade. Top with mulch to prevent the surface roots from drying out, but be careful not to contact the trunk. It will look wildly incorrect when created for the first time, but it is essential to the plant’s health. When you plant too deep, you starve the roots of oxygen, and the tree is prone to dying within the first 2-7 years of planting. Once you start observing trees, you may even begin to notice mature ones that are planted too deeply; trees should never look like a telephone pole sticking out of the ground, there should always be a distinct root flare. If you have already planted your tree too deep, you can carefully excavate by hand around the root flare to expose it. You can even mitigate too-deep planting in mature trees, though care should be taken not to damage roots. Just carefully remove the soil until you find the root flare, then mulch.
Our soil in most parts of Colorado is notoriously poor. Whether you have sand, clay, or just decomposed granite on bedrock, amending your soil with organic matter can solve several soil problems. We often forget, however, that in life and gardening, moderation is key. When you amend the backfill of your planting hole, you should use a maximum ratio of 1 part compost to 4 parts native soil. When you amend by more than 20% organic matter, you risk “containerising the hole.” This happens when you over-prepare the backfill of your planting hole; the roots of your tree are content with the fluffy, rich soil, and never establish outside the new hole. This creates circling roots and other problems associated with container trees, thus “containerising the hole.” Trees whose soil is over-amended are more prone to overwatering because the soil holds on to excess moisture. Trees may also begin to sink and list to one side as the extra compost decomposes and shrinks in volume, especially when the compost is dug under the root ball. Thus, the bottom of your planting hole should always be firm, unamended soil. Fresh compost should never contact the roots directly and should be mixed thoroughly into the backfill soil. Depending on what kind of tree, and the soil condition, it might be wisest to skip amendment altogether, and just let the wood mulch on top do the soil work. Generally, though, just a dab of compost will do the trick. Ultimately, we gardeners see soil amendment as an act of caring; just make sure not to love your tree to death.
Nothing makes us happier at Rick’s Garden Center than seeing your nursery plants thrive. For more information on planting, see our Tree and Shrub Planting Guide, available on our website. Happy planting!
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