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Monday - May 20, 2013

From: San Antonio, TX
Region: Southwest
Topic: Planting, Trees
Title: Rock under space for Bigtooth Maple in San Antonio
Answered by: Barbara Medford


I just got a 10 gallon Bigtooth Maple in Medina TX for my home outside loop 1604 in San Antonio. I hit rock about 7 inches in when trying to plant it..I am entertaining the idea for a raised bed to level the last 6 or so inches. Is this even with it or is it a lost cause?


Okay, we have more than one problem here. The first one is that you will be planting in what is quickly becoming very hot weather. We ordinarily recommend that in Texas and other hot areas woody plants, that is, trees and shrubs, be planted in November to January. So, whatever you do, that baby needs to get into the ground quickly. Here are the growing conditions for Acer grandidentatum (Bigtooth maple) from our webpage on the plant.

"Growing Conditions

Water Use: Medium
Light Requirement: Sun
Soil Moisture: Moist
CaCO3 Tolerance: None
Cold Tolerant: yes
Heat Tolerant: yes
Soil Description: Moist soils, Limestone-based, Sandy, Sandy Loam, Medium Loam, Clay Loam, Clay, Calcareous."

"Limestone-based" means alkaline soil that has developed from limestone, not a solid chunk of limestone. We did considerable research on the type of roots maples have and one of the outstanding points is that the roots are far-reaching and shallow. In fact, maples are often not recommended because those roots come to the surface, heave up sidewalks and punch holes in basement walls. Frankly, in maple tree vs. chunk of rock, we're betting on the maple.

Ordinarily, we would not have suggested you plant a tree in such shallow soil, but since you already have the tree, we think you should dig as deep and wide a hole as is practical, preferably away from pavement, foundations, patios, etc. We assume that the root is still in the pot in dirt. Put the tree root over the rock and kind of let it spread out. Refill the hole with a mix of native soil and compost to give the little hair-like rootlets something from which they can access nutrients and water. We are not confident that such a shallow hole is going to stabilize the tree until it gets some of those roots out, so you should probably stake it.

Remember from the Growing Conditions, this plant likes moist soil, which you probably don't have in Bexar County. As soon as the tree is in the hole and staked, stick a hose down in the soil loosened by the addition of compost, and let the water just drip until the surface is wet. Do that 2 or 3 times a week until cooler weather or more rain.

The tree could still die of transplant shock because you are planting it in hot weather or because too much root damage has been done getting it into the hole, but at least you will give it a fighting chance.


From the Image Gallery

Bigtooth maple
Acer grandidentatum

Bigtooth maple
Acer grandidentatum

Bigtooth maple
Acer grandidentatum

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