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Saturday - February 07, 2009

From: San Diego, CA
Region: California
Topic: Trees
Title: Tree that will not interfere with hardscape in San Diego
Answered by: Barbara Medford

QUESTION:

I am looking for a small tap root tree that will reach max height of 20-25 ft. The area is only about 4 to 6 ft. to the house slab or driveway which I need to be very careful so it doesn't crack the driveway or house slab or get into the sewer or water pipes. Tree must be for San Diego, CA area. Be able to handle water has it will be hit by 2 yard sprinklers. Prefer green year round with no berries or flowers as I don't want the mess. Any suggestions will greatly be appreciated.

ANSWER:

That would be a find for gardeners everywhere, a tree that can be planted close to the house slab, driveway and sewer lines without roots ever interfering with those items. Unfortunately, it doesn't exist. "Taproot" is really a misnomer, because any tree is going to spread some roots out, most of them 3 to 6" below the surface, because that is where the water and nutrition are. They also need those roots for balance. In a high wind, a true taproot tree would be top-heavy and highly vulnerable to being blown down. And, we don't know how to tell you this, but almost all plants except ferns are going to have some kind of blooms and seeds (berries), because all plants are programmed to reproduce; the blooms and seeds are their reproductive process. Here is some of the research we did, hoping to find a fit for your requirements. 

Iowa State University Forestry Extension Tree Roots. According to this website, taproot trees include hickory, walnut, butternut, white oak and hornbeam, with only Juglans californica (Southern California walnut) being native to California. All of these tend to be much larger than you are looking for, and all are nut or acorn trees, which means lots of mess, year round. Trees that do develop a taproot must be planted when they are very young, as damage to the taproot can mean death to the tree.

From Florida Plants Online Dispelling Misperceptions About Trees:

"Most trees do not have taproots. In sandy, well-drained soils some trees such as oaks and pines develop deep roots directly beneath the trunk. These are commonly called taproots. Many trees never develop tap roots. When the water table is close to the surface or when the soil is compacted, taproots do not develop."

"Taproots generally do not form on trees planted in our urban landscapes. Roots grow far beyond the edge of the branches. Frequently, roots extend from the trunk as far as the tree is tall. Roots and shrubs planted in a landscape grow to 3 times the branch spread within 2 to 3 years after planting."

You might even consider a bed of blooming plants for this area, as they will have shorter roots, or perhaps some tall native grasses. You can use the same Recommended Species section and put "Herbs" (herbaceous flowering plants) or "Grasses/Grass-like Plants" under Habit. 

What we will try to do is find an evergreen shrub, probably not as tall as you are thinking, that will have less extensive roots and still provide some color to the landscape. The water from the sprinklers could also be problematic, as it might cause molds or fungi to attack the plant. We will go to our Recommended Species section, click on Southern California on the map, NARROW YOUR SEARCH by selecting on "Shrub" under Habit. Since we don't know if you have sun or shade, we will leave you to do the same thing and make other selections appropriate to your situation. If you find something that you feel will work for you, but have difficulty locating it, go to our Native Plant Suppliers section, type in your town and state in the "Enter Search Location" and you will get a list of native plant nurseries, seed companies and landscape and environmental consultants in your general area.

Ceanothus velutinus (snowbrush ceanothus) 

Cocculus diversifolius (snailseed)

Cercocarpus montanus var. minutiflorus (smooth mountain mahogany) - pictures

Dasiphora fruticosa ssp. floribunda (shrubby cinquefoil)


Ceanothus velutinus

Comarostaphylis diversifolia

Dasiphora fruticosa ssp. floribunda

 

 

 

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