Question from Peter: We just bought an older house in Poway. There are two beautiful mature olive trees in the front. Unfortunately, one has destroyed the driveway with its roots, and we need to completely replace the driveway.
First, I wanted to cut the tree down. But now that i know it is an olive tree, I would like to keep it, if possible. I was wondering how I can prevent the roots from invading the driveway again. For example, I was thinking about digging a trench and filling it up with concrete to create a barrier. Would this work? And how deep should the trench be? Any other suggestions?
Answer from Pat: You are wise not to cut down a mature olive tree. Once an olive tree has reached an advanced age it is valuable for its beauty, drought-resistance, Mediterranean atmosphere, and historic resonance. Olive trees in California date back to Mission days. Olive trees are also highly sought after now since they fit in with current styles and environmental ideals. You would have to pay a pretty penny to purchase another one. If you wanted to get rid of it, it would be far better to sell it than to cut it down.
Now that you realize your olive tree’s true worth, the wise course would be to keep it and design your garden around it to take full advantage of its value, beauty, and the romantic Mediterranean atmosphere it can lend to your front garden. One solution immediately occurs to mind. You could dig it up and move it further away from the drive. Fortunately olive trees can be readily transplanted and seldom die in the process. You will need an expert horticulturist to do the job, and the best time for transplanting is fall. Start by digging a new hole and testing the drainage as described in the box on page 40 of my organic book. If drainage is inadequate, choose another location.
Basically the system is to prune the tree artistically to shape it and reduce its amount of top growth, then trench around the roots preserving as much of the root ball as possible. Keep the rootball damp, cover it with tarpaulin or burlap to hold it together and tie with ropes. (Don’t let it dry out.) Next, dig under the roots, slide the tarp or canvas under the root ball and tie securely. Then use a rented crane to move the tree into the new hole. Remove the ropes and canvas and position the tree properly before refilling the hole. I would also drench the roots with rooting compound before covering them with earth. (This worked for me when transplanting a tree in my garden.) Refill the hole. Water thoroughly and deeply every day for three days. Then water three times a week, and then once a week and gradually taper off. Additionally I would treat the ground with humic acid which is an amazingly effective transplanting fluid and stimulates rooting.
The other solution is to leave the tree where it is and protect the drive as you have suggested by installing a root barrier. First dig through the drive and cut off the roots that are destroying it. I have often done this with pine roots in my drive. These are just shallow roots, and in the case of my mature old pine trees, cutting off these roots directly under the surface of the drive never harmed the trees.
Once you have gotten rid of the surface roots under the drive, you will need to dig a narrow trench which should be 30 inches deep. Line the side of the trench next to the drive with a professional root barrier then refill the trench. Professional root barriers work better than poured concrete which can crack and then you would be back at square one. Professional root barriers are made of various substances. The best is stainless steel. I have a stainless steel root barrier buried in the bottom of my own garden to keep out plumbago. It is 30 feet long and 2 1/2 feet wide and came in a roll. A friend who is a professional horticulturist installed it for me and it is just about indestructible. It has been there many years and has done a good job. To make one like it simply purchase a roll of stainless steel sheet metal of the width and length you need. Other materials for root barriers are rubber, plastic, fiberglass, and various metals. Berkey Supply online carries several types of professional root barriers. After cutting the roots of the olive tree and installing the root barrier, treat the remaining roots on that side of the tree with humic acid to stimulate growth of feeder roots and maintain the branches on that side of the tree. Cutting the roots under the drive and those on the edge of the drive should not harm the tree as long as you continue to care for it properly.
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I read your response to Peter from Poway concerning the olive tree roots that were destroying his front driveway. We have a 50 year-old olive tree in the backyard of our home in Claremont. It’s well-established, and beautiful. But, it was planted, apparently, too close to the cement block wall dividing our property from the neighbors in back, and the roots appear to be damaging the wall. My husband is planning to take it out, but when I read your comments, I wondered if you might have some direction as to how to find a possible buyer, rather than just chopping it down. I really hate to lose this tree, but the thought of just chopping it down is even worse. Any ideas? Are there people who would purchase a tree like that, and if so, how does one go about finding them? It seems it would be very difficult to access the tree from its location in the backyard. You’ve given me hope that there might be a way to save the tree. I’ll look forward to your response. Thank you so much!
We are growing olive trees in the Warner Springs area of San Diego County. We have decomposed granite soil and have some hot days in summer 100 degrees or so and occasionally some snow in winter. We only have about 12 trees right now and unfortunately don’t know the names of the ones we have. We want to plant more trees on about an acre. Can you give us the names of some that might grow well up here? We like to cure some olives and use the rest for olive oil. Thank you
In my opinion you could probably plant and grow ‘Mission’ olive trees in Warner Springs and they would survive. ‘Mission’ is a Mexican variety. It is self-fertile (does not need pollinator) and it is the best-known commercial variety in California, good for all purposes—pickling, fruit (black or green) or oil. However, there is always the slight possibility that one winter might be cold enough to harm your crop even if it did not harm the trees. I doubt it would kill them. The variety ‘Arbequina’ is reputed to be hardier than Mission. The meaning of the word “hardy” in respect to a plant means it’s more able to withstand cold temperatures. ‘Arbequina’ is also self-fertile and it bears small rounded fruit good for table fruit or oil.
There are fancier Spanish and Tuscan varieties you could grow that are hardier than ‘Mission’. The hardiest varieties grown in California are ‘Frantoio’, ‘Maurino’, ‘Leccino’, ‘Arbequina’, ‘Pendolino’, and ‘Coratina’. ‘Ascolano’ is the hardiest of olive varieties grown in Tuscany for olive oil, but the fruit can’t be cured for bottling. The fruit is very large, which is great, but it bruises and doesn’t turn black when ripe, and it needs a pollinator. (‘Frantoio’, ‘Leccino’, and ‘Pendolino’ are recommended as pollinators for ‘Ascolano’.) Two other varieties have been found resistant to cold in Southern California and these are ‘Barouni’ and ‘Sevilliano’, but if I were you I would choose between ‘Frantoio’, ‘Maurino’, ‘Leccino’, ‘Arbequina’, ‘Pendolino’, and ‘Coratina’ . Perhaps choose more than one and enjoy having a variety of types and characteristics. The size of the fruit varies and the oils also taste different from one another.
Hi. I have apple and orange trees, and a apple bonsai tree. I am planning to have 150 olive trees. Need help to decide which one…..
Please give me more information. I cannot suggest the best olive tree for you without knowing where you live and for what purpose you wish to grow 150 olive trees. If you want them as a screen or hedge, you should plant a largely fruitless variety, such as ‘Bonita’, ‘Little Ollie’, ‘Skylark Dwarf’, or the larger ‘Magestic Beauty’ or ‘Wilsoni’. If you want the trees for ornamental purposes, then go to look at the specimens instead of choosing by variety. ‘Swan Hill’ makes less pollen.
If you want these trees in order to grow commercial olives as a crop for oil or fruit your choices come down to four or five. ‘Frantoio’ is the variety grown in Tuscany for oil but may prove more difficult to grow here and need more care and hates fog. These trees need a pollinator which should be ‘Pendolino’, ‘Morino’. or ‘Peccino’. ‘Barouni’ takes high temperatures, ‘Picholine’ has small fruit, gourmet Greek type, ‘Rubra’ also has smaller fruit, black when ripe. ‘Manzanillo’ is more spreading and is good for pickling or oil, fruit is purplish and ripens early, does well in frost-free areas, ‘Sevillano’ has a shape more like an oak, ‘Ascolona’ has large fruit with a small pit. ‘Mission’ is taller and may prove more difficult to knock off all the fruit so you harvest all the olives.
If I were raising for fruit fro pickling or oil and living in Sunset Zone 22 or 23 I would probably choose ‘Manzanillo’. If for fruit only perhaps ‘Ascolona’ but fruit bruises easily which makes it harder to handle.
I have a tree grown close to the wall of my house I dnt want it to cut down but I’m ofraid that roots or get thick and start raise the house
When a tree is too close to the foundations of a house, the best thing to do is cut it down. Yes, the roots are likely to get too thick and could very likely damage the foundations of the house or get into pipes. Plant another tree further away from the house and with good care it can grow much quicker than we imagine in advance.
In one case I do know of a large Monterey Cypress tree that stands on a bank and the trunk of this large tree is about three feet from the southwest corner of a house. In this case, a drainage ditch had been dug about forty years ago surrounding the house, a bank behind the house was covered with concrete, and drainage pipes had been installed by professionals, then next to the foundations of the house the area above the drainage pipe was filled with concrete and sloped like a gutter. As a result of this extensive and very expensive drainage work, done at least forty years ago, no rainfall could sink into the ground at that spot, thus no tree roots invaded it. The tree is now very large—over fifty years old, and the trunk slopes away from the house. It has never damaged the foundations of the house, but this is an unusual case and the drainage job was done early in the life of the tree. In most cases the best solution is to bite the bullet, cut the tree down and plant another in a better location. Trees that are too close to homes with branches extending over roofs also present a fire hazard.
Thank you so very much for your detailed reply. I very much appreciate it, and I think the tree would, too. Do you know a local source for the stainless steel root barrier? I found one at http://www.bamboogarden.com/barrier.htm.
Also, do I need a horticulturalist to prune back the tree before I cut the root? Can you recommend one?
I am sorry I cannot recommend tree people or horticulturists, but I can tell you that olive trees tolerate heavy pruning. The main thing is to take out any dead growth, remove any twiggy growth or suckers emerging low on the tree, and prune existing growth by cutting back the foliage and twigs to create compact rounded clumps at the upper ends of the main structural trunks and branches.
Looking at photographs of olive trees in magazines and in books at a big bookstore to get an idea for the shape to aim for, mainly a series of clumps of well-shaped foliage surrounding the upper ends of the larger trunks and branches. But don’t go as formal as the bonsai style olive trees advertised online. If you hire a reputable tree company complete with an arborist and then stay there to watch, you should end up with a pleasing job. Local botanical gardens and horticultural societies can be good sources on information of companies to do such jobs. Whoever you hire, tell them not to “lace out” the tree. It’s fine to let air and light through but “lacing out” is the wrong approach with olive trees. A company such as Heritage Olive Trees, might be able to give you additional advice.
Regarding stainless steel sheets, any local sheet-metal company should be able to help you obtain what you need. As you suggested, bamboo growers are always a good source of information on root barriers.