Olive Tree Care
Planting a Tree of 15-gallons or Less
Olive trees prefer well-drained soil in a location with full-sun. When planting an orchard, assemble all other needed materials first; the trees are the last ingredient.
If you are preparing a new site for a full-scale orchard, it is helpful to make an initial soil test. Once you understand the nutrient composition in your soil, you can tailor your fertilization program to your soil. When you submit your soil sample, indicate that you intend to plant olive trees so that the results can be generated for this crop. Olive trees prefer soil in the neutral range (5.5 – 7.5 pH); the soil does not need to be Class 1 agricultural land for the olive trees to thrive. If the field has previously been planted to a crop in the nightshade family, it is a good idea to test for verticillium levels in the soil. If verticillium levels are high, refer to the UC Davis IPM website for suggestions on soil treatment to avoid infecting your newly-planted orchard.
If you intend to rip or disk the soil first, do so before you lay out the orchard. Otherwise, simply auger individual holes for each tree, leaving the resident ground cover intact (the auger should be at least a few inches wider in diameter than the tree’s pot). If you auger holes into soil with a significant clay component, disturb the sides of the holes to avoid shellacking (which makes the walls difficult for the root tips to breach). Watch for low spots in your orchard where water may linger late in the season. Vernal pools, seasonal creek beds and slopes with significant runoff should not be planted with olive trees.
The density of your spacing will depend upon your intended method of harvest and other cultural activities. At McEvoy Ranch, our most successful orchards are planted 15' x 17' (15 feet between the trees, 17 between the rows); this spacing allows the trees sufficient space for mature growth while still permitting access down the rows by tractors. It is often preferable to triangulate the trees from row to row to give each tree the greatest diameter possible in which to grow. In terms of orientation, the slope of the land should be your primary consideration, but if all else is the same (for example, if your land is perfectly flat), north/south running rows are ideal for maximum sun exposure. If you are planting a few trees in your garden, a good rule of thumb is not to plant any closer together than 12 feet, unless you are planting a compact varietal (Arbequina, Koroneiki, Maurino) or want to plant a hedge. Olive trees planted into hedges can be placed at 5-foot spacing. This chart calculates total trees per acre according to your preferred spacing.
An irrigation system is extremely useful when establishing an olive orchard in the western United States. Drip irrigation is particularly well-suited for olive production; ½- inch or ¾-inch lines work very well and can be run along the ground or affixed to tree stakes. Install the irrigation system before planting the trees. For more information on watering, please see Irrigation Systems.
Deer love to eat olive trees. If you have deer roaming your land, you can assume that they will find and eat your trees. An orchard will require full-field, 8-foot fencing in some form. It is easier if the gates are placed in the corners of the fields, as it makes chasing out the deer (when they inevitably find their way in) a much simpler task. Small plantings can accommodate cylindrical, individual fences for each tree.
Small trees need to be staked when they are planted. One stake should be sufficient, though two work together nicely for smaller scale plantings. Place the stake upwind of your tree so that the tree blows away from the stake and does not damage its bark. The tree should be affixed loosely to the stake with a figure-eight tie of some pliable material (spaghetti hose, plastic chain, plastic tape, etc.). Wooden or metal stakes are both practical but note that treated wooden stakes are prohibited in organic production. The stake can be driven in anywhere from 4 inches to 1 foot away from the trunk depending upon the size of the tree. Trees planted in orchards with a predominate strong wind direction can be planted on a slight angle into the wind (see ).
Gophers and Other Rodents
Gopher baskets should be considered if the gopher pressure is extremely high, if the planting is small enough, or if the trees themselves are large and therefore expensive to replace. Gopher baskets take extra time and money and those factors should be weighed against your desire/ability to replace the trees. If you are only planting a handful of lovely 15-gallon trees in your yard that has a very high gopher population, then baskets are probably a good idea.
One homemade version entails cutting heavy-duty chicken wire to size then placing the piece of chicken wire on top of a 5-gallon bucket. Fit a second 5-gallon bucket into the first one, molding the chicken wire to a “perfect” basket. Use a basket one size larger than the size of your tree (i.e., use a 5-gallon basket for a 1-gallon tree) and leave the rim of the basket above ground to minimize the likelihood of gophers climbing over the top of your basket.
Voles, rabbits and any number of small rodents find the olive tree’s bark appealing. Plastic trunk protectors, or grow tubes, can be purchased at many vineyard supply dealers to help guard the trunks against small teeth. Paperboard milk cartons can also work, although they deteriorate quickly. The plastic tubes are a fairly cheap investment for the potential gain; it is often in the spring when the grass is high that damage is done to the bark. Keep grass cut around the trunks through the winter and spring, because by the time the grass is mown it is frequently too late to save a girdled tree.
Fertilizing While Planting
When you plant the tree it will be your last opportunity to directly access the root ball. Take advantage of this moment by placing some compost and/or other fertilizers in the planting hole, particularly if the soil pH needs adjusting. Mix your materials well with native soil for an even medium for the tree’s roots. If you are using a manufactured fertilizer, follow the rates indicated on the label for planting.
The planting hole for an olive tree does not need to be deep. In fact, olive trees should be planted on a mound to encourage drainage away from the trunk. The crowns are sensitive to rot (as are the roots) if left to sit in water. The tree will settle once you have planted; plant high to accommodate this settling so the tree will remain above soil grade. Do not plant the olive tree into a basin for watering; it will succumb to verticillium or some other malady.
Water your tree well and tie it to the stake once it has been planted. If your young tree has any flowers or fruit, strip them off this first season, so that all the energy can be directed towards vegetative growth. Remove the tag and reaffix it to the stake or drip line so that it does not girdle the tree; draw a map immediately so lost tags are not a problem (see).