If you are still considering whether olives are suited to your growing conditions, please read Planting Site Considerations before you purchase your tree(s). Once you’ve decided to actually grow trees, the following instructions will come in handy.
Planting your tree
If you plan to plant your tree in the ground, the optimal time to plant is between May and August to ensure the tree has ample growing time to establish itself before fall—however I have planted trees on Saturna Island as late as mid-October and have had no problems. In general I see better overwintering and subsequent growth with trees in the ground rather than in pots.
If you’re planting more than one tree give ample space between trees for growth and room to move between trees. Trees can grow twelve feet or more in diameter (depending on watering regime, soil fertility and variety). Traditional spacing between trees is 16-20 feet, although, since in our climate the trees grow and mature much more slowly you can space them much tighter, say 12-14 feet.
Olive trees are simple to plant. Providing you have chosen the right site, you should only have to do the following:
- Dig a hole no more than twice as wide as the pot the plant is in. Don’t dig the hole deeper than the pot itself as this may cause the plant to settle below grade after the first thorough watering. Use the native soil you’ve dug out to refill the hole (get rid of any large stones, boulders or pirate treasure). Don’t add amendments such as potting soil, manure or compost to your planting hole. You want to encourage the tree to grow into the native soil—adding amendments will discourage that process.[1] You can always add compost or other nutrients as a top dressing once the tree is established in the ground.
- Remove the tree from the pot. If the rootball looks compacted (rootbound) lightly muss up the outer roots (to free them from the root mass). Unwind any roots that are circling the outer rootball. Put any potting soil aside that drops from the root ball as you take it out of the pot—use that soil for mulch around the tree rather than adding it to the hole you’ve dug. Don’t be afraid of disturbing the root mass; once it’s in the ground (or in a new pot) it will grow new roots rapidly.
- Place the tree in the hole, ensuring that the root ball has no more than two inches of soil on top of it and that the tree trunk is not below soil grade.
- Water the tree thoroughly once the tree is planted. Subsequently make sure the soil is kept reasonably moist for the first couple of months after planting.
- Stake the tree if it won’t stand up on its own or if you’re worried about the effects of wind on the tree. Use a stake only for the first two to three years if possible—a tree that is tightly staked after that time will not develop a strong trunk as quickly as an un-staked tree.
- Olive trees are not heavy feeders but you can add compost, sea weed or fish emulsion every few weeks during the growing season. If you have very acidic soil then add lime to the soil (Calpril is a good option, or Dolopril).
Planting in pots
If your home site is unsuitable for planting olives in the ground, you can grow them in pots. Repot into a pot that is only one or two sizes bigger. Overwintering a potted plant is easy if you can move it to a well-protected but reasonably cool spot on your property for the winter. Some customers have successfully stored their trees in un-heated garages or other out-buildings when they are away for the winter but do not try to house your potted olives in your heated house. Olive trees need some cold in the winter to enter a semi-dormant winter phase. Trees kept in a heated house will not enter this dormant phase and will usually acquire nasty pests such as brown scale.
In our wet coast winter environment, most winters are mild enough for olives to survive without protection when kept in pots. Just keep in mind that trees in pots are especially prone to freezing, because the pots don’t offer much insulation and the bottom portion of the soil in pots is often wet in the winter. A little bit of freezing is okay but prolonged freezing will harm olives since they are never completely dormant. Here are some suggestions for overwintering your trees in pots cribbed from a UK nursery website (Big Plant Nursery which seems to be offline):
“In areas where the minimum winter temperatures are between -2°C and -5°C, olive trees require no winter protection and will even tolerate drops down to -8°C for short periods, providing the daytime temperature rises sufficiently. In areas with lower winter temperatures, your olive tree can be protected with several layers of horticultural fleece wrapped around the trunk and crown of the tree. Like many plants grown in pots, olive trees have not yet evolved to tolerate frozen roots; if this happens, they can suffer drought through not being able to take up water or worse still, the roots will be damaged which can result in subsequent poor growth or even death of the tree. But fear not! This can be prevented by adding several layers of bubble plastic to the inside of the pot when re-potting the plant or simply add layers of bubble plastic to the outside of the pot and secure with twine (not quite as attractive, but just as effective).”
[1]More on soil: If you think your soil lacks nutrients then consider changing it slowly by adding compost or seaweed as top-dressing once or twice a year rather than trying to amend the planting hole itself. Alternatively, you can try to create your own soil by bringing in topsoil and creating a deep (four feet) planting bed for your trees. Just make sure that the bed drains well. Be prepared to water consistently and probably often (even once the trees mature) if you choose this option.
Here are planting recommendations for olive trees and potted landscape trees from two University of California, Davis, publications:
“Place the tree in the hole slightly higher than grade level and place about one inch of soil on top of the root ball while building up the grade slightly with the original soil from the hole and some surrounding soil. Do not add soil mix, compost, or fertilizer to the planting hole. The tree has to grow out into the native soil; adding a nice soil mix to a large hole creates a potted effect and limits root growth out into the native soil.”
“Dig the hole no deeper than approximately 2 inches (5 cm) less than the depth of the soil in the container or the depth of the soil ball. Planting a tree too deeply or in loose soil may lead to the root ball settling below grade and potential crown rot problems. The basin for watering a newly planted tree should be constructed so that water will drain away from the trunk.”
For more information on planting and caring for olive trees you can go to these links:
https://cesonoma.ucanr.edu/files/27176.pdf
For an extensive explanation of planting and training trees (in this case landscape trees) try this link: https://anrcatalog.ucanr.edu/pdf/8046.pdf