OLIVE BONSAI SPECIES
NATIVE EUROPEAN OLIVE BONSAI
There are two commonly used Olive species in Europe for bonsai - the European Olive (Olea europea) and the Mallorcan Olive (Olea europea var. silvestris), commonly referred to as Ullastre. The standard European Olive has heavy, hard deadwood and slightly large leaves, whereas the Mallorcan Olive has much more striated deadwood and incredibly small leaves. Both, however, make excellent bonsai tree material.
For both European and Mallorcan Olives, allow the new shoots to elongate in spring until the new growth hardens off sometime in May. At that point, it is possible to cut the shoots back to two leaves and then perform partial outer canopy defoliation, removing 80-90% of the leaves from the outer canopy of the tree. This will induce a second flush of growth, which will be smaller in size and produce more branch ramification in a single growing season.
As the second flush emerges, allow the secondary shoots to elongate again to 6-8 leaves and then cut them back to two. Repeat this process throughout the growing season. Do not prune in fall, though, as this may produce another flush of growth that will not harden off before the first frost, potentially resulting in branch dieback.
For a more in-depth look at pruning techniques, please consider joining our online bonsai learning platform Bonsai-U!
Wiring and Styling
Wiring and styling these species is best done either in the winter, just after the leaves have fallen or in late spring, just after performing partial outer canopy defoliation. Keep in mind that if you wire in winter, it is best to avoid heavily bending branches, as this can cause dieback in the subsequent spring season. Utilize aluminum wire for these species, as it is softer on the bark and will cause less damage. Wire will likely need to be removed within 1 to 2 months after application to avoid biting into the branches. It is possible to rewire these trees multiple times in one year.
Repotting European and Mallorcan Olive bonsai is best done in early Spring just as the buds begin to swell. This usually happens sometime in March in the northern hemisphere. When repotting, it is okay to remove all of the original soil, as these species are quite strong and respond well to this treatment. Also, it is possible to cut nearly all of the roots without subsequently weakening these species (although we do not recommend this).
Use a slightly more water-retentive soil medium, such as Aoki Blend or a mixture of akadama, lava rock and pumice in a ratio of 2:1:1. The soil particle size should be approximately 3/16 inch (4mm) for medium and large trees, and slightly small for shohin size bonsai.
These bonsai species do well if kept slightly dry. As a general guideline, check the water twice per day during the growing season from early Spring through late Fall. Most Olive bonsai will need to be watered once per day. Water as the soil surface becomes dry and avoid misting the foliage, as this can lead to burn and disease. In the winter months, check once per day and water as needed, which could be as little as once every 5-7 days depending on the climate and the individual Olive bonsai.
Fertilizing Olive bonsai will be dependent on the stage of development of the tree. For example, younger trees are best fertilized with a high-nitrogen synthetic fertilizer to rapidly increase their size and vigor, starting from the early spring through the end of the growing season. Older, more refined deciduous bonsai should be fertilized with a milder organic fertilizer with a lower nitrogen value. This fertilizer should only be applied after the first set (or second set) of growth has completely hardened off so as to avoid producing overly large leaves. For example, if you plan to defoliate them in May, do not apply fertilizer until after the second flush of growth has completely hardened off later in summer.
Olive bonsai trees do best if kept in full sun in the spring as the new growth is emerging. This helps produce more vigorous growth as well as smaller leaves. As the temperatures heat up in summer, it is possible to keep them in full sun; however, they can benefit from partial afternoon shade as well.
Olive bonsai are susceptible to a number of pests including fruit flies, scale and borers. The most common disease that affects these species is olive scab. For a comprehensive understanding of what fungicides and pesticides to use on your deciduous bonsai, please join Bonsai-U!
If you would like to learn more about how to care for native European Olive bonsai species, please consider joining our online learning platform Bonsai-U. Each week a new tutorial or live Q&A session will be uploaded to the site, providing you with in-depth information about bonsai design, care, maintenance and display. We look forward to seeing you soon on the platform!