Periodicity in Carob Tree (Year of Existence, Year of None)
One of the common situations encountered by carob growers is that the tree yields abundant crops one year and significantly less the next year. This situation, popularly known as the "year of existence – year of none", is called periodicity (alternative or irregular yielding) in horticulture. Sources define carob as a species that shows significant periodicity, especially when growing conditions are poor.
In this article, we discuss what periodicity is in carob, the relationship between the crop load of the tree and shoot development, the factors affecting yield such as pollination, climate and water, and the maintenance approaches to reduce periodicity, together with their sources.
What is Periodicity?
Periodicity is when a fruit tree shows a yield pattern that fluctuates between years in the form of "abundant product – little product" instead of a regular yield. A year with abundant crops is called "year of existence" ("ten years" in English), and a year with low crops is called "off year". This situation, which is known in many fruit species such as olives, apples and pistachios, is also an important cultivation subject in carob.
Tous and Ferguson (1996) define carob as a species that "shows strong periodicity", especially when growing conditions are poor. This statement carries two important messages: First, periodicity is an inherent tendency of carob; second, this tendency becomes more pronounced as the conditions of the tree worsen. Therefore, periodicity is not completely "fate"; it has an impact on care and growing conditions.
Balance Between Crop Load and Shoot Development
In understanding periodicity, it is important how the tree distributes its resources. In fruit trees, in general, the intense crop load of a year directs most of the tree's energy to the fruit; this may limit shoot development in the same period and flower formation in the following year. In the year with few crops, the tree develops more shoots and leaves and prepares for the next year with abundant crops.
An observation specific to carob is compatible with this general mechanism. In a comprehensive review, it is stated that the intensity and onset of shoot development in spring depend on the crop status of the tree or branch: Vegetative development is delayed and decreased in fruit-bearing (in "present" state), while shoot development is stronger in non-fruit-bearing (absent) trees (Dahmani et al., 2023). In the same review, it is stated that vegetative development in carob usually occurs in two periods in spring and autumn, with autumn shoots being weaker or sometimes absent.
- Year of existence: Heavy fruit load, weakened shoot development
- Year of absence: Few fruits, strong shoot and leaf development
- Cycle: The imbalance between crop load and vegetative development is repeated between years
This cycle can have a self-feeding structure: A very abundant year causes the following year to be weak; and a weak year can pave the way for the tree to overload again the next year. The aim of cultivation is to obtain a more balanced yield by reducing the amplitude of this fluctuation.
Pollination and Fruit Set
One of the important sources of the yield difference between years in carob is pollination and fruit set. Most carob trees are female trees and pollen must come from male or male trees in order to bear fruit. Tous and Ferguson (1996) state that pollination in carob occurs by insects (bees, flies, etc.) and wind. In the guide of the General Directorate of Forestry, it is stated that carob is generally pollinated by wind (General Directorate of Forestry, 2020).
It is therefore important to have enough pollen sources in the garden. However, the recommended proportions differ in the sources:
| Source | Recommended approach |
|---|---|
| Tous and Ferguson (1996) | In new commercial gardens, the ratio of male or male trees to female trees should be 1:8; in traditional gardens, male branches are grafted onto female trees |
| Morton (1987) | In a planting of female trees, one male tree for every 25-30 female trees; In Southern Europe, male branch grafting is applied to female trees instead of male trees |
This difference indicates that the appropriate ratio may vary depending on the region, variety, and structure of the garden. When establishing a garden, seeking insights from local experts and sapling providers is the best approach.
The weather conditions of the pollination period are also decisive. Carob blooms in autumn; Tous and Ferguson (1996) state that flowers bloom in the September–November period. Erbaş (2024) emphasizes that autumn rains can inhibit pollination and affect fruit set. In the Agroforestree database, it is stated that fruit size is affected by the level of pollination and fruit set as well as environmental factors (Orwa et al., 2009).
Climate Events and Frost
Adverse weather events during the flowering period can directly reduce the yield of a year and trigger the periodic cycle. Morton (1987) states that frost during the flowering period can reduce or completely prevent fruit set. Tous and Ferguson (1996) also state that frosts of −4 °C and below can kill young trees or shoots and flowers in adult trees.
In such a year, the tree bears much less fruit than expected; the next year, it can produce abundant crops with the accumulated resources. In this way, a single negative event from the outside can put the tree in a periodic cycle. Therefore, when establishing a carob garden, it is important to choose areas with a low risk of frost and a suitable climate for the species.
The Role of Water and Nutrition
Tous and Ferguson's (1996) emphasis on "more pronounced in poor conditions" suggests that water and nutritional status have an impact on periodicity.
Water: Carob is a drought-tolerant tree, but it needs sufficient water for a regular and commercial crop. Tous and Ferguson (1996) state that an average annual rainfall of approximately 500–550 mm is required for a profitable crop. Erbaş (2024) states that water doses of 100 mm per year are clearly reflected in the yield in adult orchards. In the guide of the General Directorate of Forestry, it is stated that irrigation in spring and autumn will positively affect the yield (General Directorate of Forestry, 2020). Morton (1987) states that irrigation should be done in very dry seasons for trees grown for fruit.
Nutrition: Tous and Ferguson (1996) state that carob responds to nitrogen fertilization by increasing pod yield. However, there are different approaches to fertilization in the sources; for example, the General Directorate of Forestry guide states that organic fertilizer can be used in the first planting, and fertilization is not recommended in the following years. For this reason, it is the best approach to make the fertilization decision based on soil and leaf analysis and with expert opinion.
The general principle can be kept in mind here: A tree stressed by water and nutrients will have a harder time recovering from a year of abundant crops. Balanced water and nutrient management can help the tree develop both fruit and new shoots each year, reducing fluctuation.
Variety Selection and Periodicity
The tendency to periodicity may differ from variety to variety. Morton (1987) uses expressions such as "yields regular and good yields" (Santa Fe) and "yields abundant and regular crops" (Tantillo) while describing some carob varieties. These definitions show that regular yield is a feature that can be taken into account in variety selection.
In a current review, modern carob varieties; It is emphasized that it has been improved in terms of agronomic characteristics such as growth power, pod and seed quality, yield stability and resistance to biotic stresses (Gadoum et al., 2026). Yield stability is the opposite of periodicity and reveals the importance of variety selection in new garden establishment.
The average yield of carob under favorable conditions is reported to range from 2.5 to 5.0 tons of pods per hectare (Ben Hsouna et al., 2026). However, significant deviations from this value can be seen in individual trees and over years; periodicity is also one of the primary reasons for these deviations.
Practices to Reduce Periodicity
When the information in the sources is brought together, the main approaches that can help balance the yield of carob can be summarized as follows:
| Adequate pollen supply | Keeping the appropriate proportion of male or male trees in the garden or grafting male branches to female trees. |
| Choosing a suitable location | Prefer areas with a low risk of frost during the flowering period. |
| Water management | To carry out support irrigation in dry years and critical periods; to avoid waterlogging in the root zone. |
| Nutrition | Basing the fertilization decision on soil and leaf analysis. |
| Pruning | Maintaining a healthy crown structure of the tree by removing dry and diseased branches; taking into account that carob generally requires little pruning (Tous and Ferguson, 1996; Orwa et al., 2009). |
| Variety selection | To prefer varieties known for their regular yield in new gardens. |
| Record Keeping | To recognize the periodic pattern early by keeping annual yield records on the basis of trees or parcels. |
None of these practices alone completely eliminates periodicity; however, when applied together, it can contribute to reducing the difference between years.
Reflection of Periodicity on Trade
Periodicity affects not only the producer but also the carob trade. When a large number of trees enter the year of existence or absence at the same time, it can lead to fluctuations in regional and national yields. This is a factor that affects the supply of raw materials, stock planning and therefore the supply chain. For businesses that process and export carob, it is important to balance this natural fluctuation in yield with proper storage and supply planning.
Frequently Asked Questions
Why does carob produce a lot one year and less a year? This is called periodicity. Sources describe carob as a species that shows marked periodicity, especially when growing conditions are poor (Tous and Ferguson, 1996). The balance between crop load and shoot development, pollination, frost and water status can be effective.
Does carob bear fruit without a male tree? In order for female trees to bear fruit, pollen must come from male or male trees. It is common practice to have male trees in gardens or to graft male branches to female trees.
Can periodicity be completely prevented? It is difficult to prevent completely; however, balanced water and nutrient management, adequate pollination, and appropriate variety selection can help mitigate surge.
Does irrigation reduce periodicity? Sources state that irrigation positively affects yield (Erbaş, 2024; General Directorate of Forestry, 2020). Not keeping the tree under stress can contribute to reducing fluctuations.
Carob with Carob Türkiye
The yield pattern of the carob tree affects the entire supply chain, from the garden to the processing plant. At Carob Türkiye, we supply carob fruit, crumbs, flour/powder, seeds and extracts. Our products Carob Fruit and Our Products You can review it from the pages; For your wholesale and export requests Contact Now You can reach us on our page. For general information about carob What is Carob? You can also read our article.
Domestic resources
Republic of Turkey Ministry of Agriculture and Forestry, General Directorate of Forestry, "Carob Orchard Facility Project Feasibility Report and Investor Guide", Ankara, 2020. Eskisehir.
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org/ 10. 3390/ plants12183303 Morton, J. F., "Carob", Fruits of Warm Climates, Miami, 1987. Growables.
org/ information/ TropicalFruit/ CarobMorton. htm Orwa, C., Mutua, A., Kindt, R., Jamnadass, R., Simons, A., "Agroforestree Database: a tree reference and selection guide, version 4.0 – Ceratonia siliqua", World Agroforestry Centre, 2009. apps.
worldagroforestry. org/ treedb2/ AFTPDFS/ Ceratonia_sili... Gadoum, A., Difallah, A., Adda, A., Merah, O., "Carob Tree: A Review of Traditional Uses, Medicinal Properties, and Future Perspectives in Sustainable Forestry", Life, 16(3), 448, 2026. doi.
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