How to Grow Carob from Seed?
Carob seeds actually germinate easily; however, since they have a very hard and waterproof shell, germination is both low and irregular when planted without pre-treatment. The germination rate can be significantly increased with simple methods such as slightly abrading the shell or applying hot water.
In this article, we explain why carob seeds are difficult to germinate, seed selection, pre-treatment methods tried in Turkey and abroad, germination conditions, seedling growth and why seedlings grown from seeds should be grafted, together with the results of research.
Why is Carob Seed Difficult to Germinate?
Carob seed is a hard, shiny brown and flat-oval shaped seed. According to the monograph published by IPGRI, seeds germinate easily, but since the seed shell is very hard, the shell must be abraded with pre-treatments such as acid or hot water. The monograph also states that carob seeds do not need to be kept in a cold environment to break sleep (Batlle and Tous, 1997).
In a study conducted at Akdeniz University, it is emphasized that carob seeds have a very hard shell and do not absorb water easily, so germination is difficult without pre-treatment. This type of physical sleep is a common feature in the legume family (Güneş et al., 2013).
The problem is not in the viability of the seed, but in the inability of water to reach the seed. When the shell is eroded, the seed absorbs water, swells and germinates in a short time. In the Alanya Carob geographical indication certificate, it is stated that the seeds have a very hard and impermeable shell that negatively affects germination (Turkish Patent and Trademark Office, 2025).
Seed Selection and Preparation
The first step to successful germination is choosing the right seed. The recommendations in the sources can be summarized as follows:
- Seeds should be taken from fully ripe pods and from the final harvest (Batlle and Tous, 1997).
- In the geographical indication certificate, it is stated that that year, that is, one-year seeds, should be selected for germination.
- Light, empty or wormy seeds should be removed before planting.
- For this, the seeds are placed in water; most of the defective seeds float to the surface and can be easily separated.
According to the IPGRI monograph, carob seeds can remain viable for up to 5 years when stored in closed containers, at low temperature and dry; nevertheless, it is recommended to use seeds from the current season. The World Agroforestry Centre database also records that seeds can remain viable for up to 5 years when stored at 5 °C in an air-dry state, and that there are approximately 500 seeds per kilogram (Orwa et al., 2009).
The source of the seed is also important. Wild carob seeds are generally used to grow rootstocks in nurseries. In the Alanya geographical indication certificate, it is clearly stated that wild carob seeds, called "delice seeds", are used in germination.
Pre-Treatments That Accelerate Germination
Different methods have been tried to erode the shell of carob seeds. The effect of these methods has been demonstrated in numbers in studies conducted in Turkey.
Research Results in Turkey
In a study conducted at Akdeniz University, three different pre-treatments were applied to seeds taken from a wild genotype with the 'Etli' variety in Demre and the results were compared with untreated seeds (Güneş et al., 2013):
| Pre-treatment | Application | Culture variety germination (%) | Wild genotype germination (%) |
|---|---|---|---|
| Control | No action | 13,57 | 13,57 |
| Mechanical etching | 1–2 mm notch on the shell opposite the belly | 98,77 | 92,60 |
| Hot water | 5 minutes in 100 °C water, followed by cold water rinsing | 77,80 | 74,10 |
| Sulfuric acid | 20 minutes at 98 percent acid, followed by washing with plenty of water | 92,60 | 95,07 |
In the study, it was observed that all pre-treatments accelerated germination and seedling development compared to the control. The mean germination time was realized in the longest control and the shortest in mechanical etching; the average time in mechanical etching was measured as approximately 4 days. Hot water application increased germination compared to control, but germination was not fast and regular. Germination rates of wild and cultivated seeds were found to be similar; the researchers interpreted this result as the culturing process did not affect germination behavior (Güneş et al., 2013).
In another study conducted by the same research group on wild seeds, different sulfuric acid concentrations were tested at 26 °C for 30 minutes; the lowest germination was obtained in the control with 22.92 percent, and the highest germination was obtained in the acid application with 93.06 percent and 98 percent (Güneş et al., 2010). A previous study examining the effect of pre-treatments on germination time and seedling growth at Akdeniz University was also presented at the IV GAP Agriculture Congress (Yasin and Gübbük, 2005).
International Applications
In the IPGRI monograph, it is stated that good results were obtained with one of the following methods or a combination of fresh seeds planted in March-April at the IRTA-Mas Bové research center in Spain (Batlle and Tous, 1997):
- Soaking in tap water at room temperature for 15 days
- Toss in boiling water and stir quickly for 10 minutes, then soak in cold water for 24 hours
- Soaking in concentrated sulfuric acid for 1 hour and rinsing with tap water to prevent complete dissolution of the seed coat
- Soaking in 25 ppm gibberellic acid solution for 24 hours
In another study cited in the monograph, 99.1 percent germination was achieved in seeds treated with 80 percent sulfuric acid for 30 minutes, while different doses of gibberellic acid did not have an effect on germination. Julia Morton, on the other hand, states that in Cyprus, seeds are kept in moist sand for 6 weeks or more, seeds that swell to about three times their normal size are sieved and separated, and germination can remain at 25 percent in this method (Morton, 1987).
Which Method at Home and on a Small Scale?
Research results show that mechanical etching provides both high and fast germination. This method can also be easily applied at home: The seed coat is lightly abraded or notched with a file, sandpaper or nail scissors from the opposite side of the umbilical point without damaging the embryo. Hot water application is also a practical alternative.
The sulfuric acid method, on the other hand, is only suitable for professional nurseries and laboratories with appropriate protective equipment and experience. Concentrated acid can cause severe burns; it should never be tried in a home environment.
Germination Environment and Conditions
After pre-treatment, the seeds must be kept at the appropriate temperature and humidity. In the IPGRI monograph, it is stated that the most suitable germination temperature for carob seeds was found to be 25 °C and 27.5 °C in different studies. In the study of Güneş et al., the seeds were germinated at 25 °C on soaked blotting paper.
Seeds treated and washed according to the monograph are usually soaked in water for another 1–2 hours before sowing, and sometimes surface disinfection is carried out with diluted bleach. Then the seeds are sown either in plastic trays kept at 20–30 °C in the greenhouse, or in tall plastic pots placed directly under the canopy.
Traditional Method Applied in Alanya
The germination method applied for rootstock production is described in detail in the Alanya Carob geographical indication certificate (Turkish Patent and Trademark Office, 2025):
1. Soaking and weeding: Wild carob seeds are kept in chlorine-free water (purification or natural tap water) for 6 hours; the seeds that rise above the water are thrown away.
2. Germination in a humid environment: The seeds settled in water are taken to germination crates to be kept in cloth, paper towel or peat for a week. The cloths must be constantly moist; the crates are covered with cling film and sweating is done.
3. Potting up: 2–3 seeds are left in small pots and the strong seedling is used.
4. Bag staggering: Seedlings that have two leaves are taken into plastic bags of 15×25×34 sizes.
Growing seedlings
The carob seedling develops a taproot that quickly goes deep after germination. Therefore, it is important that the containers in which the seedlings are grown are deep. In the IPGRI monograph, it is stated that tall plastic pots with a diameter of 12–15 cm and a depth of 35–40 cm are used for direct sowing.
According to the monograph, mixtures are usually used as a growing medium, in which soil, humus, perlite and peat are mixed in different proportions, and sand is added to improve drainage and structure. The points to be considered during the seedling period can be summarized as follows:
- Seedlings should be watered regularly, but overwatering should be avoided; excess water can lead to precipitating and root rot diseases.
- Stalls with seedlings must be clean and disinfected; some pathogens can live on dirty surfaces and infect young seedlings.
- Seedlings should be transported with caution, the root ball should not be distributed.
- Young seedlings are very sensitive to frost; they should be sheltered in frosty regions.
Morton states that the seedlings are surprised when they reach about 30 cm in height and if tubes or similar methods are not used, the taproot is cut 6 months before planting in the field. However, he also emphasizes that large trees cannot be transplanted successfully.
From Seed to Seedling: How Long Does It Take?
With proper pre-treatment, carob seeds germinate within a few days. In the study of Güneş et al., the average germination time varied between about 4 and 6 days, depending on the application.
It takes longer for the seedling to reach the thickness that can be grafted. According to the Alanya geographical indication document, it takes about 1.5–2 years for the seedlings to reach a diameter of over 10 mm for grafting after germination. In the IPGRI monograph, it is stated that rootstocks should be grafted 1 year after germination in the nursery or 2 years after germination after planting in the garden.
The time to bear fruit is even beyond this. According to the observations conveyed in the monograph, trees in gardens established with grafted saplings begin to bear fruit in the 5th-6th year, and trees grown from seeds and grafted later begin to bear fruit in the 7th-8th year.
Why Should Carob Grown from Seed Be Grafted?
A carob tree grown from seed does not have the characteristics of the mother tree. Since carob is a foreign pollinated species, each seed is a genetically different individual. The IPGRI monograph states that rootstocks grown from seed differ greatly in growth strength, growth pattern and cold resistance.
More importantly, the sex of the trees grown from seeds cannot be known in advance. In natural populations, about half of the trees are male and male trees do not produce pods (Batlle and Tous, 1997). For this reason, seedlings grown from seeds should be grafted with a productive female or hermit variety if fruit production is aimed. In the geographical indication certificate, it is stated that saplings are produced by grafting the carob variety specific to the region to the seedlings obtained.
This does not mean that growing from seed is worthless. Seed is the main way to provide the rootstock needed for grafting; Since carob does not root easily with cuttings, commercial sapling production relies heavily on rootstocks grown from seeds. In trees planted for purposes such as afforestation and erosion control, saplings grown from seeds can be used directly, as fruit yield is secondary. We discuss grafting methods in our article "Grafting Techniques in Carob Tree".
Frequently Asked Questions
How many days does carob seed germinate? Seeds with eroded shells begin to germinate within a few days at the appropriate temperature (approximately 25 °C). In studies, the average germination time was found to be between 4-6 days depending on the application.
What is the easiest way to germinate carob seeds? The easiest and most effective method at home is to gently erode or notch the seed coat from the opposite side of the belly point. In trials with this method, over 90 percent germination was achieved.
Does the seed of carob bought from the market germinate? Ripe and healthy kernels can germinate. However, sources recommend using seeds from fully ripe pods and the last harvest for best results. If it is not known when the kernel was harvested and how it was stored, the result is not guaranteed.
Does carob grown from seed bear fruit? If a female or herma comes out, it can bear fruit, but about half of the trees can be male and fruit quality is variable. Therefore, seedlings are grafted in cultivation for yield purposes.
From Core to Tree, From Tree to Product with Carob Türkiye
A small and hard carob seed is the beginning of a tree that can exceed a century if the right conditions are met. The same seed also has an important place as a valuable raw material in industry.
As Carob Türkiye, we supply carob fruit, cracks, flour/powder, seeds and extracts. The structure and uses of the seed What is Carob Seed? You can read our product in our article. Carob Seed You can review it on the page. For your wholesale and export requests Contact Now You can contact us on our page.
Domestic resources
Turkish Patent and Trademark Office, "Alanya Carob / Alanya Carob – Mahreç Sign, Registration No: 1705", 2025. ci.
turkpatent. gov. en/ Files/ GeographicalSigns/ 7bbe4a8b- 399… Yasin, D., Gübbük, H., "The Effect of Some Pre-Treatments on Carob (Ceratonia siliqua) Seeds on Seed Germination Time and Seedling Growth", Proceedings of the IVth GAP Agriculture Congress, Şanlıurfa, pp. 192–195, 2005. avesis.
Mediterranean. edu. en/ PUBLICATION/ fcee4aaf- 5cd9- 45b0- b44b- 6f9ca... Foreign sources
Güneş, E., Gübbük, H., Ayala-Silva, T., Gözlekçi, Ş., Ercişli, S., "Effects of various treatments on seed germination and growth of carob (Ceratonia siliqua L.)", Pakistan Journal of Botany, 45(4), 1173–1177, 2013. pakbs.
org/ pjbot/ PDFs/ 45(4)/ 06. Güneş, E., Gübbük, H., Yaşin, D., "The Effect of Different Sulfuric Acid Concentrations on Seed Germination of Carob (Ceratonia siliqua L.)", Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Horticulture, 66(1), 2009 (publication 2010). doi.
org/ 10. 15835/ buasvmcn- hort:4520 Batlle, I., Tous, J., "Carob tree. Ceratonia siliqua L. Promoting the conservation and use of underutilized and neglected crops. 17", Institute of Plant Genetics and Crop Plant Research, Gatersleben / International Plant Genetic Resources Institute, Rome, 1997. ISBN 92-9043-328-X. hdl.
handle. net/ 10568/ 104277 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.
Scientific Resourcesworldagroforestry. org/ treedb2/ AFTPDFS/ Ceratonia_sili...
