@dimitrov Does the pot have a drain hole?
All plants love and need water - just not too much or too little; and, watering plants is a science unto itself. A big part of the science of watering is determining appropriate intervals between waterings. The challenge in that lies in the fact that "appropriate watering intervals" vary significantly as weather patterns and seasons change, making it essential that the prepared container gardener has a strategy to cope with the fluctuations.
Your olive is drought tolerant, but shouldn't be allowed to dry down completely, and the advice to water when the top inch or two of the soil column feels dry deserves some scrutiny. If your pot is 25cm (10") deep, and the top 5cm (2") feels dry, the bottom 15cm (6") of the soil column could still be 100% saturated with water. The overly overly broad advice to water if the soil is dry to 5cm (2") or the second knuckle is responsible for a very high % of problems related to excessive amounts of water (and too little air) in the root zone. These problems are related to poor root function or root diseases. Lack of oxygen caused by too much water and not enough air can rob your plant of a huge fraction of its genetic potential, nearly all. I'm not saying your plant is over-watered, only that you would be better served to eliminate using a finger to test for soil moisture unless the pot is very shallow - 12cm (5") or less. There is no sense in trying to fix what is potentially an under-watered plant into an over-watered plant. In deeper pots, it's relatively inconsequential how dry the top several inches of the soil column is. Moisture levels at the BOTTOM of the pot are far more critical.
The best time to water your olive is when the grow medium is on the dry side but not completely dry at the bottom of the pot; and one of the best if not the best methods of determining soil moisture status at the pot bottom is through use of a tell, which can easily be made with a wooden dowel rod 65-80mm (1/4 - 5/16"). Simply cut it in appropriate lengths and sharpen in a pencil sharpener. You might find this additional input re use of a "tell" to be helpful:
Using a 'tell'
Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.
Watering in small sips in order to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions - which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma and creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.
In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.
Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.
One of the most reliable methods of checking a planting's need for water is using a 'tell' (more reliable than a 'moisture meter'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16" (75-85mm) works better. They usually come 48" (120cm) long and can usually be cut in half or in several pieces, depending on how deep your pots are. Sharpen both ends of each tell in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell's tip comes out nearly dry. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.
What are you doing about fertilizing, which is also a critical part of your care regimen?
Al
