If you are growing figs in containers, it is absolutely critical that you water them correctly. Any tree-sized plant, particularly one that produces fruit, must be watered carefully, because it relies exclusively on the garden caretaker for all its water. Overwater, and you're facing waterlogged roots and root rot. Underwater, and your fig is in serious danger of drying out completely and possibly damaging the tree.
Watering starts with a well-draining soil, based on coconut coir, sphagnum moss, and perlite. Including in your containers anything like garden soil or compost is a recipe for a muddy mess that promotes moldy roots and other disease. You also want to cover the soil and shallow roots with a layer of mulch, to prevent the sun from baking away the upper level of moisture.
The objective is to completely saturate your soil with water once a week. Note that this doesn't mean flood your container and wash away your fertilizer. You simply want to bring your water volume just to saturation, so that any excess beyond field capacity flows out the bottom. Then, you want to let the soil dry down over the succeeding days as the plant takes up water and nutrients. Before it becomes too dry, you will water again, but again, only as much water as the plant needs.
Step One. Check on the rainfall totals in your area. To do this, go to Precip.ai and type in your zipcode to get started. Of particular interest is the record for Rainfall in the Last 7 Days. You can also go to Weather.gov and check for rainfall for the last 72 hours/3 days. Each of these will give you an idea of how much watering your figs have received naturally. Figs generally need 1" to 1.5" of watering (rainfall or artificial) per week in the Summer to produce healthy fruit. This can increase depending on the size of your tree and the number of fruits developing.
Step Two. Determine field capacity. For this, we are going to need the garden hose. Record the rainfall for the last 3 days and the last 7 days, using your resources above. Now, use the hose in 5 second bursts to add water to your container. Then pause at least 30 sec, to let the water work its way into the growing medium. You are looking for the water to work its way entirely through the medium, until you see it eventually run out the bottom of the container.
Work in 5 second bursts of water followed by 30 second intervals to allow the water to be absorbed. Count the number of 5 second bursts, and when you observe the water running out the bottom holes of the container, record the number of bursts it required. This will tell you how much water is required to fully irrigate that particular container. For my 24" by 13" whiskey barrel, that could take 5 or more 5-sec bursts of water.
Step Three. Repeat 3 days later. Make a note of any rainfall accumulation in the past three days (Weather.gov) and average temperatures. Then repeat the field capacity experiment, which will probably be smaller than your first trial. What you now know is that starting from saturation on Saturday, and with a known temperature and rainfall, How much watering will it take to bring the container up to field capacity again on Tuesday. This is a rough gauge for how much you need to water and how frequently.
Again, remember that drawing down the water in the containers is key to avoiding mold and disease problems. You never want to be completely dried out in the container. If the Tuesday reading is the same as your initial field capacity test, then you know that your containers are drying out quickly, and so you must decrease your watering interval. If, however, your container is quickly at capacity on re-wetting, then you know you probably need to stretch the interval between waterings to a few more days.
