From my perspective as a Desert Rose (Adenium obesum), the question of watering is the most fundamental aspect of our relationship. I am not a thirsty tropical plant; I am a child of arid, sun-scorched landscapes. My very being is designed to store vast quantities of water within my thick, swollen caudex (that bulbous trunk you find so charming). This reservoir is my survival mechanism. Therefore, my watering needs are not about frequent sips but about infrequent, deep feasts that mimic the rare, heavy downpours of my native habitat. The single greatest threat to my life indoors is not underwatering, but overwatering, which leads to the rot of my precious water-storage system.
You must abandon the concept of a strict schedule, such as "every Tuesday." My thirst varies dramatically with the seasons, the temperature, the humidity in your home, and the amount of light I receive. Instead, you must learn to speak my language through the soil. The most reliable method is the finger test. Please insert your finger into the soil, going down about 2-3 inches (to about your second knuckle). If the soil at that depth feels completely dry, even a little bit crumbly, then I am ready for a drink. If you feel any moisture or coolness at all, I am still content and you must wait. When in doubt, it is always safer to wait another day or two. I can endure drought far better than I can endure soggy feet.
My watering needs change with my internal clock, which is synced with the light levels of the year. During the late spring and summer, I am in my active growing season. The days are long and bright, and I am busy producing new leaves and flowers. This is when I am thirstiest. You will likely find that my soil dries out more quickly, and I will welcome waterings more frequently, perhaps every 5 to 10 days, always contingent on that soil dryness test.
However, as autumn arrives and daylight wanes, I begin to slow down. When winter comes, I often enter a period of dormancy, especially if I am in a cooler spot. I may drop most or all of my leaves—this is a normal and necessary rest period for me. During this time, my water needs plummet to nearly zero. You must water me very sparingly, only enough to prevent my roots from desiccating completely. This might mean a light watering only once a month or even less. Overwatering a dormant me is a sure path to a fatal case of root and caudex rot.
When you have determined that I am truly thirsty, the method of watering is crucial. A timid sprinkle on the surface will not suffice. You must provide a thorough, deep watering. Pour water evenly over the soil surface until you see it freely running out of the drainage holes at the bottom of my pot. This ensures that my entire root system has access to moisture. It is absolutely critical that I live in a pot with excellent drainage and that you never let me sit in a saucer full of water. After watering, always empty the saucer. My roots need access to air as much as they need access to water, and "wet feet" will suffocate and rot them.
I will communicate my health to you through my appearance. If you are watering me correctly, my caudex will feel firm and full, my leaves will be glossy and turgid during the growing season, and I will reward you with blooms. If you are overwatering me, my leaves will turn yellow and feel soft and mushy, and the caudex may become soft and squishy—a very dangerous sign. If you are underwatering me for an extended period, my leaves will wilt, dry out, and drop, and my caudex may begin to shrivel and wrinkle. Wrinkling is my signal that my internal reserves are being tapped; it is a call for a deep drink, but one that should still only be answered after you have confirmed the soil is dry.
