It is a common myth that gravel in the bottom of a pot helps with watering. People believe that a layer of gravel in the bottom of pots will improve drainage and keep the soil from spilling out, and besides, that’s how we’ve always done it, so it must be right.
Water naturally settles toward the bottom of the soil, but if you have partially filled your pot with gravel, that soggy soil bottom is now higher and closer to your plant’s roots. Basically, it’s like having a smaller pot. It can cause water to pool, which keeps the roots wet, leading to root rot. Gravel is also heavy. If your pot is large enough to accommodate gravel in the bottom, try using crushed aluminum cans or packing peanuts instead and it won't weigh 100 pounds.
Sponges are a great alternative to gravel. You can save your old dish-washing sponges. Cut them up and layer the bottom of your garden pot before filling it with dirt. Sponges soak up water and prevent it from flushing out the bottom. The roots can drink from the sponges whenever they are thirsty.
Then there is the coil method, which is probably as old as container gardening itself. This relies on the capillary action of cotton cloth. Bury a length of cotton cloth in the soil around your plant, coil it gently around the base of the plant, and then drape it into a large bowl of water or a gallon jug. As long as the bowl is slightly elevated above the surface of the plant's pot, it will slowly wick water down to the roots.
Of course, there is the ever popular method of dunking your potted plant in a sink full of water. It works well if plants need more than a regular watering, or if the soil has shrunk away from the sides of the pot. Simply fill your kitchen sink or an outdoor reservoir with water, and set your potted plant in the water. By the end of the day, your plant should be thoroughly watered. The soil slowly absorbs the water and expands with it throughout the day.
The diaper trick is handy if you want to make your soil super-absorbent. Use a clean unused diaper. The same absorbents that keep your baby's bottom free of moisture can hold the moisture in your container plants. Slice open a clean diaper and shake out the contents to mix in with your soil.
Keep a pencil handy. Knowing your plant's water needs is important. Peace lilies and impatiens will let you know immediately that they are thirsty. Other plants are a bit more secretive. Stick a pencil an inch into your soil and pull it out. If dirt sticks to your pencil, you probably don't need to water. This knowledge can help to prevent drowned plants.
Hanging baskets are pretty, but they dry out easily, stressing the plants living in them. There are three good tricks for keeping a hanging basket watered. One is lining the basket with plastic. Either pot liners or a grocery bag would work. Be sure to poke drainage holes in the bottom of the liner. Lining the pot helps retain moisture by keeping the soil from drying out quickly.
Using mulch is another way of preventing water evaporation in a hanging basket. It's a good idea for any potted plant. In fact, it's a must for potted plants. Sometimes soil will flush out the bottom over time, leaving the roots exposed. Mulch helps to protect the top soil and holds in moisture.
If you have a hanging basket in full to partial sun, you can also try ice cubes. Put a few ice cubes on top of the soil and walk away. The ice slowly melts, giving the plant a nice cool drink, and it doesn't run over or spill out the sides. It's a good way to save time and water.
Potting mix usually has large portions of peat moss. Once dry, it seems unwilling to absorb water. To give thirsty soil an incentive to drink, add a drop or two of dishwashing liquid to your watering can. The soap will break the surface tension of the water, allowing it to penetrate and soak the dry moss.
My favorite method is the slow-release reservoir. There are several variations of this. You could punch some holes in the bottom of a coffee can and plant it next to your plant, opening side up. The plant will grow around it. Filling the container every few days with water will let the water slowly penetrate the root zone, keeping any moisture-loving plant happy.
For smaller containers try empty glass Coke bottles, filled with water and then plunged upside down into the soil. Or you could use plastic soda bottles for better access. Simply cut the bottom off, poke holes in the cap, and set the bottle upside down in the soil next to the roots. Fill occasionally, using the hole you cut out of the bottom.
The Peace Corps encourages farmers in South America to plant pots with their crops. Unglazed terra-cotta pots, especially those with no drainage holes, will "sweat" water, giving the roots around them a steady drink. Sink the pot to its neck and fill it with water. Depending on how quickly the water leeches out, it should provide a steady supply of water to established plants. It's even aesthetically pleasing if you use smaller terra-cotta pots in a larger pot.
Gallons of water go to waste in air conditioner runoff. Try running a drain line from your A/C to a thirsty plant nearby.
Another good way to conserve water in container gardening is double potting. If you have one pot with a plant, place it inside a slightly larger pot. Then fill the gap within the larger pot with soil and add moss and/or stones and pebbles on top. When you water, water both the plant and the soil around the first pot. This will lessen evaporation. It's a great alternative for plant watering if you go on vacation or leave the house for an extended period of time.
There are many adaptations one can utilize to save time and money and avoid frustration when watering your container plants, indoors or outside. I hope these suggestions have given you some inspiration to manage beautiful, bountiful pots full of blooms.