Compared to plants growing in the ground, plants in containers are growing in a limited volume of soil. This means that they don't have much of a reservoir of moisture to draw on to meet their water needs. They are dependent on you, the gardener, to give them a drink when they get thirsty. Depending on the size of the container, its exposure, and weather conditions, plants in pots may need watering daily -- or even twice daily during hot spells. Larger containers with their greater volume of soil will require the least maintenance, while hanging baskets, which generally contain a relatively small volume of soil and are more exposed to drying winds, need the most watering attention.
Find a Plant Sitter
It can be a challenge to make sure your container plantings and hanging baskets don't dry out while you are away. The best option is to find a plant sitter, someone who can come daily to check on plants and water as needed while you're away. A responsible neighborhood teen looking to earn a little extra money is often a good bet for vacation plant care. If you have a helpful neighbor and just have a few smaller containers or hanging baskets, you might load the plants in a wagon or garden cart and wheel them over to the neighbor's yard where they'll be easy to take care for in your absence -- and you can offer to return the favor with their plants when their vacation time comes. I pop my hanging baskets that need daily watering into my grown kids' long unused little red wagon and give them a ride to my neighbor's driveway before we leave on a trip; then I fetch her plants the same way to return the favor when she's out of town.
Move to the Shade
If you don't have a reliable plant sitter, move containers small enough to transport easily to a shaded, wind-sheltered location and water them well right before you leave. Remove any saucers that might hold standing water so that pots won't be left sitting in water after a rain.
If containers are too large to move easily, erect temporary shade cloth structures over those in full sun to keep plants cooler and reduce water loss. You can also place purchased plant watering bulbs or spikes in the pots or make your own from recycled 2-liter soda bottles. These devices let water slowly seep into the soil, maintaining a steady supply of moisture for the plants. While they may not provide enough water to see plants through a two-week vacation, using these plant watering devices can make it easier to leave for a long weekend and know plants won't dry out.
Make a Pre-Vacation Harvest
If you're growing edibles in your containers, harvest all vegetables that are likely to be overripe before your return, such as zucchini, beans, and cukes, even if they aren't mature yet. This will prevent plants from getting the signal to stop producing. Give your flowering annuals a good going over as well, deadheading those blossoms that are likely to go to seed before your return; this will help them continue to keep producing new flowers.
Consider Drip Irrigation
If you like to garden in containers and take frequent or extended summer vacations, you may want to consider investing in a drip irrigation system controlled by an automatic timer. Set up a system with drip emitters going to your individual containers and you'll be able to take off on vacation and be confident your plants will be in good shape on your return. Many garden and home stores carry kits that make it easy to set up a simple system.
Susan Littlefield is horticultural editor for the National Gardening Association.