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If you are going on vacation from four to five weeks this is a tried and true way to keep your potted plants, as well as large ferns in hanging baskets watered without depending on someone to tend them in your absence. Watering succulent plants is not recommended using this method, learned from experience! 
Hanging baskets - water a few days before you are leaving being careful not to overwater. Take a clear plastic dry cleaner bag, put over the fern leaving the hanger exposed to hang up, then once hung, gather at the bottom the excess plastic loosely securing with a twist tie. This works like a greenhouse effect. Use a twist tie at the top where hanger protrudes.
The big heavy plastic zippered comforter bags are excellent to put several plants in the bag after watering, then zip them into their greenhouse atmosphere.
I have used this method for saving five hanging asparagus ferns from outside for four years. You may want to check them over the winter and add a little water to them.
This worked so well for me I thought it worth sharing. Sorry I do not have pictures, but I think it is easily visulized from my description.
If you need to go away and have some plants that will need special care (mine were tiny plants being trained for bonsai that needed daily small watering), try this method. If you have large Mason or other clear jars with lids (or probably even clear bowls that would align to the pots they are in) add your plants, water them, and close them up. It becomes an instant terrarium! I did this a few days "before" going on my vacation to make sure it worked and it did so swimmingly!
Plants were doing great after coming home a week later!
I had never found a system to water the plants when going on vacation that would water the plants only when they need to be watered like a good gardener would. But then I found this system that corrects this flaw: 
You need a big plastic bottle with its cap and another smaller plastic bottle that can fit inside the big one, leaving a space of 2 or 3 inches. Cut the bottom of the big bottle and the top of the small bottle to keep only its straight part. Fill the small bottle with water up to the edge and you set it on the soil next to the foot of the plant. Put the big bottle on top of the smaller one with its cap on tight. You push it into the soil on a few inches so that the volume between the two bottles is a closed space.
When the temperature rises, the water in the small bottle evaporates and flows down along the inside of the big one and goes down into the soil. When the temperature is low, the water does not evaporate and stays in the small bottle, the plant is watered according to the temperature. Keeping only the straight part of the small bottle is important, otherwise the water evaporates but goes back into the small bottle. You can put more than one set for a big plant and you can use it for plants outdoors or indoors. Hope this helps! Here's what it looks like:
I have many houseplants and I have found an excellent way to keep them from drying out when we go on vacation. Water plants first, then tent smaller house plants with plastic wrap.
If I am going away for a weekend, I worry about my 'plant friends'. I either leave them in a dishpan 1/2 filled with water, water the plants thoroughly then add a few ices cubes to the top of the soil to melt slowly, or use this little trick I created!
If you are going on vacation, water plants in an enclosed porch, with shutters down.
ThriftyFun is one of the longest running frugal living communities on the Internet. These are archives of older discussions.
Two ways to protect your potted plants when you are away on vacation. You can wick roughly with a strip of paper towel from a cup of water to the plant. Wet the paper towel before applying.
You can also tent the plants with clear plastic bags. That way the moisture will be kept in the plants so they won't dry out, and should work for a few weeks.
By pam munro from LA, CA
Going on Vacation? Well, here's an easy way to make sure your indoor plants stay watered while you're away. Save small empty bottles like the kind that hold Benadryl, cough syrup or liquid ibuprofen. Start by thoroughly watering your plants then after cutting the bottom of the plastic bottles off with a serrated knife, razor blade or scissors then bury the bottles upside down several inches into the soil.
These tiny bottles will release water gradually as your plants need it. You can use 16 oz. water bottles for large plants, or big 2 litter plastic pop bottles for outdoor plants.By Cyinda
Great idea for a short vacation. For a longer one, try a plastic milk container. The tricky part is propping it up so it doesn't fall over or get knocked over by squirrels. Also, think about getting more plants that can handle less water. Here's a good list: http://www.oldhouseweb.com/gardening/Detailed/806.shtml
(05/01/2009)
By Allison
On my smaller easy to lift houseplants, I fill the bath tub with just a bit of water and then lay down a old bath towel in it and place my plant containers on it so that while gone they can slowly water them selves from the bottom up. (05/01/2009)
By Julie
Tips for watering you plants when you travel. Post your ideas!
If you cannot afford fancy watering systems for your houseplants while on vacation, gather them all up and place in the bathtub with an inch of water. They will be just fine for at least two weeks.
By Bobbie (07/19/2005)
By ThriftyFun
Fill a one to two liter bottle with water; insert upside down into soil. As soil dries out it will absorb the water. Depending on the size of your pot and type of plant, one liter will last one to two weeks.
By J.Sorensen (07/22/2005)
By ThriftyFun
This worked for me, when we were gone for a month.
Hanging plants I enclosed in plastic (from dry cleaner) and closed with a twist tie.
Other plants I did a similar thing with plastic bags.
Tip: succulent plants if enclosed in plastic will rot from the moisture.
This method worked much better than having someone come over to water them! (07/27/2005)
By Syd
Fill a container with water. Cut a section of COTTON rope. Dip one end into the water, the other end into the soil. The rope will carry the water to the pot. Make sure the reservoir of water is large enough for the job.
Larger pots need more than one rope to keep them moist. If it is very hot, use plastic wrap to cover the water reservoir, to help minimize evaporation. (08/09/2005)
By artdzyne
Water Worm is an easy to install, inexpensive way to solve the problem, lasts up to 4 weeks or more. http://www.sykart.com/keenie/worm/ (01/20/2007)
By pj
I water my plants well before leaving on vacation and close all my blinds and turn the heat down. They works great they are alive when I get home and not dried out. (01/31/2008)
