1. Watering by wick, mat or self-watering pots: These growers have the easiest time when going away. Unless the vacation is more than a couple weeks, the plants will never dry out. You cannot use these methods unless you’ve already set up for it, since they all require different soil that is much lighter and less water-retentive than normal soil.
2. Increasing humidity in the plant environment. This is tricky sometimes, and it depends on how long you will be gone. If you give everything a good watering (not a drenching, though) before you leave, covering the plants or plant stand in plastic sheeting will retain moisture for up to a week or more. Just be careful that you don’t overwater, or you will return to mush piles. Grouping plants together will also help conserve moisture.
3. Domes: Use community trays such as perma-nest trays that have matching plastic domes for a good sealed cover. This will work basically the same as using plastic sheeting. Just be careful, because any time you trap moisture in with plants, there is a chance of drowning or rotting.
4. Use a "plant babysitter" using pre-measured water. The big danger with having someone else do your watering is that they will drown your plants. Watering too little is much better than not enough. Put all your plants in trays, or even a baking dish/foil pan. Figure out exactly how much water it will take to give them each a safe drink without drowning them. Measure this amount into an empty milk jug and leave for your plant-watering person.
Temps: While you are away, keeping a consistently moderate temperature for your plants is important – anywhere between 65-75 degs. F. If the temperatures dip at night, powdery mildew and rot will likely occur. Also, if the temperatures are too warm, plant growth is accelerated, causing the plant to utilize more water and dry out faster. Plants are also susceptible to rot if they are in a covered environment and temperatures are high.
Light: If you grow on light stands, you probably already use timers. If you don’t, it’s easy to set them up, and you should be using them anyway. Use timers whenever possible to offer consistent lighting. If you grow your plants in natural light, you shouldn’t really need to change much if you plan on leaving your windows uncovered. Avoid changing to a new location just before a vacation, since plants could be burned from too much light, or they could begin reaching from too little.
What other ideas do you have? Please share them.