Hostas
The best way to ensure that a collection of container-grown plants remains healthy while you're away is to install an automatic irrigation system. These are less complicated versions of those used by professional nurserymen to keep thousands of plants alive, and are extremely easy to put together - if you are any good at building a Lego model you will have no problem at all.
There are many irrigation systems available in garden centres and DIY stores, with some more sophisticated than others and a choice of attachments for watering different parts of the garden. Pick a kit for containers, making sure it has a timing device and enough hose to reach the area that needs to be watered.
Once your system has been set up, attach it to a timing device (fitted to an outdoor tap) and programme it to come on once or twice a day, depending on the plants you need to water.
If you only have a few containers, try the recently launched AquaPod from Hozelock (available in DIY stores). This consists of a small cylinder that is linked to a timing device by a short length of hose. Inside the cylinder are five mini-hoses that can be pulled out and attached to five pot-grown plants. This gadget is really easy to use and only takes five minutes to set up.
If you don't have an outdoor tap, you can still ensure plants remain alive. Move containers and hanging baskets from a sunny patio or deck, and put in a shady place where they will dry out less quickly. The gap behind a shed or along a side return is ideal. Water well and further reduce evaporation by covering the plants with a sheet of shade netting material - this can be bought in rolls from garden centres.
Alternatively, pots will remain moist for longer if plunged into the soil. Find gaps in a border or in a raised bed, and dig out a hole. Sink the plant in so the lip of the container is flush with the surface of the soil. As the compost dries out the plant will start to take up moisture from the soil.
Keep houseplants happy
Plants sitting on a sunny windowsill will need lots of water over the summer, so it makes sense to move plants before taking a holiday - put them on a surface out of direct sunlight and water well.
If you have lots of indoor plants, soak a towel in water and lay it in the bottom of the bath. Stand plants on it and they will absorb water as and when they need it.
There, that's all there is to it. A few simple watering tricks will ensure you can have a great, stress free holiday without the worry that you'll return to find a sea of dead plants.