One of the main things we are asked about succulents is "Which ones can go outside" many succulents can go outside during the summer but the main thing to bear in mind is a few key factors. These are Temperature, Light and Water.
Temperature
The temperature is reasonably easy to sort out, a great resource to use is World of Succulents, it's an essential online encyclopedia for succulent lovers, it has care advice and information on most plants. Simply check on this website if you're unsure on the plants minimum/maximum temperature range, on a lot of websites you'll also notice zones for temperature ranges, we tend not to use these as we find they can be a bit too generalised. We're down in Devon so the temperatures tend to be a bit more warmer than the rest of the UK. Frost and snow are a lot less of an issue as well, if unsure get yourself a Min/Max thermometer and keep an eye on the forcast.
We grow a lot of our plants outside all year
Light Levels
Some plants can be scorched if suddenly exposed to high levels of sunlight having been in the shade for a while, this can be something to bare in mind when receiving plants in the post as well, they will have usually been in the box for 3 days or more. To help acclimate them you want to let them adjust, usually a week at a time from one spot to the other before finally going into direct sunlight.
Some plants will change colour depending on how they are kept, Aeonium Kiwi are a good example as the photo below shows, the one on the left has been in the tunnel, the plastic is designed so it dosen't quite let all the light through where as the one on the right has been outside for a few weeks.
Aeonium tabuliforme will actually be more dinner plate like when grown with a little shade and can become more elongated when grown in full sunlight, completly changing its form depending on the conditions.
If a plant is scorched by the sun the plant will usually recover, the best thing to do is to put it back into shade and leave it be, the leaves may recover but if there is permanant damage to the leaves don't worry, these will usually grow out given time or they'll fall off and new leaves will take their place.
Water
You have to think about where the plant has developed before thinking about how much water it wants. A plant that has evolved in the desert won't do very well if watered too much or sat in a dish. As a rule of thumb you always want to let the plant dry out completley before watering, though plants don't make it easy for us, some go dormant at certian times of the year when they won't want much water at all. You should always aim to get it right of course but It's better to underwater than to over water!
A lot is to be said about the soil mix, certain composts have a wetting agent built in, this can be great for some plants but a nightmare for succulents. For example for most of our Sedums and other plants that prefer being outside we use a 50:50 mix of good quality compost and horticultural grit. If you have heavy clay soil you may need to add more grit.
Great Outdoor Plants
When planting on jobs locally the main succulents i'd recommend are Sedums, Delosperma, Sempervivums and Lamparanthus, they are really tough, especially the Sedums and with good drainage they grow brilliantly, all of these are available on our website.