As soon as the minimum temperature for the plants is reached permanently, they can be moved out of their winter quarter. Mediterranean plants with sturdy leafs such as olive, laurel and oleander can already be put outside in the beginning of April if no permanent frosts are expected any more. However, you should still watch the thermometer and consider that potted plants are permeated by the frost much faster than the garden bed. Thus, the roots can be damaged quickly. But if temperatures drop only a few degrees below zero, it is usually sufficient to cover the plants with fleece, blankets or the like.
Tropical plants should remain in their winter quarters until temperatures no longer fall below 10°C. Balcony beauties such as geraniums, fuchsias, or angel's trumpet should remain protected, as well, until mid-May. However, you can now start to prepare them for their summer habitat. Diseased, dead and weakly grown shoots can be removed. The time is now also favourable for a cut back. The plants are thinned out and brought to shape so that they will sprout out again forcefully. Furthermore, they should be checked for vermin. Very often they can be found on the undersides of leaves. The affected areas can either be cut off generously or be washed off, for example with soft soap. Depending on the vermin, various biological remedies might be used which should, whenever possible, be preferred to chemical plant protection products.
Now it’s also a suitable opportunity to re-pot your plants. The new diameter of the pot should be approximately 3 cm larger than the old pot. But you don’t need to do this every year. It can also be sufficient, if the dimension of the plant allows it, to remove the plant from its pot and replace the old soil with fresh one which has higher nutrient content.
Generally, you should make sure that both temperatures, inside the winter habitat and outside where the plant will be moved to, are similar on the day you plan to take out your plants. This way your plants do not suffer a cold shock. And even if it is very inviting to put the plants quickly into the long-awaited spring sun, you better put out the plants on a cloudy day since plants first have to get used to the new lighting conditions. To avoid sunburn, the plants first have to be placed in a shady space. If this is not possible the plants should be spanned with a thin cloth in order to protect them against UV radiation. Ideally, you find a shady area close to a wall where temperatures are always a few degrees higher. This way, your plants are well prepared to shine in summer again in their full glory.