The GARDENA gardening expert
In this case, I would advise you to determine the pH value of your garden soil using a ground sample, or to have it determined at your local garden centre. Your information indicates that your soil may be too acidic, which however can only be assessed in connection with the plants growing in your garden – rhododendrons and blueberries etc. require an acidic soil. If possible with regard to your plants, you can then raise the pH value to approximately 7.5, by scattering 100 g/m2 agricultural lime for a rise of 1 pH respectively, and working it into the earth. It may also be the case that the soil in your garden property is relatively severely densified, which also promotes the growth of moss in a bed. You can loosen up the soil through more frequent soil processing, lime conditioning and the addition of humus, compost, dung and leaves.
As far as your query on mosquito prevention is concerned, there are indeed plants around which these pests feel unwelcome. The variegated Swedish ivy (Plectranthus coleoides), for example.
However, it is said that such plants have more effect if they are planted in larger numbers, for example on balconies and patios. I am sceptical as to whether one can plant large numbers of plants in an operation designed to keep mosquitoes away from the entire garden, in the form of a protective hedge – that cannot work, as the mosquitoes only react when in direct proximity to the plant fragrances.
However, even gardeners of yore knew that walnut trees keep mosquitoes away. Through their strong evaporation, they generate high air humidity and cool the air – and heat-loving mosquitoes hate both of these things. Therefore, walnut trees have always been popular planted close to a house, for example under a bedroom window, or around seating areas. They then act in a similar manner as the shady chestnut trees in beer gardens.