M Ljin: Wind is indeed a great problem in much of the highlands so shelter is key for providing a growing environment. Did you hear that the structure she grows in is called a 'polycrub'? They were developed in Shetland to stand up to the extreme wind conditions possible in the exposed islands as a community project and named polycrub after the local growing areas that had been built of stone walls and called 'planticrubs' (
source). The stone walls also keep the free ranging sheep out of the food growing area...
Even on Skye we have some sheltered areas that have pretty impressive trees, and the 'great glen' that runs through the highlands SW-NE to Inverness again has some beautiful wooded areas. Shelter builds shelter, so once some trees are established natural regeneration spreads slowly (give or take overgrazing from deer/sheep pressure).
You can gain a couple degrees easily by adding shelter, but not much more than that, so to get good summer temperatures for warm climate crops like tomatoes, even courgettes (Zucchini) we need some sort of greenhouse effect. Because of the wind, plastic is unfortunately much safer to achieve this than glass....