Climate in Holland and what (not) to grow
In Holland, along the sea, there are generally no hard winters or very hot summers, but it can be quite wet at times. It is nothing as a Mediterranean climate or continental East European climate. This may limit the sort of vegetables you want to cultivate, which grow well in your country of origin. As it can still be cold, near freezing at night , till middle of May, you have to be careful not to plant outside, without protection, tender vegetables .
To check which weather you can expect in the near future, look at
www.weatheronline.co.uk/Netherlands/Noordwijk.htm
As the climate here is quite similar to the one in England, you can use all the advises for which vegetables/fruit to grow and timetables provided for England by the Royal Horticultural Society:
You could also use advices given for North of France.
Be careful when buying seeds from countries with warmer climate: the vegetables may struggle with colder temperatures. Some vegetables as peppers, eggplants( aubergines)and cucumber are better grown under cover. Don’t try melons outside: they will not get sweet enough!
In recent years, wet spells in summer have caused great problems to grow tomatoes on the Estec site: tomato blight (and also potato blight) is a fungus which causes plants to get brown and tomatoes inedible! Good ventilation is essential (remove a lot of leaves), overhead protection against the rain advised, preventive treatment possible if you don’t mind using chemicals (some allowed for organic gardening). The spores remain on the soil and are transported by the wind. Grow cherry tomatoes; they will have more chance to ripen before the blight strikes.