This is a question I saw posed elsewhere and it got me thinking. The assumption was that a central part of being a witch was casting spells, which seems to me to say that you are not a witch if you don't cast spells. Now I have some serious issues with this idea, in fact I think it is completely wrong. While I can certainly acknowledge that in the mind the correlation between witches and spell casting is popular I don't believe that you have to cast spells to be a witch. Maybe the key lies in identifying if there is a different between magic and spells.
One can perform simple acts of magic without having to be performing a spell in my opinion. You can add magic to your cooking through the use of a few words and some herbs or by stirring the pot a certain way. You can say a few words when searching for a car park, draw on the strength of the earth to fill you with strength when facing a troubling time, or hundreds of other instances where you choose to enact a little magic in your life, are these spells? Some would perhaps say yes, in which case I guess you would have to say that spells are a part of everyday life for a witch.
For me personally I define spells as something more elaborate, something that you put time and effort into creating, enacting and following up, they have structure. I can count on one hand the amount of times I've actively worked a spell. When I've taken the time to create, prep and perform a working for a particular purpose. What makes these spells different from simple acts of magic for me? A spell seeks to make a significant change and therefore needs to be imbued with significant power. When you first begin the process of deciding to do a spell you are starting the process of building power towards your desire. The entire process is a building of magic and the spell is the focus for that magic, it is a ritualized act and therefore is something that should be used sparingly in my mind.
So for me the answer is simple - you do not have to do spells to be a witch, nor is your level of 'witchiness' dictated by the amount of spells that you do. But I'm sure not everyone would agree with me and that's fine too :)