Frozen fruit mixes are great for boosting plant numbers without risking fruit going mouldy before you eat it. Sainsbury's do a Four Berry Medley 1kg bag of blackberries, blackcurrants, raspberries and strawberries for £3.90. The strawberries tend to be enormous and might be a bit flabby defrosted whole, but they are excellent when blended in smoothies.
A couple of scoops of pea & hemp protein powder, a splash of kefir, a couple of handfuls of frozen fruit, and either a banana or half an avocado and you've got a lovely smoothie. The ones made with avocado are halfway between a smoothie and a mousse, very luxurious. Just by rotating the frozen fruit bags it's easy to notch up 10 different fruits in a week, before you even start to look in the fruit bowl.
On one Zoe podcast they said they could tell which participants in the project used Tabasco sauce, from the results of their poo tests, and adding a pinch of mixed herbs and spices to meals encouraged a more diverse microflora. So I'm going to keep counting the nutmeg I grated over my warm milk as "a plant", and the cardamom in my coffee.
I agree that the game of trying to eat MORE plants is much more fun than the usual dieting schtick of concentrating on all the things you aren't supposed to eat.