Squeeze the lemon juice into a clean jam jar. Add three times the amount of extra virgin olive oil, season with salt and pepper, then screw the lid on and shake to emulsify.
Add the rocket, watercress, pea shoots, apples, beetroot and beetroot leaves, if you have them, to a large bowl. Drizzle over enough dressing to completely coat the ingredients, add the marjoram, toss again and serve.