Add lemon juice to a medium bowl of water. Peel celeriac and cut into 5cm-long matchsticks. Place celeriac in lemon water to prevent browning. Set aside.

Peel skin and pith from oranges and cut crossways into 1cm-thick slices.

Divide the orange, olive, rocket or spinach, onion and fennel among shallow serving bowls.

Combine orange juice, vinegar and olive oil in a jug. Season with salt and pepper, and whisk until well combined.

Drain celeriac and arrange over orange mixture. Drizzle with dressing and gently toss to combine. Serve immediately.