Why has my Meyer lemon tree dropped all its leaves, but the branches still look healthy and were healthy during the summer?

• Citrus trees defoliate when they are stressed to save themselves.
• Has the tree dried out at any stage? Has it been frosted? Is it planted in a sheltered spot in well drained soil? Has too much fertiliser been applied? 
• If the tree is in the garden make sure it is clear of weeds and grass as they both compete for nutrients. Clear away a 50cm diameter area and apply Tui Mulch & Feed to keep the soil moist and suppress weeds.
• Consistently water in the growing season, for established trees water every week, for newly planted trees water every 2-3 days. 
• Feed the tree in early spring once the risk of frost has passed. If the tree is planted in the garden feed with Tui Citrus Food; if it is in a pot apply Tui Enrich Citrus & Fruit controlled release fertiliser. Apply more fertiliser in late summer.
• Apply fertiliser around the drip line (the area where the foliage extends to).
• To stimulate new growth and root growth apply Tui Organic Seaweed Plant Tonic at a rate of 100ml per 9L watering can. Once the tree shows signs of recovery reduce seaweed applications to every 2-4 weeks.