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I just put in a large planter box for semi-dwarf citrus (5' wide x 3' deep) as part of a landscape project and would love suggestions on what to fill it with for best results. A bottom layer of gravel for drainage. And then--? A 50/50 mix, or a 70/30 mix? Additional compost worked into it? Any and all thoughts would be greatly appreciated!
Afternoon @mark9912
Now that is a decent plater box! 
I am not particulary knowledgeable for citris plants I am afraid.
@MitchellMc however is. He is offline atm and hopefully will be back soon but he will know what would be best.
Dave
Hello @mark9912
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about what to fill your citrus planter with.
For your large planter box designed for semi dwarf citrus, creating a well-draining and nutrient-rich soil mix is key to long-term success. Since citrus trees dislike sitting in waterlogged soil, starting with a bottom layer of gravel isn’t necessary and may even hinder drainage by creating a perched water table. Instead, ensuring the planter has good drainage holes and using a high-quality, well-structured soil mix will give the best results.
A great option is a 70/30 mix, with 70% premium-quality potting mix designed for fruit trees or Australian natives, and 30% coarse sand or perlite to improve drainage. This combination allows for excellent root aeration while retaining enough moisture to keep the trees healthy. Adding compost is beneficial, but it should be well-aged and mixed in at no more than 20% of the total volume to avoid excessive nitrogen, which can lead to weak growth.
Incorporating a slow-release citrus fertilizer at planting will provide essential nutrients, and topping with an organic mulch like sugarcane or straw will help retain moisture and regulate soil temperature. Keeping the mulch a few centimetres away from the trunk will prevent rot. Regular feeding with a liquid seaweed solution or citrus-specific fertilizer throughout the growing season will support strong root development and fruit production.
If the planter is exposed to full sun and wind, consider positioning the citrus trees with some protection, especially in their early establishment phase. With well-prepared soil and ongoing care, your semi dwarf citrus should thrive and reward you with abundant fruit for years to come.
If you need further assistance, please let us know.
Eric
