How Often Do I Change The Soil In My Garden Planters?

Changing Soil In Garden Planters

A question that frequently pops up from new owners of garden planters is how often should they change the soil within them. In this helpful article, we aim to provide an answer to this question and also provide some general information and tips about keeping plant life healthy within outdoor planters!

  • Most garden soils in outdoor planters should be replaced every 2-3 years. Over time, nutrients get depleted and the soil can become compacted. Replenishing with new soil gives plants fresh nutrients to thrive.
  • For annual plants, we would recommend replacing the soil each year. Annuals have a shorter life cycle so they take a lot of nutrients from the soil.
  • If you have perennials or shrubs in a garden planter, the soil may only need replacing every 3-4 years. Perennials and shrubs are not as hard on the soil as the nutrients do not get depleted as quickly.
  • Containers with vegetables or herbs will need soil replacement more frequently - yearly or every other year. Vegetables feed heavily from the soil so rotating in new soil encourages better yields.
  • Always be on the lookout for signs that your soil needs refreshing such as poor plant growth, lackluster flowers or vegetables and wilting plants. These can indicate the nutrients have already been drained from the soil.
  • When refreshing planter soil, remove old soil and roots, then wipe down planter walls. Refill with a quality potting mix enriched with compost or fertiliser.
  • You can also top-dress containers yearly by adding an extra inch or two of compost to replenish nutrients. This compost should be mixed into existing soil.
  • Consider the planter size - larger planters will need complete soil replacement less often than small containers. Small containers (less than 10 inches wide) usually need yearly soil replacement.
  • For planters with mixed plantings, choose a general-purpose soil mix that is suitable for all of the plants or replenish each plant's roots with soil specific to their needs.
  • You can improve the drainage of a garden planter by mixing in materials like perlite, vermiculite or small gravel. Fresh soil tends to get compacted over time, so these additions will reduce compaction.
  • Before transferring plants back into a planter, examine roots and prune out any diseased, dead or circled and matted roots. This will encourage new healthy root growth once the plants are resituated in the planter.
  • Water newly planted containers well and let them drain. After this, you should continue a normal watering schedule with extra watering in the first few weeks to help the plants transition.
  • Consider rejuvenating the planter as well. Scrub interior walls to remove salt, mineral deposits and any algae build-up.
  • Stagger plantings if you have a large number of containers to refresh. This spreads the work over seasons and allows you to reuse and amend soil as you go.
  • If you are finding that your plants have poor growth even though you are following all of the best practices, it may be worth testing old soil before replacing it. Take a sample and get the pH tested to see if it needs adjusting. Soil pH changes over time and can become too acidic or alkaline; after testing you can adjust the pH before refreshing the soil if needed.