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Introduction to Top Dressing Cannabis Plant Nutrients

March 19, 2018
Top dressing is a simple way to provide your cannabis plants with a diversity of nutrients. This method of feeding, which involves spreading nutrients onto the top layer of your soil, is easy to do and effective when it comes to promoting strong, healthy growth. While foliar feeding provides a quick solution to nutrient deficiency, top dressing is a great way to prevent deficiency in the first place.

There are a number of ways to go about top dressing your soil–you can make it as complex or simple as you want. In this article, we’ll take a look at the benefits of top dressing, as well as how and when to apply it top dressed nutrients.

Benefits of Top Dressing Cannabis 

Top dressing is a non-invasive way to add vital nutrients to your soil throughout the season. It’s commonly used to refuel your soil food web and replace the nutrients that have been consumed by your cannabis plants.

When choosing a feeding method for your cannabis plants, consider these benefits of top dressing:

  • Reduces the need for other types of feeding–including liquid and foliar feeding
  • Vital nutrients are slowly introduced, which helps prevent nutrient burn
  • Promotes a healthy, thriving soil ecosystem
  • Allows you to create your own custom blends of nutrients, including non-water-soluble nutrients and organic products

When to Top Dress Cannabis Plants

Top dressing cannabis plants requires a bit of foresight into the future. Nutrients delivered via top dressing take time to make their way into the soil food web, so you don’t want to wait until nutrient deficiencies are apparent.

Instead, observe your plant growth and consider what nutrients are being used at different parts of plant growth. For example, your plants want lots of nitrogen during the vegetative stage, followed by high potassium and phosphorus levels when flowering.


What are the best nutrients for growing cannabis?

You’ll also need to consider your soil’s nutrient content. If you have a simple soil that does not contain high levels of nutrients, you can top dress every three weeks to replenish your soil. On the other hand, if you have a complex soil with amendments, you might not need to top dress more than a few times throughout a season. Growers with complex soils commonly top dress once when their plants are beginning to flower to give them a boost.

How to Top Dress Cannabis Plants  

In essence, top dressing is an easy practice that will help your garden flourish if you follow a few simple steps. Here’s how to top dress your cannabis plants at the start of their flowering stage.

Step 1: Create Your Mixture

Top dressing is similar to amending your soil in that it gives you the chance to take raw nutrients and create a blend that you think uniquely benefits your garden. We all know plants want NPK (nitrogen, phosphorus, and potassium), but there are numerous ways to source these nutrients. When top dressing, you can add NPK from multiple sources to diversify the inputs while also including macronutrients and trace minerals.

Common mixtures include the following ingredients:

  • Worm castings
  • Kelp meal
  • Crustacean meal
  • Azomite
  • Gypsum
  • Bokashi
  • Bone meal


How to Maintain/Amend Your Super Soil Mix

Step 2: Apply Top Dressing  

Starting with worm castings, apply a thick, even layer. You can then add other nutrients as recommended for top dressing. However, when feeding, less is always safer. Many choose to go a bit below the product’s recommendations to protect their crops.

Step 3: Water in the Nutrients

After applying the top dressing, use a hose to water your plants. This helps the nutrients seep into the soil beds. If you use any sort of a drip system for watering, the nutrients may not fully seep down to your plant’s roots.

It’s that easy to apply extra nutrients to your cannabis garden with top dressing. With just the effort of three simple steps, top dressing is a method every attentive grower should keep in the toolbox. Got any more tips on top dressing cannabis? Drop a comment below!

Lead image by Leafly

Trevor Hennings's Bio Image

Trevor Hennings

Trevor is a freelance writer and photographer. He has spent years in California working in the cannabis industry.

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