Part 2: What to Use, and When Fertilizing Container Gardens: A Beginner’s Guide

Fertilizing Container Gardens 2

When you’re new to growing vegetables and herbs in pots, figuring out the how, when, and what of fertilizing container gardens can feel overwhelming. This article is the second in a three-part series that offers a beginner-friendly guide to feeding your potted edibles.

In part 1 of the series, I talk about fertilizing basics, including the special challenges plants face when growing in containers and why feeding them is essential to their health.

This article, part 2 of the series, provides my four-part recommendation for fertilizing and offers three sample schedules you can follow depending on the plants you’re growing and your gardening goals.

Part 3 of the series is designed to give you in-depth information about the four types of fertilizers and supplements: liquid fertilizers, liquid supplements, granular fertilizers, and granular supplements.

A 4-Part Recommendation for Fertilizing Container-Grown Vegetables and Herbs

All of the following recommendations can easily be classified into one of four main categories:

  1. Liquid fertilization
  2. Liquid supplements
  3. Granular fertilization
  4. Granular supplements

For a basic beginner’s approach, you can get by doing only the first one, liquid fertilization. I think this is the bare minimum if you want to grow healthy food in a pot.

If you’re overwhelmed by this information, or if you’re just too busy to fuss with it, simply pick up a bottle of liquid organic fertilizer and start there.

That alone will probably take care of most of your problems, and greatly improve the quantity and quality of the food you grow.

An ideal fertilization regimen for container plants would include all four of these categories. If you have a special baby in a container, do all four. Your plant will thank you for it.

I do all four of these for some edibles that I grow in pots—especially fruit-intensive plants like tomatoes.

There are a few key exceptions that I’ll talk about below.

As you learn more, you’ll figure out which bits and pieces are most important for different plants, for different problems, and for different uses.

  • When I first noticed the visual difference in my aloe plants after they got a handful of mineral sand, something clicked, and I haven’t planted aloes without trace minerals since.
  • When I saw how much resin accumulated on a calendula plant that grew in a tomato pot with regular high-potassium fertilizer, something clicked, and now I always use high-potassium fertilizer on calendula.
  • When I first saw the visual difference in my strawberries after they were treated with liquid seaweed, something clicked again. I don’t grow strawberries anymore, but if I see someone else’s strawberries suffering, I know that a little liquid seaweed will probably fix them right up.

This is the learning curve, and with each new experiment, you’ll add another piece to the puzzle.

Schedules for Container Plant Fertilization

As I said above, I think the best basic, beginner’s plan for fertilizing container plants is to use a simple, well-balanced, organic liquid fertilizer. There is more information on specific fertilizers below.

The Basic Schedule

Regarding the schedule for using fertilizers, I generally would recommend one application every two weeks.

So, a basic schedule would look like this:

  • Week 1: Liquid fertilizer
  • Week 2: Skip
  • Week 3: Liquid fertilizer
  • Week 4: Skip
  • Repeat indefinitely

An Intermediate Schedule for Certain Situations

If I notice that the soil smells off in a certain pot, I will often apply aerobic compost tea to restore healthy microbial life to the container. I apply this on the off weeks when I am not giving liquid fertilizer.

If I am growing a crop that specifically appreciates some liquid seaweed, like strawberries, or leafy spring greens that have survived into the heat of summer, I will also apply the seaweed on the off weeks.

So, an intermediate schedule might look like this:

  • Week 1: Liquid fertilizer
  • Week 2: Liquid supplement
  • Week 3: Liquid fertilizer
  • Week 4: Liquid supplement
  • Repeat indefinitely

An Advanced Schedule for Special Plants

If I am growing tomatoes in a pot, I go all out. I use all four categories, and I give the plants everything in my arsenal to ensure a healthy life and a good yield.

An advanced schedule for special plants would look something like this:

  • At planting: Granular fertilizer and granular supplements
  • Week 1 after planting: Skip
  • Week 2 after planting: Liquid supplements
  • Week 3 after planting: Liquid fertilizer
  • Continue to alternate a week of liquid supplements and a week of liquid fertilizer until fruit set, then:
  • At fruit set: Granular fertilizer and granular supplements
  • Week 1 after fruit set: Skip
  • Week 2 after fruit set: Liquid supplements
  • Week 3 after fruit set: Liquid fertilizer and liquid supplements
  • Continue applying liquid fertilizer and liquid supplements each week until the end of the growing season.

Any time I’m applying a lot of fertilizer and supplements, as in the example above, I cut back on the dilution strength of the liquids and the volume of the granular. The general idea is to give less, more often.

A Few Key Exceptions

I distinguish between leafy annuals and woody perennials in my fertilization schedules.

Some woody perennial plants don’t appreciate the extra nutrients, and you can cause more harm than good by overdoing it with regular fertilization.

Woody herbs like rosemary and lavender are especially sensitive to this. I fertilize rosemary about half as often as I fertilize other plants, and I fertilize lavender rarely if ever.

Blueberries benefit from special treatment in a container. They love seaweed, iron, and acidity. Watering with vinegar is beneficial here. Give your potted blueberries some extra love and they will pay you back with plenty of tasty berries.

When I’m growing tomatoes in a pot, as I said above, I go all out. I use everything in my arsenal to get the plant as productive as possible. I normally don’t worry about burning plants with too much fertilizer, because I only use mild organic fertilizers and I dilute them well. In this case, however, I always keep a close eye on the leaf margins to make sure that I am not overdoing it with the tomatoes.

 

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(This is an updated version of a post that was originally published in October 2015.)

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