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Fertilizing Potted Plants

Early to bed, early to rise, Work like hell: fertilize. - Emily Whaley

Fertilizing PlantsWhether you are growing indoors or out, fertilizer is essential to the success of container gardens. The easiest way to go about fertilizing potted plants is by preparing a nutrient solution and pouring it over the soil mix. The fertilizer is absorbed by the roots and quickly adds what is missing from the existing soil. Even if your potting mix is perfect from the get-go, it will soon become depleted of nutrients as they are constantly used up by plants and leached out by watering. The faster a plant grows the more fertilizer and water it will require. Consequently, as watering is increased so is leaching and nutrient loss.

Once you’ve selected a fertilizer (make sure you use an organic one!), you’ll need to apply it about once every two weeks for container grown plants. This assumes that you’re growing in a high quality, compost rich potting mix that will help retain nutrients. With that said, some gardeners prefer to fertilize with a weak nutrient solution every other time they water. If this is your preference, make sure to use about 1/5 the amount called for on the label.

Granulated and easy to use, Happy Frog All-Purpose Fertilizer provides gentle slow-release feedings over time. Recommended for vegetables flowers, ornamentals and all types of container gardens. Mix 1 Tbsp per gallon of soil or topdress 1/2 to 3 cups monthly per established plant.

Tip: When adding fertilizer to potted plants use organic blends (derived from many nutrient sources). Organic fertilizers are just as effective as chemicals, will not burn, and supply the required macronutrients (N-P-K) as well as a large selection of minerals, micronutrients, amino acids and vitamins.

When you fertilize is also very important. Plant nutrient needs change with different stages of growth. For example, to get the most from annual bedding plants, start them on a high nitrogen fertilizer to promote growth and leaf development, then switch to a low nitrogen, high phosphorous solution to encourage blooming.

Fertilizer Facts

If you aren’t familiar with how to buy fertilizer here is a quick tutorial on what to look for:

There are three numbers on the front of every bag or bottle of fertilizer. The numbers are always in the same order and stand for the percentage by weight of the N-P-K or Nitrogen, Phosphorus and Potassium contained in the fertilizer. Each of these is necessary for healthy plant growth and development. Read more about fertilizer numbers here.

For example, a bag of all-purpose organic fertilizer might carry these numbers, 5-5-5. The first number indicates nitrogen (N), which promotes lush, green growth and overall plant health. A fertilizer high in nitrogen is a good choice for leafy vegetables grown in containers, such as lettuce and Swiss chard. Natural sources high in this nutrient include blood meal, feather meal and liquid fish emulsion.

The second number indicates phosphorous (P), which is used to develop healthy roots and is necessary for fruit and flower development. Blooming plants, like tomatoes, peppers and most ornamentals, benefit from nutrient solutions rich in phosphorus, especially when they are ready to set buds. Organic fertilizers known for their phosphorus content include bone meal, seabird guano and many liquid blends.

The third number is potassium (K), which is necessary for stem growth and overall plant vigor. Potassium is used especially on root crops such as carrots, beets and potatoes, but also on young trees during the fall to encourage strong roots during the winter months. Sources of organic potassium include sul-po-mag (sulfate of potash magnesia), palm bunch ash and many liquid fertilizers.

Note: Plants can absorb nutrients through both their roots and through leaf pores. Foliar feeding (applying fertilizer solutions through leaf pores) can supply nutrients to your plants immediately. It is especially effective for giving fast growing plants, like vegetables, an extra boost during the growing season.

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10 Responses to “Fertilizing Potted Plants”

  1. The Organic Life on June 10th, 2016 at 5:29 am #


    Great article. Thank you for taking he time to write a detailed instruction on fertilizing potted plants. Organic fertilizers are always a better choice than the chemical ones. I strongly advocate the use of organic products for gardening and home kitchen.
    Will definitely explore more in this wonderful website of yours.


  2. Leonard Hooper on March 30th, 2017 at 6:02 am #

    I was wondering how much cow manure to use in my plant pots?

    • Grandpaw Grizzly on June 30th, 2018 at 1:10 pm #

      How much cow manure to use in plant pots depends of course on the size of the pots (volume) but the best answer is probably don’t overdo it. I made a 50-50 manure/soil mix for 3 large pots to see if I would get bigger tomatoes. One plant quickly died from root rot. I saved the other two by aerating the roots with a long thin stick and watering only once a week. I did however mist spray the leaves daily at daybreak before sun photosynthesis. The manure seems to hold humidity for too long if there is too much of it and potted plants get waterlogged. I think better to stick to a vermiculite potting mix for pots with little manure.

  3. Amy Weiler on July 9th, 2017 at 11:16 pm #

    Should I fertilize my outdoor potted plants in the morning or evening?
    Should I fertilize them before or after watering?

    Thank you.

    • Grandpaw Grizzly on June 30th, 2018 at 1:24 pm #

      In Oregon, where the summer sun is scorching hot, I found the potted plants on my outdoor patio enjoy watering with nutrients solution at early dawn. Photosynthesis then produces new plant growth from the water the same day. If dawn is too early for you, wait until dusk. Do not water during a hot sunny day as the sun will virtually boil the water; that’s when the leaves turn brown. Watering in the evening is okay but you won’t get the same advantage of morning smoothly increasing photosynthesis as the sun gradually gets hotter. Evening water basically sits at the bottom of a pot until the next morning, which is more risky than helpful to the plants.

  4. Sonia laporte on July 11th, 2017 at 5:34 am #

    BonJour, A friend gave me a lovely orchid. I do not know how and when I have to fertilize it. And what kind of fertilizer to buy. Many thanks for your help. Have a lovely day. Sincerely yours, Sonia Laporte

  5. Janice lintner on September 9th, 2018 at 5:43 am #

    I need an organic fertilizer that will run through a fertilizer injector in our irrigation system. We have 32 hanging baskets, 62 boxes and 2 cottage gardens. We’ve had problems with the organics in that they clog the drip lines requiring much maintenance. Any recommendations?

  6. Brian on December 5th, 2018 at 5:41 pm #

    Hi and thanks for the info , but I made some liquid seaweed fertilizer and would like to know the dilution ratio for pot plants. Cheers Brian.

  7. Md Ikram Ali on January 2nd, 2019 at 11:14 pm #

    When we use NPK fertilizers on cucumbers, green peppers or some other crops, we apply it at different stages — growth, fruiting and flowering. But what about leafy vegetables like cabbage, kale or lettuce? How can we apply fertilizers to them accurately at different stages? We would like to grow large lettuce heads, but have not had much success.

  8. Susan on June 17th, 2019 at 11:41 am #

    I love how plant clippings look in my clear glass vase of tap water. How long can I keep such clippings in the vase of water? Is there some sort of fertilizer I can put in the water to lengthen the look of it?

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