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Knox Gelatin Fertilizer for Houseplants

Jill is a former Master Gardener and Naturalist who enjoys cooking, abstract painting and stewardship.

Pick unflavored gelatin. The ingredients, such as dyes and artificial sweeteners, found in flavored and/or diet products may inhibit plant growth.

Pick unflavored gelatin. The ingredients, such as dyes and artificial sweeteners, found in flavored and/or diet products may inhibit plant growth.

Knox Gelatin: An Organic, Nitrogen-Rich Fertilizer

Do your houseplants have yellowing, splotchy leaves? Are the seedlings you started indoors an unhealthy shade of pale green? Chances are, they're suffering from a nitrogen deficiency.

A solution of Knox unflavored gelatin and water is a good, inexpensive organic source of nitrogen that's been proven effective in promoting plant growth.

Why Do Houseplants Love Knox Gelatin?

As reported by Peter Tonge in The Christian Science Monitor, a two-year study conducted on 49 species of houseplants by Dr. H. W. Scheld of the University of Houston's Department of Biology found Knox gelatin to be an effective fertilizer for home gardeners if applied in a diluted form once a month as part of regular watering.

Scheld's study gave Knox gelatin plant food the green thumbs up primarily for three reasons:

  1. Knox plant food does indeed promote healthy plant growth.
  2. It's an inexpensive source of nitrogen.
  3. And it's unlikely to result in excessive nitrogen build-up, which can harm plants.

Extracted from the collagen in the bones, skin and connective tissues of animals, Knox gelatin is an organic substance. Because it's organic, it breaks down more slowly in the soil than the inorganic nitrogen found in synthetic fertilizers. And that means you're less likely to overfeed your houseplants, potentially harming them.

Use one packet of Knox per one quart water.

Use one packet of Knox per one quart water.

How to Make Knox Gelatin Plant Food

Here are the directions for making gelatin fertilizer, direct from Knox's website.

The recipe makes one quart of fertilizer suitable for most houseplants. Although Knox's site recommends cold water, if you have difficulty getting the gelatin to dissolve, you may want to soften and dissolve it in hot water, and then add enough cold water to make one quart.


  • 1 envelope Knox Unflavored Gelatin
  • 1 quart water, divided


  1. Measure 1/4 C. water into a quart container.
  2. Sprinkle 1 envelope Knox unflavored gelatin over water.
  3. Allow to soften for 1-2 minutes.
  4. Add 1 C. water to gelatin mixture.
  5. Stir until gelatin is dissolved.
  6. Add additional water to make 1 quart.
  7. The fertlizer is ready to use. Use it once a month for watering houseplants.

Recipe Tips

  • Do dissolve the gelatin completely before adding more water.
  • Don't allow the mixture to pool on the soil surface.
  • Do add more water if the mixture seems too thick.
  • Don't use flavored/diet gelatin, which may contain dyes & artificial sweeteners that inhibit plant growth.
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Read More From Dengarden

Enjoy your lush, happy plants.

Enjoy your lush, happy plants.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

Questions & Answers

Question: Can you use gelatin mix for outdoor plants?

Answer: Sure, you can apply it to any plant that would profit from a boost of nitrogen. As noted in the article, however, you should avoid giving a dose of nitrogen to some plants, including plants that are fruiting.

© 2013 Jill Spencer


Kristen Howe from Northeast Ohio on November 25, 2015:

Jill, this was another interesting gardening hub on how to take care of house plants with that gelatin. It sounds intriguing. I might keep that in mind for next year's plants.

Jill Spencer (author) from United States on October 20, 2015:

Hi Reynold Jay, thanks for stopping by and commenting.

Reynold Jay from Saginaw, Michigan on October 19, 2015:

Hi Dirt Farmer--What a great idea and you make it look esy too. Well done and my plants will be much better now.

Jill Spencer (author) from United States on September 13, 2013:

Thanks so much, Thelma! Knox gelatin fertilizer is an easy and inexpensive way to give your houseplants a nutritional boost. All the best, Jill

Thelma Alberts from Germany on September 13, 2013:

This is a great informative hub. I will make this for my plants as soon as possible. Thanks for sharing. Voted up and pinned for later use. Thank you.

Jill Spencer (author) from United States on September 13, 2013:

Sounds good, Suzie! Appreciate it. I'll add a link to your air purifying hub here, too. It makes sense: Knox fertilizer = happier houseplants = cleaner air! (:

Suzanne Ridgeway from Dublin, Ireland on September 13, 2013:

Hi Jill,

Love this idea, what a great tip! Linking this one to my air purifying hub also, if that is okay? Thanks again, for a useful idea we could all do! Votes, sharing and pinned!

Jill Spencer (author) from United States on June 04, 2013:

Interesting! Perhaps Knox has updated the directions. There's no need to use hot water. the gelatine dissolves in cold water and tap water just fine.

Ex-IL Farmer on June 04, 2013:

I remember the actual recipe on a Knox packet as one packet dissolved in 1 QUART of HOT water. Stir until all dissolved. Then add 1 Quart of COLD water. Do not use until mixture is nearly air temperature to not injure the plants. Makes 2 quarts.

Jill Spencer (author) from United States on March 07, 2013:

@ Glimmer Twin Fan--I know! I always have packets of Knox left over from making pie filling. Why not put it to good use?

You're welcome, Deb. Try sprinkling just a little bit on the seeds that you sow, too. But not too much.

Deb Hirt from Stillwater, OK on March 07, 2013:

I had no idea! Thanks for the great tip, Jill.

Claudia Mitchell on March 07, 2013:

This is fascinating. I had no idea one could use this as a fertilizer. That will save me a lot of money in the future. Thanks Jill!

Jill Spencer (author) from United States on March 07, 2013:

Hi ExpectGreatThings! To get the heart, go into a text box in edit mode. Click the symbol icon in the tool bar at the top of the box & select the one you want. I mostly use em dashes. Thanks for stopping by! --Jill

ExpectGreatThings from Illinois on March 06, 2013:

I have never heard of this and can't wait to try it! On an unrelated subject, how did you get the little heart in one of your capsules (Why do houseplants [heart] Knox gelatine)?

Jill Spencer (author) from United States on March 05, 2013:

Hi Eddy. Thanks!

And Radcliff--I don't blame you. Why waste all that good cooking on houseplants when you can use a leftover pack of gelatin! Take it easy, Jill

Liz Davis from Hudson, FL on March 05, 2013:

This is interesting. It may sound weird, but I wonder if bone stock (homemade, of course) would do sort of the same thing. It contains a substantial amount of gelatin. This is probably a moot point because I don't think I'd be willing to share my bone stock with the plants. LOL Thanks, Jill. I will pick up some gelatin and give this a try.

Eiddwen from Wales on March 05, 2013:

So interesting and thank you for sharing.I vote up and share.


Jill Spencer (author) from United States on March 05, 2013:

Hi Lee. It's a good way to use those leftover packets of gelatin! Nice to hear from you. Hope your Florida garden in winter was a success.

Lee Raynor from Citra Florida on March 05, 2013:

Hey Jill

Interesting, I never heard of this before now.

carol stanley from Arizona on March 05, 2013:

What a unique idea. And an inexpensive way to take care of house plants. Does it work on silk plants??? Just kidding. Voting up, pinning and tweeting...

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