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Time to Fertilize those Tomatoes

August 6th, 2010

Just a reminder if you live in the colder northern climates, that it’s time to give your tomatoes a little fertilizer to ensure that they remain productive until the end of the season. Tomatoes are heavy feeders so they appreciate a little fertilizer mid-season to keep them growing and producing heavily until frost. If you fertilize now, you give them a little boost so they set new blooms and will produce a last flush of tomatoes before the cold fall weather.

You want to make sure you use a fertilizer that’s rich in potassium and not too high in nitrogen, otherwise they will only produce lots of leaves. Fertilizing is vital if you’re growing your tomatoes in pots, as they use up the nutrients quickly in the limited amount of soil. They can benefit from some topdressing with compost and fertilizer each month.

I like to give mine a mid-season side dressing of bat guano, each plants gets a Tablespoon or two. Because of the make up of guano, it is very beneficial for fruiting plants and trees. I find that it helps my tomatoes green up nicely and set lots of new fruit this time of year. My bat guano comes courtesy of my dad, who harvests it from a local church belfry every couple years. You can also water every 3-4 weeks with a fish/seaweed emulsion as tomatoes really love that as well. Since I have very poor soil in the front garden, I use a very weak fish emulsion each month on those tomatoes, about 25% strength, my favorite is Neptune’s Harvest Organic Fish & Seaweed. Side dressing with comfrey leaves is also beneficial for tomatoes, you can add the chopped leaves at planting time and mid-season.

Do you fertilize tomatoes mid-season? Do you use anything special?

15 Comments to “Time to Fertilize those Tomatoes”
  1. Julia on August 6, 2010 at 7:02 am

    ooh, thanks for the reminder! I have a bottle of the Neptune’s Harvest Seaweed fish emulsion just waiting for this moment! :)

    Reply to Julia's comment

  2. Kaytee on August 6, 2010 at 7:43 am

    Bat guano? I’ve never heard of that being used, but most manures are beneficial for the soil, so I see why it works. I should get out there and fertilize those tomatoes now!

    Reply to Kaytee's comment

  3. Turling on August 6, 2010 at 10:02 am

    My son has been asking about bats and wants to build a bat house. Now, I see there is good reason to.

    Reply to Turling's comment

    • Susy on August 6, 2010 at 10:20 am

      Bats eat tons of mosquitoes, which is another great reason to have them around. We have a bat house, but none have moved in yet. I’ve heard it can take a few years.

      Reply to Susy's comment

  4. MAYBELLINE on August 6, 2010 at 12:00 pm

    Dr. Earth is applied when they are transplanted and then a couple of time during the summer. I won’t fertilze the tomatoes anymore this season. I would like them to be finished so I can concentrate on fall planting.

    Reply to MAYBELLINE's comment

  5. Sense of Home on August 6, 2010 at 2:47 pm

    I use organic fish emulsion, no guano handy.


    Reply to Sense of Home's comment

  6. Rose on August 6, 2010 at 3:15 pm

    Ayuh, I’ve already given them their bone-fish-blood meal treat and the nettle tea has flowed! However next year I’m going to try and not cram the pots so tightly, there was barely room for the roots in the pots I had!

    Reply to Rose's comment

  7. Aubrey on August 6, 2010 at 8:36 pm

    I learned from a man who wrote an organic book about tomatoes growing that if you trim (cut off a ton) leaf matter you will actually get much larger tomato yield. It works!!

    The other thing I have learned that is amazing is to dry your egg shells in the winter months and blend them in a blender (or put them in a bag and crush them) then when you plant put a 1/4 cup of dried egg shell in with your transplant. It works, my tomatoes are generally around 12 feet tall and yield like crazy!

    Last tried and true hint, when you transplant a tomato, bury the plant stem and all so that only about three inches of the plant stick out. In other words if you have a 12 inch plant 9 inches of the plant would go in the ground. The plant will grow a root system on the entire stem that you put in the ground, and will be a much stronger plant.

    If you grow them like this you will need a six foot structure to hold them up, TRUST ME! (and it will need to be staked into the ground with a large metal fence post), it will be much to large for a garden store cage, we make our own from fencing with 4×4 holes about 3 feet in diameter.

    ok that is my little blog book on tomatoes! ;-) I should send pictures, my friends die when they see them, but I swear its just these tricks that work every year.

    Reply to Aubrey's comment

  8. Jaspenelle on August 6, 2010 at 9:13 pm

    I am currently struggling with my tomatoes a bit, 4 of my 6 plants are doing great (Black Krims and Yellow Pears) but both my Italians (huge beefsteak tomatoes) keep getting really big and right as the begin to turn red the bottom gets a black spot that grows rapidly. It is if they are rotting from the bottom up. They are all in the same bed so I am not sure what the problem is.

    I am going to the local garden shop this weekend though for fertilizer and to see if they have some advice for me. I’ve grown tomatoes since I was a teenager (though it is only my second year in this climate) and never had them rot on the plant before…

    Reply to Jaspenelle's comment

    • Susanne on August 7, 2010 at 7:59 am

      This sounds a lot like blossom end rot to me. Unfortunately I had some losses to it, too. You might have a look at for help!

      Reply to Susanne's comment

    • Susy on August 7, 2010 at 8:04 am

      It does sound like blossom end rot, which affects italians more than others I have found. I also have some plants in the same bed with the same nutrients/soil/watering and some of the Italians get blossom end rot and the beefsteaks are find.

      I’ve read that sometimes the first few tomatoes to set have this problem and it should get better with the later tomatoes. It’s hard to know what really causes it, since everyone seems to have a different reason and plants getting the same conditions some have it while others do not.

      Reply to Susy's comment

  9. […] This post was mentioned on Twitter by mark mile, Susy Morris. Susy Morris said: Time to Fertilize those #Tomatoes #edible #tomato #fertilizer […]

    Reply to Tweets that mention Time to Fertilize those Tomatoes | Chiot’s Run —'s comment

  10. Susanne on August 7, 2010 at 7:56 am

    I did not feed tomatoes in mid-season until this year – frankly because I’m only just getting into the deeper mysteries of fertilizing. For example: I put a good handfull of horn chippings in almost every pot of edibles at planting time only to discover that this was just perfect for lettuces and chives, but not so much wanted with tomatoes and beans. Although it’s nice to have a tomato plant with a really beautiful dark green foliage for a change :-)

    I found some organic fertilizing drops especially for tomatoes and so far added liquid seaweed for an extra dose of potassium every week or so. It’s not so easy to find something like “Neptune’s Harvest” in Germany. I was glad to find some liquid seaweed in stores after all. It is so highly recommended in almost every better book on gardening I had my hands on the last couple of years – but most of them were British, Canadian or from the US.

    It’s the same with comfrey pellets, by the way. I shy from making a brew by myself on my balcony, as it is described as quite a stinky operation. But you wouldn’t get any pellets in Germany… at least I couldn’t find any (yet).

    Reply to Susanne's comment

    • Susy on August 7, 2010 at 8:01 am

      It is quite a stinky operation to make comfrey tea. I made it once and now I just use the leaves around my plants.

      Great to hear about how it is to garden in Germany!

      Reply to Susy's comment

  11. Sheryl at Providence Acres Farm on August 7, 2010 at 2:44 pm

    Good timing! My tomatoes desperately need some extra food. I just can’t seem to find the time…

    Reply to Sheryl at Providence Acres Farm's comment


This is a daily journal of my efforts to cultivate a more simple life, through local eating, gardening and so many other things. We used to live in a small suburban neighborhood Ohio but moved to 153 acres in Liberty, Maine in 2012.

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