Slow Release Fertilizers Reviewed (5 of the BEST)

Hand fertilising
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If you have been following my blog for a while you will know that I sing the praises of slow release fertilizers as a means of keeping your container plants fed throughout the growing season.

I am constantly asked what slow release fertilizer do you recommend?

Hence, why this article on reviewing the 5 best slow release fertilizer that I would recommend being used in gardens, particular container gardening was written.


Slow release fertilizer is specific feed for plants in containers that releases their nutrients slowly over time. This is usually over six months but can be up to a full year. The main advantage is that the plants get the right nutrients when they require it, without the compost becoming depleted. It is best for those forgetful gardeners who forget to feed their plants.

We all have busy lives, working and doing other things, and often forget that the plants in containers need to be fed and watered at least once a week with a liquid fertilizer.

 Slow Release Fertilizing
Fertilizing is very important.

The need to be fed often as the plants in containers are often hunger and go through their nutrients very quickly. An unfed plant is an unhappy plant. Slow release fertilizer replaces the laborious task of feeding containers plants once a week.

Imagine instead if feeding the container plant 1 time during the growing season and then forgetting about it. You can if you use a slow release fertilizer once in spring. Remember to feed your container plants at the recommended dosage as written on each package.

The Advantages are:

• Plants get the nutrients when they require it.

• Only feed one time a year in spring during the growing season.

• Can be stored for use over a number of years

• As less feed is required, you will save money in the long run.

• A wide range of choice available.

The Disadvantages are:

• If your plant is already sick the nutrients will not be absorbed quickly. You will still need to use liquid fertilizers in this case until the plant recovers.

• You can overdose plants, as you can add too much feed to the containers. This will not only waste money but can damage the plants and is because overfeeding can make plants more susceptible to diseases and pest attacks. Overfeeding is as dangerous as underfeeding.

What follows is my top 5 slow release fertilizer for use in container gardening.

1) Gro-sure All Purpose 6 months Feed

Product: Gro-sure All purpose 6 months Feed

Best Place to buy:

Size of the compost package: 22.8 x 16.8 x 11cm

Shipping Weight: 2.26kg

My score: 9.5/10

Gro-sure slow release plant feed has been specially formulated to grow healthy plants. This ready to use granules are ideal for pots, window boxes, and hanging baskets, where it will provide enough nutrients for 6 months.

The granules are activated by increasing warmth in the compost, where plant roots are able to absorb the nutrients. It contains more potassium for extra blooms and extra fruits, with added trace elements for green, healthy leaves and root development.

• One application feed plants for 6 months continuously. Will provide plants with their nutrients requirements over the whole growing season.

• Can be used for all non-ericaceous plants.

•  Can be used in pots, beds, borders, window boxes, and hanging baskets.

• Contains 12% nitrogen 7% phosphorus and 19% potassium, with added micronutrients.

2) ChemPak Slow Release Feed+ Forget Garden Plant Year Long Fertilizer

Product: ChemPak Slow Release feed+ forget Garden plant year long fertilizer

Best Place to buy:

Size of the package: 18 x 10.6 x 5.6cm

Shipping Weight: 0.798kg

My score: 8.5/10

This is a once a year feed and forget fertilizer that continuously releases its nutrients to the root system of the plants.

It is ideal for trees, shrubs, perennials, and annuals, both acid-loving or not. Recommended for long term feeding of container plants to ensure that they flourish during the growing season.

• It is ideal for feeding your container plants for those who are forgetful at home or for professional gardeners.

• Perfect for all types of plants in ericaceous or non-ericaceous compost.

• Long lasting fertilizer. As it comes in a large 750g pack and you only need to use a small amount.

• Comes with a 100% satisfaction guarantee. If you are not happy with the product, the seller will either replace the product or give a total refund.

• Has a composition of 15% nitrogen, 6% phosphorus and 12% potassium, and plus micronutrients.

3) Osmocote Controlled Release Plant Feed

Product: Osmocote Controlled Release Plant feed

Best Place to buy:

Size of the package: 16 x 6 x 23.5cm

Shipping Weight: 0.750kg

My score: 8.5/10

The granules used in this product is coated with a unique outer shell that controls the release of nutrient, so that plant in containers get the nutrients at the right time when they need it the most. It feeds container plants for up to six months.

Osmocote comes with a composition of 14% nitrogen, 14% phosphorous and 14% potassium, so giving balanced requirements to the plants, ensuring good top growth and a strong root system.

Suitable for growing trees, shrubs, annuals and perennials. This slow release fertilizer is also suitable for growing vegetables and fruits, to increase yields

• Produces stronger and healthier plants.

• Feed annuals, perennials, shrubs and trees in containers for six months.

• It is a controlled release formula, so will only feed plants when they require it and not before.

• Can be used for all plant, both acid loving or not.

4) Miracle-Gro All Purpose Continuous Slow Release Plant Food

Product: Miracle-Gro All Purpose Continuous Slow Release Plant Food

Best Place to buy:

Size of the package: 20 x9.6 x 8.6cm

Shipping Weight: 1.08kg

My score: 8/10

It is claimed that using this slow released fertilizer can result in plants that are twice the size of unfed plants. Miracle-Gro has a unique mix of 10 nutrients that are carefully balanced to provide plants with the required amount of these nutrients for better top growth, blooms, and fruits.

The fertilizer is ideal for all plants-apart from ericaceous plants, where an alternative feed needs to be used- both indoor and outdoor, in pots, window boxes, and hanging baskets.

• Feed plants up to 6 months.

• Temperature controlled coating to release nutrients when the growing conditions are right for feeding.

• Ideal for all non-ericaceous plants, including fruits and vegetables.

• Excellent for all pots, containers, window boxes, and hanging baskets.

• Feed up to 40 containers of standard size.

5) Slow Release Fertilizer Tablet

Product: Slow Release Fertilizer Tablet

Best Place to buy:

Number of tablets: 200

Shipping Weight: Unknown.

My score: 9/10

This slow release fertilizer comes in a convenient tablet form that contains 14% nitrogen, 7% phosphorous and 14% potassium with added magnesium and trace elements. As with all slow release fertilizers it works by temperature increases in the compost, where nutrients are slowly released to where the plant needs it the most, the roots.

It is excellent for annual hanging baskets and pots. The slow release tablets can also be used in permanent containers, where perennials, shrubs, and trees can be fed by using these tablets in early spring.

• Feed plants up to 6 months

• Temperature controlled coating release nutrients when the growing conditions are right for feeding includes added magnesium and trace elements.

• Ideal for all plants, including fruits and vegetables.

• Excellent for all pots, containers, window boxes, and hanging baskets.


I have been using slow release fertilizers for a number of years in my containers full of shrubs, annuals, and perennials. I have used it to grow my tomatoes, peppers, soft fruit, and my summer bedding plant.

My plants did very well in producing better blooms, more fruit, and healthier plants, all with one feeding per year.

If you want to replicate my results in your container garden, then I would recommend using one of these slow release fertilizers. I have chosen the best 5 and now it is up to you to decide which one to choose.

If you have any questions or any remarks you want to make, please do so in the comment box below, where I look forward to receiving them.

Why not try some today.


20 thoughts on “Slow Release Fertilizers Reviewed (5 of the BEST)”

  1. Interesting article, I have a great passion for growing plants but I didn’t know how to maintain it and fertilizers should be used. This article is really helpful and I think slow-release fertilizers are better for beginners like me. I really enjoyed reading this article and this article helped in choosing the best slow-release fertilizers.

    Thank you for sharing such useful information. Good job, keep on.

    1. Hi Supportcme

      Thank you very much for those kind words and I hope my review helps you to make an informed decision.  I hope it has made it crystal clear.



  2. Love this!  I am a super busy mom who loves to garden and I definitely need something that I can set and forget.  Most of my containers have fruits and vegetables in them and I know fertilizer makes a huge difference.  I have historically used standard fertilizer that needs to be applied throughout the year but I will definitely be trying one or a few of these slow release options.  

    I saw options 3, 4 and 5 were all suitable for fruits and vegetables.  Is there one you would recommend over the others for that purpose?  I have to make sure that it is safe as I have young children and animals.  

    Thank you for the great article and your help.  

    1. Hi smctee

      Thank you very much for your feedback, as it is very much appreciated.  All 5 slow release fertilizers that are reviewed, are highly recommended by me. 

       As with all garden chemicals, it is best to keep safe from children and animals, so store them in a secure location.   In the soil, it does not matter as it will be mixed with compost and so will not be harmful. Always practice safety first.

      Kind Regards


  3. Ha! These are for me!

    I don’t remember how many times I’ve destroyed plants because I forgot to water them. I’m surprised that most of them are still alive. 

    I want to get Gro-sure. I guess it comes with instructions on how much to use, right? Because some of my plants are way bigger than others.

    Thanks in advance!

    1. Hi Kate 

      Thank you for those kind words.  Watering and feeding as just as important, and one cannot survive without the other.   All slow release fertilizer has instructions on the package,, so you can never overdose your plants.  Here is to your success in the garden.

      Kind Regards


  4. I love container gardening.  i grow my kale and spinach in big pots on my porch, and they’re not only absolutely gorgeous, but I can pick a salad anytime I like, and it just grows more leaves.  It’s awesome.  I never knew there were slow release fertilizers.  I’m surprised the lady at the garden center has never mentioned this to me.  I use a fertilizer that I have to add whenever I water my plants.  How silly, right?  I’m so glad I came upon your article (and your wonderful site)!  This is going to make my life so much easier now that I know about slow release fertilizers!  Thanks!

    1. Hi Babs

      Thank you very much for those kind words.  If you look after a plant, then a plant will reward you will fruits and flowers, ignore them and they will sulk and die.  Do you want them to sulk or do you want the plants to survive? This is why it is recommended to feed your plants regularly or feed them using a slow release fertilizer.

      Kind Regards


  5. I am not a professional gardener but what I have in the yard are tomatoes, bell peppers, mint, red chilli, aloe vera, and oregano. I have it because those are easy to take care of. I guess I’m lucky because they are still ok despite of the little amount of time I have for them. Honestly I don’t use any fertilizers and they all grow and bear fruits. The problem is that it only bears a few and fruits doesn’t grow that big. 

    Do you think it’s because I don’t put fertilizer? When I read your article, I was surprised ’cause I never knew there were fertilizers that you can feed the plants once in 6 months. It’s really good for people who got no time.  Thanks for all the helpful information.

    1. Hi Missus B

      Think of plants are young children, in order to grow and flourish they need to be fed, watered and generally looked after.  Ignore one of these at your peril, as the plant will surely die.   Yes, you need to feed your plants regularly in order to produce, and small fruit is a sure sign that your plants are hungry.  They would appreciate a good feed.  Slow release fertilizer is ideal in containers where nutrients will be consumed faster andIi hope I have pointed you in the right direction.

      Kind Regards


  6. Thank you for recommending slow release fertilizers. I sometimes forget about these products so this is a really helpful reminder that they are out there. I appreciate also that you’ve pinpointed container gardening. With slow release fertilizers I like that they only need to be spread once per year, saving time and money. I will remember not to overdose the plants, thank you. I’m with you I like the Gro-sure All Purpose fertilizer due to its array of uses and high potassium. I’ve bookmarked your page here, well done!

    1. Hi Pentrental

      I thank you for those kind words and highly recommend the choice that you have made.

      Kind Regards


  7. Thanks for the review of these 5 slow release fertilizers. I have been wondering what options I have for our home garden and was looking for some answers. You have clarified all my questions and now I feel ready to buy the one that will work best for me.

    I read through the specs and your score for each and do think that any of these top 5 will work. The next thing I did was to have a look on Amazon to see which I can get here in Dubai without having to wait a long time for delivery. I have two choices, the first and the last on your list.

    I will go with number 5 as it is a bit cheaper, yet about as effective. The Slow Release Fertilizer Tablet will work for not only the vegetables but for the shrubbery and trees that we have in the back area of the villa. I think I will get enough for the next year. Will this product store well since I will only have to use 2 times over the next year. Are there any special storage conditions i.e. in a cool dark place?

    1. Hi Dave

      Thank you for those kind words.  Slow release fertilizer is a must for gardeners who forget to feed their plants.  The best way to store them would be in a  dark dry place, where any moisture egress is avoided.  Otherwise, you will lose your fertilizer and the nutrients will be leached out.

      Kind Regards


  8. Great information here.  I think I will try one of these on my outdoor containers (window boxes and a couple hanging baskets), as I tend to forget to feed them and have watched too many plants turn to dust, despite my best intentions.

    One question for you, and I’m sure this shows my inexperience, but is there any danger of the nutrients being released too much/too soon, or being diluted, depending on how much water the containers get?  My window boxes are protected by a roof overhang and don’t get much rain directly in them, but the hanging baskets are out in the open, so I’m wondering if the nutrients in the slow release fertilizer would still be able to work their magic.

    Thanks – very helpful stuff!

    1. Hi Jordan

      Thank you for your feedback.  The answer to your question is no, as the slow release fertilizers have been designed to release their nutrients when the plants require it most.  So if it needs it , it will be released and when it don’t then the nutrient will be held back.  The slow release fertilizer works as long as the required watering is kept up.  Nutrients are harder to uptake when the compost is dry. You can use  watering spikes in order to help the forgetful gardener,



  9. Hi Antonio,

    Bit late here but thanks very much for this interesting article. I was wondering, what in the case of container grown tomatoes? I saw in another of your posts that you would feed with a liquid tomato fertiliser during the growing season, which is what I do. But in that case would adding a slow-release fertiliser as well not end up over-feeding them?


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