Plants Do Not Need to Be Fed – Stop Fertilizing!

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Robert Pavlis

Everybody tells you that plants need to be fed. Thousands of gardening books and blogs confirm the fact. Fertilizer companies certainly continue to make you feel as if you are letting your plants down if you don’t fertilize. And most nurseries try to push their products at checkout.

I have good news for you. In most garden situations, you do NOT need to fertilize.

The idea that ornamental gardens need fertilizer is a big myth.

Which rose fertilizer has the correct NPK?
Which rose fertilizer has the correct NPK?

Which Plants are We Talking About?

This post is all about plants growing in soil. It includes all ornamental plants, but does not include containers, or raised beds that do not have real soil in them.

The other exception is vegetable gardens, where some of us have a very short season, and we need high growth rates to produce something before frost comes.

It does apply to soil that contains some clay (holds nutrients) but not sandy soil which needs to be treated differently.

Microbe Science for Gardeners Book, by Robert Pavlis

Why Fertilize Plants?

Before proceeding, I need to define fertilizer. In this post it includes both synthetic and organic, including things such as manure and compost. After all, they all provide the same nutrients for plants.

The idea is pretty simple. We are living and need to eat, so we feed ourselves on a regular basis. Plants are living and so it follows that they also need to be fed. This seems to make sense, but it’s wrong.

Plants do need nutrients, there is no doubt about that.

Except for oxygen, hydrogen and carbon, plants get most nutrients from the soil. The thing gardeners forget is that soil is like a big refrigerator of food. It has lots of food stored up ready for plants to use. It is not like a cupboard with empty shelves. It is more like a large restaurant walk in freezer ready for the weekend rush. It’s loaded with food.

Assume your refrigerator contains lots of apples. When you go to the store, do you buy more apples? Of course not. You already have too many.

Fertilizing is a lot like buying these apples. You should only do it if you are running out of apples.

When you fertilize you should only be adding the nutrients which are missing from soil. There is no point adding extra potassium if the soil has lots.

How do you know what the soil is missing? There are two options; (a) grow stuff and (b) get a soil test done. I prefer option (a), just grow stuff. If it grows, you do NOT have a nutrient deficiency. You can do a soil test, but they have limited value for most gardeners.

The problem with many gardeners is that they don’t do a soil test, and they don’t trust their own plants which are showing them the nutrient levels are fine. Instead they believe marketing programs, social media and many sources of gardening information.

Roses Need Special Fertilizer

If you understand and believe what I have said so far, you will know that this title is wrong – Roses don’t need special fertilizer – they probably don’t need any at all.

Google for images of rose fertilizer. I did that and found a bunch of different products, all of which are “special rose fertilizers”. I have put a collage of these together in the above image.

I even found a special fertilizer for Knock-Out Roses – wow, I didn’t realize they were that different from other roses – it is just marketing to get you to buy more stuff.

How can all of these products be a good rose fertilizer and at the same time have different formulations?

They can’t all be right. At best one formulation is correct, and the others are wrong. But even that one is probably wrong as I will explain in the next section.

The reality is that there is no such thing as rose fertilizer, or orchid fertilizer, or tomato fertilizer, except in the minds of fertilizer manufacturers, their retailers and their faithful customers – and years ago I was one of those customers.

If manufacturers can’t agree on the right NPK formulation for roses – there is certainly an issue here.

Replace Missing Nutrients in Soil

Daylily starting to boom - 32 flower spikes - 150 blooms, never been fertilized
Daylily starting to boom – 32 flower spikes – 150 blooms, never been fertilized

I know some of you are still not convinced. Why would you be, when so much of the world is telling you that you must fertilize. But consider this example.

You get a soil test done on your soil and it contains lots of all the required nutrients except that you are low in nitrogen.

Your gardening friend down the street also had their soil tested. They have lots of nitrogen and lots of all the other nutrients, except they lack potassium.

Should you both use the same fertilizer for your roses?

Clearly the answer is NO. You need to add nitrogen, and your friend needs to add potassium.

The reason to fertilize is to replace the nutrients missing from your soil.

You do not feed plants – you feed the soil, by adding the missing nutrients. Plants will then take what they need from the soil refrigerator.

But …. Farmers Need to Fertilize

Actually farmers DO NOT need to fertilize to grow plants. They do have to fertilize to maximize yields, grow a good sized crop and make a profit, and there is nothing wrong with a profit.

Studies have shown that for soil in both the US and England, for various crops, the added fertilizer increases yields by 40 to 60%. What that means is that without fertilizer farms would still produce about 50% of the crop they now produce.

Gas plant (Dictamnus alba) at Aspen Grove Gardens
Gas plant (Dictamnus alba) at Aspen Grove Gardens

Fertilizer is important on farms, and it is of value in home vegetable gardens, but it has very little value in a landscape garden. Most gardeners do not care about producing bigger seed heads, or bigger root systems, or taller plants.

They do want more flowers and less pest problems, but too much fertilizer can result in more green growth in place of flowers, and more soft growth that is tastier to bugs (so I am told – this may be a myth?).

Ornamental gardens are perennial and long term projects, not annual growth races to beat Mr. Winter.

My gas plant produced 20 flower stems this year, without fertilizer. Should I really fertilize in the hopes of maybe getting 22?

The Proof – Aspen Grove Gardens

I started Aspen Grove Gardens 15 years ago. No fertilizer or transplant solutions have been used. None of the ornamental beds have received fertilizer, compost or manure. The soil is not particularly rich but it does contain 40% clay. I do mulch with wood chips which decompose and add very small amounts of nutrients. Fall leaves stay in the beds, mostly where they fall. I use the cut and drop method of cleaning up the garden – what the garden produces stays in the garden.

I grow 3,000 different types of plants, and most of them grow just fine. They flower well and I have few pest issues. Do I have the biggest roses? Probably not. Do I have the most flowers on my gas plant? Maybe not. But I also do not waste valuable resources by using fertilizer and I don’t spend time hauling it around.

I am also not polluting my local rivers and lakes by having excess fertilizer run into them.

This is not an isolated case. Lots of experienced gardeners do not fertilize.

Is Soil Depleted of Nutrients?

This is a common opinion that many people share. Agriculture removes nutrients from soil every year as they harvest the crops, so nutrient levels must be getting lower?

I thought this was true myself, but a year ago I checked into it. I wanted to know if we needed to remineralize the soil. I could find no evidence that this was an issue.

Fertilizer Recommendations

If you are running a farm and you get soil tested, the lab will make a fertilizer recommendation based on maximizing profit. This is a critical point. The lab balances the cost of the fertilizer, with the increase in yield, and estimates the point were it still makes financial sense.

This makes a lot of sense for a production farm where profit is critical for a livelihood.

What happens when a homeowner gets soil tested? The lab tries to apply the same logic for the homeowner. How much fertilizer is needed to maximize profit? Except that in the case of an ornamental bed there is no data to do this calculation and profit has little meaning.

I have spoken to the Ontario Government and they have verbally acknowledged that they do not know how much fertilizer ornamental beds need. The same situation exists in the UK and the US. This kind of science has not been done.

Fertilizer recommendations from a lab are at best, a guess, based on agricultural experience. But the goals for agriculture and ornamental home gardens is very different.

Look at Leaves for Nutrient Deficiencies

Lots of social media memes tell you that you can do this – but it does not work. I have discussed this in Can Leaves be Used to ID Nutrient Deficiencies?

Should You Fertilize?

I like to keep gardening simple. Start by assuming your soil has all it needs. Plant stuff. If it grows, you do not have a problem so don’t fertilize.

If you have problems growing a lot of different plants, it may be a nutrient issue. Then have the soil tested and follow recommendations.

If most plants grow well, and a few don’t, it is not the soil, except for the odd plant that is very fussy about pH. Solve this by getting different plants.

Adding a bit of compost, or manure from time to time is a good idea – not for the nutrients, but the organic matter will improve soil health.

This suggestion will not apply to all soils, but most soil containing some clay and/or organic matter will hold lots of nutrients and don’t need to be fertilized.

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

39 thoughts on “Plants Do Not Need to Be Fed – Stop Fertilizing!”

  1. Catherine, I agree. I am inclined to think that most people can see the difference for themselves. Like the William Rathge studies showed us years ago with the landfill studies, most of the waste is being done by corporations and businesses, not the individual consumer. It’s not even logical. In many cities, the people don’t even have yards to contribute to the waste. For example, in my city, 80% of the people live in apartments. Of that remaining 20%, how many do you think mow and fertilize their own lawns and gardens? On my very long street? It’s me (occasionally) and one other (occasionally) . The rest use a lawn service or they just kill their lawns with lack of maintenance. And the lakes are still full of algae. But it makes the advocates feel like they’re doing something if they punish the individual. Fertilizer is expensive. We’re not likely to waste our money if it’s not needed, those few of us who do fertilize.

    Funny thing: according to my local ag agency, it’s clippings and leaves that clog up and contribute to the water pollution more than fertilizer. But what do they know? The cities in the US by federal law, cities aren’t even supposed to drain the streets to the waters anymore but they can be grandfathered in, which doesn’t stop the pollution from continuing.

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  2. I came here to know the exact answer whether the plants need fertilizer to bloom as i found the vinca seeds germinating and finally blooming on the brick walls. This article concludes that plants do need fertilizer for better performance but they can also bloom and fruit without fertilizer in less quantity. But i am still confused why the hell that vinca bloomed which is growing on the brick joint with cement mortar?

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  3. I’ve raised ducks, using a little blue baby pool for their swimming needs. Water from that poopy-pool gave me the biggest squash, tomatoes, and most corn I’ve ever had. I also notice a difference between watering with tap water vs. rain barrels.
    I don’t have a green thumb but as far as I can tell it makes a big difference. Sometimes I do diluted fish emulsion with mixed results.

    PS We don’t have much dirt where I live, just clay on top of massive limestone rocks.

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  4. With phosphate and potash expected to become exhausted in 80 years at which time the population is expected to grow to about 11 billion, in percentage terms, how short might we be of food.

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  5. I have compared fertilized tomatoes, roses, and cannas, as well as some herbs such as rosemary and basils, side by side with non-fertilized ones. The differences are very striking. The fertilized ones are bigger with bigger leaves and blooms, as well as more and faster growth. Flowering plants have more flower heads and they bloom faster. My mom also doesn’t believe in fertilizer but all her plants are either under performing or non performing. Before I started trying out with fertilizer I never thought plants could do this well. I thought what she had was how plants were supposed to behave. She has a tomato plant bought at the same time I bought mine. The plants were about the same size when we bought them. They are planted in two different areas in the garden, but mine is well fertilized with organic fertilizer and hers has no fertilizer at all. Mine is now three times bigger than hers a month later with very well set fruits. Also, my mom’s roses had never been fertilized and they didn’t produce good leaves or flowers. This year, I started fertilizing. The roses have consistantly produced bigger blooms and healthier leaves when I fertilized according to schedule and they seem to slow down when I don’t. Even the rose that was almost killed by scales recovered after application of fertilizer and proper watering. I use only OMRI listed “organic” fertilizer (NPK usually hovering around 5-7) as well as chicken manure and compost. There are plants that do not need much care to thrive, but they also appear to perform better with support of a little fertilizer. For those of us who are worried about heavy metals, encourage some pill bugs or rollie pollies to come to your garden. They are great decomposers and they eat up the heavy metals and feed your garden at the same time. With respect to house plants, my mom’s house plants had never been fertilized until this year. The flowering plants have produced more and bigger flowers and stayed in bloom longer. This was just with a handful of bonemeal and feathermeal. A few months later, some of them have bloomed again but the flowers are much smaller. I am speaking from personal experience. It is not true that house plants or ornamental plants do not need feeding. Those of you worried about cheated by merchants should do your own research and learn your fertilizers and organic amendments. We eat everyday, and I do not know why people think plants can be left on their own and expect to do well (it depends on what you consider doing well. My mom thought her plants were doing well, until she has seen how much better they can do with a little more support).

    In your photos, the daylily leaves are light colored which is sign of nitrogen deficiency. The leaves are not as glossy as they should be. You might want to look up gas plants and see how much bigger their leaves and flower heads can get. Also, the areas around the plants appeared to be well mulched with dried leaves. When dead organic matters decompose they can also provide nutrients for the plants. Also, “weed-like” wild varieties such as gasplants and daylilies will do more OK than cultivated varieties. In fact, some nitrogen fixing weeds die if you over fertilize. Potted plants are not as lucky. They are restricted to a pot and the soil we use is usually potting soil which loses water and nutrients quickly. If you don’t want to fertilize you should at least change the potting soil once in a while so the plant can get some organic matter still present in the soil.

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    • The day lilies are not wild lilies and they flower well each year. My gas plant is huge and flowers really well and I don’t need it any bigger.

      Re: “If you don’t want to fertilize you should at least change the potting soil once in a while so the plant can get some organic matter still present in the soil.” – plants don’t use organic matter.

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    • Catherine, I had the very same experience as you! I was raised to believe that fertilising wasn’t necessary. My mom never used it. As an adult I did my research and realised that it makes perfect sense, especially in potted plants. I’m guessing this guy probably got lucky with a nice bit of land that has high fertility. By the time he exhausts it he will probably be dead and it will be someone else’s problem.

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      • Look around you at all the natural areas – nobody fertilizes them!

        Growing in a pot is nothing like growing in ground. First – you don’t use soil. Second – you water a lot washing nutrients out of the pot.

        And if you actually read the article, you would have seen, “This post is all about plants growing in soil.” The article is not about potted plants.

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  6. Fertilizers can also add toxic material to soil, like lead and arsenic. There’s an organic loophole as far as I know. Conventional poultry farms are typically high in arsenic (added to feed to combat parasites from filthy overcrowded conditions). All of the poultry stuff finds its way into “organic” bags of “soil” and various fertilization products.

    Arsenic will stunt plant growth (one of the more potent herbicides) and it’s not beneficial to have in your plants for you or for nature.

    Lead has been especially found in the slow release “extra minerals” formulations.

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    • You also find the heavy metals like lead and arsenic in plant material. In fact some plants have a tendency to accumulate them, in effect concentrating them in the plant biomass. So one would need to find the concentration from all these sources and compare them to see which is actually adding more heavy metals.

      Reply

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