Feed Me? Don't Kill Plants With Love (i.e. Fertilizer)

Yes, you can kill a plant with love. This is especially true if you believe that one way to love your plants is to feed them.

It is so very important to understand that fertilizer, be it for your houseplants, fruit trees, gardens and lawn, isn’t food. Again, fertilizer is not plant food. The ads, the labels and even some books refer to fertilizer as plant food. It isn’t.

Virtually all plants make their own food from sunlight (or artificial light), air and water. That’s it. No one goes out into the forest to fertilize the trees, shrubs and understory plants, and yet they survive and, in many cases, thrive. No one goes into the desert of our American Southwest and applies fertilizer. And yet there’s plenty of sunlight. What’s missing is water both in the ground and in the air. But on those rare and sometimes annual occasions when the rains come to these arid areas, the desert suddenly comes into bloom. No fertilizer. But with plenty of sun as soon as the monsoon rains hit within a few days the desert becomes a sea of color. All that was added was the missing element — water. No fertilizer.

Plants have this magnificent and wonderful ability to take the air (actually carbon dioxide) and the water and use these two basic elements to convert sunlight into what we consider to be food in the form of sugars and carbohydrates. The plants then take the nutrients in the soil to produce proteins, enzymes, vitamins and other elements that are essential for plant growth. This is where fertilizer comes in.

But, and this is a big but, in our gardens and in the ornamental and edible plants we grow these plants have been bred in a way that requires elements similar to vitamins (for humans) that allow them to be greener (as in your lawn), have larger fruits (as in fruit trees) and to flower in all the glorious colors and scents that we yearn for (think roses) and this is where fertilizers come in.

Now, you can do some incredible growing in the desert. The Israelis (among others) have mastered this by bringing water to the arid areas where plants are grown in the sandy soils. As long as the water holds out all we need to do is add the nutrients necessary for the particular plants, in this case vegetables, and you can grow just about anything as nutrients and fertilizer is added to the water and the desert becomes productive agricultural land.

But the guy on TV yells at you telling you that your lawn is screaming “FEED ME!” Books and articles about houseplants tell you that you must feed your houseplants, and anyone who has grown fruit trees or berries like blueberries and strawberries knows that they need fertilizer. This has to do with how we use these plants and our ability to get the best results by boosting their production (leaves, flowers and fruits) to an optimum level.

The down side to all this, especially for areas like the East End of Long Island, is that there is a great danger in adding fertilizers to our soils because our soils are very porous and as these fertilizers are dissolved they leach down into our water table and into our bays and waterways where they become pollutants. In this situation the leached and excess nutrients often result in algae blooms that can rob the bays of oxygen that the fish and other sea life need to survive. Some of the algae blooms are also known to be quite toxic to other forms of life, including us.

There are other sources of nutrients that can cause problems, and while we don’t consider them to be fertilizers they have the same result. A case in point is the historical issue of Lake Agawam in Southampton. This small lake is shallow and has little turnover or replacement of its water so it’s somewhat stagnant. The lake is surrounded by homes with lush gardens and lawns (with lots of fertilizer runoff). Add the remaining historical, residential septic systems in the area and you have yet another source of nutrients that can leach into the lake. As the lake warms in the summer the conditions get just right for the lake water to turn toxic, and anyone who has lived here for a while knows that this kills the fish with the lake becoming a toxic spot that rapidly loses its bucolic appeal.

And at this point you may be wondering, well, if I’m adding compost to my gardens and planters why do I need to use fertilizer at all? Compost and fertilizer should not be confused; they don’t have the same function or effects. Compost is essentially a soil builder. Compost adds structure to soil, enabling the soil to absorb and even store water, and the microbial action from well-composted compost brings life to our sandy soils, which can often be very thin when it comes to the organic matter needed for these wonderful and beneficial microbes to exist and thrive. In fact, it’s many of these microbes that end up helping to break down other organic material, including organic fertilizers, into nutrients that the plants can use. It’s important to remember though that compost in a sandy soil can be critical in making your fertilizer work, but compost in and of itself offers very little nutrition to plants.

Then there is the age-old discussion of organic vs. chemical fertilizers. For quite a while there was an assumption that organics were good and chemical-based fertilizers were bad. These days though it’s a little different. The organics are still great, but some of the chemical fertilizers are not terribly bad, but not great. This has to do with how the chemical fertilizer is manufactured and how it breaks down.

Keep in mind that organic fertilizers are naturally time released. You can use a straight chemical fertilizer on your lawn and see the results in days. But the results are often short lasting, especially when your lawn is irrigated or if we get lots of rain, which is becoming more and more common. The organic fertilizer applied to the same area of lawn will last much longer since it relies on biological activity in the soil to make the nutrients available to the grass plants and not just water.

There is a caveat though as some chemical fertilizers are coated with forms of plastics or polymers. These coatings prevent the fertilizer from being fully released in the presence of moisture. Instead the fertilizer is released as the coatings break down, giving the chemicals a longer time to be available in the root zone where they are absorbed. For this reason coated chemical fertilizers have become much safer, reliable and easier to use. However, they still don’t promote soil health as they are still basically acids that harm soil microbes. On the other hand, organic fertilizers promote soil microorganisms and thus the health of the soil.

This phenomenon is not limited to lawn fertilizers. An organic liquid houseplant fertilizer or vegetable fertilizer will last longer and be much better for a houseplant than a straight liquid chemical fertilizer or a time-released chemical fertilizer like Osmocote. Another thing to consider is that a product like Osmocote may only need to be applied to the soil every three to six months while a liquid organic may need to be applied every two to three weeks.

I know this can get very confusing, but it’s so important to understand in terms of plant health and protecting our environment. For a good part of my horticultural life, I used mostly chemical fertilizers. These days, nearly all my plants get organic fertilizers, and that includes houseplants, the gardens and the lawn. But I will occasionally give a dose of a fast-acting chemical fertilizer to my small collection of roses and my fast growing tomatoes. Still, even these plants get most of their fertilizer in the form of natural organics.

Next week we’ll look at the cost of fertilizer and how to gauge the costs vs. the value of certain types and formulations. And then there’s the age-old question, is fertilizer made from lobster waste better than shrimp-based fertilizer? In the meantime, fertilize your fruit trees and berries and houseplants, but it’s way too early to feed most outdoor plants. Keep growing.