All About Fertilizing Houseplants

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Note: I republished this blog with permission from Folia Design, a Quebec City houseplant boutique. The author is Réal Dumoulin. I did the translation from French into English.

I must admit I was impressed with the article from the start, but all the more so when I realized the author had quoted me! (How often does that happen!) So, just maybe that influenced my desire to republish this … but I like to think I did so simply because it’s a really great article that covers a complicated subject quite succinctly.

Enjoy!

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It doesn’t take much fertilizer to make houseplants happy! Source: growingtogether.areavoices.com

There are many myths circulating about the importance of fertilizing plants, especially houseplants. Most people think that fertilization plays a major role in the health of their plants when in fact it’s only a minor factor in their development. What matters most in the life of a houseplant is the quality of the soil, lighting, watering, humidity and ambient temperature. However, that doesn’t mean you can completely neglect fertilization either: it still plays a small role in the quality and beauty of our indoor plants.

When Should I Fertilize?

The main rule is to only fertilize a plant when it is actively growing!

  • In general, you don’t need to fertilize plants during the winter in the average home. Most will be semi-dormant and fertilizing then would only stimulate weak and etiolated growth, susceptible to insects and diseases. However, starting at the end of February, the increasing luminosity leads to a growth spurt in most indoor plants. That’s a sign it’s time to fertilize.
  • However, there are exceptions. Any plant that is clearly growing in the winter can be fertilized, although normally at a lower rate than the one recommended on the fertilizer label, say at about ¼ to ½ of the usual rate. Plants that are getting especially bright light, for example under fluorescent lights, in a solarium or in front of a south-facing window, may continue to grow and even bloom during the winter and they’re the ones that will likely need fertilization. In addition, some plants, such as cyclamens, houseplant azaleas, gardenias, etc., are naturally in full bloom during the winter, and therefore need regular fertilizing at that season.
  • One common error is fertilizing a plant when it’s clearly in distress, something you should always avoid! When a plant is in bad shape, you need to analyze the situation and treat it according to its needs. Is it receiving insufficient light? Too much or not enough water? Is its soil too compact? Is it contaminated with mineral salts (unabsorbed fertilizer from past treatments)? Fertilizing a plant in distress may out-and-out kill it!
  • Generally, you won’t need to fertilize after repotting or top dressing, because the potting mix used already contained fertilizer. Wait at least 2 to 4 weeks before starting to fertilize a plant after either treatment.
  • Plants won’t usually need fertilizing for about 6 weeks after purchase, as they were likely treated to a good fertilizing regime in the store.

The normal period for fertilizing houseplants is from the end of February to the month of September whether they spend the summer indoors or out.

Which Fertilizer to Choose?

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It really doesn’t matter which fertilizer you use on your houseplants. Even lawn fertilizer will do! Source: www.pennlive.com

Stores offer a huge number of different fertilizers in stores and they come in different forms and formats, plus they can be chemical or organic. Naturally, you’ll want to choose the best for your plants.

However, it’s important to understand that most fertilizers are about equally good and you can use almost any one on any plant. Garden writer Larry Hodgson rightly points out that plants can’t read fertilizer labels. In other words, they’ll do fine no matter which fertilizer you use.

Slow-Release or Quick-Release Fertilizers?

Some fertilizers are in the form of granules or spikes and are slow release, that is to say that they’ll fertilize the plant over a long period. Often, a single spring application is sufficient, although a second one in early July may be useful.

Most fertilizers, though, are quick release and come in either liquid or powder form. They’re designed to be diluted in water before use, according to the manufacturer’s instructions. Just water the plant’s potting mix with diluted fertilizer, although it’s best not to fertilize plants when their soil is dry, as this can harm the plant’s roots and, eventually, the plant itself.

Foliar fertilizer is yet another kind of fertilizer. It’s designed to spray directly on the foliage and yes, plants do absorb fertilizer through their leaves. Often, liquid seaweed, properly diluted, is used as foliar fertilizer.

20-20-20? / 10-30-10? / 15-30-15? / 30-10-10?

Oh my! All those numbers! What’s a houseplant enthusiast to think? But remember from above that plants can’t read fertilizer labels and really don’t care what you use! In general, a balanced fertilized like 20-20-20 or something similar is ideal for all plants. Liquid seaweed fertilizers are particularly interesting for both foliar use and for watering into potting soil.

What About Compost?

Compost is not really a fertilizer, but a product that improves the soil’s structure and texture so that it better retains water and fertilizers. By all means, do add some to your potted plants, but you’ll still need to fertilize at some point.

Should I Use Organic or Chemical Fertilizer?

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Chemical fertilizers often come in bright artificial colors. Source: www.taskeasy.com

People have a wide range of opinions on that subject, but in fact, plants really don’t care which type you use. The choice will likely be based more on your personal values than on the plant’s needs. You can easily find organic fertilizers such as liquid seaweed if that’s what your choice.

Avoid Over-Fertilizing!

Many people use too much fertilizer, thinking that the more they give, the more beautiful and healthier their plants will be … and that’s a serious mistake! Far more plants die of over-fertilization than a lack of minerals. Excess minerals lead to tall, unhealthy growth and leaves plants susceptible to diseases and insects. In addition, the excess leads to mineral imbalances, harming the plant even further.


In short, a balanced fertilization you apply according to the plants’ needs will help your houseplants grow and flourish … but any excess will be harmful.20180427growingtogether.areavoices.com

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A Spa Treatment for Houseplants

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As houseplants start to come out of their winter lethargy, it’s time to treaet them to a good spa day! Source: www.pflanzenfreude.de

Indoor plants render great services to their owners. They decorate our homes, they purify the air we breathe, they reduce the frequency and duration of colds and flus, and their presence even helps eliminate depression and puts us in better mood (although nobody knows exactly why!). But what do we do in return for them? Very little, except to water them a bit from time to time.

At this time of the year, when the days are beginning to lengthen and our indoor plants are starting to emerge from their winter lethargy, there are a few things we could be doing to make them happier: call it a reward for services rendered!

1. A Cleansing Shower

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Houseplants appreciate an occasional shower as much as you do. Source: Claire Tourigny, Les 1500 trucs du jardinier paresseux

Houseplants absorb much of the dust in the air that surrounds them. It’s is one of the reasons they’re so good for our health. Dust is, in fact, one of their main sources of minerals. However, when dust and dirt start to accumulate on foliage, as tends to happen indoors, it clogs their breathing pores (stomata) and the poor plants start to function less efficiently. Besides, there may be undesirable insects hiding on their leaves that you haven’t yet noticed. That’s why houseplants like nothing better than an occasional warm shower, especially after a long winter.

Yes, a shower, in the shower stall or in the bath using a telephone shower handset. Just cover the surface of the soil with a rag beforehand to prevent the soil from washing away. If you can, rinse both sides of the leaves. If the foliage is really dirty, even take a soapy cloth and gently rub both sides of each leaf. The plants will love it!

2. A Little Leaching

After months of being watered in a closed system (irrigation water drains through the pot into the saucer, then is reabsorbed by the plant rather than draining into the surrounding soil as it would in nature), mineral salts start to accumulate in the soil of our houseplants, over time reaching harmful or even toxic levels. This toxicity is even more severe when we fertilize our plants frequently. To eliminate these excess salts, nothing beats leaching! Set your plant in a shower stall, bathtub, or sink and gently run warm water over the soil, letting excess water flow down the drain. Often the drainage water is tinted yellow, a sign that the soil was quite contaminated. Just soak the sol for a minute, stop for 5 minutes (this will give mineral salts a chance to dissolve), then rinse again until the water that comes out of the pot is clear, indicating that most of the impurities are gone. Finally, let the pot drain thoroughly before putting the plant back in its saucer.

3. A Bit of Grooming

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A bit of grooming – removing dead and yellowing leaves and damaged or dying branches – will benefit most indoor plants. Source:  http://www.mein-mediterraner-garten.de

Over time, most houseplants will accumulate yellowing or brown leaves, dead stems and other defects. Therefore part of the spa treatment should involve a bit of grooming. First, exfoliate… that is, remove dead or yellow leaves. If any leaf tips are brown (often caused by excess minerals in the pot, a problem you just solved through leaching!), you should be aware they will never turn green again, so just clip them off. Depending on the plant, it may be necessary to shorten or remove broken, weak, or overly long branches.  If the plant is heading straight for the ceiling, off with its head! Don’t worry, it will soon grow a new one (that is, as long as it is not a palm: never cut the top off a palm, as they don’t branch in response to pruning!). You can always use the plant’s top as a cutting and start another plant.

4. Time to Repot

After a year or two in the same pot, most houseplants are ripe for repotting. Take the plant out of its pot and remove part of the old soil mix: only a bit if you have been repotting annually, more if the plant has spent more than two years in the same pot. If you want the plant to grow in size, repot into a larger pot. If you want to slow its growth, repot into in a pot of the same size. Before reusing the same pot, clean it thoroughly. You’ll need fresh potting mix, readily available in any garden center. For orchids, buy a potting medium designed specifically for them.

5. A Plant Sauna 

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Many plants do so well once you’ve sealed them inside their plastic “greenhouse” you’ll be reluctant to take them out again! Source: laidbackgardener.blog

If you feel a foliage or flowering plant is in poor shape, a move to a very humid environment will do it a world of good. And creating one is easy. Just find a clear plastic bag and seal the plant inside. Don’t worry that it will suffocate: remember that plants recycle the very air they breathe, absorbing carbon dioxide and producing oxygen during the day and absorbing oxygen and producing carbon dioxide at night. The humidity in the bag will reach a very high level, usually close to 100%… and most houseplants adore high humidity! Leave it in its own personal sauna for two weeks, a month, maybe two months… until you see it showing renewed vigor. During this treatment, place the plant in a bright location, but away from direct sunlight, otherwise the temperature in the bag will become unbearably hot. Note too that plants sealed inside clear plastic bags will probably not need watering, even after several months.

As mentioned, most plants will love this experience… but not cacti and succulents. Unlike other plants, they can’t handle extreme humidity. Never seal them in a closed container for any length of time.

6. Feed Lightly

Most houseplants need no fertilizer in the winter and so you probably stopped feeding them in October or November. Well, March is a good time to start again. Every gardener has his or own preferred fertilizers and fertilization frequency and plants are quite accepting in this regard: notably, any fertilizer is fine with them. You can feed your dracaena or African violet lawn fertilizer for all they care: minerals are minerals and much of the labeling pretending one fertilizer is better for plant X than the other is just hype.

7. A Place in the Sun

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Place your plants in bright light and just watch them explode with new, healthy growth! Source: http://www.obi.de

As you get to the end of your plant’s spa treatment, remember that to remain in good health, your plant will need good light, usually a spot that receives a few hours of sun a day, but without ever becoming stiflingly hot. A location near a east-facing window is ideal because there is reasonable light in all seasons and it never gets hot, so you can leave the plant there all year. South and west exposures are great too, but during the summer, it will likely get too hot near the window and you’ll have to move the plant back a bit. As for a northern exposure… well, it is acceptable (although just barely) in summer, but few plants appreciate it in the winter.

8. Give the Occasional Spin

Finally, to maintain good symmetry, a plant needs to receive light from all sides… which is almost never the case indoors where all the light in a room comes from one direction, because most rooms have windows on only one side. The plant will then tend to lean towards its only source of light. To compensate for this, remember to give it a quarter turn clockwise with every watering. That will give it light from all directions and therefore better symmetry.

Why clockwise? Actually, counterclockwise would work just as well. The important thing is to be consistent and turn it in the same direction each time you water.


And there you go! Plant care equal to that of the best spas! Spa treatment will make your houseplants very happy and yet will cost you practically nothing besides a bag of potting soil and, every now and then, one or two new flower pots. It’s the least you can do for such faithful friends!

Time to Start Fertilizing Your Houseplants

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As plants start to “wake up” with the approach of spring, it’s time to think of fertilizing them again. Source: www.hunker.com

Normally, in temperate regions where winter nights are very long and days very short, it’s best to stop fertilizing houseplants in October. After all, many of them simply shut down at that time of the year anyway. They may not all go totally dormant, but their growth is often at a standstill or at least excruciatingly slow. Some do continue to keep on growing despite the decrease in lighting, but it’s better not to encourage them to produce off-season growth by applying fertilizer. That tends to result in pale, weak, etiolated growth: not what you want. I actually prune most winter growth off my houseplants: the new growth to come in spring will be much more robust!

(Gardeners who grow their plants under lights can continue to fertilize their houseplants year-round, as long as they contain to maintain 12-hour days or longer.)

Spring Has (Almost) Sprung

But with the return of longer days in late February and early March, many plants show clear signs of growth. No, it’s not summer yet, but with more than 11 hours of daylight per day (and that number increasing daily!), they’re starting to awaken and put on growth. And it’s when plants are growing that you need to fertilize them.

Use Fertilizer as a Reward

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Don’t try to “push” behavior using fertilizer: always use it as a reward! Source: www.stickpng.com & openclipart.org

Remember that the fertilizer should never be given to stimulate growth or flowering (there is too much risk of applying it when the plant is unable to use it), but instead as a reward. So, you should start fertilizing houseplants that show signs of renewed growth. (You’re growing? How lovely! Let me feed you!)

For some Northern Hemisphere houseplants, growth will have begun before the end of February, so fertilize those first, yet you’ve probably noticed others that aren’t quite ready yet. They may only start to signs of growth in mid- or late March. If so, wait a bit longer. Always follow the plant’s lead: it will “tell” you when the time to fertilize has arrived.

Which fertilizer should you use? That is of almost no importance. Just use whatever you have on hand. Read Plants Can’t Read Fertilizer Labels to learn more.

Always Fertilize Lightly

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Always fertilize lightly. Slow but steady growth is always the best. Source: Claire Tourigny, laidbackgardener.blog

The important thing is to always fertilizer lightly, probably at a much lower dose than that recommended on the product label: one quarter to one eighth of the recommended dose is sufficient for most plants grown indoors. The concept of “growth booster” type fertilizers, heavy on minerals and supposed to stimulate a faster recovery, is a marketing gimmick used to sell more fertilizer. Plants prefer to receive their fertilizer gradually, not to be flooded with more minerals than they can possibly use in a short period.


So, no rush, but if your houseplants are presently showing signs of growth, it’s time to start fertilizing them again! And certainly, most dawdlers will ready for a few extra minerals by the end of March!