If I asked you to think of a begonia, what would come to mind? Well, there are several correct answers!
Begonias are a large genus of plants that encompass popular varieties like flowering annuals and foliar houseplants. Most specimens are cherished for their unique appearances and generally low-maintenance natures. But even the most hands-off plants still need to be fed.
Proper nutrition is especially important for begonias grown indoors. Containers hold far fewer nutrients than garden soil and must be supplemented to sustain plant life year-round. So if your begonia houseplant has seen better days, there’s a very good chance fertilizer is what it craves. Below, you’ll find my picks for the best fertilizer for begonias based on extensive research and hands-on experience.
Choosing The Best Fertilizer For Begonias
If you’re new to the world of gardening, I think begonias are a great plant with which to start building your knowledge of fertilizer and nutrition. Choosing a high-quality fertilizer for begonias isn’t hard, so you can experiment with different formulas without much risk.
The best fertilizer for begonias will almost always be a balanced one. Begonias are not particularly heavy feeders — the risks of overfeeding tend to be worse than underfeeding — and respond well to both instant- and slow-release nutrition.
If you’re in a hurry to choose, here are my top picks:
Best Liquid Fertilizer
Bonide Liquid Plant Food 10-10-10
Provides begonias with an instant boost of nutrients in an equally balanced NPK ratio.
Best High-Phosphorus Fertilizer
Schultz All Purpose Liquid Plant Food 10-15-10
Suitable for both indoor and outdoor begonias or where phosphorus is lacking. Comes with an easy-to-use measuring dropper for mess-free feeding.
Best Slow-Release Granules
Jobe’s Granular Plant Food Flower & Rose 3-4-3
Organic granules provide both a fast and slow release of nutrients and are fortified with microbes to enhance soil quality.
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Granular Vs Liquid Fertilizer
Rest assured, both granular and liquid fertilizers deliver high-quality nutrition. So choosing one over the other largely comes down to personal preference. However, there are some scenarios where using a liquid fertilizer versus a granular one (or vice-versa) is beneficial.
Liquid Concentrate
Many of the best fertilizers for begonias are sold as liquid concentrates. Such formulas tend to be affordable and convenient to store. I also find that liquid concentrates are easy to measure whether you’re feeding one plant or dozens.
A defining feature of liquid fertilizer is that nutrients are delivered almost instantly. While this is great for fast-growing plants it also means that the fertilizer must be re-applied frequently.
Slow-Release Granules
Some people prefer using slow-release fertilizer when feeding begonias because they deliver a consistent stream of nutrients over several weeks or months. There are certainly benefits to slow-release granules — I’ve recommended one such formula below — but I also think there’s a bit more room for error when compared to liquid fertilizers.
Personally, I recommend slow-release granules for begonias growing in outdoor beds. If you opt to feed potted begonias with granules, I suggest keeping an eye out for salt buildup on the soil.
Fertilizer Spikes
Fertilizer spikes work much the same as granules. They are pre-measured and incredibly easy to use. The downside to fertilizer spikes is that they have a tendency to not distribute nutrients evenly into the soil.
Soil pH And Nutrients
While invisible to the naked eye, soil pH is a vital part of plant health and longevity. For begonias, the ideal soil pH is between 5.5 and 6.5. This means that begonias prefer soil that is slightly or moderately acidic.
Slight adjustments to soil pH are possible using horticultural amendments. These are best added to the soil before plants are added. According to Iowa State University, elemental sulfur is the safest option for decreasing soil pH. If you need to increase your soil’s pH level, limestone is the safest choice.
In most cases, testing and amending your soil’s pH as needed will suffice. But it can also be helpful to understand why pH impacts soil quality in the first place.
Soil pH matters in the home garden because it affects the availability of essential nutrients. A pH that is too acidic or too alkaline will decrease the number of nutrient particles available for plant roots to absorb. Unfortunately, not all nutrients require the same pH range.
At the lower end of their preferred pH range, begonias are most at-risk of magnesium and calcium deficiencies. Phosphorus availability can also be affected by overly acidic soil.
Keep this in mind if your begonias ever show signs of nutritional deficiencies — it may be the soil pH that is to blame rather than your choice of fertilizer.
Begonia Fertilizer N-P-K Ratio
Unless otherwise indicated by a recent soil test, begonias fare best when fed with a balanced fertilizer. A balanced fertilizer is one that contains equal amounts of nitrogen, phosphorus, and potassium.
The quickest and easiest way to determine how much of each macronutrient a fertilizer contains is to reference its N-P-K ratio. An N-P-K ratio is a sequence of 3 numbers separated by hyphens prominently printed on nearly all fertilizer labels. In order, these numbers represent nitrogen (N), phosphorus (P), and potassium (K).
A fertilizer’s N-P-K ratio will instantly tell you if it contains more of one macronutrient than others. It also lets you know what percentage of the total formula is made up of each macronutrient.
For example, a 10-10-10 fertilizer is 10% nitrogen, 10% phosphorus, and 10% potassium. A 3-4-3 fertilizer is 3% nitrogen, 4% phosphorus, and 3% potassium. While each of these formulas is relatively balanced, the latter fertilizer is far less concentrated than the first one.
Best Fertilizer For Begonias Reviews
Although begonias are easy to care for, not just any fertilizer will meet their needs. After researching some of the most popular formulas recommended for begonias, I’ve narrowed down the best options for use in your own garden. Most of these fertilizers are ideal for begonia houseplants as well as those grown outdoors.
Pros
- Ideal for container-grown begonias
- Balanced nutrient profile
Cons
- Not recommended for large garden beds
Don’t let the label fool you. While this liquid concentrate is designed for use on houseplants, it works equally well on outdoor containers and small in-ground beds. I personally recommend it for all types of begonias.
This fertilizer features a balanced N-P-K ratio that isn’t too concentrated. Each application should be diluted in clean water but you can easily adjust the strength to suit your plants’ needs.
You can apply this fertilizer to indoor plants every time you water normally. Since outdoor begonias’ watering needs vary with the weather, I recommend applying about once a week to prevent overfeeding.
How To Use: Mix at a rate of ⅛ teaspoon per quart of water. Apply to the soil directly around begonias, avoiding the stems and foliage. Feed as part of your normal watering schedule.
Pros
- Ideal for begonia houseplants
- Treats phosphorus deficiencies
- Easy to measure
Cons
- Not a balanced formula
If your soil falls short in terms of phosphorus, this Schultz Liquid Plant Food is an excellent fertilizer for begonias. It comes with an easy-to-use measuring dropper and is recommended for both indoor and outdoor begonias.
This is my go-to fertilizer for potted begonias of all types. The small bottle is super convenient for storage, which is a personal must when feeding one or two containers versus a large garden bed.
Aside from the boost in phosphorus, this fertilizer is quite balanced. It’s safe to apply with every routine watering on particularly vigorous plants.
How To Use: Dilute 7 drops of fertilizer per liter of water. Apply to the soil around begonias as part of routine irrigation. Repeat as often as once a week.
Pros
- Delivers instant- and continuous-release nutrition
- Made with certified organic ingredients
- Contains beneficial microbes for soil health
Cons
- May attract animals
I’m sure it’s clear that I prefer to feed begonias with a liquid fertilizer. However, high-quality granular formulas do exist. My personal favorite is the Rose & Flower formula from Jobe’s.
There are lots to like about this fertilizer. One of the main reasons I recommend this fertilizer is due to the inclusion of soil-boosting microbes. It’s also made from organic ingredients and contains both fast- and slow-release nutrients.
In my experience, the odor is tolerable compared to many other organic fertilizers. But it’s important to note that some pets and wildlife may be attracted to the scent of these granules.
How To Use: Measure granules according to the packaging instructions for feeding flowers. Evenly spread granules onto the soil around your begonias. Water thoroughly immediately after applying fertilizer to activate.
Pros
- Made with organic ingredients
- Minimal odor
Cons
- Packaging is prone to leaks
My favorite organic fertilizer for begonias is this liquid concentrate from AgroThrive. Again, this is an all-purpose formula that can be used throughout your entire garden with great results.
Of course, this fertilizer boasts a relatively balanced nutrient ratio. Begonias of all kinds will respond well to this formula. The only scenario in which I’d advise against this fertilizer is when there is a known potassium deficiency in the soil.
I recommend giving this fertilizer a try even if you’ve had bad luck using organic formulas indoors in the past. Unlike many competitors, it doesn’t have a strong odor (despite containing nutrients derived from fish).
How To Use: Mix 2 ounces of fertilizer per gallon of water to feed begonias. Apply directly to the soil as often as every 1 to 2 weeks.
Pros
- Easy to store
- Contains readily available micronutrients
Cons
- Too concentrated for some applications
Since begonia nutrition is fairly straightforward, an all-purpose fertilizer is often the best choice. Grow More offers the benefits of a fast-acting liquid concentrate with the convenience of a lightweight powder.
This water-soluble formula is well-balanced and fortified with chelated micronutrients for improved absorption. I do, however, suggest offsetting the 20-20-20 nutrient ratio by using less fertilizer or more water than recommended.
How To Use: The manufacturer advises mixing up to 1 tablespoon of fertilizer per gallon of water. However, I recommend starting with a weaker mixture to see how your begonias respond. Apply every 7 to 14 days.
How To Feed Begonias
For the best results, begonias should be fed lightly but often. This ensures the plants get adequate nutrition with minimal risk of fertilizer burn.
Liquid fertilizers should be diluted with 3 parts water before use on begonias unless otherwise directed by the manufacturer. If you prefer granular fertilizer, I recommend selecting a low-concentration, slow-release formula.
Apply fertilizer directly to the soil around the begonia’s base. Most begonias have compact root systems, so get as close to the main stem as you can without touching it.
Since begonias have rather delicate stems and foliage, I don’t recommend applying fertilizer directly to the plant. If you do get fertilizer on the plant itself, I suggest rinsing with clean water to prevent potential damage.
Be sure to water your begonias well as part of your fertilizer regime. You can lightly water the soil around your begonia before applying liquid fertilizer to protect the roots. Wait to water until after applying granular fertilizers — the water will activate the granules and help push nutrients into the soil.
When To Fertilize Begonias
Begonias grown as annuals should be fertilized immediately after transplanting to jumpstart growth and flower production. Start fertilizing perennial begonias in the spring just as new growth appears. Continue fertilizing throughout the season until the begonias start to die off or prepare for dormancy.
Many begonias survive for years when kept indoors (or moved indoors before temperatures drop). Some begonias benefit from winter dormancy and should not be fed during the cooler months. However, others grow vigorously throughout the entire year.
When grown indoors, rhizomatous, cane, and bedding begonias all benefit from light feeding during the winter. Rex begonias should be fertilized at the same rate in winter as they are in summer.
Tuberous begonias, on the other hand, must go completely dormant to survive winter. Cease fertilizing in early fall so as not to trigger new growth during this dormancy period.
How Often To Fertilize
Most begonias respond best to fertilizing every 2 or 3 weeks during the peak growing season.
Remember that all fertilizers work on a slightly different schedule. For example, slow-release granules should be applied much less frequently than fast-acting liquids. I always encourage referencing the label of your chosen formula before proceeding with any recommended feeding frequency.
Verdict: Best Begonia Fertilizers
My favorite fertilizer for container-grown begonias is without a doubt Bonide Liquid Plant Food 10-10-10. It provides an ideal balance of nutrients for all types of begonias, especially those kept as houseplants.
If your begonias crave extra phosphorus, I highly recommend applying Schultz All Purpose Liquid Plant Food 10-15-10 until the deficiency resolves. This is another great formula for both indoor and outdoor begonias. I’m particularly fond of the built-in dropper that makes measuring very easy.
For a granular fertilizer that meets the needs of begonias, try Jobe’s Granular Plant Food Flower & Rose 3-4-3. It’s my go-to for feeding in-ground or potted begonias that require a slow-release formula to grow their best.
Best Liquid Fertilizer
Bonide Liquid Plant Food 10-10-10
Provides begonias with an instant boost of nutrients in an equally balanced NPK ratio.
Best High-Phosphorus Fertilizer
Schultz All Purpose Liquid Plant Food 10-15-10
Suitable for both indoor and outdoor begonias or where phosphorus is lacking. Comes with an easy-to-use measuring dropper for mess-free feeding.
Best Slow-Release Granules
Jobe’s Granular Plant Food Flower & Rose 3-4-3
Organic granules provide both a fast and slow release of nutrients and are fortified with microbes to enhance soil quality.
