Best Fertilizer For Begonias: Ultimate Growing Guide

Best Fertilizer For Begonias: Ultimate Growing Guide

Begonias are beautiful plants that come from tropical and subtropical regions in Central and South America, Africa and Asia. If you are growing these beauties in your garden, you’ll want to know the best fertilizer for begonias.

In temperate areas, these gorgeous plants can be grown outdoors all year round. However, they also make excellent houseplants and are very popular for this. Plus, if you grow them in pots, you can place them outside during the warmer months and bring them indoors during winter.

You’ll also be delighted with the huge range available and the wide varieties of colors in their flowers. 

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Before we look at a range of fertilizers that benefit begonias, let’s discuss the different types of begonias because there are quite a few.

Types of Begonias

Did you know that there are over 2,000 species of begonias? Plus, countless cultivars have been bred over the years by commercial growers. This gives you a really wide choice of begonia varieties to choose from.

On top of that, there are also different types of begonias. To explain this further, I’m going to explain what these are so that newer gardeners and begonia growers can understand how these plants grow.

This will essentially help you with their care and allow us to discuss the different fertilizer needs.

Tuberous Begonias

tuberous begonia with brilliant red flowers

Tuberous begonias are one of the most popular types that people like to grow. Plus, there are around 4,000 registered cultivars. Most of these originated from species that are native to South America.

These hardy begonias have stunning floral displays which is why they’re so popular. Flower colors are also immense and varied with the most common ones being white, yellow, red, pink and orange.

Tuberous begonias grow from underground tubers. This means that their main growing and flowering season is from spring to summer. 

Another reason these types of begonias are so popular is that you can dig up the tubers and store them in a cool, dry spot over winter. Then, you can replant them in spring. 

Like other tuberous plants, the tubers store nutrients and water during their dormancy. For this reason, these types of begonias need to be fertilised while they’re actively growing during spring and summer.

This allows the tubers to store plenty of nutrients that will help with growth and flowering the following season.

Fibrous Begonias

wax begonia with small red flowers

Fibrous begonias are also commonly known as wax begonias. These types of begonias have succulent stems and leaves. The leaves are quite waxy and can range in color from dark green to deep mahogany. 

Semperflorens begonias are also fibrous begonias but this group is mainly made up of cultivars. These can also be commonly referred to as wax begonias. 

They are known as fibrous begonias because they have a fibrous root system rather than a tuber or rhizome. 

The easiest way to distinguish fibrous begonias from the other types is to look at their leaves and stems. These will be fairly fleshy and succulent in nature. Their flowers are also long-lasting and are available in colors of white, pink and red.

These begonia types are easy to grow because they tolerate direct sunlight and can survive on less water than other types due to their succulent nature.

These plants can also be grown as perennials in climate zones that don’t experience frosts. This makes them ideal for growing along borders and in flower beds. 

Fibrous begonias will benefit from the application of fertilizer during the warmer months as they’re likely to be dormant in winter.

Cane Begonias

cane begonia with dainty pink flowers

Although cane begonias are also a type of fibrous begonia, they are often considered in a class of their own. What sets them apart from other types of begonias is that their growth habit is slightly different.

New growth appears as a fairly tall stem or cane before this starts to branch and fill out. Once branching begins, the plant can turn it quite an attractive shrub-like plant. 

The leaves are quite large and often have attractive markings. 

Under the umbrella of cane begonias are “Angel Wing begonias” that are quite popular with gardeners and plant lovers alike.

Rhizomatous Begonias

Rhizomatous begonia with deeply veined leaves and delicate pink flowers

Rhizomatous begonias grow from underground rhizomes that travel horizontally through the soil. New growth will sprout along the rhizome. 

The leaves on these begonias can be either star-shaped or round. They will flower in winter and into spring with blooms in colors of white or pink. One outstanding feature of these begonias is that their leaves can be quite colorful with interesting markings.

This makes them ideal for planting under trees and in areas with partial shade to add some additional color.

Rex Begonias

rex begonia with colorful leaves

Rex begonias are also a type of rhizomatous begonia but they tend to stand out quite spectacularly thanks to their often, multi-colored leaves. There are cultivars available with leaf colors in maroon, silver, orange, burgundy, red and purple. 

Many of these varieties sport not only brightly colored leaves but also ones with iridescent patterns that can really add some interest to your garden landscape.

Unfortunately, these cultivars are often the most difficult to grow because they’re quite sensitive to temperature changes. Plus, they are more prone to dropping their leaves and will usually be dormant in winter.

How To Choose The Best Fertilizer For Begonias

Now that you understand a little about the different types of begonias, let’s have a look at their nutrient needs. In general, begonias are fairly heavy feeders so you want to ensure that you give them what they need to thrive.

This is when it’s important to understand the NPK of each type of fertilizer and how this affects plant growth. NPK stands for nitrogen (N), phosphorus (P) and potassium (K).

According to what I learned during my horticultural studies and what I’ve experienced in all my years of growing and tending to plants, this is what these nutrients primarily do for plants in general:

  • Nitrogen is mainly responsible for green plant growth
  • Phosphorus helps healthy root development
  • Potassium encourages plants to produce flowers and fruits

You might read information to the contrary but if you take my advice on this, you can’t go wrong.

So, if you are growing the types of begonias that you want to encourage to flower, you want a fertilizer that is relatively higher or equal in potassium to nitrogen. 

On the other hand, if you’re growing the types of begonias that are popular for their interesting leaf growth, select a fertilizer that is higher in nitrogen.

This is about as simple as I can make it and once you understand this, you’ll never have trouble choosing a suitable fertilizer for your plants again.

So, to give some examples of the types of fertilizer that I would select for begonias, here are some excellent ones that I found on Amazon.

Organic Plant Magic Slow-Release Granules

Organic Plant Magic Slow-Release Granules

Firstly, what I like about this fertilizer is that it’s organic. In my own garden, I do try and follow sustainable gardening practices and choose organic fertilizer and other products whenever I can.

Apart from the vital nutrients required for good plant growth, this product also contains over 55 trace elements and other beneficial ingredients such as kelp, mycorrhizae and humic acid.

The other thing that I really like is that this is a slow-release granular fertilizer. This generally means that you should only have to apply it once a year and your begonias will be fed throughout their growing season.

The NPK of this product is 5:4:4. This means that it’s fairly balanced and can be used for both flowering and foliage begonias. There’s enough nitrogen for healthy growth but also adequate potassium for flowering as well as plenty of phosphorus for healthy root growth.

Osmocote Smart-Release Plant Food

Osmocote Smart-Release Plant Food

This is another slow-release fertilizer that is well-balanced and can be used for both flowering and foliage begonias. The NPK ratio of this product is 14:14:14.

Using a product like this really takes the guesswork out of providing your plants with the essential nutrients that they need.

Miracle-Gro Shake ‘N Feed All Purpose Plant Food

Miracle-Gro Shake ‘N Feed All Purpose Plant Food

Here’s another easy-to-use fertilizer that comes in granular form and is slow-release. I would recommend this one for both foliage and flowering begonias. The NPK ratio is 12:4:8.

While it has a higher proportion of nitrogen when compared to the other ones we’ve looked at so far, it does still contain enough potassium to encourage plenty of flowers.

Keep in mind that this fertilizer is only designed to last for 3 months, so you might have to apply it twice during the growing season.

The Old Farmer’s Almanac Plant Food Spikes

The Old Farmer’s Almanac Plant Food Spikes

If you’re growing your begonias in pots, I really like the simplicity of these plant food spikes. Each spike is designed to last for around 6 to 8 weeks and will feed your begonias continuously during that time.

These spikes are also perfectly balanced with an NPK ratio of 5:5:5. This makes them good for both flowering and foliage begonias. These are one of the easiest ways to feed container-grown begonias.

AgroThrive Fruit And Flower Organic Liquid Fertilizer

AgroThrive Fruit And Flower Organic Liquid Fertilizer

If you prefer to use a liquid fertilizer on your begonias, I would recommend this one, especially for flowering varieties. It has an NPK ratio of 3:3:5. This means that it’s specially formulated for flowering plants.

I also like the fact that this product is totally organic and contains no synthetic chemicals. As this is a liquid fertilizer and needs to be diluted with water, you’ll get the best results if you apply it once a week during the growing season.

When To Fertilize Begonias

two different rex begonias with variations in leaf colors

Now that you have some suggestions for the best fertilizer for begonias, you’ll want to know when to feed them. I’ve already alluded to the fact that the best time to fertilize begonias is during their main growing season. Generally, this will be in early spring and right through the warmer months.

This is relevant to all the different types of begonias but not all of them do their main growing at the same time of the year. So, let me break it down for you with some simple explanations.

  • Tuberous begonias should be fed when they’re in full growth during the warmer months. This is important as they will store the nutrients in their bulbs to feed the next season’s growth and flowering. Do not feed these in winter.
  • Fibrous begonias will also need feeding during the warmer months as that is when they’ll do most of their growing. These types of begonias should also not be fed in winter.
  • Rhizomatous begonias are a little different as they flower in winter. These should be fed during the warmer months but you also want to give them a dose in early fall or autumn to ensure they have enough nutrients to initiate flowering in winter. 

For more fertilizer suggestions, check out these articles:

Best Fertilizer for Hoyas

Frequently Asked Questions

How often should I fertilize my begonias?

This depends on the type of begonia you’re growing and also the type of fertilizer you’re using. In general, begonias should be fed during their main growing season which is usually in the warmer months. Slow-release fertilizer should normally last for 3 to 6 months while liquid fertilizers should be applied once a week.

Is foliar feeding suitable for begonias?

I would discourage foliar feeding on begonias because it’s a good idea not to get the leaves wet if at all possible. This can lead to fungal diseases such as powdery mildew. If using liquid feed, apply only to the soil surface.

Should I fertilize my begonias during the winter?

Most begonias will be dormant during winter so they shouldn’t be fed.

Do begonias need well-drained soil?

Yes, you should definitely grow begonias in well-drained soil to avoid root rot.

Final Thoughts

Begonias are delightful plants that can brighten up your garden and are also fantastic for growing in pots. There are many different types of begonias and these all have different growth habits.

When selecting the best fertilizer for your begonias, first decide whether you want to promote lots of leaf growth or you also want to enjoy more flowers. For leafy begonias, select a balanced fertilizer that has plenty of nitrogen.

If you want to promote flowering, choose a fertilizer that is reasonably high in potassium. However, a balanced fertilizer will also work well. 

Fertilize your begonias only during their active growing season and avoid adding fertilizer when the plants are dormant during the winter months.

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