5 Best Bougainvillea Fertilizers | How and When to Apply

With vibrantly colored bracts of fuchsia, purple, peach, and white, bougainvillea are one of few plants to be considered a shrub-like vine. Meaning, they are vine-growing plants that can be trained over pergolas and up walls or shaped into shrubs.

A cousin to four o’clock, the bougainvillea is an east coast native of South America, from where 250 different bougainvillea varieties stemmed.

In order to maintain such lush ribbons of color, the bougainvillea is a heavy feeder, absorbing all the nutrients it finds in the soil rather quickly. Bare branches and vines will result if those nutrients aren’t replenished. This is why it’s so important to choose the best bougainvillea fertilizers for your soil.

Best Bougainvillea Fertilizers

J R Peters | Jacks Classic No.1.5 Fertilizer 20-20-20

Best Water-Soluble Granules

Jacks Classic No.1.5 Fertilizer 20-20-20

Fast-Acting liquid with a high macronutrient ratio. Perfect for improving less than perfect soil conditions when preparing the ground for planting bougainvillea.

Best Fertilizer Spikes For Bougainvillea

Best Fertilizer Spikes For Bougainvillea

Best Fertilizer Spikes For Bougainvillea

Convenient pre-measured fertilizer spikes are designed to be pushed an inch into the soil to provide a slow-release feed right through the growing season.

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Best Fertilizer Granules For Bougainvillea

Miracle-Gro Shake ‘N Feed Continuous Release 10-18-9

Slow-release granules that continue delivering nutrients for up to 3 months. Ideal for mature Bougainvillea where the soil needs improving to compensate for heavy feeding.

Choosing Fertilizer for Bougainvillea

Bougainvillea vines grow best in hardiness zone 10 and 11, but given the right winter protection, they can grow in pots quite happily in cooler regions.

Being heavy feeders, they typically absorb each nutrient at the same rate. A well-balanced NPK can maintain equal nutrient availability, supporting lush foliage growth and lots of cascading color.

When preparing the soil for planting Bougainvillea, a 10-10-10 fertilizer will be enough to keep your bougainvillea happy. In lesser soil, a 20-20-20 fertilizer can increase nutrient availability to required levels.

Bougainvillea N-P-K Ratio

Every fertilizer label shows a three-numbered formula. This is its N-P-K ratio, indicating its proportions of nitrogen, phosphorus, and potassium.

For example, a 10-10-10 NPK has 10% nitrogen, 10% phosphorus and 10% potassium. Every plant requires these three macronutrients for optimal health. Just in different proportions or NPK ratios.

Once established and growing, bougainvillea needs plenty of phosphorus and potassium, for vibrant, colorful bracts and dainty flowers. They also need just enough nitrogen to support healthy foliage.

Soil pH

Bougainvillea grows best in a slightly acidic pH, between 5.5 and 6.0, to support optimal plant health and an unrestricted flow of vital nutrients.

If your soil pH is too high, adding well-aged compost, every spring, will gradually lower soil pH, over time. But, in a pinch, you can add a bit of elemental sulfur.

If your pH is too low, working agricultural limestone in, every spring, will increase it at the same gradual rate as compost.

Types of Fertilizer

Four different classes of fertilizer offer flexible options for various usage and gardening styles.

  • Quick Release – liquid and water-soluble options offer immediate uptake of nutrients. Resulting in accelerated improvement for ailing plants in poor soil.
  • Slow-Release – Heavily concentrated granules and spikes offer a steady stream of nutrients over an extended period of time.
  • Organic – made from natural compounds like well-rotted plant material and animal bi-products that contain beneficial levels of nitrogen, phosphorus and potassium.
  • Inorganic – manufactured with minerals and chemicals, these can result in more color. The flip side to their qualities is, they can also potentially contaminate soil and nearby water sources with run-off.

Fertilizer Granules

Slow-releasing, granular fertilizers are easy to use and can provide consistent nourishment for up to nine months. With the first results showing in just a few weeks, depending on the brand. These are also less likely to cause root burn.

Granules are applied by casting them evenly around the base of shrubs and plants. No watering is needed to activate them and is less likely to leach into nearby surface or groundwater.

Fertilizer Spike

Spikes are one of the most convenient to use, especially if you have a container garden. Pre-measured in various sizes, they’re easy to push into loamy soil.  And being slow-releasing, they run little risk of burning.

Nutrients are released from the spikes by micro-organisms that naturally live in the soil. And carry the added benefit of stimulating an increased resistance to disease and pests. Unused portions can then be stored mess-free until needed.

Liquid Fertilizer

Most liquid fertilizers come in concentrated form and need to be diluted prior to use. Then, applied with a watering can or hose attachment, around your plants.

Nutrients are then immediately carried to the root system through the soil or leaves. Some liquid fertilizers are also formulated to be used as foliar sprays.

Concentrated liquid feeds are often more economical. However, caution is recommended, as over-feeding is common and could lead to root and plant burn.

Synthetic Vs Organic

Deciding between organic and synthetic options is simply a matter of preference and end-result expectation.

However, a basic understanding of how each works and affects your environment will support an informed decision.

Organic fertilizers are typically plant or animal-based, while inorganics are mass-produced using minerals and synthetic chemicals.

Organics naturally contain lower levels of nutrients but can nourish your bougainvillea plants for longer periods of time. This option can also improve the surrounding soil.

The use of inorganic feeds can result in more bracts and flowers. But, they can also potentially contaminate nearby water sources.

5 Best Bougainvillea Fertilizer Reviews

I’ve been busy testing several different fertilizer options on my own bougainvillea collection and I’ve compiled a list of the top 5 performers, based on results and ease of use.

Here are the product details, some top tips on when and how to use them, and the pros and cons to allowing for an informed decision. 

Pros     

  • Optimal nutrition for bud production and green foliage
  • Releases nutrients gradually for up to 4 months

Cons

  • May be too strong for houseplants

Whether overworked or underworked, there are always areas of the garden that may need a boost in fertility from time to time. This balanced, water-soluble option did just that for a large bougainvillea I have climbed around the back of my potting shed.

By providing my poor neglected plant with a full 20% of each macronutrient, it, quite literally, sprung back to life!

Use for ailing plants and nutrient-poor soil conditions until they have been nursed back to health. Once revived I suggest diluting the recommended quantities to avoid the risk of root, leaf, or stem scorching.

How To Use: Apply 1 tablespoon per gallon of water used. Repeat every 10-14 days.

Pros

  • Formulated for flower baskets and potted plants
  • No wasteful runoff, no mess, hazards or smells

Cons

  • Results may vary depending on climate

Jobe’s has always been a reliable brand and these 8-9-12 NPK fertilizer spikes specially formulated for bougainvillea in pots did not disappoint. This was clear by how well mine performed after I pushed them into the soil.

After one application, I could see new foliage growth and bud development, that continued for a full 8 weeks. This is such an important factor when it comes to feeding pot plants since run-off can often mean re-fertilizing, more frequently.

How To Use: Apply the number of spikes recommended per plant size every 8 weeks. Then, store in the handy, resealable pouch until needed.

3. Miracle-Gro Shake ‘N Feed 10-18-9

Best Fertilizer Granules For Bougainvillea

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Pros

  • Contains natural ingredients to feed microbes in the soil
  • Includes vital micronutrients

Cons

  • Not recommended for fully fertile soil

I found this granular option, with its simple “shake and feed” application method, worked best in semi-fertile to poor soil.

Each granule is formulated to be attractive to hungry soil microbes who then convert nutrients into a readily available form for plants. A profusion of bracts in brilliant color resulted and continued for a full three months.

I wouldn’t recommend using this on young plants or if you know your soil is fertile. The high ratio of nitrogen and phosphorus can overwhelm and lead to poor plant health.

How To Use:  How To Use: Apply the recommended dosage directly to dry soil and mix into the top 3 inches. Water thoroughly and re-apply every 3 months. 

Pros      

  • Lasts up to 8 weeks
  • Convenient resealable bag

Cons

  • Spikes may break off in dry soil 

Like my previous Jobe’s pick, these are also very easy to use. Since this one is formulated for acid-lovers, it’s the perfect choice to fertilize and raise your soil pH, if needed.

These consistently fertilized my colorful climbers, while I was off doing other things. I then came home to climbers with larger, vibrant bracts and leaves!

How To Use:  Insert the recommended number of spikes (per plant size) around flowering plants and shrubs that like more acidic soil. The slow-release formula will feed them for the full flowering season.

PROS

  • Gentle enough for use in fertile soil
  • No risk of burn when used as directed

CONS

  • May not be as effective on flowering bulbs

For gardeners who frequently add well-aged compost to their soil, try this balanced NPK from Scotts. This fertilizer supports plentiful flowering in bougainvillea, as well as many other flowering ornamentals and vegetables.

Slow-releasing fertilizer granules can be applied straight from the bag, delivering gentle nourishment for up to 2 months.

How To Use:  1 cup (9.5 oz.) covers approximately 30 square feet or 1/2 tablespoon for every 1 square foot of area. Apply every two months during the growing season, starting in the spring.

Does a Bougainvillea Need Fertilizing

In nature, the bougainvillea has adapted as a heavy feeder. As such, it requires constant access to nutrients. If your vining shrubs are growing in nicely maintained, fertile soil, they most likely won’t need any fertilizing, at all.

Neither do newly-planted ones. In less than desirable soil, you can throw in a handful of 20-20-20 granules, prior to planting. But, for the next year or two, they won’t need anymore.

If your bougainvillea isn’t flowering, don’t reach for the fertilizer just yet. These plants only bloom on new growth. If not pruned properly, long, bare, bract-less vines may result.

How to Fertilize Bougainvillea

How you fertilize your bougainvillea will depend on your application method. Diluted liquids are applied using a watering can or a hose attachment.

Apply these in the cooler hours of the day, so as not to scorch those lovely leaves and bracts in direct sun.

Dry granules and spikes can be applied any time of day and don’t necessarily require watering in. But, applying them just before a forecasted rainfall will hasten activation.

However, before any fertilizer is applied, a soil test should be done to see if your bougainvillea needs fertilizing, at all.

How Often to Feed Bougainvillea

Fertilizing frequency will also be dictated by the brand and application method you choose. Different brands have different recommendations based on their product’s formula.

For example, Jobe’s spikes need re-applying every 8 weeks, which is roughly two to three times per growing season. Scott’s granules suggest the same.

Water-soluble granules, like my pick from Jack’s Classic, should be applied every two weeks for consistent nourishment.

Again, when fertilizing potted bougainvillea varieties, the application frequency may be even higher. This is due to the leaching of water and nutrients and plant respiration in warmer climates.

Signs of Fertilizer Burn

Over-fertilizing is seldom intentional, but it does mistakenly happen. Signs include:

  • Yellowing leaves
  • Foliage wilting
  • Browning edges on leaves and flowers

Nitrogen overuse appears as excessive foliage growth and few to no bracts or flowers. Excess phosphorus causes the opposite.

Signs of root burn, in particular, include stunted growth, a wilting of new vines, as well as foliage, no new flowers, and in extreme cases, plant death.

If this happens with ground planted bougainvillea, simply cut back the damaged bits and stop fertilizing. In pots, do the same, then flush the soil with water only.

When to Fertilize Bougainvillea

The most effective time to feed a bougainvillea is when it’s actively growing. When outside and dormant, there’s no need. The duration of their active growth period depends on the hardiness zone it’s growing in.

In regions with moderate winters (where it gets close to freezing), fertilizing should begin in early spring and continue until after the last flowering.

In mild or tropical climates, bougainvillea can produce vibrant colors right through the winter months. If needed, these will benefit from extended fertilizing into late autumn.

In severe winter climates, bougainvillea can be brought inside and grown as a colorful houseplant, while everything outside sleeps. These can be fed, throughout the winter, with a diluted 10-10-10 NPK along with your other houseplants.

Best Bougainvillea Fertilizer Verdict

So, now it comes down to what to buy. My first-place choice goes to the fast-acting water-soluble fertilizer from J R Peters. A 20-20-20 feed that is suitable for instantly boosting the nutrient properties of the soil before planting your bougainvillea.

Next, Jobe’s Fertilizer Spikes, made specifically for flowering potted plants. This feed shouts ‘convenience’ and is great for locking in nutrients where others may leach out.

Alternatively, choose Miracle-Gro Shake N’ Feed. This fertilizer is perfect for mature bougainvillea that has depleted nutrients with their heavy-feeding habits. Avoid this when feeding young plants due to the high phosphorus and nitrogen.

Fast-Acting liquid with a high macronutrient ratio. Perfect for improving less than perfect soil conditions when preparing the ground for planting bougainvillea.

Best Fertilizer Spikes For Bougainvillea

Convenient pre-measured fertilizer spikes are designed to be pushed an inch into the soil to provide a slow-release feed right through the growing season.

J R Peters | Jacks Classic No.1.5 Fertilizer 20-20-20

Best Water-Soluble Granules

Jacks Classic No.1.5 Fertilizer 20-20-20

Fast-Acting liquid with a high macronutrient ratio. Perfect for improving less than perfect soil conditions when preparing the ground for planting bougainvillea.

Best Fertilizer Spikes For Bougainvillea

Best Fertilizer Spikes For Bougainvillea

Best Fertilizer Spikes For Bougainvillea

Convenient pre-measured fertilizer spikes are designed to be pushed an inch into the soil to provide a slow-release feed right through the growing season.

FAQ’s Bougainvillea Fertilizer