6 Best Raspberry Fertilizers | How and When To Use

Shrubs full of ripening raspberries have been dotting the European landscape for eons, with early evidence of them showing up in layers of prehistoric sediment.

In the classical age, the Romans carried raspberries throughout their empire, ending in Britain. Here, in the 16th century, the cultivation of this juicy fruit took hold.

By the 18th century, raspberry plants were being shipped to North American settlers who were stuck with the natural and uncultivated version that was not as sweet and had far more seeds than what they were used to.

Since raspberry bushes continue fruit production for up to 10 years, knowing how best to care for them is a must. The care includes the best raspberry fertilizer.

Best Raspberry Fertilizers

Choosing Raspberry Fertilizer

With over 200 different species of raspberries, worldwide, none of them are particularly fussy when it comes to nutrition.

Being a member of the rose family, they do well with an NPK ratio that’s a bit heavier in nitrogen, in spring, when new leaves and stems are forming. But, once buds are set, more potassium will support healthy flower and fruit formation.

Infertile soil, however, a balanced 10-10-10 NPK will provide all they need to be productive. For organic growers, compost or manure plus elements like cottonseed meal, langbeinite, and rock phosphate can achieve the same result.

Raspberry Fertilizer N-P-K Ratio

Choosing the right NPK is easy when you understand what raspberries need. Every fertilizer label includes a three-numbered formula. This is the N-P-K ratio, indicating the product’s proportions of nitrogen, phosphorus, and potassium.

For example, a 4-3-4 NPK (formulated for raspberries) has 4% nitrogen, 3% phosphorus and 4% potassium. Every plant requires these three elements for optimal health. Just in different proportions or NPK ratios.

As reflected in the above example, raspberries prefer higher amounts of nitrogen and potassium, for vibrant foliage and juicy fruit, with just enough phosphorus to maintain a healthy soil pH.

Nitrogen

Nitrogen plays a vital role in fueling the growth of sturdy stems and vibrant foliage, by fueling the production of chlorophyll. This gives foliage that green color and ensures that photosynthesized energy is available to convert starches and carbohydrates into food.

The resulting healthy plant structure then feeds and supports blooms and abundant crops of juicy berries. This multi-tasking macronutrient also fuels the proteins and enzymes that regulate water and nutrient uptake and disbursement.

Phosphorus

Phosphorus plays a key role in photosynthesis by triggering captured energy to convert starches and carbohydrates into food.

With other crops, phosphorus contributes to bud and fruit production. But, acid-loving plants like raspberries, help to regulate soil pH. So that plants can easily access other vital nutrients.

Phosphorus then moves to the cellular level. Facilitating the construction of those same proteins and enzymes that nitrogen uses to regulate water and nutrients.

Potassium

Potassium is responsible for the circulation of water, nutrients, and photosynthesized food throughout raspberry plants. By doing so, it activates 80 different enzymes, formed by phosphorus and nitrogen, that support bud, flower, and fruit formation.

Proper amounts of potassium contribute to a raspberry plant’s resistance to disease and extreme heat and drought by helping them conserve moisture. And is especially effective in encouraging tolerance for even the coldest winters when plants are dormant.

Controlled Release Vs Liquid Fertilizer

The best raspberry fertilizer can come in a liquid or slow-release form. Granules and spikes are heavily concentrated and have a specialized coating that allows for the controlled release of nutrients.

These can last for several months at a time based on ambient temperature and available moisture.

Liquids offer faster results, especially in poor soil. Nutrients are carried directly to the roots, or into foliage when applied as a spray, allowing for immediate absorption.

Liquids also give you more control over how much your raspberries are fertilized and when. But, they typically require more frequent applications.

Organic Fertilizer Vs Synthetic

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.

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

Organic feeds generally contain lower levels of nutrients but can nourish your berry plants for longer periods of time. This option can also improve the surrounding soil.

The use of inorganic feeds can result in a larger fruit yield. But, they can also potentially contaminate nearby water sources.

Effect of Soil pH on Raspberries

Raspberries thrive in a soil pH range between 5.6 and 6.2. Anything outside of this range will have a visible impact on the vitality of your plants.

Too high and the metabolism of nutrients is cut off, no matter how much you apply. Too low and your raspberries may suffer from heavy metal ion toxicity.

Adding well-aged compost is the healthiest way to increase acidity, over time.

6 Best Fertilizer For Raspberries

When determining the best raspberry fertilizer for you, first take into consideration your climate, soil condition, and your preferred application method.

Raspberries will typically grow best in regions with cool summers, mild winters, and a rain-free harvesting season. But, with a little ingenuity (and the right fertilizer), they can prosper despite colder winters or hotter summers.

I’ve tested a number of options on my own raspberries, and I’ve compiled a list of the top 6 performers, based on results and ease of use. Including product details and the pros and cons of allowing for an informed decision. 

PROS

• Formulated for increased fruiting and lush foliage
• Includes 6 different types of beneficial bacteria

CONS      

• May give off an earthy smell

This organic option from Espoma gave me not only peace of mind but also 6 different strains of beneficial bacteria for my soil!

Okay, so it has an earthy smell, but it’s suitable for use from when canes come out of dormancy, and as is the case with raspberries, will only require one more feed for the remainder of the growing season thanks to the slow-release formula.

The results really did speak for themselves, results so good in fact, that I’ve started using them as a blueberry fertilizer and on my strawberry plants, too.

How To Use: Apply 1 cup per foot of branch spread in the first month of spring, then the third, for a slow-release feed, promoting vigorous growth and lots of fruit.

PROS

• Free from animal bi-products
• Versatile enough for any nitrogen-hungry plant

CONS

• More product may be needed than other options

This is an effective option that’s free from animal by-products. I tested this nitrogen-rich fertilizer on my golden raspberries and I ended up harvesting a much higher yield with a surprisingly sweeter flavor. 

It has to be said, my dogs were attracted to the smell, but that’s fine with me given the all-natural ingredient list and assured quality from a premium brand such as Down to Earth.

How To Use: Apply 2.5-5 lbs per 100 square feet, monthly, and mix into the top 3″ of soil. New transplants – add 1-2 tbsp per hole, mix in, and water in well.

PROS

• Increases microorganism activity for health, fertile soil
• 100% Organic

CONS

• May give off an organic odor

Purely organic fertilizers often cost a little more than synthetic options, but this pick from Jobe’s was surprisingly cost-effective for the results I got.

Containing feather meal, processed manure, and tons of archaea bacteria, these granules support increased root mass, vigorous foliage growth, and bountiful berries.

How To Use: This option is ideal for newly germinated seedlings and both transplanted and established shrubs. Scatter the recommended amount around the base of berry plants, every 4-6 weeks for consistent nourishment.

PROS

• Vigorous growth and plant vitality with consistent use
• Increased yield from a focused NPK

CONS

• Not recommended for use as a water-soluble

I had to include this new, organic option from a brand well-known for its dependability. With an endorsement from the OMRI, Miracle-Gro’s biotic formula gave me an increased berry yield (more typical of inorganics) plus the peace of mind that comes from feeding plants that I’m going to eat with something natural.

How To Use: Apply evenly around plants per the recommended amount and water regularly. Then, repeat every 4-6 weeks for continuous feeding.

PROS

• Enriched with kelp and fish meal
• Encourages plentiful organic fruits and flowers

CONS

• Larger doses may be needed than with other options

Specifically formulated for berries and ornamentals that thrive in acidic soil, this 4-3-6 NPK from Down to Earth is fortified with organic compounds like kelp and fish meal. Together, these elements encourage abundant fruiting while improving resistance to harsh winter climates.

How To Use: Mix into the top 3” of soil in early spring for lush foliage. Then again when buds set for healthy flower and fruit formation. Water well following application.

PROS                                                       

• Made with discarded, local kitchen scraps
• No Manure Added

CONS

• Must be stored in a cool, dry place to avoid mold growth

I regularly compost our kitchen scraps into ‘garden gold’. So, this innovative, granular product from Ecoscraps really intrigued me.  Turns out, it’s exactly what the company name implies.

After partnering with various rubbish collection locations, applicable food scraps are collected and processed down to nutritious and easy-to-apply fertilizer granules.

The outcome is a supply of all the same nourishment to plants that well-aged compost provides but in dry form. All while reducing landfill waste. Brilliant!

How To Use: Depending on the age of your plants, work the required quantity of granules into the soil around your raspberry plants.

When To Fertilize Raspberries

The best time to fertilize raspberries will depend on the formula and application method you choose.

Slow-release options are typically applied to established shrubs and new plantings once or twice per growing season. Once in the spring, as plants revive from winter dormancy, and again in the fall to increase resistance against cold winters if needed.

Liquid options may need to be applied every 1- 2 weeks, depending on the brand, to maintain consistent nourishment. 

Fertilizer should not continue beyond mid-summer. This will prevent new foliage and fruit growth that may be vulnerable to an early frost.

Raspberry Fertilization Schedule

Given the occurrence of unexpected weather events, devising a solid fertilizing schedule may be challenging. Excess heat and rainfall can have a direct impact on fertilizer effectiveness.

As we’ve discussed, fertilizing raspberries is rather easy. A good dose of supplemental nutrients in spring will support robust root and foliage growth as they awaken from dormancy.

Once new buds are set, additional potash will increase flowering and fruiting. Beyond this, no further fertilizing is necessary.

How To Fertilize Raspberries

How to fertilize your berry bushes will depend on whether they’re organic or inorganic fertilizers. And if those are liquid or slow-release methods.

Organic granules, like those from Down to Earth or Eco Scraps, can be applied in 25-pound increments per 100 feet of raspberry row. You can apply these by working them into the soil or as a top dressing. 

Inorganic granules only require 4-6 pounds applied to the square footage.

Both organic and synthetically formulated liquid feeds need to be applied every 7-14 days to maintain consistent access to nutrients for your plants.

You may also like to read Companion Plants for Raspberries | Good and The Bad

Verdict: Best Raspberry Fertilizer

So, what’s your verdict? We all want to grow healthy and productive raspberry plants, without breaking the bank. And with so many varieties to grow, we can spend peaceful hours growing, picking, and eating these tiny morsels of sweetness. The enticing question is, “How will you get there?”.

For raspberry plants that are generally in good health and planted in nutrient-rich soil, I strongly recommend you look at Espoma’s Organic Berry Food 4-3-4 with 6 different types of beneficial bacteria to add to your soil.

If it’s a vegan fertilizer you need to try Down to Earth’s Organic Vegan Fertilizer 3-2-2 with extra nitrogen to provide a boost at the start of the growing season.

Or if you’re looking for a combination fertilizer that you can use on your raspberries as well as the rest of your veg patch, then I recommend Jobe’s Organics Granular Fertilizer 4-4-4

Raspberry Fertilizers FAQ

Is tomato feed good for raspberries?

Raspberries and tomatoes have similar nutritional needs at similar stages of growth. More nitrogen to start, with a progression to increased potassium as buds set.
This makes tomato fertilizer a good option for raspberries. Rose fertilizer is also a solid option with raspberries being a part of the rose family.
The only difference is that raspberries like acidic soil whereas tomatoes do not. So, supplemental elements may need to be added to lower soil pH when using tomato feed on raspberries.