Are you growing clematis for their gorgeous, trailing blooms yet struggling to get them to bud? Perhaps their sparsely growing foliage keeps yellowing? Well, you’re not alone.
Throughout hardiness zones 3-9, where most clematis specimens thrive, gardeners experience these same disappointing issues. Luckily, the solutions are really quite simple.
It’s just a matter of providing the right nutrients and growing environment in which clematis are revitalized and exhibit the kind of lush, colorful growth you were hoping for.
So, where do you start? Way, a good place is to choose the best fertilizer for your clematis.
Best Fertilizers for Clematis
Effective tips for abundantly blooming clematis vines are just a quick read of this article. But, if you simply need fast, reliable advice for the best fertilizer for these prolific bloomers, here are my top picks from the 6 best fertilizer options.
Best Organic Fertilizer
Down to Earth Organic Bone Meal Fertilizer 3-15-0
Boost flower production and strengthen roots with this slow-releasing, 100% natural, and organic bonemeal fertilizer.
Best Water-Soluble Fertilizer
Jack’s Classic Blossom Booster Fertilizer 10-30-20
A versatile and fast-acting water-soluble fertilizer that can be adjusted to meet your soil conditions, resulting in abundant flowering.
By the way, our site is supported by visitors like you. Some links on this page may be affiliate links which means if you choose to make a purchase, I may earn a small commission at no extra cost to you. Thanks for your support! You can find out more here.
Choosing the Best Fertilizer for Clematis
There are several important nutrients that go into an effective clematis fertilizer. But the first thing you should look for is a higher percentage of phosphorus than nitrogen and potassium.
Also, keep in mind that clematis is a relatively heavy feeder. Meaning large plants can deplete even the most fertile soil rather quickly. So, on some of my recommendations, you’ll see a pretty high ratio of all three NPK nutrients.
These are primarily for those growing in less-than-fertile soil, where compost and other organic materials aren’t regularly applied. I also have some great picks for those that are.
Clematis Fertilizer N-P-K Ratio
Now that you know what to look for, it’s time to find the best NPK ratio for your plants. Let’s start with what an NPK is.
Every fertilizer label includes a three-numbered N-P-K ratio. Indicating that product’s proportions of nitrogen, phosphorus, and potassium.
For example, a 3-5-3 NPK has 3% nitrogen, 5% phosphorus and 3% potassium. Every plant requires these three elements for optimal health. Just in different proportions.
Phosphorus and Calcium
Nitrogen supports healthy foliage growth, while potassium stimulates bud production. Yet, phosphorus is what encourages buds to properly form and open into stunning blooms.
In clematis, calcium facilitates the construction of strong cell walls. Which results in thick vines and stems that can easily support large flowers.
Clematis Soil pH and Nutrient Uptake
Clematis thrives in a pH range of 6.5 to 7.0. Adding well-aged compost to your soil will achieve this at a healthy pace. Or you can choose a fertilizer that will aid in this effort.
Watch out however by monitoring and soil testing frequently, as nutrients can be absorbed in excess of what your plants need when the pH is too low. Too high and the opposite happens. Nutrients are locked in the soil and unavailable to roots.
Granular Vs Liquid Fertilizer
The difference between these is a simple matter of what works best for you, in terms of ease of use and what you want the end result to look like. Liquid nutrients move quickly to the roots, allowing for immediate uptake.
They do a good job of keeping pH levels balanced since they are absorbed and/or washed away quickly. But caution is recommended, as over-feeding can lead to root burn.
Concentrated granules are slow-releasing and provide a consistent flow of nutrients for several months at a time, saving you time and effort.
Liquid Concentrate or Spray
Diluted concentrates work through quick root absorption when applied directly to the soil around your plants or as a foliar spray.
Liquid concentrates have a long shelf life and a little can go a long way. They can be stored securely, with no mess, lasting for a good few seasons if unused, until you’re ready to use them.
Fertilizer Granules
Granules are slow-releasing and provide nourishment for much longer. They often need water to begin activating and then nutrients are released by warming soil temperatures.
Over time they are consumed and converted into an easily absorbed form via soil microbes.
This method of fertilizer application is far less likely to cause root burn and because they continue working for a long time, you get more time to enjoy your garden. Plus, they are typically more cost-effective than liquids and granules.
Fertilizer Spikes
Spikes are conveniently pre-measured in various sizes, easy to push into loamy soil and release nutrients in a manner just like granules.
Offering the same long-term benefit, spikes also run little risk of plant burn. As a result, they’re considered more “eco-friendly” options, despite some brands being inorganic.
Organic vs Synthetic Fertilizers
Deciding between an organic or synthetic fertilizer is a simple matter of gardening style and plant performance goals.
Organics contain mild to moderate nutrient levels that are akin to what you might expect plants to absorb in a natural environment. They nourish plants and improve soil fertility all the same time.
Inorganics are manufactured in large quantities using minerals and synthetic chemicals. You often end up with bigger plants with larger blooms but the downside is the possibility of potentially contaminating nearby water sources as well as your soil.
Best Clematis Fertilizer Reviews
Thorough product testing and comparison research take time, effort, and money. I’ve had the opportunity to do some extensive testing, using a wide variety of fertilizer options.
For your convenience, here are my picks for the top 6 performers for improved blooming on healthy clematis plants.
Pros
- A readily available source of organic nutrients
- Includes vital micronutrients for optimal plant health
Cons
- May exhibit an earthy odor
These slow-release granules require very little effort, in exchange for some of my Clair de Lune specimens that ended up producing much larger flowers than the year before. All with stunning, gradient shades of lilac and white.
It’s no surprise that Down to Earth Organic Bone Meal is my pick for the best organic fertilizer. Made with 100% natural ingredients, OMRI certified, and, the convenience of being able to use it right from the start of the growing season.
With the success of my abundantly flowering Clair de Lune, it is clear to see that this formula improves nitrogen absorption and effectiveness. Thus, helping to deliver a steady flow of phosphorus and calcium and resulting in more robust root systems and vigorous growth.
How To Use: Mix in 1-2 tbsp per hole for new transplants, then water well. Side dress established plants with 2-4 oz per month during the growing season.
Pros
- Versatile use for any level of soil fertility
- Extends bloom time
Cons
- Not recommended for plants in highly fertile soil
This nutrient-rich, water-soluble formula from Jack’s is ideal for heavy-feeding climbing clematis that is growing in poor soil.
Regular applications of this throughout the growing season really reinvigorated some brother Stefan clematis that I found struggling to grow over a garden entryway, with lush foliage and long-missing buds.
This formula is highly versatile as the strength of the formula can be adjusted depending on how much water you add. So not only can you avoid foliage and root burn, but you can also flex how you nourish your plants based on whether your soil conditions are optimal or nutrient deficient.
How To Use: Mix 1 teaspoon per gallon of water. Then, apply to ground-planted clematis once per week. Potted plants will need further dilution, based on plant and pot size.
Pros
- Effective nutrition for roses, flowering perennials, and annuals.
- Slow-releasing for a longer feeding with fewer applications.
Cons
- Maybe at a slightly higher price point than other brands.
Jobe’s organic spikes offer the perfect fertilizing solution for clematis growing in fertile soil. To minimize the risk of overfeeding and root burn, this mild 3-5-3 NPK still has a higher percentage of phosphorus to support a higher bloom count.
While labeled for roses, this lower macronutrient ratio gives you the opportunity to give your clematis specimens the organic boost of nutrients they need, without worry.
I’ve used these with success for container-planted clematis that I grow on my patio. They are great when feeding smaller varieties that don’t require as many spikes, plus they are mess and odor-free once they have been inserted. Just be sure your soil conditions are nutrient-rich, to begin with.
How To Use: Apply every 4-6 weeks, starting in early spring, as new growth begins to emerge.
Pros
- All-natural source of organic phosphorus and nitrogen
- Formulated to help loosen heavy, clay soil
Cons
- Not recommended for plants that require higher potassium
This second bone meal option from Espoma requires fewer applications and is a common staple in many gardening sheds. When preparing my soil, in spring, I’ll add a dose of this throughout my perennial beds to stimulate sturdy roots and healthy foliage right from the start of the growing season.
The natural phosphorus and nitrogen this provides can’t be beaten for providing all clematis varieties with the kind of growing power they need for abundant blooms. Especially if you’re an organic gardener.
How To Use: Apply 2 oz (one heaping tablespoon) per potted plant, or around the base of each ground-planted clematis, and work into the soil. Then, water well.
Pros
- Effective in harsh and temperate climates
- Extended bloom times for most clematis varieties
Cons
- Frequent watering may be necessary to avoid root burn.
Scotts water-soluble, high phosphorus formula promises instant feeding while protecting against root burn when used appropriately. The percentage of nitrogen and potassium is lower, in this NPK, for soil that already contains them. Preventing the overgrowth of foliage with few blooms.
I live in a short growing season area so I have to start flower seeds indoors. This proved highly effective on a new range of different seedlings in early spring.
How To Use: Pre-moisten soil prior to application. Then, mix two teaspoons into each gallon of water used and water normally. Repeat every 7-14 days.
Pros
- Contains natural ingredients attractive to soil microbes
- Includes essential secondary micronutrients
Cons
- Not recommended for fully fertile soil
I found this granular option, with its simple application method, works best in the semi-fertile to poor soil around my potted climbers. In fertile soil, I found that higher nitrogen resulted in excess foliage growth at the detriment of flower production.
Using this, the bloom color was more vibrant. I also no longer saw browning around the edges of leaves thanks to the high nitrogen content.
This is formulated to be attractive to hungry soil microbes who then convert nutrients into a readily available form.
How To Use: Apply dry and evenly to the soil, approximately 1 tbsp per sq ft, for a consistent feeding that lasts for three months.
How to Fertilize Clematis
Keep in mind that a good fertilizer is only one part of clematis success. Positioning in full sun to partial shade (depending on the variety) and in moist, well-draining and slightly acidic soil will enable your fertilizer to reach its full effectiveness.
Although they’re heavy feeders, clematis benefits from low doses of fertilizer in spring, as they wake from winter dormancy. Slowly building up to the manufacturer’s recommended dosage, over time.
Avoiding Clematis Fertilizer Burn
Fertilizer burn is typically caused by overuse, so it’s important to follow the manufacturer’s instructions.
Excessive nitrogen can burn roots when applied to the soil and leaves when sprayed. Extra potassium and phosphorus can introduce needless salts that quickly absorb all available moisture, dehydrating your plants.
When to Fertilize Clematis
When to fertilize clematis depends on the formula and application method of your chosen fertilizer.
Granules and spikes, like those from Jobe’s Organics and MiracleGro, should be applied in late winter or early spring, after the last forecasted frost. Other garden perennials will also benefit from these, as new growth emerges.
Fast-acting liquids, such as Jack’s Classic or Scotts, will have an immediate effect when applied monthly, as the label recommends.
How Often to Fertilize Clematis
The frequency of clematis fertilization will also be dictated by the brand. Liquid fertilizers need applications every 2 to 4 weeks depending on the brand. Versus granular formulas, which may only require two applications per season.
In any case, clematis only need feeding while they are growing and can be seen above ground. Once they have been cut back during winter dormancy, mulching is sufficient.
Verdict: Best Fertilizer for Clematis
It looks like we have our verdict! The most effective fertilizer for clematis will be higher in phosphorus, with an NPK that supports nutritional needs based on soil quality and any nutrient deficiencies therein. As well as plant size and age.
When a multi-functioning fertilizer is what’s required, use Down to Earth Organic Bonemeal. Not only will it encourage strong root growth and abundant blooming, it can also be used in beds and borders to get the growing season off to a flying start.
For those in poor soil, a quick boost from Jack’s Classic high ratio formula will get your clematis climbing and blooming in no time.
But remember, Clematis are heavy feeders so unless you have extremely fertile soil, your flowering climbers will no doubt benefit from some additional nutrients to help them on their way.
Best Organic Fertilizer
Down to Earth Organic Bone Meal Fertilizer 3-15-0
Boost flower production and strengthen roots with this slow-releasing, 100% natural, and organic bonemeal fertilizer.
Best Water-Soluble Fertilizer
Jack’s Classic Blossom Booster Fertilizer 10-30-20
A versatile and fast-acting water-soluble fertilizer that can be adjusted to meet your soil conditions, resulting in abundant flowering.
