How to Fertilize Clematis for Maximum Blooms Each Season

Producing vibrant, exquisite Clematis flowers requires a lot of energy, which you can provide using fertilizer. I fertilize clematis from early spring until the flowers first appear. In my experience, it’s prudent to avoid fertilizing once flowers emerge, as this reduces bloom time. I’ll then resume feeding after flowering has finished to encourage more flowers. Typically, I’ll feed clematis every 4 to 6 weeks with high-potassium fertilizers such as bone meal or tomato feed.

How to Fertilize Clematis for Optimal Blooming

Signs That Your Clematis Is Lacking Nutrients

If your clematis struggles to flower, it may be due to a lack of nutrition. Clematis need fertile, well-draining soils that contain plenty of phosphorus to produce flowers. I like to add organic matter, such as compost, to increase the nutrient content of the soil and fertilize regularly.

A nutrient imbalance within the soil could also cause the lack of flowers. If the soil contains too much nitrogen, your clematis will focus on producing lots of bushy foliage at the cost of flowers. Use a high-phosphorus fertilizer such as bone meal or tomato feed to address this imbalance.

Clematis vines can suffer from fungal diseases, such as wilt and powdery mildew. If your clematis lacks adequate nutrition, it can be more vulnerable to fungal infections.

How Often Should You Fertilize?

In my experience, clematis should be fertilized every 4 to 6 weeks during the growing season. I begin feeding my clematis in early spring and continue until the first flowers start to emerge. I avoid fertilizing while the plant is in bloom because over-fertilizing can reduce the duration of the flowers.

Once my clematis has finished flowering, I resume feeding once weekly until mid-fall. I find this encourages my clematis to produce another round of flowers before winter sets in. I recommend using a high-phosphorus fertilizer to achieve optimal flower production.

Clematis growing in pots should be fertilized slightly differently than plants growing in the ground. Here, I’ll add slow-release fertilizer granules to the soil in the container twice or thrice during the growing season. I use high-phosphorus granules to promote flowering.

The Best Fertilizer for Clematis

A person pouring a measure of liquid fertilizer into a watering can

As noted, I find high-phosphorus fertilizers are ideal for clematis because phosphorus helps produce more flowers. I always choose fertilizers that have an NPK ratio of 5-10-5 or 5-10-10. Remember that fertilizers containing too much nitrogen will produce bushy foliage at the expense of flowers.

Choose organic high-phosphorus fertilizers wherever possible, as synthetic fertilizers can contain harmful chemicals. I’ve found that bone meal is a good choice because it’s widely available and absorbed quickly. Liquid tomato feed (via Amazon) can also work well because the extra potassium will supplement flower production.

Always follow the packet instructions to avoid over-fertilizing your clematis.

How to Apply Fertilizer

The method of applying fertilizer changes depending on the type of fertilizer that you’re using. Slow-release granule fertilizers can be dug into the soil at the start of the growing season. However, liquid fertilizers are the most common type. Here’s a quick guide to applying liquid fertilizer to your clematis:

Choose high-phosphorus liquid fertilizers with NPK ratios of 5-10-5 or 5-10-10.

Dilute the fertilizer according to the instructions on the packet. Add the recommended dose to an empty watering can before topping up with the recommended amount.

Apply the fertilizer as if you were watering the plant. Pour the diluted fertilizer around the stem of your clematis. Take care to avoid splashing any fertilizer on the leaves.

It’s also worth noting that all parts of the clematis plant are considered poisonous, so it’s prudent to wear protective gloves when overseeing any care with these plants.

Key Considerations

While fertilizers can help clematis vines produce more flowers, too much fertilizer can do more harm than good. Here are a couple of things to consider when fertilizing clematis.

Over-Fertilizing

Giving your clematis too much fertilizer can cause problems – especially if you’re using synthetic fertilizers. Many fertilizers contain chemicals and salts that can build up in the soil. Always follow the instructions on the packet and only apply the recommended dosage each time.

Soil Type

Clematis need fertile, well-draining soils that contain lots of nutrients, such as loamy or silty soils. You may need to fertilize more often if you’re using nutrient-poor, chalky, or sandy soils. Alternatively, add some compost, organic matter, or bone meal to these soils to improve nutrients.

The Role of Fertilizers in Plant Health, Growth, and Development

A close shot of hand filled with pellet fertilizer scattered in around the base of a plant growing in the soil

Plants need four main types of nutrients; structural macronutrients, primary macronutrients, secondary macronutrients, and micronutrients.

Carbon (C), hydrogen (H), and oxygen (O) are the structural macronutrients. These vital building blocks come from air and water absorbed by plants through their leaves or roots. These structural macronutrients are used to manufacture glucose and cellulose to create new plant tissue, which enables growth.

Plants also absorb three primary macronutrients from the soil: nitrogen (N), phosphorus (P), and potassium (K). Nitrogen helps produce bushy foliage and the chlorophyll needed for photosynthesis. Phosphorus is essential for flower production, while potassium helps plants circulate water, nutrients, and minerals.

Secondary macronutrients are minerals that also help plants grow and develop. These minerals include calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), and sulfur (S).

Different Types of Fertilizers

Fertilizers are divided into two groups: organic fertilizers and synthetic fertilizers. Both fertilizers are usually sold as either liquid feed or slow-release granules.

Organisms in the soil must break down organic fertilizers before the plant can use them. These fertilizers are made from natural ingredients, making them more environmentally friendly than synthetic fertilizers. Common organic fertilizers include compost, blood meal, bone meal, manure, and worm castings.

Synthetic fertilizers don’t need to be broken down in the soil so plants can access nutrients instantly. However, although synthetic fertilizers work faster than organic ones, they are less environmentally friendly. Synthetic fertilizers are made using chemicals and salts that leach into the soil, killing beneficial bacteria and reducing soil quality.

All fertilizers use NPK ratios to help you determine how much nitrogen, phosphorus, and potassium each fertilizer contains. Use nitrogen-rich fertilizers if you want bushy foliage. If you want your plants to produce many flowers, choose fertilizers with higher phosphorus.

Wrapping Up

Clematis are fast-growing climbers, requiring lots of nutrition to fuel their growth. Start fertilizing clematis in early spring and feed every 4 to 6 weeks until the flowers emerge. Then, stop fertilizing until flowering has finished. You can then start feeding again to get more flowers. Use high-phosphorus fertilizers to get as many flowers as possible.

For more, see our in-depth guide to the best clematis varieties to grow at home.

Editorial Director | andrew@petalrepublic.com | Full Bio

Andrew is the Editorial Director at Petal Republic. He holds a BSc degree in Plant Sciences and has trained professionally at leading floristry schools in London and Paris. In amongst overseeing a global editorial team, Andrew's a passionate content creator around all things flowers, floral design, gardening, and houseplants.

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