Clematis is a hardy perennial climbing vine with many different cultivars which typically flower in late Spring and early Summer with some varieties blooming again later in the season.
If your clematis is not blooming in the Summer, there are several reasons why this could be…
Excess fertilizer and pruning the developing flower buds off the vines in the Spring are the most common reasons for clematis not blooming. Clematis require well-draining, evenly moist rich soil, a cool root system, and full sun to display flowers.
| Reasons for Clematis not Flowering: | Reasons for Clematis, not Flowering: |
|---|---|
| Poor Soil Conditions: | Clematis does not flower well in poor soil. Nutrient-rich loam soil or soil amended with organic matter provides the optimal conditions for clematis to flower. |
| Too much shade on the Vines and Sun at the Roots: | The clematis vines and foliage prefer full sun for flowering and display fewer flowers in the shade however the roots prefer shaded cool, moist soil at the base of the plant. |
| Too Much Fertilizer: | Applying fertilizer too frequently or in too higher concentration promotes lush foliage growth but fewer flowers on your clematis. |
| Pruning at the Wrong Time of Year: | Some clematis varieties flower on last season’s growth, so hard pruning in the spring removes the growth from which the flower buds develop. Always prune and shape clematis shortly after flowering. |
| Drought Stress: | Clematis requires moist soil throughout the year to develop buds and display flowers in Summer. The stress of drought at different times of the year can cause your clematis to droop and is detrimental to the development of flower buds on the vines. |
Keep reading to for why your clematis is not flowering and to learn the best practices to ensure a good bloom the following Spring…
Soil Conditions Required for Clematis Flowering
The soil conditions for clematis to flower are very similar to rose bushes.
Clematis preferred soil conditions are:
- Well-draining soil that does not stay boggy or trap excess water.
- Nutrient-rich loam soils or soils rich in organic matter.
- Soil that is porous yet remains evenly moist so the roots can access moisture when they require it.
The reason for your clematis not flowering may just be due to the soil conditions being unfavorable.
It is therefore very important to prepare the soil well before planting clematis (by amending the soil with lots of compost) to ensure your plant has the resources required for flowering (nutrients, soil structure, and moisture).
If your soil is sandy then it will drain far too quickly and not retain enough water-soluble nutrients to thrive.
Equally, if the soil is heavy clay or low-lying and boggy then the soil structure can inhibit root development and retain too much moisture which results in problems such as clematis wilt.
Loam soil is considered ideal for growing clematis, however, clematis thrives in any soil that has been amended with organic matter (such as compost, leaf mold, and well-rotted manure) as these materials retain moisture, improve soil structure, and add nutrients to the soil.
Adding mulch around the base of your clematis every year is the best practice for maintaining plant health and encouraging flowering.
If your soil is too sandy, nutrient-poor, or the soil is overly boggy transplant clematis in the Spring to an area of the garden with more suitable soil that is amended with compost.
Otherwise, remove the clematis from the ground and dig out an area much larger than the root ball to add lots of compost and organic matter around the plant to ensure the soil conditions are more favorable for the plant to flower.
Clematis Require Sun on the Plant but Shade at the Roots for Flowering
Clematis prefer full sun (at least 5 hours) but can flower well with morning sun and shade in the afternoon.
In full shade, the clematis vines grow extensively with lots of healthy-looking foliage but the plant displays few if any flowers.
Transplant any clematis that are shaded to an area with some direct sun or cut back overhanging branches and other plants that can cast shade on the clematis to promote flowering.
However an interesting quirk of encouraging clematis to flower is that they bloom far greater with their roots in the shade with their leaves in full sun.
Whilst this is true of many plants, there is a far greater requirement for clematis to have their roots shaded in order to grow well and flower.
The roots of the clematis prefer to be in cool moist soil whilst their leaves are in full sun to promote blooms.
This can easily be achieved in your garden:
- Carefully plant bedding or other plants in the soil around your clematis to shade the area around the roots.
- Apply a layer of mulch to the soil around the clematis.
A 1-inch layer of mulch on the soil surface helps to retain moisture and prevents the sun from shining directly onto the soil so the soil does not bake in Summer and the roots remain cool.
Materials such as compost, leaf mold, and well-rotted manure are the most appropriate types of mulch for clematis as they all have a great capacity to retain moisture so that the root system remains cool in the Summer heat.
Apply mulch around the base of your clematis in the Spring before the heat of Summer and again in mid Summer for optimal flowering.
Too Much Fertilizer Causes Fewer Clematis Blooms
Clematis can often benefit from fertilizer to boost the available nutrients, however, it is important to find the right balance.
Clematis does not tolerate consistent additional fertilizer to the same extent as competition standard roses.
Too much nitrogen in the soil from applying fertilizer too frequently or in too great a concentration promotes foliage at the expense of clematis blooms.
Therefore a balance is necessary to achieve optimal clematis flowering.
Clematis in poor or sandy soils, pots, and containers, or perhaps soils that have not had an application of mulch for years generally benefit in terms of flowering more from additional fertilizer than established clematis in well-prepared soil.
If you have applied a high strength of fertilizer or have used fertilizer more than twice during the growing season then this can be detrimental to flowering.
Scale back the use of fertilizer to a half-concentrated application of well-balanced NPK (equal parts Nitrogen, Phosphorus, and Potassium) multi-purpose fertilizer in the Spring for the optimal nutrient balance to ensure clematis flowers well for the following Spring.
Pruning at the Wrong Time of Year (Cuts Away Developing Flower Buds)
Some clematis varieties bloom on last year’s growth whereas others bloom on new growth in the Spring time.
If you prune clematis in the early Spring then you can stimulate lots of vines and foliage growth without flowers as you may have cut away the flower buds that develop on last year’s growth.
It is best practice to wait till after flowering (which occurs in late Spring or early Summer depending on the climate) to prune back and shape your clematis.
Pruning just after flowering encourages more growth so more flowers can be displayed the following year and keeps the plant looking more orderly and tidy.
Pruning each year ensures that the clematis vines do not overlap and become a matted tangled mess which can also limit blooms.
Watch this YouTube video for a visual guide to pruning clematis.
Drought Stress Prevents Flowers
If clematis has a serious deficit of moist soil due to drought, hot weather, and low rainfall then the clematis can droop and it does not have the resources required for developing flower buds or displaying flowers.
To prevent drought stress affecting clematis blooms during hot, dry Summers:
- Plant clematis in soil amended with lots of organic matter to retain moisture.
- Apply a layer of mulch to the soil surrounding the clematis to further conserve soil moisture and ensure the roots are in shaded soil.
- Water the clematis with a generous soak once per week (or as often as required to keep the soil consistently moist).
To test soil moisture check the surrounding soil to a finger’s depth and the soil should be moist but not saturated.
If the ground is too hard to try this then the soil structure requires improving by adding lots of compost as mulch to improve the texture of the soil.
Ensure you water with a generous quantity when watering clematis to give it a good soak as this encourages the roots to grow and establish in the soil which increases drought resistance.
Sometimes in Summer, the combination of intense heat and sun can cause the soil to bake hard which causes water to run off the surface, in which case water slowly for a long time before applying mulch to seal in the moisture and improve the texture of the soil at the surface so that moisture can properly infiltrate.
Check periodically the soil moisture surrounding the clematis and give it a generous soak when required to ensure the clematis is not under drought stress so it can bloom in the Summer sun.
Key Takeaways:
- The reasons for clematis not flowering are because of too much fertilizer, poor soil, drought stress, pruning off the developing flower buds in the Spring, and because of too much shade on the leaves and flower buds.
- Clematis requires full sun and shaded roots, with rich, moist soil to flower.
- Some clematis varieties flower on least years growth so pruning in the Spring can remove the flower buds and cause the clematis to not flower.
- To ensure that your clematis flowers, plant clematis in soil amended with compost, in full sun, and apply mulch at the base of the plant to keep the root system cool. Apply a half-strength fertilizer in the Spring when the weather warms, if the clematis is potted or in poor soil. Water the clematis in times of drought and prune or shape the clematis vines after flowering to avoid removing flower buds.