How to grow Ceanothus

It can seem like Ceanothus are all much alike, especially when looking at a selection of young plants in the garden centre. There are subtle differences, however, and so to choose the right plant for your garden, consider the following:

Deciduous or evergreen

The vast majority of Ceanothus are evergreen shrubs - those that keep their leaves year-round. If you want to screen an ugly wall or provide a backdrop for winter-interest plants, then an evergreen would work best.

If your garden is more exposed, choose a deciduous Ceanothus - those that lose their leaves in winter - as they are less susceptible to wind and frost damage.

Flowers

Ceanothus are grown for their impressive flowering display. To best appreciate this, choose one that compliments the design of your garden:

• Flowering time – Are you after colour for a specific time of year? Ceanothus flower either in late spring to early summer or from late summer onwards

Spring-flowering Ceanothus

Spring-flowering Ceanothus

Summer and autumn-flowering Ceanothus

Summer and autumn-flowering Ceanothus

• Flower colour – What shade of blue best suits your planting scheme?  Don’t forget pink and white cultivars are also available

Ceanothus for colour

Ceanothus for colour

• Fragrance – Would you like scented flowers? Some cultivars are noted for their light fragrance

Ceanothus for scent

Ceanothus for scent

Eventual size and shape

There is much variety in the size and habit of Ceanothus. Are you after a spreading, low-growing plant for ground cover or perhaps a compact, bushy shrub for a mixed border? If you want a plant for wall-training, choose a vigorous, taller-growing cultivar. Check the labels of plants you are considering for the eventual height and spread, to ensure they're suitable for your needs.  

Ceanothus for ground-cover

Ceanothus for ground-cover

Ceanothus for informal hedging

Ceanothus for informal hedging

Buying

• Ceanothus are widely sold in garden centres as container-grown plants. You may find taller-growing types have been grown up and tied-in to a support; these make good specimens for wall-training
• Look for plants of a balanced shape, with a number of evenly-spaced branches
• Avoid those showing signs of stress, damage or disease, like those with broken branches or yellowing leaves
• Check the rootball if you can - roots should be developed enough to be visible through the holes in the base of the pot, but not be so congested that you can't see any soil  
• Use our Find a Plant tool for stockists nearby

When to plant

• As these shrubs are susceptible to root damage in wet, winter soils, it is best to plant them in the spring
• On a very free-draining soil, planting could also be done in the autumn  
• If you buy a container-grown plant during the summer, plant it as soon as possible and water it regularly  

Where to plant

Bear the following in mind when choosing a site for your plant:

• Ceanothus flower best in full sun and can be disappointing in a shady spot
• Plants need a sheltered location, away from frost pockets and strong winds – against a south-facing wall is ideal
• Allow enough space for your plant to grow into – these shrubs look their best when fully grown and most won’t tolerate hard pruning to restrict size
• If you would like to train your plant, for example up a wall or along a fence, you will need to have supports, like wires or trellis, in place before planting

How to plant

Prepare your soil

Ceanothus like a fertile, well-drained soil and won’t thrive where it is heavy or overly wet. To improve drainage, dig-in some organic matter, like leaf mould or well-rotted manure, before planting.

Our guide below takes you step-by-step through planting your Ceanothus.

Watering

Like most shrubs, newly-planted Ceanothus should be watered regularly and thoroughly, especially during summer, for the first few years until their roots are well-established.

Once established, they are fairly drought tolerant and shouldn’t need regular watering – it is this trait that makes them a popular choice for dry and Mediterranean-style gardens.

However on very free-draining soil or during prolonged hot, dry spells they may need some additional water to support continued healthy growth.

Ceanothus are susceptible to damage in very wet soil, so take care with automatic irrigation systems. Ideally the soil should be allowed to dry between waterings.

Feeding

Ceanothus need little or no regular feeding in most garden soils. However to encourage strong new growth after pruning, plants can be fed annually in spring. 

In March, sprinkle a balanced fertiliser on the soil around the plant, such as Growmore at 70g per square metre (2oz per square yard), and mulch with a layer of bulky organic matter like home-made compost or well-rotted manure. Leave a mulch-free circle immediately around the base of the plant to prevent rot.

Deadheading

It is not necessary to regularly deadhead Ceanothus and indeed many produce such an abundance of flowers that this is often impractical. However removing spent blooms from smaller and slower-growing types can improve vigour, while deadheading formal wall-trained plants maintains a neat appearance.   

Tying-in trained plants

Ceanothus can be trained up walls, along fences and even over doorways. If you intend to train your plant for a more formal look, then new shoots will need regularly tying-in to supports.

Ideally use garden twine for this, as wire can cut into branches as they grow. Tie securely. Check ties at least once a year, repositioning or replacing any that are broken or have become too tight.

Ceanothus are pruned differently depending on flowering time and whether the plant is evergreen or deciduous:

Evergreen Ceanothus

These can be pruned to maintain a bushy, compact shape. However, regular, routine pruning is not essential.

Late spring and early-summer-flowering evergreens

Prune these immediately after flowering, using secateurs to cut back long, flowered shoots by one-third to a half. If needed, you can lightly trim these plants again in late summer.

Suitable for those like Ceanothus arboreus ‘Trewithen Blue’, C. dentatus, C. impressus and C. thrysiflorus ‘Skylark’.

Late-summer-flowering evergreens

These bear flowers on current season growth, i.e. shoots produced that year. They may also bear a flush of spring flowers on shoots that grew the previous summer. Prune in spring, using secateurs to cut back previous season, i.e. last year’s growth, by one-third to a half.  

Suitable for those like Ceanothus ‘Autumnal Blue’ and C. ‘Burkwoodii’.

Deciduous Ceanothus

These shrubs, including those like Ceanothus × pallidus ‘Perle Rose’ and C. × delileanus ‘Henri Desfossé’, are not quite as straightforward to prune as evergreens and need more regular attention to flower well. Bearing flowers on new growth, they are best pruned in early- to mid-spring to encourage strong, new shoots each year.

Pruning young, deciduous Ceanothus

Develop a framework of branches on free standing shrubs by shortening all stems in the first year by two-thirds to an outward-facing bud. In the second year, prune the previous season’s growth by up to two-thirds and shorten any sideshoots to 10-25cm (4-10in) from the main stems.

Pruning established, deciduous Ceanothus

From their third growing season onwards, prune main, flowered stems by around half. Cut back weaker sideshoots harder, by up to two buds from the main stems, and thin out congested and unproductive growth from the centre of the plant.

Wall-trained plants

Ceanothus can be trained to cover walls and fences, providing an attractive backdrop for other plants, an effective screen or a feature in itself. Being vigorous shrubs, careful and regular attention is needed to develop a well-balanced framework of branches that fills, but doesn’t outgrow, the allotted space.

Pruning times and techniques still depend on the type of Ceanothus you have chosen, as detailed above, but you’ll also need to follow advice on training as a wall shrub. See our guide below for more information.

Renovating older plants

Evergreen Ceanothus generally do not respond well to hard pruning into older wood, so it is better to replace overgrown plants than to try renovation.

However deciduous Ceanothus do tolerate hard pruning, carried out when plants are dormant between late-February and March, and can be pruned down to just above ground level if necessary. Response will be fairly slow; encourage strong regrowth by feeding and mulching in the spring after pruning.  

While these shrubs can be difficult to propagate, it is possible to create new plants from your Ceanothus by taking cuttings or growing from seed.

Ceanothus from cuttings

Taking cuttings is the easier method and will produce a new, flowering plant in two to three years. Methods differ for evergreen and deciduous plants:  

• Take semi-ripe cuttings from evergreen Ceanothus between mid-summer and autumn, selecting healthy, current season growth. Rooting is encouraged by taking heel cuttings, where a sideshoot is pulled away from a main stem with a sliver of bark attached, and by keeping cuttings in a heated propagator. Cuttings usually need a growing season before they have rooted well and can be potted on or planted out
• Take softwood cuttings of deciduous Ceanothus between late spring and mid-summer from new, non-flowering stem tips. Dipped in a rooting compound and kept in a warm, humid environment, the cuttings should root in four to six weeks and can then be potted-on individually

Ceanothus from seed

It is also possible to raise new plants from seed, but this can be difficult owing to a hard seed coat and dormancy of the embryo inside. If you want to have a go, in late winter, pour hot water over seeds and allow to soak for 24 hours. They will then need stratifying (keeping) in cold, moist conditions for up to three months and warm, moist conditions at 16-18°C (61-65°F) thereafter, with germination taking up to three months.

Most Ceanothus are named cultivars and these won’t come true to type if grown from seed.

Please be aware that some Ceanothus are protected by Plant Breeder’s Rights, and you are not allowed to propagate them for sale - check the plant label for details.

Problems

Ceanothus do not tend to suffer from many pests or diseases, but they are susceptible to attack by scale insects, including brown scale, and the disease honey fungus.

More commonly it is unsuitable growing conditions that cause a problem, with plants suffering from:

• Wind scorch and frost damage in exposed locations
• Poor growth, dieback and root rots in overly wet conditions
• Leaf yellowing due to nutrient deficiency in shallow, chalky soils

If your Ceanothus doesn’t seem to be thriving and you are not sure what is wrong, the below guides are a good place to start.

Or, if you’re a member of the RHS, you can use our online Gardening Advice service, via MyRHS.