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Growing ceanothus – a beginners guide
Last Updated on January 21, 2020 by John
This is a large genus of shrubs that are very versatile and beautiful. Many of the shrubs are native to California which is why the plant is colloquially referred to as the California lilac. Of course, this name is a bit misleading as it is not a lilac at all.
This ceanothus bush grows between 30 and 180 cm tall, and some varieties will grow into a mound shape while others grow prostrate and turn into small trees if you let them, they can even be used for hedging and will produce a mass of flowers from May onwards.
In spite of the differences between the different ceanothus varieties, you can easily recognize any of the plants with their distinctive flowers and leaves. The leaves are oval in shape with two stages. Each leaf contains three veins that run parallel from the base to the tips. The leaves are glossy and green on top and grow between 1.27 cm and 7.6 cm in length. They typically look like holly leaves but much smaller.
The flowers are often blue but they can be found in different shades. A few varieties will produce pink blossoms or white blossoms. The ceanothus flowers themselves are very small but they will grow in dense clusters and absolutely cover a bush making the most impressive display.
As you walk by you will no doubt smell the intense fragrance they have an offer when they bloom between March and May. Another nickname for this shrub, the most common variety, is that of the soapbush. It is called this because it is said that if you mix the flowers with water you can form a lather similar to soap.
Perfect for bees and butterflies
When you plant these bushes you can naturally attract many butterfly species as the plants offers food for butterflies. They also attract other beneficial insects such as bees. If you are growing a habitat garden this is a must.
Germination – which is fairly difficult
These bushes grow in dense fields and they are fairly difficult to germinate so we recommend taking cutting instead. if you do want to try and grow them from seeds you should collect ripe seeds from a healthy plant or purchase them from a trusted Nursery. Store the seeds in an airtight, dry container. If stored properly you can keep them for up to 12 years while you prepare your garden for planting but ideally, you want to get them sown as soon as possible after going through the process outlined below.
When you are ready to germinate from seed you should put the seeds through stratification beforehand by placing them in hot water for 5 or 10 seconds and then immediately placing them in cold water and then cold stratify for up to three months to mimic the conditions they would receive naturally, and then keep at 16-18°C (61-65°F). Germination can take up to three months.
Taking cutting is usually much easier than growing from seed but it would still be described as moderately difficult. If you want to take a cutting from evergreen varieties then this is best done in late summer, to early autumn by taking semi-ripe cutting.
For deciduous varieties then its best to take soft-wood cutting in late spring.
Alternatively, you can purchase a smaller plant from a nursery or garden store and enjoy beautiful blooms much sooner as they often flower even as very smaller pot grown plants.
When you are ready to plant, make sure that your ceanothus is planted in fertile well-draining soil and ideally in full sun. Check the pH levels beforehand as they should be between 6.5 and 8.0 but if you have a good mix of plants in your garden ceanothus will likely thrive too.
These plants do well in full sun but will also thrive in partial shade but regardless of their location be sure to give them extra water during the driest part of Summer. You typically don’t have to fertilise these at all and in fact, doing so can be detrimental depending on the type so we recommend just mulching around the base of plants with compost or well-rotted farm manure in late winter to increase soil fertility and protect the plant from ground frost.
Although they are very hardy in most parts of the UK, they prefer to be planted in a more sheltered spot where they won’t be exposed to cold winds.
Ceanothus is not a plant that needs pruning but they do benefit from pruning using a good pair of secateurs to encourage them to bush out more and produce more flowers or to simply keep them under control and shape.
When you prune depends on what variety you have as it all depends on when it flowers. For evergreen varieties, if you have an early flowering varity that flowers in late spring to early summer which include C. impressus, C. thyrsiflorus‘Skylark’. These varieties should be pruned straight after flowering, which you can prune by as much as half if needed. They can also benefit from a light pruning to tidy them up at the end of summer.
If you have a later flowering variety such as e.g. C. ‘Autumnal Blue’, C. ‘Burkwoodii’ which typically flower late summer, we recommend pruning them back by about a third in spring, to remove some of previous years growth.
If you have deciduous ceanothus then we strongly recommend pruning them for the first couple of years in early to mid-spring to encourage a good strong framework. Its recommended that you prune by as much as two thirds in the first year and then in the second year prune the previous year’s growth by about two thirds again. Once established, you can prune the main flowering stems by about half and remove any weak growth.
Ceanothus so usually benefit from pruning but it’s not essential and many varieties grow well without any pruning at all.
Types of ceanothus
There are over 50 types of ceanothus.They range in size from low-growing to medium-sized to tree-like sizes so you can pick the one that best suits your space.
The low-growing shrubs are best suited for sloped gardens especially if you want to use them for erosion prevention or as a ground cover shrub. Many of the lower growing shrubs will tolerate more water and shade compared to other varieties.
Ceanothus repens also known as creeping blue blossom will grow between 1m and 1.5m high and will typically spread out 3m. This particular variety offers clusters of blue flowers with ovate green leaves and is a small, but a vigorous evergreen shrub.
Medium shrubs are designed for slightly larger areas. The Julia Phelps variety will grow between 120 and 180 cm tall and spread out between 210 cm and 270 cm. You get dark, Indigo flowers with dark green leaves. This particular variety can handle a wide range of environmental conditions.
The Louis Edmonds variety is wider than it is tall so it is best suited for certain garden situations where that is a necessity especially those attempting to use the plant as ground cover. This particular plant will reach heights between 120 and 180 cm, and spread out up to 450 cm. The flowers are blue with green leaves.
Tree like shrubs
The larger varieties take the form of small trees. The Ray Hartmann variety can grow up to 360 cm and 540 centimetres tall. It has lavender-blue flowers with dark green leaves. This particular variety will grow very fast and can grow up to 300 cm in only a few years.
Ceanothus do not suffer from many problems but they can sometimes be affected by honey fungus and scale insect which should be treated at the first signs. Honey fungus is a fungus they attack the roots undergrowth causing the plant to die. There is not a chemical cure for this so affected plants are best removed.
Scale insects are easy to identify as they have scales and such the sap from plants and usually leave sticky honey due on the leaves. Scale insects can be sprayed with pesticides but it can be ineffective to adults as the waxy scales protects them so the best to time spray in when the nymphs hatch which is usually June to July as the scales are still soft and so spraying with a bug killer is effective for a short period.