This is one of a new series of posts based on real questions I have been asked. Feel free to add to the answers or include your ideas and experiences.
I don’t think ceanothus are as popular now as they were 20 or so years ago and I am not sure why. It may be because they are not the hardiest of shrubs and so many were killed by the ‘beast from the east’ a decade ago. When you need a hit of blue in the garden (and who doesn’t) they are hard to beat. The most popular are the evergreens, that flowers in late spring but there are deciduous kinds, that bloom in late summer and should be treated like buddleias and these include some with pink (though pale) flowers. Many evergreen species have white flowers but it is only the blues that attract attention.
Anyway, the recent question was ‘My evergreen ceanothus appears to be losing its leaves and appears to have a great deal of lichen on it. It did not flower at the usual time. It is usually full of flowers but this year very minimal.’
Ceanothus are fast-growing shrubs and give quick results but they are naturally not very longlived. Pruning can help to keep them compact and actually increase their longevity. Ideally they should be lightly clipped over immediately after flowering and this will keep them compact and will promote lots of new growth that will carry the flowers the following spring. The trouble is that most people only prune when they want to reduce the size of a shrub and don’t bother with ‘maintenance’ pruning. If left to grow naturally, the base and centre will open up and, because they grow so quickly, they can even become unstable.
I have, in the past, hard pruned, an old, overgrown ceanothus and they sometimes break from the base but not always.
The fact that this specimen was covered in lichen told me a couple of things and, I am afraid, is a bad sign. Lichen is rarely a good sign, even though it does not actually harm the plants. But lichen needs light to grow and it cannot thrive on a shrub that is healthy and covered in dense foliage. You only get lichen on old shrubs with poor vigour. Lichen is only abundant when the air is clean and usually in damp climates. As I say, it does not parasitise the shrubs and it is only sitting on the branches to get into the light. When shrubs and trees are suffering from some other problem or are just old and lacking vigour they are often colonised by lichen.
So, the chances are that this ceanothus is simply old and past its best. There is not much that can be done in this situation and it is probably best to dig it up. Of course, no one wants to hear this and most people hope that shrubs will last for decades and it is disappointing when a shrub has a short life. Many of the most popular shrubs, popular because they grow quickly, have short lives, including artemisia, buddleias and cistus.