Bonsai and Lime Sulphur

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Using Lime Sulphur as a Winter Wash for Bonsai

Lime Sulphur still has its uses as a winter wash for (outdoor) bonsai. Mix Lime Sulphur with water at a rate of approx 1:25 to 1:50 and spray over the trunk and bare branches to kill any overwintering insects, bacteria or fungi. Rinse off the soil surface and bonsai pot with water afterwards to remove any temporary staining that the diluted lime sulphur may cause (This is purely for aesthetic reasons). I use a lime sulphur winter wash only on my deciduous trees however I understand that some enthusiasts also spray their coniferous evergreens; the needles may however have a temporary white colour that disappears by Spring.

A lower rate of dilution (approx 1:25) with water is useful for cleaning and brightening the trunk of trees with smooth bark such as Hornbeams, Beech and Chinese Elms. Simply spray the solution onto the bark, allow to dry and the bark becomes a subtly lighter and brighter colour. Again, for aesthetic reasons rinse away any excess solution that lands on the soil surface or the pot.

Mixing Lime Sulphur with water at a rate of between 1:25 to 1:50

Add between 4 to 8 teaspoons of lime sulphur to 1 litre of water.


Add between 2 to 4 teaspoons of lime sulphur to 1/2 litre of water.

One teaspoon holds 5ml of lime sulphur.

Lime Sulphur as a Bird Deterrent

As with many enthusiasts, I have great problems with birds (in particular blackbirds) in late Winter and early Spring using the soil surface of my trees as a dust bath and making a mess while foraging for food.

By accident I have found that spraying my trees with a diluted lime sulphur winter wash is an excellent way of reducing the attraction of my bonsai to birds. Birds have a good sense of smell too! I have since found that if the lime sulphur solution is sprayed as soon as the first birds come to feed in and around your bonsai in Winter, they immediately 'learn' that your bonsai do not smell appetizing and will not return to feed or take a bath for the remainder of Winter and Spring.

And please, before I receive e-mails condemning this advice, the smell of the lime sulphur dissuades any feeding long before a bird would consider ingesting it.

Finally. Does Lime Sulphur Actually Preserve Deadwood?

Yes and No.

Lime Sulphur kills all (or at least most) bacteria and fungi that cause the breakdown and deterioration of wood that we know as 'rot'. It also produces a temporarily hostile environment against bacteria and fungi. However, the anti-bacterial or anti-fungal effect of the lime sulphur is relatively short-lived in comparison to its bleaching effect. Most enthusiasts will have seen lime-sulphured wood begin to turn green and support bacteria within a relatively short period of time.

This short term protection requires that the lime sulphur be applied on an annual or even 6 monthly basis to ensure that all of the wood remains stark white (if this is required) and to keep the majority of bacteria and fungi at bay.

Not only is the anti-bacterial effect of the lime sulphur relatively short-lived, but it only has an effect on the parts of the deadwood that it is able to access. As has already been discussed, lime sulphur is only able to permeate the wood of a tree to a certain depth (depending on the density and condition of the deadwood). Whilst lime sulphur is able to kill bacteria on the surface of the wood and possibly to a depth of a few millimetres on a soft wood), the underlying layers of wood will remain unprotected.

If bacteria is able to access the underlying layers of wood that the lime sulphur cannot (for instance though fissures or breaks in the integrity of the wood or through deadwood exposed only to the soil), rotting will continue unabated.

In summary; lime sulphur cannot and should not be regarded as a preservative that will protect deadwood from rotting or breaking down. While it is able to preserve shallow or thin areas of deadwood for a period of time, it is not a reliable method of rot-prevention.

For the dense and hard wood of Yews, Junipers and Pines, lime sulphur is probably going to be sufficient as these woods are naturally resistant to rotting. On species with softer wood such as privet, bougainvillea and most deciduous species, a proper wood preserver or wood hardener must be used.