How To Use Lime Sulphur On Roses

Who doesn’t love the allure of beautifully maintained rose bushes, especially when they start to put on their glorious display in spring.

We are reader-supported and may receive a commission on purchases made through links on this page.

Australian gardeners have had a love affair with roses for many years. For rose collectors, there are always new varieties and hybrids being created. The problem is finding room in the garden for ‘just one more rose bush’.

Although roses are fairly easy to look after, they do require a little maintenance.

Winter is the optimum time for pruning roses and it’s also the best time to treat them with lime sulphur. This helps to control fungal diseases as well as some common rose pests.

If you’ve never used this product before, you might be wondering what exactly lime sulphur is. Here’s a quick explanation.

What is lime sulphur?

Lime sulphur is a mixture of calcium hydroxide (builder’s lime), sulphur and mineral oil.

The mineral oil helps the product to adhere to plant surfaces such as stems and leaves and also helps to control sap sucking insects.

When mixed with water in various amounts, it can be sprayed on plants to control fungal diseases and certain pests.

And, yes. It does have a very strong sulphur smell which you will either love or hate.

Keep in mind when using this product, that it’s quite concentrated and you do need to dilute it with water.

Another caution is not to spray lime sulphur on your roses during hot, sunny days because it may burn the leaves.

You might be interested to learn that lime sulphur was first invented back in 1851 by Grison who was the head gardener at the vegetable houses in Versailles. 

What does lime sulphur treat?

Lime sulphur is a fairly versatile product and can help to treat the following fungal diseases on roses and other plants:

  • Powdery mildew
  • Black spot
  • Anthracnose
  • Blight
  • Leaf curl
  • Rust
  • Brown rot

It also kills various sap sucking insects such as:

  • Scale
  • Mites

How to use lime sulphur on roses in winter

During winter, roses are dormant. It’s also the time when we like to give them a hard prune to cut back any wayward growth and help them keep their lovely shape. Winter pruning also sets our rose bushes up for a glorious blooming season starting in spring.

After you give your roses their winter trim, is the best time to dose them with lime sulphur. This helps to kill any fungal diseases that may be lurking on the plants or in the soil around the base of your rose bushes.

Here are some steps to treating your roses with lime sulphur in winter:

  • After pruning, remove any leaves, twigs or other debris from around the base of the plant.
  • Mix your lime sulphur in the ratio of 20ml per litre of water. It’s a good idea to have a separate sprayer that you use just for applying lime sulphur.
  • Spray your rose bushes liberally ensuring the spray coats all the stems. Do this in the early morning or late afternoon in late winter. Avoid spraying when it’s going to be sunny if you can.
  • Don’t forget to also spray the soil around the base of the plant. This helps to kill any fungal spores that may be overwintering in the soil beneath the plant.
  • Avoid spraying your roses if you’re expecting freezing weather. It’s better to wait until the danger of frost has passed.

How to use lime sulphur on roses from spring to autumn

Don’t be afraid to treat your roses during spring right through until autumn if you have fungal or pest problems.

Before doing so, remember these important tips.

  • Make a weaker solution by mixing 10ml of lime sulphur with 1 litre of water. At this dilution level, it’s safe to use on your roses while they’re actively growing.
  • Spray in the early morning or late afternoon. Never spray your plants during the middle of the day in summer. This is because the solution will react with the sunshine and burn the leaves on your roses.
  • Avoid spraying if the temperature is likely to exceed 32 degrees Celsius.

FAQ

Is lime sulphur good for black spot on roses?

Yes, lime sulphur can be used to treat black spot on roses, along with several other pests and diseases. However, if you are applying lime sulphur outside of winter there are some extra precautions to take to ensure you don’t damage your roses.

Photo of author

Annette Hird

Annette Hird has an Associate Diploma of Applied Science in Horticulture. She has worked in a variety of production nurseries, primarily as a propagator. She also had the responsibility of a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.