Black spot

[Kintsugi]

Hello Everyone!

I live in Australia where it is currently late spring nearing summer in a week.

We are having a heatwave at the moment, but I live in an area where there is still rainfall once to twice per week.

I have just settled a few days ago on a hobby farm that is 3000 m2 with a small cottage and the majority of the land filled with a mix of fruit trees, cottage garden and a few native species. The majority of the garden is roses and hydrangeas (50+ rose bushes of all varieties around 1.5 - 2.5m tall including many climbing and 100 hydrangeas, 50 agapanthus, lots of azaleas and camellias).

The bad news is that after we put in an offer for the property, they seemed to have let it go, and they didn’t seem to spray for fungus in winter or clear away debris in an area where it is a known problem.

When we received the property, the entire garden of roses is riddled by black spot. The majority are still blooming but some aren’t. Half of the hydrangeas also have some black spots in the stems and leaves as do the camellias.

I can’t spray as the weather has been too hot and will be hot for the next two weeks at least.

I’ve cleared the dead leaves all weekend and given the roses some food.

Other than that, what should I do? Should I prune everything completely back now or will it kill the plants to prune in this season?
And if I don’t prune will they all die by next year?
I had a gardener come to assess it and he said to just leave the leaves on as it is on there now and they’re blooming, but that goes against what I have read elsewhere...

I’m feeling worried as we definitely overpaid for the house because of the beautiful garden and we can’t afford to replace all of the plants.

Does anyone have experience with black spot?

Thank you in advance

 

[Sheal]

Black spot on roses is a fungus and can be controlled by spraying at the beginning of the growing season if you so wish. Meanwhile if the roses aren't badly affected the diseased leaves can be removed along with any debris at the base of the plants, as the ground will harbour the spores too. Major pruning is generally preferred near the end of winter/early spring when the plants are dormant but will do little harm any time of year, If you think it's necessary. If the black spot problem is major then I would prune them now and burn or dispose of the remains in a bin. Don't put them on a compost heap or elsewhere outside because this will transfer the spores. Being early in your growing season there is a good chance of them recovering well and also producing flowers later on in the summer. Don't forget to water the roses well during dryer spells and water at the base of the plants, this helps to avoid the problems with black spot and other diseases.

 

[DirtMechanic]

I have controlled it with this systemic fungicide.

 

[Kintsugi]

Black spot on roses is a fungus and can be controlled by spraying at the beginning of the growing season if you so wish. Meanwhile if the roses aren't badly affected the diseased leaves can be removed along with any debris at the base of the plants, as the ground will harbour the spores too. Major pruning is generally preferred near the end of winter/early spring when the plants are dormant but will do little harm any time of year, If you think it's necessary. If the black spot problem is major then I would prune them now and burn or dispose of the remains in a bin. Don't put them on a compost heap or elsewhere outside because this will transfer the spores. Being early in your growing season there is a good chance of them recovering well and also producing flowers later on in the summer. Don't forget to water the roses well during dryer spells and water at the base of the plants, this helps to avoid the problems with black spot and other diseases.

Thank you so much for your advice.

My only concern is that I would have to prune them back completely as all leaves and stems are affected. Would this have an effect on photosynthesis for the plant?

 

[Sheal]

Is it possible for you to post one or two photo's of them please @Kintsugi. It will be easier to judge how much you can prune.

 

[Kintsugi]

 

[Kintsugi]

 

[Kintsugi]

These are some of the bushes.

90-100 per cent of leaves are affected on all of the bushes.

 

[Sheal]

I need to work through these pictures and give you information as I go. I will leave this until tomorrow as it's getting late here now to start a lengthy post.

 

[Kintsugi]

Of course. Thank you for all of your advice

We are not staying in the house for another 1-2 months so it won’t bother me if they need to be pruned completely or even if the black spots stay on. I would prefer to do whatever is healthiest for the roses without worrying too much about aesthetics.

 

[Sheal]

Looking through the pictures the soil in the garden doesn't look as if it's been fed or mulched for many years, therefore all the plants especially the roses are suffering. It would be good to get a few inches of compost and or well rotted horse manure if possible, down on all the areas that contain shrubs, now and as an ongoing thing from year to year. There's no need to dig it in, worms will take it down. Roses in particular love horse manure! If you move any plants - blood, fish and bone fertiliser can be mixed with the soil that you back fill the planting holes with to give them a boost. Don't just drop any fertiliser into the bottom of a hole as it will burn roots on direct contact.

Pruning as I've said is best at the start of the growing season but with yours being diseased they are an exception. Prune back all the stems by two thirds but avoiding old wood as this may not re-shoot, unless you can see leaf nodes on it. Cut about half an inch above an outward facing leaf node. Remove any dead stems and any overcrowded stems in the middle of a shrub rose, the aim with this type of rose is to create an open cup shape to allow air circulation. After pruning remove any remaining diseased leaves. They'll look bare for a while but will eventually re-shoot. Any climbing roses you may have I would prune down by half at least, thinning out branches and again remove any dead stems or diseased foliage.

Apart from the smaller patio roses - roses are best planted in open ground, they need room to spread their roots and take up nutrients. You have one in the pictures above that is in a small pot and looking quite sickly. I would get that in the ground as soon as possible and feed and water well on planting. Apart from the climbing roses I would move all those that are against house or garden walls. The ground will be much dryer there and will need continuous watering during summer.

The aim with roses is to give them as much space as possible. They need air circulation to help keep them disease free so are best not planted too close to other roses or other types of shrubs. Soil around the base is best kept clear of any debris and weeds, as this will harbour unwanted disease and insects. I feed my roses two to three times during the growing season to keep them in condition. The last feed is given approximately six weeks before autumn starts to set in when they start to become dormant for winter.

I have moved house since the picture below was taken of my rose bed. The bed was 17ft long and had nine roses. It's to give you an idea of how much space they need. Some rose lovers like to underplant with smaller shrubs or ground hugging plants but I prefer not too as I think it makes a big difference to keeping disease at bay. They grew on coastal sandy soil so I mulched them with home made compost at least twice a year, not that you can see that in the picture.

I have a few roses that I planted in my current garden eighteen months ago, but with a different climate here things are a little more challenging.

I hope this post has been helpful, feel free to ask any further questions.