Hello, everything is in the title. I got bare root roses and can't plant them right away so I put them in a container with this year's tomato growing medium. I was wondering if there is any risk that I'm taking there.
Thank you very much.

There are some things that can affect both plants, like verticillium wilt and root-knot nematodes. If this is bagged soilless mix rather than garden soil, and the tomatoes were healthy, I wouldn't worry about it. Did the tomatoes have some kind of problem?

Yes, the tomatoes had a disease, that's why I'm worried I made a mistake by doing that. It was bagged soilless mix added with garden soil.

Do you know what disease the tomatoes had? If not, what were the symptoms and can you tell us what country you are located in?

I'm in France (Orléans) and the tomato plants only bore two tomatoes, had grey/purple stems, never grew much, and the leaves were also kinda purplish. It was weird. I asked the same question in another forum and they said it's not possible, I hope it's true. Anyway, thank you for your answers

Purpling of tomatoes can be caused by a few different things, such as the curly top virus (which apparently can occur in Mediterranean areas) and phosphorous deficiency. There are some pictures below. As far as I can see the virus isn't likely to affect roses.

Virus:
https://www.google.ca/search?q...

Phosphorous deficiency:
https://www.google.ca/search?q...

Thank you for the links, it could be both but most probably the virus, it was very similar. It seems that I'm safe then.
Thanks again!

Sue ...

If I am reading this correctly ... and I may be wrong ... it is not necessarily a "disease" issue, but more of a nutrient deficiency when you mention "phosphorous deficiency". Am I correct ?

If that were true, it would matter if it were roses or tomatoes ... right ?

Yes phosphorous deficiency is a nutrient deficiency and would affect any plant where the amount of available phosphorous was insufficient for that particular plant. I don't know off the top of my head how tomatoes and roses compare in their phosphorous requirements/uptake and their susceptibility to deficiency. My guess would be tomatoes have a higher requirement, but anyway it sounds like chirchi's roses are only temporarily in the tomato mix until they can be planted, so even if P deficiency was the problem it wouldn't necessarily be an ongoing issue once the roses are out of the potting mix and in the ground.

Thank you, Sue. Thank makes sense.

Going back to plant diseases ... I had heard that a good rule of thumb was that the plant diseases impacting, let's say roses, rarely impacted other plants, unless they were of the same plant family of roses.

So far, I have found that to be true. Of course, I haven't tested that in a true scientific manner ...

Some plant diseases can be very specific to a certain plant or family, others can have a wide host range encompassing many different families so it really depends on the disease. It also happens that different strains of the same pathogen can be more specific. Even diseases that tend to be very host specific, like rusts, don't restrict themselves to the same family where they have multiple spore stages. To give an example I'm most familiar with, the daylily rust fungus, Puccinia hemerocallidis, affects daylilies but needs Patrinia plants to complete its full life cycle. Not only are daylilies and patrinia not in the same plant family, one is a monocot and the other a dicot.

To give an example of a disease that affects many different plants, according to this article from the U of Hawaii, southern blight (caused by the fungus Sclerotium rolfsii) can affect 500 plants in 100 different families
http://www.extento.hawaii.edu/...
And according to this article from U of Wisconsin Extension, both rose and tomato are hosts:
http://hort.uwex.edu/articles/...

I looked in the USDA mycology database, they show about 2,600 different fungi that are recorded on tomato, and for rose it is over 4,000. Not all plants are necessarily equally affected by the same pathogens though, so I don't know if all these fungi actually cause disease. I looked at fungi because the majority of plant diseases are caused by fungi so that doesn't take bacteria, viruses, phytoplasmas etc. into account. Nematodes (tiny worms), at least one of which appears to affect both tomato and rose as I mentioned above, are also usually lumped in with diseases.

WOW ! Thanks, Sue. So much for rules of thumbs !

In practice, though, it's going to be less likely that all one's different plants would be equally affected by a single disease so if something seems to be wiping out all kinds of different plants in a particular area of garden one would more likely suspect some environmental problem. If it's only a specific plant or plant family then you'd suspect a pest or disease first. But there are exceptions so while you initially would indeed look for a distribution pattern and include that in your process of elimination, rules of thumb aren't always right.