Newly Registered
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Joined: Fri Jun 15, 2012 1:19 pm

Black veins on rosa rugosa

Can anyone tell me what this is? I'm new to rose growing and I don't know if this is a disease or something natural to this type of rose. These are not spots, they are dark streaks that follow the veins of the leaf.

Greener Thumb
Posts: 824
Joined: Sun Jul 05, 2009 8:31 am
Location: Hurst, TX USA Zone 7b/8a

Rugosa leaves should be medium to dark green, just like the veins look like. It would appear that the soil is too alkaline and the plant has developed an iron defficiency where it cannot absorb naturally occuring iron from the soil. Too much watering can also contribute to this effect. If you have not been watering too much, confirm by purchasing a soil pH kit at many nurseries in order to determine if the soil is alkaline (pH > 7) or acidic (pH < 7). Kits that do not give numeric results will instead give special colors when alkaline and a different one when acidic.

If the soil is alkaline, amend the soil using garden Sulphur, iron sulphate, green sand or one of many iron-chelated liquids sold at plant nurseries. The liquids help bring the soil pH into an acidic range faster than the others but it still take a few applications to bring everything back to its normal state. Apply per label directions since some of these compounds can burn the roots if you apply too much.


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