Rain and Roses

ParvsJune 29, 2013

Hello! I tried searching for something on this topic but to no avail.

I recently purchased several rose plants from the local orchidarium, during the summer (April). They were lush with leaves and blooms. In May the rainy season has started and I've noticed that the leaves of my plants started falling off. They are not in a shaded area. They are in an area where they get at least 6 hours of sun everyday (except when stormy). One of the plants' leaves all fell and the stem seems to have dried up and growing moss, though the roots look healthy. Should I put them in the shade? If not what's happening to my roses? I fertilized about 2 weeks ago with Urea diluted in water . and I grow my roses in Large pots. Temps in my area (the past few weeks) range from 15 to 23 degrees Celsius. Thanks so much for any response =)

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Your description of the leaves falling off, canes shriveled and moss growing sounds as though you've burned the plants with the urea. NEVER use urea on potted plants. It is too strong, usually around 45% nitrogen, which will fry the plants. The strongest water soluble fertilizers are usually less than half that nitrogen concentration. Urea can only be used very sparingly on roses in the ground, and then only with copious water. At least for the one whose canes are all dried out, it may well be dead. Too much nitrogen at once pulls all the water out of the plant, "burning it". If you want, you can try just keeping the plant well watered, making sure you don't rot it from keeping it too wet. Make sure the drainage is good and do not put the pot in a saucer where the water will collect and be drawn back into the pot. IF the roots are alive, your only chance of saving the plant is to flush out as much of the remaining urea as possible. The only way to do that is to keep watering it and letting the drainage water flush out and away from the pot. From your description, though, I don't have much hope for the one with shriveled canes. It sounds dead to me. Kim

    Bookmark   June 29, 2013 at 3:43AM
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michaelg(7a NC Mts)

Sorry for the English units--but two teaspoons of urea per gallon of water would be the maximum concentration. I would use one teaspoon/gal with potted plants. Don't fertilize plants at all for a few months if the potting mix was pre-fertilized.

What do the dying leaves look like? Do they have spots? Are they old leaves or young leaves? Fungi and too much/too little water can cause leaf drop.

    Bookmark   June 29, 2013 at 1:39PM
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@kim - Hi! I've been using urea on other plants I didn't know it was bad for them. The other plants are fine only the roses reacted this way. I had a feeling it couldn't be saved but no harm in trying =) Thank you =)

@michaelg - Hi! I use 2 teaspoons for about 2.5 to 3 gallons. over here potting medium is just regular soil and was advised to fertilize 2 weeks after purchase. The dead leaves look dried up, old leaves. Is it ok to leave the pots under the rains? or should i move them to a shaded area? Thank You =)

    Bookmark   July 1, 2013 at 6:31AM
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michaelg(7a NC Mts)

Since you have moderate daily high temperatures, roses may be grown in full sun or half-day sun. Rain itself does not harm roses, but frequent wetting encourages fungal diseases. Do the leaves develop dark spots before yellowing and dropping? That would be black spot disease.

Another possibility is that the combination of heavy rain and heavy soil in pots results in saturated soil. The fine feeder roots of roses must have access to oxygen. A mixture of 75% sand and no more than 25% heavy soil will drain. Of course the soil you are using may already contain some sand. Rotted animal manure is a good additive and fertilizer.

If plants are water-logged, the leaves turn limp and yellow. It tends to affect the lower leaves first.

Urea per se is not harmful, but people often use too much because it is so concentrated a source of nitrogen.

    Bookmark   July 1, 2013 at 11:02AM
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Roses require a more balanced diet, Parvs. Urea is only nitrogen. If you wish to use it, you'll also need other products to supply the potassium, phosphorus and micro nutrients. Nitrogen is one of the easier ones to do damage with. Potted plants are at a significantly greater risk of damage due to their limited root room/soil ball; increased soil heat; much greater potential for water stress and the use of saucers under the pots. Drainage water filters into the saucer with the salts collected from the soil, including any fertilizers. As it evaporates, it leaves behind those salts. Further watering draws more salts into the mix where it all eventually reduces like a soup stock. Each time that water is drawn back in to the soil ball, it brings the more highly concentrated salt with it. This can eventually become so caustic and toxic, it can greatly damage, or even kill the plant.

For potted plants, you would probably do better using a water soluble, balanced fertilizer. Follow the directions precisely and always water the plants well BEFORE you fertilize. Any "salty" preparation applied to a dry or water stressed plant is going to water stress and burn it further. Save the urea for your lawn and vegetable garden, or for any rose garden planted in the ground. And, add other nutrient sources to provide the other required nutrients. Kim

    Bookmark   July 1, 2013 at 1:23PM
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@michaelg - yes some of leaves are spotted before they yellow. and I read that keeping leaves wet especially at night was not good for the plant. it rains here mostly between 12 noon and 10 pm during the rainy season. As much as I would like to use animal manure, my neighbors and the building owner will probably kill me if i did. =)) is it ok to add perlite to the soil(read this somewhere) to keep it from getting too packed in the pot? THank you so much =)

@kim - Noted. I was at the plant place today asking around for fertilizers, I was offered brown looking pellets that are water soluble. they called it complete fertilizer, but they don't know the composition) do you think this would be a good alternative fertilizer? . I will upload a photo of the fertilizer when I get home. thank you so much =)

    Bookmark   July 2, 2013 at 11:17PM
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michaelg(7a NC Mts)

In the US, brown fertilizer pellets would probably be poultry manure.

Yes, perlite will loosen soil mixtures if it is thoroughly mixed in before planting.

Most roses are susceptible to black spot disease during mild or warm rainy weather. The spores germinate when wet for 8-12 hours. Spots develop in a week and kill the leaf within a few weeks. Many gardeners apply a fungicide regularly to prevent its spread. Moving the plant out of the rain would help, but then you would need to watch for spider mites.

    Bookmark   July 3, 2013 at 9:25AM
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If you have to look for replacement plants, I've grown Flower Carpet roses in large pots and never had problems with black spot, mildew, Japanese beetles, aphids or spider mites. And I live in a super rainy, humid area.

    Bookmark   July 3, 2013 at 4:29PM
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hi this is the "complete" fertilizer i was told to use, alternating with the urea every 2 weeks.

    Bookmark   July 4, 2013 at 11:42AM
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michaelg(7a NC Mts)

Does it smell like something organic? Does it dissolve in water (manufactured fertilizer) or decompose in water (processed animal manure)?

This post was edited by michaelg on Thu, Jul 4, 13 at 11:55

    Bookmark   July 4, 2013 at 11:52AM
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this one i was told to use to get better root systems

    Bookmark   July 4, 2013 at 11:49PM
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and this one I was told to use to stop the appearance of white flaky things on the stems.

    Bookmark   July 4, 2013 at 11:52PM
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it dissolves in the water and smells like soil =)

    Bookmark   July 4, 2013 at 11:54PM
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