I’m an inexperienced gardener near Bangor, Maine, who has some rose plants that have done well over the years. This spring, they were growing like gangbusters, with fresh new stems and leaves and then the buds. Then suddenly some have started to look very crispy. I have sprayed with neem oil, but I really don’t know what is causing this.
While trying to find information on this, I learned that it’s best to not water the leaves unless they are being watered in the morning and will have time to dry during the day. I usually deluge everything with water in the late afternoon, so I will stop that and use my long wand to water at the base. They all get water regularly and some plants are doing fine.
They get hours of intense morning sun that has usually been just fine for them. Any help or suggestions would be appreciated!
You’ve recently experienced a heat wave. That increased heat increases the plants’ need for water. Spraying foliage with water in extreme heat conditions is actually beneficial as it cools them and increases their supply of water. That extreme heat doesn’t generally support fungal growth. Neem is an oil. Oils seal the petioles, the pores on the undersides of the foliage which open and close like our pores do to allow for transpiration of water (sweating). The hot sun shines on the leaves causing the plant to need to “sweat” but the oil seals in the “sweat” inside the tissues, cooking the leaves and possibly the stems. The sun shines on that wall behind the plants, reflecting its heat back out to the air around them heating it up which can cook them. The wall remains hotter for a while longer than the sun shines on it and that helps to increase the water needs of the plant. If the canes of the plants are all brown to the bottoms, they may be dead. If there is still green at their lower levels and if they are still normal looking and not shriveled, don’t prune that dead growth off them as that live growth requires shade from the hot sun until it can begin generating new canes and foliage to shield it from the sun and heat. Check to make sure the soil is moist and consider increasing the water the plants get. The East is getting incredible heat currently and your plants are going to need more water just as you and your animals do. Hopefully you haven’t fertilized recently. The photo you supplied resembles several issues, fertilizer burn is one. Heat damage from a hot spell and from reflected, radiated heat is another. Spray burn from sprays applied in heat and sun is another. You need to do some investigating to determine if these are salvageable or if you should remove and replace them once the weather is appropriate to do it.
Neem oil could be the cause. Oils and hot temperatures can cause this type of damage, and lack of water. Roses should be watered before spraying anything on the leaves.
Hi! Thank you @roseseek and @Rosejoy for the advice. Yes, I was aggressive with the neem oil, much more so in the past because in previous years I had been pretty neglectful of them. I have stopped spraying them and have been soaking the base with water. The intense heat is gone now and we’re back to 70s in the day and 50s at night, so I hope that helps.
The advice to water before spraying is good, but NOT spraying any time there are temps of 80 F and above is a good rule to follow. Always check the label before using anything. You should also investigate the wood at the crown of the plants. If they are green and turgid, not shriveled, they have a chance and your water is well used. If they are green and shriveled, they have some chance. If they are all brown and dried, chances aren’t real good. If they are own root plants, something may regenerate from the roots. If they are budded, you’re likely to get root stock suckers, if anything. Good luck!
Thank you! The wood is green, so I am doing nothing to them but watering them regularly. We’ve had cool and cloudy days with rain, so I hope they come back as strong as ever!
Good! Congratulations! Once you begin seeing new shoots forming, all that old dead stuff can be safely removed. I’m glad it appears to have worked out favorably.
