Forsythia brown spots

Question

Hi, I just planted a bunch of Forsythia to be used as a privacy hedge. When I planted them I mixed in black cow compost & high phosphorus fertilizer per instructions. I mulched around each bush leaving about 5-6 inches space from the stem to prevent rot.

I’ve also installed drip irrigation. The lady I talked to at the store said to water them every day. So with the irrigation, I have it timed to go on at 5 am and run for an hour. Each bush has x2 1gph drippers (one on each side). So each bush is getting 2 gallons each day…

I noticed recently some brown spots on leaves for a couple of the bushes:

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I went back to the store and talked to another person who told me it is fungus and that I am watering too much so I don’t know who to believe. I don’t usually have the greenest of thumbs.

Looking for some direction here…

Should I trim off the brown spotted branches? Or spray with fungicide?

What should I set my watering timer to? (ie, how long to run the water each time & how often?)

Thank you!

Answer 1

You get an A+ for effort. You obviously care very much about your forsythia plants, maybe just a bit too much. That is a LOT of watering and naturally overwatering can lead to fungal diseases. Really it’s only the first week that newly planted plants need to be watered everyday. After that plants need to be weened off being given water so that their roots grow deep and strong in search of water in the ground. The high nitrogen of cow manure can also sometimes cause problems with root development. As far as the watering goes, this article may help:
https://www.gardeningknowhow.com/garden-how-to/watering/watering-new-plants.htm
For the fungus use copper fungicide or need oil