Sawdust mulch could cause garden woes

QUESTION: I live in the heart of Amish country. I was wondering if I could use the sawdust from one of the many local sawmills as a mulch around my trees in the yard rather than use the conventional cypress chips? The sawdust is plentiful and would be much cheaper than the chips. Do you foresee any problems with my using it?" - Hank Wolgast
ANSWER: On the surface it would appear to be a great substitute. However, fresh sawdust right off the saw can be very acidic depending on the type of wood being used. A good rule of thumb, if you decide to purchase the sawdust, is to pile it where it will be undisturbed and let it sit one year. The rains and natural decomposition will leach out most of the acid and then it can be used for mulch the next few years. Or of course, simply use "regular" mulch!
QUESTION: "What can you tell me about setting up drip watering cans or buckets? " - Mike Samolinski
ANSWER: If you are going to set these up to water trees or shrubs in hard to reach places, here's something that you might want to try, using five gallon buckets. Drill approximately five or six 1/8 inch holes at the base of the bucket, about one inch apart. Fill the bucket with water and it should take about an hour for the water to run out. This allows most of the water to go down to the root system where it is needed.
QUESTION: "I planted several gallon-size rhododendron shrubs last summer and they seemed to be doing well. Now that winter has passed they have tiny black spots on the leaves and some leaves that are yellowish or brown and dead looking. What would you suggest I do to help them along this spring?" - Karen Pirino
ANSWER: There is a product that you can use that comes in powder form to spread around the base of the plants and then wet it in. The product is called Subdue and is a fungicide made by Scott's. It sounds like your plants are suffering from a fungus that often afflicts rhododendrons.
QUESTION: "I have a variegated hibiscus plant that, for the past two years, has gotten tons of buds, but never bloomed. The buds just dry up and stay on until they fall off. What would cause this? It is planted in full sun from about 12 noon to 3 p.m. and we have a sprinkler system so it gets watered periodically throughout the day." - Darlene Melvin
ANSWER: One possible reason could be that your plants are getting too much water which might result in the buds not having time to develop fully. In a plant's life cycle, buds form, become flowers then extend to seed. It's a theory of mine that if a plant has everything it needs (or too much) there is no incentive for it to reproduce. As I say, just a theory of mine!
Firstly, try cutting back on the water. Another thing that you may try next season before the plant begins to bud is to put one tablespoon of Epsom salts in one gallon of water to dissolve then douse the roots of the plant. This is a way to shock it without harming it. I do it with wisteria and get beautiful flowering every year.
QUESTION: I have a border in front of my patio lined with dwarf nandinas. The soil stays very wet all the time. My nandinas drop their leaves and die. Could you recommend a small shrub I could replace them with that likes a wet soil?" - Alice
ANSWER: Although I don't recommend planting any type of plant in wet soil, I recently wrote a column titled "Damp soil? Here are seven plants with wet feet." If you missed it, here is a link: What I would recommend is raising the soil level around your patio (a process known as berming) and diverting the water so you can plants the plants you desire.
The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to and for resources and additional information, or to subscribe to Steve's free e-mailed newsletter, visit
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