Q I recently read in the paper to put newspaper under mulch to help keep out weeds. How many layers of paper do you need to put down?
A Newspaper and layers of cardboard work well under mulch.
They are porous and allow water and oxygen through, but they are an extra layer of help to keep weeds at bay. For newspaper, two to three sheets should do it, and for cardboard, one layer. Over time, they both will disintegrate, but it allows you to use slightly less mulch and I think it helps the mulch stay in place better. I have also used shredded junk mail under the mulch. The layer is not too attractive, so it needs to be covered with mulch.
QI have a lot of weird spores growing in my flower gardens. They look like someone has thrown up. They are yellow, pink and brown. This is the yearI put hardwood mulch down. I was going to spray but am wondering what I should use.
A You have slime mold. This is a very basic type of fungal organism and comes in a wide range of colors. It isn’t hurting anything, but it does look pretty gross.
Rake it off, wash it off with a strong spray of water and lightly turn the mulch, aerating the mulch.
When it is done breaking down, it will go away on its own.QMy mimosa tree has lost all its leaves. They started by getting lighter green;
then they fell off. We had some pink blooms. I had one sprig of regular green leaves, and now they have fallen off. It’s about 5 years old, 30 feet tall. Is it too late to save it?
AI have actually had several such emails and calls in the past few weeks. Mimosa trees are beautiful when in bloom, and I am seeing more and more of them in the wild. Unfortunately, I consider them trash trees for several reasons. One, they are highly susceptible to a disease - which I think you have - called mimosa wilt. It typically attacks a tree when it is well established, usually at 7 to 9 years of age.
It is caused by a soil-borne organism called fusarium wilt. The trees can die almost overnight, or it can be a bit gradual. You will occasionally see a sap coming out of splits in the trunk. There is no control for the disease, so once it hits, you may as well remove the tree - there is no saving it. Once the tree dies, you may end up with numerous root suckers coming up all over the yard. Mimosas also set hundreds of seeds,which drop and germinate, and that is why we have so many seedling trees coming up in the wild. Mimosas can be invasive, which then hurts native species, so I would not recommend planting another one.
Q I’m getting calls about the rose rosette virus and how to prevent it. Several people think we need to ask garden centers and nurseries not to buy any more roses so it can’t get here. I don’t think that would work or will happen, but is there anything that I can share that will help?
A Rose rosette has been a problem for years, but we had more problems with it last year than ever before. I think one of the main reasons is that more and more people are planting Knockout and other care-free roses. Thus more disease problems, because more plants are out there.
One other thing I just learned this year is that the mite that spreads the rose rosette virus lives on the top of the rose bush over winter. Heavy pruning of the roses before new growth, and destroying the cuttings, could help limit how many mites survive.
If you think back to 2011-12, we didn’t have a winter, and many of our roses, especially Knockouts, were blooming in February. Many people didn’t prune them at all, orvery little. And then we had more rose rosette. In fact, our recommendation was that you did not ever need to prune Knockouts as severely as hybrid teas, saying a light shearing was fine. Now we are re-examining that, and recommending that all bush roses be cut back to about 10 inches or so in the dormant season - late February. If you have the wild multiflora rose in your area, eradicating that can also go a long way in getting rid of the mites, which breed there as well.
Roses have traditionally had problems with diseases and insects. Hybrid teas get black spot, and they look ugly if you don’t spray. The new care-free roses gave us nonstop blooms with no spray schedules, and people have flocked to plant them. Rose rosette is a virus that can attack all roses, and there is no cure. Breeders are working on rosette-resistant varieties,but so far haven’t found any.
Proper pruning and good sanitation - removing plants when they have it - can help in the long run. I don’t think we will ever see gardens without roses, or at least I sure hope not.
Janet Carson is a horticulture specialist for the University of Arkansas Cooperative Extension Service. Write to her at 2301 S. University Ave., Little Rock, Ark. 72204 or email her at
HomeStyle, Pages 33 on 07/20/2013