Horticulture Guy

Q. Is there anyway to stop the new growth on my Poplar trees after pruning the lower branches. Is there a product available or will it just be constant cutting the new sprouts away as they appear. I have 5 huge trees that are a real pain and yet enjoyable on the warm days. Joye Blair - Puyallup, WA

A. There is a product used by some professional arborist called Tre-Hold Sprout Inhibitor. The active ingredient is a plant hormone that inhibits buds from developing. Therefore it is used to prevent suckering and water sprouts on trees both ornamental and fruiting. It is usually mixed with latex paint because the application is sensitive to sunlight. I believe there is a Ready-to-Use version that is premixed with latex. The application is effective for about 2 or 3 years. This product is not widely available to homeowners but you may find a local nursery that can order it for you. You can also hire a certified arborist to make the application for you.

-- HG

Q. All three of my beautiful Ornamental Cherry trees are full of brown leaves. It’s as if the leaves from fall didn’t drop. I took a branch to the Master Gardeners at the Farmer’s Market, but they didn’t know what it might be. They told me to pick the leaves off, but the trees are ten years old and huge. I don’t have a ladder tall enough. All the new leaves are green. My son is getting married this summer, I will have tons of company, and they look horrible. Yet I hate to cut these beautiful trees down if the leaves just didn’t blow off due to our mild winter. Your advice is much appreciated. I saw the same thing on a cherry tree in Olympia a few weeks ago. Bonnie Westmark - Puyallup, WA

A. It sounds to me like you Ornamental Cherries have a disease called Brown Rot. This is a fungal disease that will attack flowers and leaves. The diseased flowers and leaves eventually turn brown and fail to senesce (a fancy horticultural term for drop). The failure to senesce works to the advantage of the disease. The infected brown leaves contain spores that are carried through to the new season. The spores then germinate from the diseased leaves and flowers forming a grayish fuzz when conditions are favorable (read cool wet spring). Eventually the disease can spread into smaller branches (twigs). Therefore the condition you describe is not likely due to our mild winters but rather Brown Rot. If you intend to keep these trees you will need to remove tree debris below the tree since some infected leaves will fall. If you cannot reach the tree yourself you should contract a certified arborist to clean out the infected twigs and leaves. The cuts should be made into healthy tissue below the infection. I recommended the pruner’s blades be cleaned with rubbing alcohol if a cut is made into diseased tissue. This prevents the spread of the disease via pruning. A certified arborist can also recommend the appropriate time in spring to make a fungicide application if necessary.

-- HG

Q. I have a maroon Japanese lace leaf maple. Its about 24″ high and about 40″ across. In the top middle branch I get green leaves that aren’t the same as the rest. Besides being green they don’t have the same pattern. WHY? Bob Hanna - Auburn, WA

A. Lace leaf maples are clonal cultivars of the Japanese Maple (Acer palmatum) selected for their interesting leaf shape and color. These clonal cultivars are commercially propagated by grafting cuttings onto common Japanese Maple (Acer palmatum) rootstock. Cuttings can also be rooted. It faster to graft them and the resulting plants are generally more vigorous and become saleable faster than rooted cuttings. Many laceleaf maples use what is called a “high-graft” so that the plants have a nice straight long trunk. This means that most of the trunk is the plain green Acer palmatum. Low-grafts on the other hand are usually closer to the soil line. When a graft is made of a cutting the top of the rootstock is left in place until the graft takes and then it is removed leaving only the laceleaf cultivar. Often the rootstock will attempt a “coup d’état” in the form of suckers. This is obvious in a low-graft plant since they look out of place growing from the base of the tree. But in a high-graft they are less obvious except in this case where there is an obvious difference in leaf shape and color between the rootstock and the graft. Follow the “offending” branch back to the trunk and remove it. Keep an eye out for future suckering of the rootstock so you can literally “nip it in the bud” (couldn’t you just image Kelsey Grammer as Frasier saying that?).

-- HG

Q. We have a large red maple tree in our yard. There are white spots on the trunk and limbs. Looks like someone put dabs of white paint on it. Is this a disease? First year we noticed it and we have enjoyed it for many, many years. Rolly Opsahl - University Place, WA

A. It does not sound like a disease. It does sound like lichens have colonized your tree. Lichen are what I have heard referred to as farming fungi. There are many species of fungi that “go into business” with various species of algae or cyanobacteria both of which can produce energy from sunlight, which the fungi cannot. The fungi provide the support and protection for these organisms, which allows them to grow in what would be inhospitable places without the fungi’s help (e.g., rocks and tree bark). The fungi receives energy in the form of sugars in return. Scientists still debate on the level of coercion that the fungi exert on their business partner. This is why some do not call this arrangement symbiosis. The crustose lichen are a group of lichen that are particularly thin and can often look like paint dabs as you have described.

-- HG

Q. What would be causing my Sod to be rolled up during the night? I laid the new sod about two weeks ago on some bare spots that died because of standing water. There is a wetland behind me and I have no fence at the back of my property. I did not put any fertilizers in the new sod. I just laid it. I hope what I have provided helps you. Everett Perrin - Tacoma, WA

A. Well there are two separate issues that you have to deal with. First you need to address the standing water problem. Lawns will not grow well in waterlogged soil and the bare spots are just the first warning signs. Sod is only a short-term solution to the problem. Consider hiring a professional to address the drainage of the soil in your yard. It is most likely raccoons and possibly opossum or skunks that are rolling back your sod at night. These animals feed on many insects like grubs, pillbugs (potato bugs) slugs and other insects that are either in the soil below the sod or are attracted to the underside of the sod. These animals have a keen sense of smell and can easily find this kind of insect activity. Since the sod has not knitted into the soil below (and this will be slow going if the soil below is as wet as you indicate) it is quite easy for these animals to roll it back and feed. Controlling the insects will remove the food source. The other option is to try using sod staples or pegs to secure the sod and discourage the animals from rolling it back.

-- HG

Q. I have a Norway Maple, 2 years old, that’s showing signs of powdery mildew especially on new growth. What do you recommend? Jack Ravenel - Tacoma, WA

A. First I would see if there is a way to improve air circulation around the trees. This will keep the leaf surfaces dry which will inhibit the powdery mildew fungus. Even the moisture from dew is enough to encourage the fungus if it does not dry off quickly. You can get dew when night temperatures are much lower than day temperatures and the water in the air is “squeezed” out onto the leaf or other surfaces. If the tree is small enough you can remove and destroy infected leaves. But since you indicate that powdery mildew is showing up on new growth you may consider spraying with a fungicide. An organic fungicide like Sulfur or Copper would be effective.

-- HG

Q. We have a large Tulip Tree, about 25 years old. For the first time we have a fly infestation on the tree and all over the driveway and cars. We powerwashed the drive, etc. but to no avail. Are flies attracted to Tulip trees? There seems to be no other attraction for them except the tree. Thanks for your attention. Geoffrey Geiger - Forked River, New Jersey

A. A shout out to my home state! Tulip trees or Tulip Poplars often harbor aphids – tiny sap sucking insects that excrete what is euphemistically called “honeydew”. Well they digest the proteins and sugars from the tree sap and there is often left over sugar in their excrement. This drips on the leaves of the tree and anything below it like driveways and cars. You know the saying: “like flies to sugar”. If you control the aphids in your trees you will solve the problem. You will probably need to contract out a professional tree service that has the proper equipment to spray large trees.

-- HG

Q. One of the vines on my new Clematis wilted followed by the other three doing the same. I nearly threw it away, but instead replanted it in another spot. This spring it sprouted and produced a beautiful many-vined plant. Around a month ago it again started to wilt. Again I pruned it down and planted it into a large pot. It sent a vine over 6 feet tall and once again it has started to wilt. I have three other plants that are just fine. Each time I replanted it I replaced all the soil with good Miracle Grow garden soil. George Mello – Tacoma, WA

A. This sounds like a condition called Clematis Wilt. It is believed that a fungus causes Clematis Wilt. The leaves and the stem should have turned black (especially on the inside when stem is sliced open. If instead they simply turned brown then it could be physical damage to the stem, like a slug eating through it or something of that nature. I am not sure from the phrasing of your question if you have one plant that you divided or multiple plants. Some cultivars are more susceptible to this condition than others are. It is believed that there is lack of resistance in the species Clematis lanuginosa, which was used in many breeding programs that produced commercially available hybrids. So any progeny of C. lanuginosa is potentially more susceptible to the disease. But the nature of the problem is inconsistent is as you mentioned. Some plants get knocked back completely or partially, others not at all. Clematis wilt usually doesn’t usually kill a plant completely. Most people yank the plants when they wilt back assuming they are dead. You did the right thing and waited. It seems that the fungus doesn’t attack below the soil line. I have seen suggestions to plant the clematis a few inches deeper than it is in the pot so it has below ground nodes. This can be accomplished by removing the two lower sets of leaves (2 nodes) on each stem and planting them below ground. When the disease does hit cut back the infected shoots back to healthy tissue. This could mean a cut below the soil line. Other suggestions are to apply a broad-spectrum fungicide as a preventative.

-- HG

Q. I have a rhododendron that is infested with rhododendron lace bug. Last year I bought an insecticide to rid my infested rhododendron of lace bug. Unfortunately it didn’t work. I realize that I need to spray beneath ALL the leaves to truly be effective-, which is the problem. Should I remove most of the leaves and then spray? Whatever I use, I will need to cover the rhodie with netting to keep the birds out. I’m assuming any “good killing” spray will be harmful to birds. Thanks, Anni Watkins - Tacoma, WA

A. This is a good candidate for an insect alert so for those of you with rhododendrons that want to inspect for signs of lacebug look for a yellow to brown speckling on the surface of the leaves. But as you have alluded to all the activity is below the leaves where the lacebugs and their juvenile nymphs are feeding. So any spray does not necessarily need to be beneath all the leaves, but rather beneath all the leaves that have lacebugs on them. They feed like aphids with piercing sucking mouthparts extracting sap. The “lace” of the adult insect’s wings can only be seen under a microscope since the adults are only about 1/8 of an inch long. What are usually most visible on the underside of the leaves are the insect’s excrement and the nymph’s shed exoskeletons, which are shed at each stage of growth. Often a large infestation of Rhododendron Lace Bug is a sign that the rhododendron may be under stress. Sometimes infestations are exacerbated by drought, high a pH soil (they prefer to be somewhere between 4.5 to 6.0) or too much direct sun. Since you have not mentioned any beneficial insects present feeding on the Lace Bugs like Ladybugs then a spray is an effective alternative. But your assumption that any “good killing” spray will be harmful to birds “ain’t necessarily so”. Both insecticidal soap and neem oil will control Lace Bugs. Or you can use the best of both worlds and use a new neem soap, which is derived from the neem oil, and works like a souped-up insecticidal soap since it also has neem’s insecticidal properties (anti-feeding, growth regulator). Humans have been using neem on their own bodies (especially in India) and I have even seen neem toothpaste recently at the supermarket. You won’t have to net off your rhododendrons to protect the birds when using neem-based garden products.

-- HG

Q. I have a large Maple tree. Last year small (ball bearing size) round empty bright orange pods started growing in clusters on the leaves. I took a leave to Peninsula Gardens and nobody there knew what they were. When the leaves fell off we raked all of them up off the ground hoping that it would’nt happen again this year. Well, they are all over the tree again. They start out with a pale green color and then turn bright orange. They are hollow. What is on my tree? Gina Forbush - Gig Harbor, WA

A. These sound like tiny galls. Galls are irregular growths that can appear on plants. They can be biotic (caused by insects or microorganisms or abiotic (caused by environmental factors). If you have a red or silver maple most likely cause by an insect called the maple bladdergall mite (Vasates quadripedes). A chemical excreted by the organisms that acts like a growth regulator creates biotic galls. This is because this chemical(s) gives the host cells different “instruction”. Sometimes insects can be found inside the gall since the gall is formed to protect it. In the case of the maple bladdergall mite it is thought to be an enzyme the mite produces when feeding. The female also lays its eggs in the gall. The eggs hatch and the offspring feed in the gall until large enough to venture out on their own. Then new galls are produced where the offspring feed. This year’s offspring are now finishing feeding and will move back into the bark of the tree to hide in cracks and crevices by the end of July. Since the mites are small (less than 2mm long) there are plenty of hiding places on a maple tree. Fortunately the maple bladdergall mite damage does not pose a threat to the overall health of the tree. On smaller trees you can pick off infected leaves and dispose of them to reduce the future population. This will only work if you remove the leaves before they move to the trunk and branches in July. Then in late winter/early spring before bud break you can use a dormant oil spray to smother the overwintering mites. Be sure to get full coverage of the trunk and all the branches.

-- HG