'Bonita' Ash and Ash Decline Disease

Q. I planted a very large ‘Bonita’ ash tree this year and was worried about ash decline disease. This last May we noticed there were not as many leaves growing as we expected and many of the ones that were growing scorched and fell off. After 4 months of very good care to water, fertilize, and condition as told, the ‘Bonita’ ash tree does not look as we were told when we bought it. While it has grown taller, it had not filled in much.

'Bonita' Ash Tree recently planted.

A. Ash Decline disease can be confused with a lack of water. It may also be confused with poor planting practices and leaving the ash out too long before planting.

Possible ash decline disease. The only real way to say it is ash decline is to send a sample to a plant pathologist familiar with the disease.

                    Nearly all ash trees are susceptible to ash decline disease, particularly if it has Arizona ash genetics in it. ‘Bonita’ ash does. So do ‘Modesto’, ‘Raywood’, ‘Rio Grande’, and other ash trees commonly sold in nurseries.  That being said, this disease is usually not a problem on young ash trees as long as they are not stressed and there are no diseases present that might cause it to spread. Young ash trees are normally very strong and healthy.

Disease Pressure

            The keys to resistance are “disease pressure”; how much of this disease is present on ash trees in your neighborhood and the “health” of your trees. The disease agent that causes ash decline is not terribly virulent. It is not like a disease such as fireblight which can be terribly destructive under the right conditions. If the ash trees in your nearby neighborhood don’t show any symptoms (branch or limb dieback) and kept healthy, then most likely the tree you planted will live disease free for many years to come.

Give Them Water and Fertilizer and See if they Recover

            Make sure your tree are not water and fertilizer stressed. All ash trees are “mesic” in their water needs. Even desert ash trees, such as Arizona ash, grows near waterways. Like mulberry, all ash trees are dioecious; there are male trees and female trees. There is little difference in the health of a male vs. female ash tree.

Ash tree surrounded by lawn and well fertilized and watered. They are mesic and can withstand a lawn.

            Ash trees can get big. Make sure they get enough water as they get bigger.  Getting enough water is one key to having a thick and broad canopy and staying healthy. The irrigation under the tree should be enlarged every two to five years to compensate for their increase in size.

Keep Ash Trees in Good Health

            The other important ingredient regarding canopy density and health are annual fertilizer applications. At least once a year and its canopy density, apply a fertilizer high in nitrogen, the first number on the fertilizer bag. Examples might include 16-6-8 or 16-16-16.

Ash tree about 3/4 mature and surrounded by grass. They can get big. Their need for water is not as much as mulberry but close.

            Ash trees don’t care much for rock on top of the soil unless their roots are growing in a rich soil underneath it. Periodically rake any rock away from the trunk of the tree, enlarge the irrigation system, apply compost to the soil surface and fertilizer. The rock can be raked back the same day you are finished.

Established Trees and New Artificial Grass

Q. I have a small tree planted in 1998 that has roots growing under some artificial grass. It was put down many years ago. I have a tree that is sending big roots underneath this grass for probably 10 feet or so. This mound is probably 6 inches or more in height. I need to know if I pull this artificial grass back and cut that root if it would kill the tree.

Tree roots under artificial grass may be dead and can be removed.

A. Sounds like maybe the small tree was planted 23 years ago before the artificial grass was installed. If the tree was planted before the artificial grass then probably the tree roots got no water. If they got no water then the roots are dead and cutting them is no problem.

Ash tree roots grow where there is a steady supply of water, air and fertilizer. In the desert, ash trees need water and air first and fertilizer second. In lawns ash tree roots will grow near the surface of the soil because that is where the best balance of water and air can be found easiest. And when the lawn is fertilized, the tree loves it!

Will the Tree Fall Over?

So maybe the tree will fall over and maybe not. It would be difficult to say without looking and making some guesses. Tree roots provide anchorage for the tree as well as take up water. If the soil is dry under the artificial grass, then no roots are sent out by the tree or they die if there is none. Trees do not send roots out into dry soil, and they do not get larger unless they have access to water. Larger still if the get water AND air. So possibly that root is still alive. Find out for sure.

We don.t know but it looks like this tree will not get water from neighboring plants.

 Trees can "steal" water from neighboring landscapes, other plants, lawns and other places. As this tree gets larger it will need more water. It can get more water by adding emitters.

            Trees send roots out in one or more directions in the presence of water. Tree roots don’t respect property lines and walls. In sandy soil, moist soil can be found about 0 to 18 inches from a source of water. In a heavier loamy soil, moist soil will be further; maybe 18 to 36 inches from its water source. If roots find a preferred mix of water and air, they proliferate. If the soil stays dry, then they don’t. Tree roots, like us, are lazy. When we hand water mature trees we have to guess where the roots are. If water has been there over and over, then its a good guess roots are their too. If we continuously wet the soil in the same spot and its close to plants, roots will multiply.

Make an Educated Guess

            What to do? Look at the area and find the possible permanant sources of water where tree roots might grow. Those spots might have the greatest chances of tree roots. If there are plenty of places where water was applied, cut the offending root back in increments until the offending root is not a problem. Leave as much there as you can. 

Stake the Tree

Stake the tree for one to two seasons of growth and apply water to the same areas over and over that were not root pruned. Soon after the root was cut, prune the tree and remove one quarter to one third of its canopy. Check for reestablishment of the roots after the second year of growth. The first couple of years the tree will grow slowly. Generally, if tree roots growing from the trunk are evenly balanced, about half of all existing living roots can be removed without damaging the tree if they have balanced growth from the beginning.

Succulents for Las Vegas Gardens

Q. I have a succulent garden which is under our patio cover.  Periodically a plant that seems to being doing well suddenly goes sour. I use a moisture meter and try not to overwater.

When propagating plants from seed or cuttings sanitation is very very important. These are babies just getting started!!!

A. All cacti are classified as succulents but not all succulents are classified as cacti. What we consider succulents from our deserts usually require more care than cacti from our deserts. This means they usually need more protection from the sun, wind and a bit more water.

Sanitation

I am a firm believer in keeping everything as clean as possible. First is the potting soil. When potting soil is reused, sanitize it or get new potting soil.

            Do this easily by putting the moist soil, or the entire container a few days after an irrigation, in a clear plastic bag in full sun during the summer. Make sure there are no air leaks. Let it sit like this for about three days. Heating up everything to about 160F. for at least 30 minutes sanitizes it. This method is called solarization. 

            Sanitize or sterilize all of the equipment with 70% ethyl alcohol: particularly anything with a blade.

            Sometimes the plant part (seeds or cuttings) were not healthy or strong enough until they grew roots. Some older fungicides, namely Captan, Thiram, Zineb (dust, powder or wettable powder), were available to protect the roots until the plant got established in the ground. We would put a small amount on the flat end of a wooden toothpick in a seed packet and shake it (seed treatment) or dip cuttings to protect the roots until the plants were established.

Branch Dieback in Citrus (Orange)

Q. I have a ‘Eureka’ lemon tree with a branch or two that are dying. Is this borers?

Lemon tree with single branch dying back.

A. Probably not borers but a disease. Look for sap near the location where the branch died.

Single Branch Dieback of Lemon Most Likely Shoot and Twig Dieback Disease

Branch dieback in citrus, particularly lemon, is very confusing. It is not likely to be a borer problem. Most likely it is a disease issue called “shoot and twig dieback” of citrus. A lot of federal funding went to California to answer a branch dieback disease questions for homeowners and commercial growers, with lemon branch dieback found to be quite common.

            If it were me, I would cut the dead branches back and eliminate the dead branch to a place where it was healthy and growing in the direction I wanted. As a precaution, I would sanitize the pruning shears with undiluted 70-90% ethyl alcohol before and after each branch removal. Treat the fresh cuts with copper sulfate (Bordeaux mix) as a precaution.

Tree Planting Requires Proper Hole Preparation in the Desert

Q. I had a boxed mastic tree planted recently. I didn’t like how it was planted. It was planted with the trunk not straight, the top of the roots exposed, the soil in the hole was dry, and I had them remove the bottom of the box. They were going to plant it with the bottom of the box still under the root ball.

Mastic tree planted too shallow. Also the area is very small for such a large tree.

A. I looked at the pictures you sent to me, and I agree it was not planted well. Sloppy planting. The hole was dug too small, and it was not planted deep enough. About 30% of the soil should be amended for drainage and moisture retention. Out of sight, out of mind. The soil surrounding your tree may or may not have enough amendments added.

Watch this video on planting trees in Arizona that I thought was pretty good.

Mastic (Pistacia lentiscus) trunk was planted with the trunk at an angle which is less of a problem than the exposed rootball (above).

            Mastic is related to pistache (Pistacia lentiscus). Like all pistache trees, it is mesic in its need for water. This tree is Mediterranean in origin rather than western Chinese or Central Asian. Water requirements for both are similar and both develop red fall color. It grows well in a lawn where it gets plenty of water or surrounded by other mesic shrubs for the same reason.

            When planting on a slope, the lowest side of the hole should be used for judging the hole depth. Add water at the top and sides of the hole, not the bottom. This tree is fine growing in soil covered in rock. If this tree shows signs of poor growth in a few years, add a layer of compost on top of the soil and water it in. Water should be applied on the “uphill” side of the tree but three feet at least from the foundation of the house.

Dry Hole Problems

            The problem planting in a “dry hole” is removal of air pockets. Dry soil pushed into the rootball (and using the butt end of a shovel to shove it further) may or may not remove them. Usually not. When planting in a slurry of soil the air pockets are removed at planting time (look for the bubbles), less “transplant shock”, and less concern about tree stability (staking) after planting. Air pockets in the soil will not do that.

Wet the Soil

            Making a slurry is easy to do. Just use a hose during planting. Sometimes a dry soil can be compensated in the first few months by circling a moist rootball with a “moat” or donut on top of the rootball when planting and wetting the soil after planting. Either that or apply water slowly or several times to get it to soak in.

            This tree grows about 25 feet tall with about the same spread when fully mature. Pay attention to branch direction and the house when planting. Dig the planting hole at least three times the width of the plant container. Amend the soil removed from the planting hole with “organics” of some sort to keep the soil loose, friable, and well drained after planting.

How Close to the Home?

            I wouldn’t plant it any closer than 8 to 10 feet from a house to accommodate the watering and branch growth. Trees should be planted as close to vertical as possible. When trees are planted from a wooden box, usually the bottom of the box is removed first, and the sides are removed after lowering it into the hole. Fill the hole half full and then ADD water to make a slurry. Never add dry or hot soil to a planting hole.

UNR Extension Tours of Southern Nevada Gardens

 

            Join the Master Gardener Docents, starting Saturday, November 12, for guided tours of the beautiful and interesting Extension gardens (corner of Paradise and Windmill) as well as its interior courtyard. Lots of different plants to look and learn about. Learn which plants performed the best and why? Learn which plants use the least amount of water and, finally, where you can get them! Dates vary to make it convenient for you! The tours are seasonal, so our fall series of tours is happening now, but the tours will stop in early December and will resume again in the spring, usually from April to June. 

            Tours are conducted two to three times a month from until April. Register in advance on Eventbrite by typing in Garden Tour in Eventbrite’s search bar. Future tours start mid-mornings and oftentimes last one and half hours. The tours are scheduled on Eventbrite and attendees need to sign up there.

            The Extension Botanic Gardens feature over 1500 species of plants, including many found nowhere else in the Las Vegas Valley! Docents lead attendees through highlights of the gardens and answer many different and tough questions about these plants and where you can get them.

            Please wear comfortable walking shoes! Tours are fun, informal, and full of exercise. Come join them! For more information call Lauren at 702-940-5432.

Location for Planting Meyer Lemon

Q. I have received two Meyer lemon trees. I want to know the best place to plant them. My house faces southeast, the sides are northeast and southwest, and backyard faces northwest. Due to very hot summer days is it best to plant on northeast side if house gets morning sun and shade in afternoon or in the backyard that gets more sun during mid-day to evening? Does direct hot sun harm trees during summer?

Meyer lemon fruit is ready to harvest from late December and into January. The orangish yellow fruit is more round than a true lemon and can grow about the size of a baseball. You better like lemons alot because when it gets older you can have lots.

A. All these places have their limitations. Probably the most damaging is direct late afternoon sunlight. Plant it where it will get some relief from the late afternoon sun. Plants in orchard are protected by other plants. In our hot desert the intense sunlight is very damaging. It can damage an open area (unshaded) of a fruit tree in less than 20 minutes. Then there are wind problems particularly, side yards where wind can “channel”. 

Leaf footed plant bug on citrus. Yes, they can be a problem on citrus.

            Meyer lemon (not a true lemon) is hardy to about 25F. Select a plant that is bushy with lower limbs as low as possible to shade the trunk.  It needs at least 6 to 8 hours of sunlight each day.

            Citrus will not like to be surrounded by rock unless the soil is amended. At planting time dig a hole deep enough for the container and three times wider. Make sure at planting time the soil is amended with compost or at least small pieces of wood that will rot with water and fertilizer.

            It is okay to surround it with rock but make sure the soil gets a surface application of compost or wood chips once a year. This may mean raking the rock back, applying it, water it in, and then raking the rock back. Or applying the compost/wood chips over the rock and watering it in if the rock is big enough so it does not become an eyesore.

            Be careful when pruning it. I would let it get established first as a bush and then remove lower limbs only as needed. Shade the trunk as long as possible. Sun, wind, and cold are the three things to worry about.

Nutrgrass in Lawns Good Riddance!

Q. We have had nutgrass in our lawn (Tiff type Bermuda) for many years. There used to be a solution that would kill it or keep it at bay.  I haven’t seen it for the last 3 plus years.  It seems unless we can pull out the root and little “nut” at the end, it just keeps spreading. Any suggestions?

Nutgrass in a Tiff-type bermudagrass

A. Used to be that nutgrass, also called nutsedge both the purple and yellow types, were common problems in nursery soils. Once established in landscapes they were both tough to get under control because of the “nut” you mentioned. If the top was killed, the nut would regrow new “blades of grass”. The top, which looked like a lawn grass at first glance, would grow faster than the surrounding grass, or a light green color, and became a problem in well-manicured lawns or other stands of grass.

Nutgrass with an attached "nut" which oftentimes breaks from the mother plant when it is pulled. Leaving behind the "nut" is the most common way for this weed to spread.

            The best chemical control is with a product containing “Halosulfuron-methyl”. Look for this in the ingredients of the product. It may be called a trade name like “Sedgehammer” or others. That’s why its important to read the ingredients of a chemical and not just the trade or product name. This product may be hard to find so it may require buying it online from Do My Own pest control.

            It will require more than one application to kill the “nut”. The top will die, and you think it is dead, but the nut may regrow new “blades of grass” in a few weeks so watch for it. It is important to follow the label directions for these products exactly. In the past the problem has been the resprouting of the nut after the top died. It is very important to reapply this chemical as soon as regrowth is seen, or the spreading of the nuts will make the problem worse.

            The hybrid bermudagrasses are a good choice for lawns in our area. They can use about 25% less water than tall fescues lawns and typically have few weed or disease problems. Just for your information, the “Tiff-type” hybrid bermudagrasses come in different varieties such as ‘Tifdwarf’, ‘Tifgreen’, ‘Tifway’, and others. Tiff type bermudagrasses are used on golf courses and isn’t the same grass as our weed, Common bermudagrass.

Toyon Can Develop Fireblight Since it is in the Rose Family

Q. Does this look like fireblight disease to you on established toyon? Toyon is in the rose family of plants.

Toyon can catch fireblight bacterial disease in the spring and summer months.

A. Toyon is a California native plant in the rose family and related to Photinia. Both plants are susceptible to fireblight. When the plant is dead it can be hard to say. Sometimes susceptible plants only lose their flowers and sometimes the entire plant dies. With prolonged wet weather this disease can be vicious. Sometimes plants “linger” with this disease, and it can lie dormant until cooler and particularly wet weather.

Fireblight bacterial disease on new spring growth.

            Look for bacterial “ooze” coming from wounds. This “ooze” are wet spots on tree limbs or the trunk. During wet weather this ooze may attract insects. Observing this plant can be a good way to know otherwise you have to send it to a plant pathologist and know for sure. Best way, when in doubt, is to assume its fireblight and remove it and get the dead plant off the property before it has a chance to spread. Be sure to sterilize any pruning equipment when you are finished.

Fireblight on Asian pear in early summer

Citrus in Las Vegas Nevada

            

 I was accused of not wanting citrus in our area. That isn’t true. Nothing wrong with growing citrus here. But I want you to be aware of its problems when citrus is grown here and adjust your expectations accordingly. This is the Mojave Desert. Las Vegas and the high or middle deserts can have cold winters, unexpected early spring frosts and winds. It can survive cold temperatures ranging from the mid to low 20’s all the way to no freeze at all depending on the type of citrus.

Sour orange rootstock grows from the base of this orange tree because the top died when it froze leaving the rootstock to grow and produce fruit that has dropped on the ground.

            Early spring light frosts can be a problem for all fruit trees including citrus. All it takes is a few minutes of freezing temperatures just before sunrise. If flowers are open or close to opening, part or all your fruit is dead. The fruit or flowers drop from the trees a week or two later even though bees were plentiful.

Many citrus are subtropical

Citrus originates from different parts of Asia. This means they prefer growing in soils that have some organics in them. Desert soils don’t have any or very little. When soils are covered in rock, the soil organics are fine right after planting and these organics can last last several years. After several years, the soil “organics” used at planting time are depleted and must be replenished. This can be done by raking the rocks back, applying fine wood chips to the soil, and raking the rock back or applying these same amendments over large rock and watering it in.

Citrus can yellow and eventually dieback if the soil is not improved when it grows in rock.

Citrus can also yellow when grown with woodchips if the woodchips are not thick enough or if planted and watered incorrectly. Most yellow leaves can be turned green again if an iron chelate (I would recommend iron eddha for the chelated iron) is applied to the soil in early spring.

            When purchasing citrus be aware that these are fruit trees that are “iffy” when grown here. Sometimes they work and sometimes they don’t. Adjust your expectations accordingly.