Xtremehorticulture

Xtremehorticulture of the Desert

Windbreaks and Screens in Desert Landscapes

5 Comments / desert landscape design /

Q. I was hoping to put up nice strong wind and sun block on the west and south west corner of our front yard, approximately 20 feet each way.  Could you give us some suggestions? I’ve talked to the neighbor on that side and we were thinking probably some kind of large bush. A. Windbreaks and screens for sunlight in the desert are usually best if they are close to the affected area. The reason is that plants used for screening or deflecting wind have to be pretty big to do any good when they are far away. Windbreak diagram but I cant remember where I got this from on the internet. sorry.             Larger plants require more water. If you put a windbreak close to the area where wind is a problem, then you can use smaller windbreaks and smaller plants and achieve the same thing. If wind or sun is a problem all year long then you would select evergreen plants.             If this problem is seasonal, you would select deciduous plants that drop their leaves in the fall and allow wind or sun through during winter months. Bill Stillman pomegranate windbreak in Bullhead City, AZ             General rule of thumb is that wind is affected on the downwind side of a windbreak from 5 to 8 times its height, depending on the type and direction of winds.             To be effective, windbreaks made from plants should be at least two layers thick and not a single layer or a few plants planted in a straight line. The majority of wind will be diverted over the top, bottom and around the sides of windbreaks. Wind that does go through a porous windbreak will be slowed.             How much it is slowed depends on how “porous” the windbreak is. Try to achieve about 20% porosity. In other words, about 20% of the windbreak has holes or pores in it. This lets wind through it, slows it and decreases the amount diverted up or around a windbreak. Fact Sheet on Establishing a Windbreak in the Desert             In the desert, think about structures to do this more than plants. These structures would be things like walls or trellises that can be covered with vines rather than large plants. A vine covering a wall or trellis will use far less water than plants the size and density needed to reduce wind speed and sunlight. Great way to add screen and windbreak in a desert landscape             Also, using a structure and vines or small shrubs in combination will achieve a more permanent solution to the problems and occupy less space in small residential landscapes. Avoid wood structures which crack and check in our dry heat. Instead use cement and metal options that are more resistant to our harsh environment.

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Raywood Ash Showing Signs of Dying Back

5 Comments / dead branches, limb dying /

They seemed to be fine after our week of 117F weather. Q. Four years ago we planted two Raywood ash trees in our back yard. They have been very healthy and have grown wonderfully to over 25-30 feet. One is growing in the grass and the other in decorative rock. We usually water about 30 gallons every 2-1/2 week in the summer. Both trees are planted in a wide circular of dirt and mulch, about 25 feet apart. There are no other plants near these trees, so they are not susceptible to any weed killer or fertilizer that should not be used near the trees. They seemed to be fine after our week of 117F weather.             Two weeks ago one began to lose leaves. Now the other one is doing the same thing. We gave them a little extra water because the leaves are beginning to dry and feel like crepe paper and turning yellowish. We checked the limbs and bark and there doesn’t seem to be any seepage, cuts or insect damage. A. My first reaction is the trees are not getting enough water. When leaves begin to drop over the entire tree it usually points to a problem with the trunk or roots. Since water affects the entire tree, the amount of water applied is also looked at closely.             Thirty gallons every 2 1/2 weeks is not enough for trees 25 to 30 feet tall. So they must be getting water from somewhere else besides your deep watering. It is good to water trees infrequently but every two weeks is quite extreme for trees that have no other source of water.             I would normally give 30 gallons of water three times a week when temperatures are in the 110F range. Once the temperature drops back around 100F I would drop it to twice a week.             As long as this amount of water is spread in a 3 to 4 foot diameter basin under the tree or distributed by multiple drip emitters under the canopy it should wet the soil deep enough, about two feet down.             You might consider is that the extra water the trees were getting might have “dried up” for some reason. When this happens, the leaves on the tree would scorch, dry up, turn crispy, and drop. This leaves the roots to rely on other sources of water to support its size.             When tree roots find water, their roots expand into a wet area. In areas where very little water is present, tree roots grow poorly. Tree roots can spread, if water is present, distances of two to three times their height. So your 25 foot Raywood ash could have roots as far as 75 feet from the trunk.             Tree roots do not necessarily grow symmetrically around the trunk. The greatest abundance of roots is in wet areas of your landscape or your neighbors. Also, if your neighbor had a pretty wet landscape, the roots could be over there. If that is the case, how your neighbor waters, or doesn’t water, could affect your trees.             I would construct a basin or depression under your trees about four to five feet in diameter and deep enough to hold about 30 to 40 gallons. I would fill this basin with water once a week for the next several weeks.             Leaves that are crunchy will not grow back. They will dry and fall from the tree. You will have to wait for a new flush of leaves if water is the problem. This might take a couple of weeks.             To supplement the tree you can plant under the canopy of the tree (not in the lawn) with other plants that require watering. This will help to supplement that trees water requirement.             The tree in the lawn is puzzling. This would make you think there is another problem but if things happen to BOTH trees it usually points to a management problem; water, fertilizer, pesticides, etc.             When one tree is affected it usually points to outside factors that are more hit and miss like diseases. However, ash is not affected by that many diseases and is a good tree for Las Vegas.

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Come Join the Discussion on Desert Horticulture

Leave a Comment / answers to questions, find answers, Yahoo discussion group /

 A number of my readers also catch my responses and pictures on my online blog called Xtremehorticulture of the Desert. This allows me to post pictures of problems as well as pictures I have accumulated over the past 30 years.             Blogs primarily focus on one person’s contributions and don’t allow for much discussion to occur. For this reason, I started a horticulture discussion group on Yahoo. The Yahoo discussion group called Desert Horticulture allows you to join the group and post questions or contribute to the answers to questions that are posted.             Please come and join us in these horticultural discussions. If you can’t find it, send me an e-mail and I will help connect you. Join Desert Horticulture Discussion Group

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Fescue Lawn Invasion by Bermuda or?

Leave a Comment / bermudagrass weed control /

Q. I have a small fescue lawn that is being taken over by what appears to be Bermudagrass or some type of large blade thick dense grass that is much greener and thicker than the fescue grass. What can I use in our climate to kill the invading grass without killing my fescue? A. Bermudagrass that invades lawns is not typically dark green and is not dense in a bunch. It produces stolons so you can usually identify it because it wants to creep along the surface of the lawn. Bermudagrass stolon creeping on to the sidewalk             If it is dark green and in clumps, it might be a fescue or rye. Because bermudagrasses will not grow in shade, if we keep the lawn mown high, do not use line trimmers to edge the lawn, do not mow or line trim the grass next to sprinkler heads and keep it dense and healthy, it usually keeps bermudagrass out due to shading of the soil.             Once you have bermudagrass it is tough to get rid of. You should get it when it first invades if possible. This would be with spot sprays like Roundup in these locations and reseed.             You do this in the fall. After one week you cut or remove the sprayed grass from those locations and reseed it or cut small pieces of sod and resod those areas. Keep it wet the first two weeks as it starts to root into the soil. You gradually back off on the frequency of irrigation and increase the amount on those spots. This forces it to root more deeply. Finally, after about 8 weeks, you revert to your sprinkler system.

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Getting Rid of Tomato Diseases in Containers

Leave a Comment / crop rotation, rotating vegetables, soil solarization, solarizing /

Q. I grow tomatoes in boxes I have built. I know one is supposed to plant tomatoes in a different place every year and I don’t want to just throw away the dirt in these boxes. I don’t have many places to put this dirt so my question is, “Can I put this dirt in my compost bins?”   I have two cement block bins. What, if anything can I do to that dirt in order to use it in the same boxes next year at planting time? It’s expensive to buy all new dirt and I am poor. A. Being poor is a good reason to grow your own food. I wish more poor people did it. If you want to grow tomatoes in the same soil year after year, it is probable you will have increased problems down the road if you don’t do something about it. In our climate, problems are mostly due to accumulation of soil diseases over time.             Growing different crops in this same soil helps reduce this problem and is called crop rotation, an important practice in organic vegetable production. By growing different crops from different families in the same soil, we help in interfering with this buildup of disease problems. Tomato foliage disease, probably early blight.             In the off season when you’re tomatoes are not in production you could put some cold weather vegetables in that soil until you are ready to plant tomatoes again. This can be radishes, beans, beets, broccoli, lettuce, spinach, endive and the like. This will help to reduce the disease cycle but, unfortunately, soils need a bit longer rest from the same crop than just one season of production.             You can solarize this soil by using the sun and this will help to reduce some of the disease potential. If these are small boxes, moisten and put the soil in a clear plastic bag for a few days in full sun and let it bake. If you can get the temperature of the soil in the plastic bag over 165°F for at least 30 minutes you will substantially reduce disease problems. Nice pic and discussion on solarization from Ventura County Extension             While you’re at it and the soil is removed, you should surface sterilize the sides of boxes as well. You can sanitize them using a bleach solution or other sanitizer.             If the boxes are too large to do this, after you’re tomatoes are finished for the season, spade the soil deeply with a spading fork and turn it over. Make sure it is well aerated and as ‘fluffy’ as possible.             Do not turn the remaining tomato plants over in the soil and decompose them that way. Remove and compost them, solarize them or discard them if you can’t compost them.             Moisten the soil lightly and cover it with clear plastic making sure the edges of the plastic are buried and the plastic is sealed around the edges. Let it bake in the sun for several days.             Regardless of whether you took the soil out of the box or not, amend it with more compost and a starter fertilizer and replant. And by the way, if the containers are emptied, wash down the inside and sterilize it with a 10% bleach solution and let it air dry before you fill it again.

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Leaf Drop on Trumpet Creeper Can Be Due to Many Things

1 Comment / leaf stripping /

Q. We planted three “creepers” this spring and all but one is thriving.  As you can see from the photo the leaves are being stripped.  I’ve checked at different times of day for bugs but all I can see are a few ants. Any suggestions? What the reader called “creeper” which I think is trumpet creeper. A. I believe the plant is one of the trumpet vines or trumpet creepers judging from the foliage. I will post your picture on my blog.             Are you sure the leaves are stripped or is the plant dropping its leaves? These plants will require at least eight hours of full sun each day. They like full sun. If they don’t get enough light, they will drop their leaves.             If they are watered too often, they will drop their leaves. Or, if they are being watered the same, if one spot does not drain water as well as the other spots, you might have leaf drop.             Some plants will drop their leaves shortly after planting or if they are planted in locations that are radically different in light levels from the nursery. Check to see if these stems are still supple and bend easily and not dead. If they are still supple and there is plenty of sunlight, you will probably see new leaves coming out.             You should be aware that as the plant gets older, it will lose its leaves on the older wood unless there is no growth coming from those older stems. On those older stems you should expect them to be without foliage as they get older unless you prune the plant to maintain that foliage.             Leaves being stripped off the plants don’t make sense to me but there are A LOT of things that don’t make sense to me. I suppose it is possible an insect could be stripping the leaves off but I would think you would see its presence. I don’t know of any night feeders that would be stripping them off.             As a precaution, flush the soil around the plants with LOTS of water, several times. Add a good fertilizer such as a Miracle Gro, Peters or Scotts product. Get on a watering schedule for trees and shrubs and not for flowers. Let’s see what happens.

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Nectarine Fruit Scarring Due to Thrips Damage

1 Comment / fruit damage, fruit skin scabbing /

Q. My nectarine fruits have this corky appearance on the outside on their skin. They do this every year. I don’t apply any pesticides. I sent you a picture. Why does this occur? Nectarine scarring noticed by reader. A. I will post your picture on my blog as well as some others which are similar that are common to nectarine. Thrips damage to nectarine fruit at the UNCE Orchard             Nectarine fruit is a hairless peach fruit. Not having this hair on the skin allows a lot of things to damage the fruit. Hair gives a lot of protection to fruit and slows down water loss from the fruit as well. When the fruit skin is damaged by blowing sand, disease, and insects the skin reacts by growing a corky surface which we could relate to as “scabby”.             Instead of scabby, we call it russeting of the skin. In plants we are probably most familiar with Russet Burbank potato which has that naturally rough, dark brown, corky skin.             Russeting is due to damage to the skin. If this type of damage continues, the entire fruit could be covered with this corky surface. From your picture it appears that it’s started and then stopped for some reason since it only covers a small portion of the fruit. So we are looking for something that happened to the fruit when it was pretty young. One of the several products that contain spinosad insecticide. Thrips control is difficult.             The usual reason for this in southern Nevada would be thrips damage. Thrips are tiny insects that cause damage to soft plant tissue very early in the spring. If they are left uncontrolled this damage can cover the entire fruit or even cause the fruit to drop from the tree.     I was a little confused because the damage was only in a small area of the fruit and you did not use any pesticides to control them. But with uncontrolled thrips you would have expected the damage to continue and cover the entire fruit.             I forwarded your picture to a friend at Dave Wilson Nursery in California and he confirmed the thrips damage. You would apply Spinosad insecticide, an organic pesticide, with the wetting agent so that the entire fruit is protected from thrips. You apply this immediately after flower petal fall in the spring for about three applications about a week apart.

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