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Thursday, July 14, 2011

Japanese Privet Does Not Like Dry Feet

Readers plant appears to be Japanese privet which
does not like dry soils
Q. I have four bushes like the one shown. They were planted about six years ago and have never done very well. Each year around this time they look as shown. Can you advise and suggest anything?

A. From the looks it appears to be Japanese privet which must have soil around its roots that does not go dry. It will not do well in rock landscapes. They do well in a turfgrass landscape. This might be a case of the wrong plant in that location. You would have to increase the frequency of the watering and improve the soil in that location.

This is what Japanese privet will do in a rock landscape
with drip irrigation - drop its leaves on some branches
along with branch dieback
            The amount might also have to be increased but since I dont know the amount I would suggest increasing the frequency to about three times a week. The amount depends on the size of the plant but a three foot tall plant might require five gallons or so each watering. A ten foot plant might require perhaps 20-30 gallons at each watering.

Tomato Cracking May or May Not Be Your Fault

Radial cracks on an heirloom tomato from the orchard
Q. I have this problem. Our tomatoes develop cracks at times usually about half way to maturity.  They also rot on the bottom.

A. Tomato cracking can be from the variety of tomato you are growing or it can be how you are managing your irrigations or a combination of both.  Rotting of the bottom of the fruit can be caused by irregular irrigations.

Heirloom tomatoes with longitudinal
cracks (top right and top left) from irregular watering
            Some varieties of tomatoes, particularly heirloom types, are subject to what are called radial cracks.  These are concentric, circular cracks around the top of the fruit.  These might be reduced by growing them under light shade probably know more than about 30%.

            Cracks along the length of the fruit can be a particular problem after a heavy rain. Sometimes when the tomato fruit is near maturity very wet soil can result in a lot of water taken up by the plant with lots of it sent to the fruits. The fruit swells and cracks due to excess water taken in by the fruits and the skin.

Blossom end rot on tomato, picture submitted by reader
            Use a mulch on the soil surface to help keep the soil more evenly moist. This can result in less cracking to the fruits because the soil is kept more evenly moist. This can be straw, shredded or even sheets of newspaper or landscape fabric cut into strips.  As I said, tomatoes will do better if they have some light shade when they are growing.

What's Happening In The Orchard In July: Limb Damage and Wormy Peaches and Nectarines

Fruit Tree Limb Split Due to Heavy Fruit Load
Limb Damage Due To A Heavy Crop Load.  Too much fruit on a single limb and the weight can cause the limb to separate from the trunk.  We get it at the orchard if we do not thin the fruit enough on the limb or if the limb has a poor attachment to the trunk.  Make sure that limbs which support fruit are attached to the trunk at about a 45 degree angle.  Peaches should be thinned so that the fruit is about 4 to 6 inches apart along the limb.  Summer pruning, talked about here on this blog, will help to keep fruit loads more manageable and cause less damage to the tree.  During summer pruning, usually around April and May, excessively long branches on peaches and nectarines are pruned back so they are no longer than about 18 inches.  This helps to distribute the crop load for the next year which is born on the wood which is produced this year.
Flagging in new growth at the top of a peach tree

Wormy Peaches, Nectarines And Even Almonds. Peach twig borer in the adult stage is a brown month about 1/2 inch long.  After eggs are laid by the adult moths, worms or larva enter soft fruit usually near the stem end.  When they enter near the stem end they leave behind some brown excrement that looks a little bit like wet, dark brown would grindings. 

CloseUp Of DieBack Of A Young Peach Stem Due
To Peach Twig Borer
But earlier in the season when there is no fruit they attack something else that is soft and tender - - newly growing shoots.  They bore into the soft ends of the shoot where they tunnel and cause the newly growing tip to die back as you see in the picture.  Later in the season when there is soft fruit they attack the fruit instead.

It is important to get these insects under control very early in the season.  There can be several generations each growing season and their numbers are not additive but multiply at very high rates so their numbers increase rapidly.  

Peach Twig Borer Larva in Almond Husk
These little guys will also attack almonds.  They get into the husk where it is essentially just like the fruit of a peach.  They can get inside where the nut is located and cause damage there as well.

We use pheromone traps to begin to identifying when they are flying and add a very high density so that we get some mating disruption.  Then we usually use either sprays of Bt or spinosad.

For more information see the University of California IPM online web site at

Tuesday, July 12, 2011

Roses Can Be A Good Landscape Plant For The Hot Desert

Roses Should Never Be Grown
In Rock Mulch
Q. I read your column and have a question. I have two rose plants both have very dried blossoms on them. WHAT should I do?  Cut them back 1/3, fertilize, or leave it alone until the weather cools?  The heat has “mummified” the roses that did bloom. All on the branches. We lived in Hawaii for many years, and I am uncertain how to grow roses here...Hawaii so much easier!

A. Roses do surprisingly well here in our desert.  We have two rose societys here in the valley with some very avid rose growers, some with hundreds of roses in their yards.  The best time of year for roses is in the spring in the fall, months from February to May and then later when it’s cooler again beginning about mid September into mid December. 

If they are planted in front of a wall with reflected heat (west and south facing walls) they will do well all winter long.  The worst time of the year for roses, and the time when they struggle the most, is June through August.  The flowers do exactly as you are talking about.  They will bloom and the flowers shrivel up and die very quickly in our heat and lack of humidity. 

Never grow roses in a rock mulch here always use a wood mulch.  The best wood mulches are chipped or shredded landscape plants that arborists normally take to the landfill. 

Roses growing in Las Vegas in wood mulch
Roses do great on drip irrigation.  Use two, 3 gallon per hour emitters per rose plant and irrigate for 1 hour.  That will deliver 6 gallons of water.  In the heat of the summer irrigate three times a week if you are using wood mulch.  Go to twice a week in mid or late September, once a week in mid to late October, and once every 10 days after the leaves drop.  Repeat this in reverse in the spring as the temperature gets hotter starting with once a week on February 1.

Fertilize in January with a slow-release rose fertilizer plus a soil-applied iron chelate applied under the wood mulch next to the emitters.  The fertilizer stakes work great and are not as messy.  The best soil applied iron chelate is going to be one which contains the chelate EDDHA. 

I know that Plant World Nursery on Charleston carries this iron chelate but it is always expensive.  So does Grow Well on Nellis.  You only need a small amount per rose plant.  I would fertilize a second time, two weeks before the second crop in the fall comes on. 

What should you do now?  Remove any of the flowers that if mollified and cut off any dead or dying branch is and leave it alone until after leaf drop in late December.  Do your pruning at this time.