Xtremehorticulture

Xtremehorticulture of the Desert

Oleander Toxicity Probably Not A Problem for Vegetables When Composted

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Q. I read you said recently that oleanders can be composted. Just for clarification, can they be composted for vegetable gardens since they are toxic? A. Yes! They can be used for mulching and composting! Mulching is when the plant is chopped up into small pieces and laid on the soil surface. Composting is the controlled rotting of the plant so that it can be mixed in the soil as an amendment and fertilizer.             There is contradictory information circulating on the Internet about the safety of oleander but the study below strongly suggests that there is no problem with it when it is composted and used for growing vegetables. They do warn that it is not safe to eat the compost (why someone or an animal would do that I don’t know). It is also not a problem to compost eucalyptus as well. Composting Oleander Recommendations             The smoke when burning oleander is a problem if inhaled. Although about 60% of our landscape plants are poisonous to some degree, oleander is one of the most toxic along with Datura spp. (a.k.a. Jimson Weed, Angel’s Trumpet, Thorn Apple), Nightshade, Castor Bean (Rosary Bead), Rhubarb, Moonseed, Lantana, Yew and Wisteria.

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Clean up Debris to Reduce Skeletonizer Populations

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Q. Although I was able to control the grape leaf skeletonizer all summer, I came back from a three week trip with 99% of the leaves stripped and dried up.  The grapes were picked in August and September. Should I still treat the vines with BT or just forget it since it is October and the leaves would have soon turned brown anyway? Skeletonizer feeding on the bottom side of grape leaves. A. I would just let it go at this point. The only thing I worry about a little bit is regrowth (new leaves produced) because the temperatures are still warm. Regrowth will drain stored food reserves from inside the plant.             These reserves are used for next year’s production but there should be plenty of “food” left even if it regrows this fall. I would not worry about it if that happens.             Make sure you cleanup the leaves at the base of the plants. This is where the pupal stage (cocoon) will overwinter and if you do not cleanup this debris the attack on the plants next year will be earlier and more intense. The adults are winged moths so they will move from neighbor’s vines to neighbor’s vines. 

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Curled Leaves on Pomegranate

Leave a Comment / cupped leaves, Curled leaves, deformed leaves /

Q. Our pomegranate tree has been planted for 5 years. We’ve had some fruit the past 2 years.  Lots more this year. I just spotted one already split with critters on it. The leaves look shriveled. Gave it fruit tree fertilizer and an extra watering. Any other suggestions would really be appreciated. A. I looked at the pictures you sent to me and your pomegranate does not seem to be very full. The reasons they tree may not have filled out is because of the shade or not enough light during the day, not getting enough water or not fertilizing at the beginning of the growing year.             Don’t worry about the curled leaves. This can be fairly common on pomegranate.             They like to be deep watered just like any other landscape tree or shrub or fruit tree and watered about as often as well. If you want good production, don’t treat them like a cactus. So in short, fertilize the tree in late January or February and start weekly irrigations the first week of February.             I would construct the basin around the tree about 3 feet in diameter and 3 to 4 inches deep and fill the basin each time you irrigate. If you are to use drip irrigation, and they will perform good on drip irrigation if they’re getting enough water, then make sure you have about four emitters and you run them long enough to deliver the water they need.             The critters you see are leaf footed plant bugs and normally soap and water sprays would be enough to knock them back but you’ll have to apply it weekly to the undersides of the leaves and all over the foliage.             Pyrethrins sprays will also work on them. And if you are hard-core, the insecticide is Sevin will kill him but don’t spray when the plant is in flower and spray very early in the morning or at dusk when bees are not present. I hope this helps.

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What Caused Jalapeno Leaves to Be Stripped from My Plant.

Leave a Comment / Hornworm damage /

Q. I went away for three days and when I returned all the leaves were stripped from my jalapeño plants. Do you know what did this? A. Leaves stripped from vegetable plants is usually because of their tomato hornworm. Tomato hornworms are large caterpillars with the spine sticking from their rump. They can come in a variety of colors but we usually see green ones.             They are voracious eaters and can remove leaves from plants at an alarming rate. They also leave behind a lot of large feces that could be confused with mice.             They select only tender tissue and may leave behind more woody stems because they are not as delectable. When plants are very young and tender, they will consume the entire plant.             You do not see them during the day because they hide and come out to forage at dusk and during the nighttime. To find them, go out at dusk with a flashlight or in the early evening hours.             Another interesting way to find them is using a black light, the same way to find bark scorpions. Hornworms shine with an eerie green iridescence under a black light.             Your plant will recover but you don’t have much time left for pepper production. When leaves are removed this stimulates the plant to produce new leaves from existing buds in the crotch or axil of the leaf. The problem is now the plant will focus on producing new leaves first rather than flowers and fruit.             Protecting your plants from these creatures is easy to do by going out at night and removing them by hand. Protect plants with sprays of Bt or Spinosad which are considered organic controls. Just about any vegetable insecticide will control them as well.

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Pine Top Dieback Means Damage Near Top

Leave a Comment / Pine tree died back /

Q. The top of my pine tree died.  Bottom branches look as healthy as ever, green, supple new growth on all of them.  It is about 20 years old.  Its watering has been successful for my 14 years in this house, infrequent and deep – it has options to gather additional water from adjacent areas (lawn and garden) if it wants. Why did it die?   Can I remove the dead top?  And what will happen?  A. I looked at the picture and I tried to identify the tree. The needles are not very long so it did not look like one of our common pines such as Afghan or Mondel pines. It actually looked like a spruce from the branches and the needle length. The kind of tree is very important in determining what caused the problem.             Whenever we have a portion of the tree die and the rest of the tree appearing healthy, it usually pinpoints the problem at the trunk or limbs where the green foliage is closest to the brown or dead foliage.             If I were on site I would get a look at the trunk or limbs at the juncture between healthy and dead areas. I would look for mechanical damage in that area. I can’t tell you why there would be mechanical damage but that’s what I would look for. This is not something we would normally see with pine trees.             If this is a spruce and not a pine then it might be heat stress. Spruce trees cannot tolerate our climate and soils very well and have difficulty lifting water from the roots to the upper limbs. If this is a tree that is not tolerant of our hot dry climate or desert soils than this could be drought at the top of this tree causing it to die back.

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Control Root-Eating Grubs Organically and Conventionally

4 Comments / Grub control in lawns, insect control turfgrass /

Q. I found grubs in the dirt with my plants. I put some Triazicide around the plants. Will this help? A. Triazicide is a conventional insecticide, found at any nursery or garden center, which is very effective at killing grubs. The major advantage of conventional insecticides like this one is the residue or residual left behind after the application. For those preferring organic methods, this is also a major drawback.             There are organic alternatives to grub control which are very effective. These include pyrethrum applied as a soil drench for an immediate kill, milky spore bacterium and beneficial nematodes. Milky spore bacterium and beneficial nematodes also give you long-term plant protection from grubs.             In your case, you need something to kill the grubs. Once you kill the grubs, it may be no longer necessary for a product like Triazicide to hang around in the soil.             A residual product like Triazicide becomes important when protecting valuable plants from an infestation which may be imminent. In cases such as these, mark the calendar when the insect threat might occur and apply this type of product two weeks to a month before this date.             I would not use this product around food crops but lawns and ornamentals are more suitable. But always read and understand the methods of application stated on the label.             Triazicide comes in several different formulations (liquid concentrate, granules, ready to use liquid, etc.) and each formulation is applied a little bit differently. Basically the poison is applied to the soil surface and water is used to wash this poison to where the grubs are actively feeding. Applying too much water can move the product beyond the area where it is needed.             Manufacturers want you to be successful with their products so you will use them again and recommend them to others. They try to provide the best information possible so that you are successful.             Be cautious around your outside pets like dogs and cats since any insecticide, organic or conventional, moves easily from the soil surface, through the pads of their feet and into their body. I would not let them walk in the area until the surface where it was applied is totally dry.

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When to Cover Winter Tender Plants in the Mojave Desert

Leave a Comment / cold damage, freezing damage, winter protection /

Q. When should we cover Pygmy Palm, Bougainvillea and other plants that will freeze here in Henderson?  I have burlap to cover them. Bougainvillea freeze damage A. Both of these plants can tolerate temperatures to near freezing and they don’t seem to have problems at temperatures below 45° F that causes chilling damage to some plants. Some tropical plants such as tomatoes may show chilling damage to fruit at temperatures below 45° F. This is why it is best to not refrigerate tomato fruits.             It seldom freezes in the Las Vegas Valley before Thanksgiving. After Thanksgiving you might expect freezing temperatures at the higher elevations such as in Summerlin or in very low spots in the Valley where cold air collects. In Henderson, this might be in the old Pittman area or along the wash.             Cold air, being heavier than warm air, settles into low geographic areas. Cold air tends not to settle on gently sloping land or hills.             Freezing temperatures are more frequent where plants are exposed to wind. Plants growing along major streets tend to freeze more often than those in protected backyards. Major streets are urban canyons that channel cold wind in the winter. Backyards are more nestled away from these exposed urban canyons. Sehgal palm cold damage             Plants growing close to brick or cement walls that face West or South are less likely to freeze than plants growing further away unless wind is involved. Brick and cement walls exposed to the sun store heat during the day and radiate this heat at night keeping the plants a few degrees warmer. If wind is involved, it removes this radiant warmth making these plants more susceptible to freezing temperatures.             Bottom line, when the weather forecast is for freezing temperatures, cover the plants with an old sheet, blanket, or in your case burlap, before nightfall. Drape this covering over the soil or any surface that can radiate heat at night. Remove this covering the next morning after temperatures are above freezing.             In open areas, expect freezing temperatures after Thanksgiving and up to March 1. In protected areas, expect these temperatures anytime between mid-December and mid-February but watch your local weather forecast closely and adapt this recommendation accordingly.

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Imidacloprid a Problem for Pollinating Insects?

Leave a Comment / colony collapse disorder, honeybees, insecticides /

Q. Do you recommend using imidacloprid in the grass to kill grubs? Does it harm pollinators? What would you advise? A. That particular chemical is suspected of possibly damaging pollinators. Nothing has been conclusive about it but logic tells us that if we have a systemic insecticide that can persist in a plant for 12 months that it is possible this chemical may be in flowers, pollen or nectar. We just don’t know. For this reason I tell people if they are going to apply it to plants that bloom then apply it immediately after they have finished blooming. I also tell them that it is safest to use on plants which do not have flowers that attract bees. Lawn grasses do not attract bees so I don’t consider that to be a problem for pollinators. Even though it is labeled for fruit trees, I would not personally use it on fruit trees if I am planning to use the fruit. If I were to apply it to fruit trees or any ornamental tree that has flowers that attract pollinators, I would not apply it until after bloom until we have more conclusive evidence that it is not a problem with pollinators. That’s what I am currently recommending regarding this product.

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Replacement Plant for Photinia

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Q. I have several Red Tip Photinia that I use as a screen from my neighbor. I would like to replace them with some a bush that would be about 3 to 31/2 feet tall and handle our soil an weather better. I want to spend a little time trimming them. Texas Rangers are good but need a lot of trimming. Any Suggestions? A. Bob Morris forwarded me your message.   I am a Certified Horticulturist working in the Las Vegas area since 1992.  I suggest you look at Dwarf Myrtle and Dwarf Youpon Holly. Both are tough evergreen shrubs growing to about 4 feet by 4 feet. Hope this helps. Andrea Meckley, CH [email protected]

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