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Friday, July 21, 2017

Pear With Leaf Browning

Q. I have a Kieffer pear tree that is newly planted about 4 months. It's located along a wall that runs north-south and gets full sunlight. For the past few weeks I've noticed that dark splotches are beginning to appear in some of the leaves. It usually starts along the tips or edges. Recently, the tree is beginning to show yellowing on all the leaves on the edges. I have a picture attached. I'd be very grateful for any help!

A.  Leaf browning along the edges of the leaves on pear is quite common during the heat and strong winds of summer. The temptation is to give it more water which can actually damage the tree and might even kill it. Some of this damage to leaves is common during the heat and winds of summer. In pear trees oftentimes leave damage becomes black and can look like a disease. Don't panic!

Browning or blackening of pear leaves is quite common when they are damaged.

What to do?  
Make sure the tree is staked during its first year of growth. Staking a tree is supposed to force the roots not to move in the soil during the tree/s establishment. It is not supposed to immobilize the tree above ground. The tree above ground should move and sway with the wind but the roots should have no movement.

Water the tree frequently during the first month of establishment and then try to "wean it" off of frequent watering when you start to see new growth. All trees and shrubs go through a stage in their establishment from container to the ground where new roots grow into the surrounding soil. Once roots have begun to grow and the tree becomes established, there will be a flush of new growth from the tree. Remove the stake after the first growing season.Try not to water more than every other day when temperatures are near 110° F. Give the soil a chance to drain before you water again.
Pear leaves can yellow and have brown spots when needing iron.
Add compost and iron. Sometimes these trees just do not have enough nutrients in the soil to get them through the summer. For a young pear tree like yours, add about one half cubic foot of compost in a circle around the tree without touching the trunk. Like a donut. Before applying the compost to the soil surface, put a couple teaspoons of iron chelate beneath it and water everything in to the soil with a hose. The most effective iron applications this time of year are sprayed on the leaves but it is a little hot to do that now.
Cover the soil at the base of the tree with wood chip mulch. This is particularly true of fruit trees. Fruit trees preferred to grow in soils that have organics in them. The decaying of woodchip mulch on the soil surface in the presence of water adds organics to the soil. Covering the surface of the soil with rock does not. Keep the wood chip mulch away from the trunk the first few years.

Problems with Crepe Myrtle in North Florida

Q. I have a problem with my Muscogee crepe myrtle here in north Florida. I planted it last year and it had nice, healthy purple flowers. Then I pruned it, added some iron chelate and epsom salts to the soil and these little warts sprouted all over the tree. I cut them all off and they are growing back. Will this tree do anything this year or should I replace it?

A. The iron was a good idea, not sure about the Epsom salts, but be careful when you prune crape myrtle. Some of these warts, as you call them, probably resulted from your pruning. Pruning the wrong way can cut off all of the future flowers for a while.
            I posted some tips on handling crape myrtle but it was in the desert. Maybe some of these tips can help.

 Spread 4 to 6 inches of woodchip mulch beneath the tree where it's irrigated.That will help build the sand and return nutrients.
            Iron should be applied to the soil in early spring. Later than this might not help much. The best iron chelate contains EDDHA as the chelating agent. Apply it in January. Apply a Rose type fertilizer at the same time.
Crape myrtle in sandy soil. It can be good for it provided you add nutrients to the soil, organics, iron and fertilize once or twice a year.
            One application of fertilizer per year is normally all that you need when growing it on most soils. On your sandy soils, I would split the fertilizer application in two; apply half in the spring and the other half late summer or early fall.
Crepe myrtle sets up its flower buds in the late summer and fall for next years blooms. Don't cut them off.
            These growths along the trunk and limbs look like the tree is trying to send out lots of new suckers to perhaps compensate for the pruning you did. Allow them to grow only where you want new growth. Otherwise, remove them as soon as you see them.
Crape myrtle can look like this growing in sandy soil if it gets the right nutrients and organics.
            Flowers grow from the ends of the branches. So if you removed all of the ends of the branches, it will not flower that year. It has a good chance of flowering next year and years after provided you did not make the same mistake pruning.
            The best time to prune this tree is immediately after all the flowering has finished. When pruning, do not shear off all of the ends of the branches. No, no, no. This removes all of the flowers for next year. Remove entire branches. This type of pruning is called “thinning”.
            If branches are healthy, do not prune them back at all unless they are too long.

Thursday, July 20, 2017

Fasciation on Plants Can Be Fascinating

Q. Not Sure the type of Cactus but it does well in my yard.  I  do not understand what happens to the top of one and the other produces flowers?

Readers pictures of his cacti with and without fasciation.

 A. Technically called fasciation but commonly called cresting in cactus. Sometimes cresting can add lots of value to some cacti. It is more of a curiosity than anything else. The usual method for getting rid of it is to cut it out and it seldom comes back.

Read more about fasciation and cresting on Wikipedia

It can happen to other plants as well from my collection.
Fasciation on asparagus

Fasciation on European pear.

Fasciation on rose.
Fasciation on ash tree
Fasciation on boxwood.

Wednesday, July 19, 2017

Challenges of Growing Tropical Plants in the Desert

MoCa Family Farm Is our farm in the Philippines. It is certified for agritourism and we are certified to teach many classes in tropical horticulture and farming through RLearniong Center. I would invite all of our friends to visit our Facebook page and become our Friends! We grow many different tropical fruits, vegetables, herbs and spices on our farm.
Q. What are the main challenges in growing tropical fruits in the desert?  Fruits like mangos, lychee, longan, jackfruit. It seems like Las Vegas has all the same conditions as Southeast Asia, except the humidity, but my understanding is that humidity is good for preventing disease. Are the 
colder temperatures in winter the only impediment to growing these fruits?

A.  Having a small-scale family farm in the Philippines and growing a wide variety of different fruits, herbs, spices and vegetables I can tell you the challenges can be many trying to grow these in the desert. There are some things we can grow quite easily while there are others that pose a lot of challenges. But I encourage people to try.

Many of our annual vegetables in the desert are perennial in the tropics. Take for instance tomato, peppers and the like.

Pruning guyabana (soursop) at MoCa Family Farm RLearning Center. We emphasize keeping our fruit trees small so they are easier to harvest.
But I think you are talking mostly about tropical plants such as banana, mango, papaya, perhaps tea, coffee. Each tropical plant presents its own set of problems. But as I tell many of my students, when you grow plants, the further these plants are from originating in the desert or desert adapted, the more time, energy and money it will take growing them.

Avocados at MoCa Family Farm
Here is a partial list of things to consider.

Temperature. Many tropical plants can handle desert heat but they cannot handle cold in any way, shape or form. Damage to tropical plants can start when temperatures drop below 50° F. Some tropical plants experience chilling injury at refrigeration temperatures. Think of putting a banana or tomato in the fridge. And of course freezing damage. When temperatures drop below freezing, most tropical plants cannot handle it. If you're growing a tropical plant that experiences these types of damage and of course you have to protect them from it. This might mean a greenhouse, hoophouse are wrapping these plants for thermal protection.

Immature rambutan growing in the Philippines
Light intensity. Sunlight is more intense in the desert and there is more of it than in most tropical climates. Planting tropical plants on the east or north side of a structure may be enough to protect them. Planting and filtered light such as from an open tree canopy or shade cloth may be enough.

Sunburn on Apple fruit growing in the Mojave Desert
Humidity. Some tropical plants and even temperate plants grow best with some humidity. In the Mojave Desert it is common to experience relative humidity at 30% or below for many days of the year. This can pose problems for some tropical and even temperate plants in flowering and fruit set. We experience fewer plant diseases in the desert because of low humidity.

Very poor fruit set on Bing cherry growing in the Mojave Desert with 12 other varieties of sweet cherry. I speculated it was because of low humidity and poor fruit set. Flowering was fantastic.
Soils. Surprisingly, tropical soils can have very low organic content and still be dark to black. Desert soils where rainfall is under 10 inches per year have unacceptable organic content even for cactus! Our soils organic content is far below 1%. The soil chemistry is usually unacceptable for many tropical plants with too much alkalinity and salts. Desert soils need organic content of 2 to 3% for lawns, palm trees, many of our trees and shrubs. 5% organics would be nice to have for fruit trees and 10% for growing vegetables. Even in the tropics, the addition of compost to the soil to grow vegetables is a very good idea if the soil has never been farmed.

Typical Mohave Desert soil in the Las Vegas Valley. Extremely low organic content.
Daylength. The amount of darkness a plant receives can act as a "trigger" for flowering in some plants. In the tropics daylength is not such a big deal since there is not much variation during the year. Instead, the alternation of wet and dry seasons can trigger flowering in some tropical plants.

I hope you can see that growing tropical plants in a hot/cold desert climate can be very tricky. How that plant is managed in our temperate, desert climate depends on which plant you want to grow. But in the very least you have to address soil barriers with compost and surface mulch, avoid planting in South or West facing exposures, keep them from freezing or possibly chilling injury and be aware of problems that might be associated with humidity. This is the bare minimum that you must think about if you plan on growing tropical plants in the desert.