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Saturday, February 14, 2015

Crazy Roots of Tomato Is Due to Nematodes

A. This is definitely root knot nematode judging from your photos. There really is no way to totally rid the soil of nematodes. In the past, soil fumigants were used on a regular basis to knock these critters back. Soil fumigants are being eliminated from the pest control arsenal due to environmental concerns.
Your options are to move your growing area to a new location that is not infested, grow in raised beds or containers and use resistant varieties. There are some vegetable varieties more resistant to nematodes than others.
Roots of tomato plant from reader
Use varieties that have a capital “N” after their name. This stands for “nematode resistant”. An example would be the tomato, Better Boy VFN which is resistant to Verticillium and Fusarium diseases as well as nematodes.
Build up your organic matter content with lots of compost. Nematodes don’t like soils with high organic matter.
Be very careful of transferring soils contaminated with nematodes to new beds or containers. This includes using contaminated gardening utensils. Make sure utensils are sanitized between locations.
It is possible for this pest to migrate from your existing soil to a new raised bed constructed on top of contaminated soil. You might to consider laying thick plastic underneath the raised bed. Make sure the plastic is sloping slightly for drainage and make the bed at least 12 inches deep.

Here are some links back to my blog where I have written about nematode in the past.

Monday, February 9, 2015

Shoestring Acacia Height Can Be Lowered

Large shoestring Acacia. Some are more upright than others while others are more rounded. This is because of how they were propagated, grown and location.
Q. I have a tall (40-50ft) shoestring Acacia tree that is too close to the house. The leaves accumulate on my flat roof and clog the scuppers. This has caused interior flooding on occasion as the water overwhelms the vents and skylights. My question is, can this tree be topped or does it need to be removed.

A. Yes, you can reduce the height of this tree. There is a pruning technique to lower its height called “drop-crotching” which is very different from topping. Topping is extremely damaging to trees while “drop-crotching” lowers the height of a tree while maintaining the tree’s form as much as possible.
This shoestring Acacia was topped. This is NOT how we want to lower the heights of trees. The method we are looking for is called drop crotching. Most likely the reason it had to be lowered is because the signage was blocked. This was the fault of the designer or landscape architect. Topping was the fault of the tree butchers.
            Very large trees cannot be reduced in size to very small trees. There is a limit how much a tree can be reduced in size by drop-crotching. When lowering the size of very large trees dramatically, reduce their size over a period of several years rather than doing it in one season.
This is not the same tree but it was done by the same pruning crewon a tree close by.. These cuts were made in the wrong locations on the tree with absolutely horrendous care.
When drop-crotching a tree you need to find very specific spots to cut where the form of the tree is not totally destroyed.
You would first identify the vertical branches providing the most height. Trace these vertical branches to lower side branches. Remove the vertical branches just above the juncture with the side branches.
You would repeat this at all of the locations that contribute to its unwanted height. By pruning in this fashion, you will retain as much of the trees natural form as possible.
A guide to drop-crotching can be found http://pubs.ext.vt.edu/430/430-458/430-458.html

If drop-crotching is not acceptable then removal is the only other option.

Forcing Tulips to Bloom Again

Q. I recently purchased tulips already in a container and they bloomed for almost 10 days. The roots were sitting in water, and I had to add a little each time so their roots reached the water. How can I save the bulbs for later planting next year? Can I keep them cold all year until next year?

A. This is the beginning of February and you are not too late to plant now if you are able. Could you plant them in some containers and enjoy them that way rather than planting them in the ground?
When tulips bloom, they are exhausted. They consume a lot of energy stored in the bulb to push the leaves and flower out. They need many weeks or months after that to rebuild that corm to its original size or even larger.
So after bloom the leaves must remain attached to the plant while they rebuild the corm. Once the corm has rebuilt its size, everything green could be cut back and slipped back into the refrigerator for six weeks. They can be then be repotted again and forced to bloom.
You can repeat this cycle several times as long as they rebuild the corms each time and receive eight weeks of chilling in the refrigerator. You can do this to nearly any spring flowering bulb.

It would be very difficult to keep them for a year in a refrigerator or even specialized containers for that length of time because of storage diseases primarily. It should not stop you from trying it though. They will bloom again as long as they have about six weeks of cold temperatures. Give it a try!

Pruning Globe Mallow and Bird of Paradise

Q. We have a very old globe mallow shrub that looks bad after a frost. When and how should it be pruned to bring it back to its former glory? Do Mexican Red Bird of Paradise need regular pruning? How can one tell what and where to cut?

Globe Mallow growing in extremely poor soils in Las Vegas.
A. Globe Mallow can be a spring flowering perennial which means it can live for over two years provided it does not get damaged. Growing in the desert without irrigation it can be rather scrubby. But with a small amount of water and fertilizer it can be a beautiful woody shrub that can grow 2 to 3 feet tall and 3 feet wide.

Close close-up of the flower of globe mallow growing under stressed conditions.

If the globe mallow is looking kind of old and ratty you can cut it down to an inch of the soil and totally renew it or you can selectively cut down some of the older stems and renew it slowly.

If you want to keep it bushy from head to toe then take about one third of the oldest wood out now, next year take another third and the following year take another third. This will renew it over a three-year cycle and help keep the foliage and flowers from top to bottom.

You would do this pruning immediately after it finishes flowering.

Flower of the desert bird of Paradise
Mexican red bird of paradise usually gets a pruning to the ground every few years because of hard freezes. You have a couple of choices, much like your globe mallow. You can cut it to the ground or selectively remove one third of the oldest wood to the ground and in a three-year cycle.

You would do this pruning during the winter months or before new growth starts in the spring or after flowering is finished.

White Crust on Soil Surface Is Alkali or Salt

Q. I dug up some of our native soil and amended it with 50% planting mix. The next day after it dried, this white substance appeared on the surface. Is this salt or alkali? I know my soil will effervesce when you pour vinegar over it.
Salt deposit left on soil surface of the readers soil.

A. Salt and alkali are pretty much the same thing. Alkali should not be confused with alkaline. Alkaline refers to pH. Alkali refers to salts. Soils that create bubbles or effervesce when vinegar is applied to them have quite a bit of calcium carbonate, or lime, present.
Salt deposit left on drip emitters

The old-timers who grew things in desert soils would refer to "white alkali" and "black alkali". I think the word “alkali” has remained in our vocabulary, but not the difference between white and black types, and it is just as confusing now as it was then.

White alkali refers to the white salt accumulation on the top of soils. These white salts were usually sodium sulfate, sodium chloride, and magnesium sulfate.

Black alkali on the other hand left blackish spots on the soil surface usually composed of sodium carbonate and organic matter. It was understood that black alkali was more damaging to plants in soils than white alkali.
Salt deposit left on soil surface after an irrigation
In fact, when ranking these salts and their injurious effects on crops, sodium carbonate was considered the worst while sodium chloride (table salt) was somewhere in the middle and sodium sulfate the least injurious. When you had black alkali salts, many farmers would just give up and walk away from those soils.

The salts in your picture look like white alkali. I would have to guess it is a mixture of salts containing calcium, sodium and magnesium and carbonates, sulfates and chlorides. You wouldn't know unless you submitted the soil for a soil test.

When salts accumulate on the soil surface it is best to take a flat-nosed shovel and scrape off the top inch or so and dispose of it. Then begin activities that reduce the salt content.
Salt deposits left on block wall after water evaporates.
Most salts are removed with water and flushing. Level the soil surface as much as possible. Sprinkle the soil with water to push the remaining salts deeper into the soil. The idea is to push the salts deeper than the roots of your crops.

If the soil does not drain easily, there may be a high sodium problem. If this is the case, apply gypsum to the top of the soil and rake or rototill it in as deep as you can. Then begin your irrigations.

Gypsum is used to remove sodium from the soil and replace it with calcium. Sodium is a bad player in soils and prevents drainage. Substituting calcium for sodium improves drainage. Also, mixing compost in the soil will help in the removal of salts and make them less injurious to plants.

Learn more about salts, soil, water and irrigation of the desert

Mulch Recommendations for Fruit Trees

Q. Please provide me with recommendations for types of mulch for fruit trees.

A.  By definition, mulches lay on top of the soil surface and are not mixed with the soil. There are organic mulches such as wood chips and there are inorganic mulches such as rock and plastic. Most mulches shade the soil surface, help to conserve water and reduce weed problems.
Results in one year of fruit trees planted with and without surface wood mulch.
Mulches made from wood decompose over time as long as moisture is present. Decomposing wood mulch enriches the soil. Rock, plastic and bark mulches do not. Their purpose is primarily to add beauty and reduce weed problems.In the case of plastic inches that are exposed to sunlight, they are intended to warm the soil early in the spring for faster route and plant development.
Even if you have rock mulch, pull the rock mulch away from fruit trees
and apply 3 to 4 inches of wood mulch in the an area as large as possible
underneath the tree.

Any wood mulch, not bark mulch, works well around fruit trees. The best kind is a mixture of different types of wood and decomposes in 2 to 3 years. You don't want to use only bark mulch if your purpose is soil improvement.
Decaying wood does take nitrogen from the soil but this is not a problem as long as trees and shrubs are fertilized annually.

Wood and rock mulches help keep the soil cool, conserve water and reduce the work required for weeding. Only wood mulch enriches the soil. Rock mulch contributes to mineralization of the soil which means it contributes to the depletion of organic matter, it doesn't add to it.

Some of the best mulches for fruit trees are woodchips from a variety of trees but excluding trees with long thorns such as many of the mesquite trees, athel and salt cedar and palms. Palm trimmings decompose very slowly. Woodchips from trees with long thorns end up puncturing the bottom of a sneaker or vehicle tires.

Just about any wood source will pose no problems including eucalyptus, cedar, and even oleander. An excellent mulch is also the residue left behind from stump grinders.