Xtremehorticulture

Xtremehorticulture of the Desert

Compost’s Role in Landscapes

Leave a Comment / compost, landscaping, soil improvement /

            Using composts as soil amendments in vegetable gardens has been a no-brainer in the past. We knew it contributed to soil organic matter content. Most vegetables benefited from high levels of soil organic matter so we had no problem adding it to vegetable beds. How much organic matter is enough?             We were taught in school that productive agricultural soils generally contain from 2 to 5% organic matter; some required more than others depending on what was grown. In soils with adequate amounts of organic matter, additions were not needed. But that concept of “one size fits all” when it comes to organic amendments is being challenged and the challengers are winning. We have been educated that the ideal soil has 5% organic matter in it. But is that really enough for all plants?              We were told by scientists that landscape plants would not benefit from the addition of organic matter and that amending the soil at the time of planting was not necessary. Those of us working in arid and desert soils of the West and Southwest quietly challenged that generality and continued to add organic matter like composts to our landscape soils. We could see the benefit. What is a “healthy soil”?             Research during the past 20 years has challenged some of our previous thinking.  In many of our soils, regular additions of organic matter and its decomposition to humus is a necessary step in maintaining a vibrant and “healthy” soil and productive plants. Terms like soil health, soil food webs and soil ecology have become mainstream now. We have always been told that a healthy and vibrant soil contains lots of worms. But does their presence really indicate that’s all that’s needed?             Composting is the process used to convert organic matter into humus and employs many of the same microorganisms that perform the same function in soil. The concepts are very similar. The major difference is that composting provides a greater degree of control over organic matter breakdown than if it were left to an unregulated soil environment.             Fungal and bacterial colonies, earthworms and soil inhabiting insects feed on organic matter. Microbial slimes and gums are produced when organic matter is converted to humus. These byproducts of composting and organic matter breakdown help cement soil particles together. Most mushrooms are “saprophytic” which means they “feed” off of dead things, not living things. The presence of mushrooms in a soil is one sign that something in the soil is decomposing or breaking down. This decomposition is important for recycling, building organic matter and renewing life in the soil.             This altered soil structure is filled with voids that permit the entry, percolation and exchange of water and gases. Improved soil structure or “tilth” is a major benefit from the breakdown of organic matter or the addition of compost.             Byproducts from the decomposition of organic matter and the feeding by soil organisms improve the soil further by altering the soil chemistry and providing organic compounds that stabilize nutrients and assist in chemical reactions necessary for plant survival. Some companies capitalize on the idea that compost adds “life” to soils like this ad campaign by Viragrow, Inc.             When organic matter declines, humus levels decline as well. “Soil health” declines and with it landscape plants suffer. The rate of decline depends on many things including the type of soil, climate, management, nature of the organic matter and other factors. Renewing soil organic matter with compost             If deteriorating soil health is not caught soon enough, large volumes of quality soil organic amendments, such as compost, are needed in a process called soil remediation to bring the soil “back from the dead”. Compost additions to soil improve it by adding aeration, improving water retention while also improving drainage at the same time, and rebuilding life in the soil.             With these additions we see the improvement in soil health reflected in our landscape plants; more vigorous and healthier growth, more tolerance to environmental extremes, small amounts of fertilizer achieve greater results, less water is needed and plants experience fewer pest problems. Managing soil health             As managers of plants we must also manage our soils. The percentage of organic matter in a soil, and thus its humus content, is terribly important. Most soil test results provide the soil organic matter content.             But, is knowing the organic content of our soils enough? To know how much and when to put it back, it is best to know how fast it disappears. Knowing the rate of organic matter decomposition is a powerful management and budgeting tool. With this type of knowledge we understand how often and how much compost to budget for to maintain soil and plant health.              Similar to the composting process, the most powerful external factors controlling the conversion of soil organic matter into humus and its eventual disappearance are moisture and temperature. If soils are kept moist, accumulated soil temperature is the driving force in the loss of soil organic matter. At higher temperatures, soils decompose organic matter faster than in cooler soils. Hot, moist soils need additions of organic matter more often than cool, moist soils. Compost used as a fertilizer             Organic matter releases the nutrients it contains for plant uptake only when it decomposes. By decomposing, plants benefit as well as the macro and microorganisms that live in the soil. Decomposing organic matter also helps support beneficial soil bacteria, fungi and earthworm populations. The decomposition process of organic matter contributes to the breakdown of soil minerals which in turn further release the native plant nutrients they contain. There are enough nutrients in compost that it can act like a fertilizer. Composts very in their nutrient content so it is difficult to claim them as a fertilizer. Some contain more nutrients than others. It depends on the components used in making the compost.             In ways not well understood yet by scientists, the addition

Compost’s Role in Landscapes Read More »

Smelly Potting Soil in Oven Disputed

Leave a Comment / fungus gnat, Potting soil /

Q. Earlier in March you talked about fungus gnat problems in potting soils. You recommended baking the potting soil in the oven. But I’ve heard this stinks up the whole house! I might try it in a gas grill outside, but not inside. Potting soils are lightweight soil mixes that usually contain peat moss and perlite as part of the soil component to minimize weight and maximize porosity. A. I used to think the same thing about baking potting soil in the oven. The common response by gardeners is not to do it for that very reason; it stinks up everything! But we tested it recently and it worked just fine as long as the temperature of the oven was below 180F. I think the smell problem occurs when the temperature of the oven is set too high.             I prefer “solarizing” potting soil in sealed, clear plastic bags for a couple of days to kill fungus gnats. The temperature of the soil does not have to be as high as it does to kill everything in the soil, a.k.a soil sterilization. If the temperature of the potting soil reaches 140 – 150 F for 30 minutes, through and through, it’s enough to kill insects.             To sterilize potting soil, completely ridding it of all insects as well as harmful microorganisms, the temperature must reach 180° F for 30 minutes throughout the soil. Attaining this temperature by solarizing is doable if there is plenty of sunshine, the soil is moistened, placed in a clear plastic bag and left in the sun long enough.             To be on the safe side, I solarize the soil with one side facing the sun the first day. Then I turn the bag over and solarize the other side on the second day. I check the temperature with a temperature probe through the plastic bag to make sure the temperature was high enough.             I would not recommend putting potting soil in a gas grill and firing the temperature up high. Low temperatures in gas grills are harder to control. Excessively high temperatures will “burn up” the organics in the potting soil. That’s when it gets stinky.             This cool, overcast spring presented some real problems. Cool temperatures and overcast skies did not allow solarization to reach the temperatures needed inside the bag. I enlisted the aid of a brave volunteer with an oven that had accurate temperature controls. She placed a half bag of potting soil on cookie sheets and into a domestic oven.             The lowest thermostat setting for the oven was 160° F. The temperature inside the oven stayed around this temperature for 30 minutes and the soil allowed to cool inside of it. Voilà. No fungus gnats and no off smell.

Smelly Potting Soil in Oven Disputed Read More »

Western Redbud Better Choice but Harder to Find

Leave a Comment / Eastern Redbud, redbud, Western redbud /

Q. I can never find Cercis occidentalis, Western Redbud, at local nurseries. Any idea where I can locate it? Western Redbud after flowering A. Thanks for giving me the Latin name for this tree instead of just Western Redbud because that eliminates all confusion about which tree you might mean. If you like a reddish pink splash of spring color in about March on a small tree, you will like this tree when it flowers. The Redbud most people buy is an Eastern Redbud but it is not as suitable for our climate and soils as its Western cousin or even the Mexican Redbud. Mexican Redbud             Eastern Redbud is the tree that people call “Redbud” from the East Coast to the West Coast. Western Redbud is unique. It has never gained the same popularity. This is the same tree that polkadots the Grand Canyon with rosy plum color every spring. Eastern Redbud has some soil issues in the West and not as adaptable as Western Redbud             But Western Redbud has significant advantages over the Eastern Redbud in our climate and soils. First off, Western Redbud handles the chemistry of our soils much better than Eastern Redbud. That’s because it evolved here. It is native to southern Nevada and specifically the Charleston Mountain Range of Southern Nevada. It is small, seldom reaching heights over 20 feet tall, the perfect size for a single-story home and smaller patio-sized landscapes.             However, it will not tolerate having “wet feet”. In other words, don’t water it too often. Give it a lot of water when you do water it and then hold off and let the soil dry before you water it again. It is native to the foothills of dry Southwestern areas including Utah, Arizona and California. It’s one of our desert natives.             I also think the Western Redbud is a prettier tree when it’s flowering than the plain old Redbud.             Try our State Forest Nursery located in the north part of the Las Vegas Valley. They specialize in local native plants. 702-486-5411.

Western Redbud Better Choice but Harder to Find Read More »

When to Fertilize Lawns

Leave a Comment / fertilizer, lawn, turfgrass /

Q. When is it time to start fertilizing lawns again? Lawns can be beautiful but they need regular feeding. The light green color of this lawn is an indicator it needs an application of nitrogen fertilizer. That nitrogen fertilizer will turn that light green lawn into a dark green lawn in a matter of a couple days. A. It depends on whether the lawn is fescue, only Bermudagrass or Bermudagrass overseeded in Fall to maintain green winter color. Fescue lawns and overseeded Bermudagrass lawns are fertilized the same during winter months. Ammonium sulfate fertilizer contains only nitrogen that the plants need when their color is not dark enough. The sulfur in the sulfate is also important for plants but in the case of light green color, all that’s lacking is nitrogen.3 to 5 pounds of this fertilizer spread evenly over 1000 ft.² of lawn and watered in will turn the color a deep green instead of light green.             Fescue and overseeded Bermudagrass should have been fertilized last Thanksgiving to maintain dark green color through winter. If this fertilizer application was missed and temperatures get cold, the lawn can turn brown when it gets very cold or just light green if it does not.             The next fertilizer application to fescue lawns would be when air temperatures enter the 60s. Fertilize Bermudagrass that was not overseeded when temperatures enter the 80s. Once or twice a year add a better quality fertilizer to the lawn like this one. It has a little bit of phosphorus, the middle number. Lawns don’t need a lot of phosphorus because we don’t grow them for their flowers and fruit. I would like to see the potassium, the last number, higher than this but this is a good lawn fertilizer.             Established lawns require fertilizers containing high nitrogen, and occasionally an application of iron, for dark green color. However, they will perform best if this fertilizer contains also low levels of phosphorus and moderate to high levels of potassium.             For this reason, fertilizers similar to 21-7-14 or 10-5-10 are frequently recommended for lawns. Some people use only high nitrogen fertilizer such as 21-0-0 and omit phosphorus and potassium.             I think this is a mistake and a good lawn fertilizer should be applied at least once during the growing season. Instead, experiment and try fertilizing with only half the amount of fertilizer recommended on the bag. This is all that is usually needed if you are not bagging lawn clippings but mulching them back into the lawn using the mower.

When to Fertilize Lawns Read More »

Digging Holes to Plant Fruit Trees

Leave a Comment / planting fruit trees /

Q. How big do you dig your holes for fruit trees? This was a hole dug for a bare root fruit tree about 1 inch in diameter. The whole is about 3 feet wide and not much deeper than needed for the roots. The soil taken from the whole was mixed about 50-50 with compost and used for planting around the tree roots. Water was added to the hole at the same time the soil was put around the roots. The trees were staked to prevent the roots from moving. A. I generally like to dig holes for fruit trees in five or 15 gallon containers about 3 feet wide and just deep enough for the root ball from the container. But the size of the hole depends on the condition of the soil for planting.             If the soil is a very poor soil, I make the hole wider but not any deeper unless the soil does not drain water in several hours after filling it. These situations are rare. I don’t like deep holes for plants because of soil settling issues and causing plant problems later. Finished planting fruit trees at the Ahern Orchard in Las Vegas. Berms or doughnuts were created around each of the trees so they could be watered as soon as they were planted. They were watered three or four times immediately after planting to remove air pockets and sell the soil around the roots.             Our desert soils can be unusually hard but in some parts of the Las Vegas Valley there are “caliche layers” that are as hard as cement and require a jackhammer to break through them. If you or your neighbors have a pool and this layer was not found when it was put in, then you don’t have a caliche problem.             The soil removed from the hole should be mixed with compost before planting. Use a mixture one part compost to one part soil. Another option is to use an “imported” soil mix for planting.             If the compost used in the soil mix is “rich”, no fertilizer is needed for the first year after planting. If the compost is not rich, then add a starter fertilizer high in phosphorus to the soil mixture before planting. Rich compost is usually made with some sort of animal manure.             Plant the tree the same depth as it was in the container making sure that the roots are covered with no more than 1 inch of soil.             As this soil mixture is added to the hole, add water to the hole at the same time you add the soil/compost/fertilizer mixture. This slurry of water and soil mixture removes air pockets and results in a tree held solidly in the soil after planting. Small trees will not require staking if done right.             Surround the plants with a donut and fill this donut with water several times during the next week before you turn it over to the irrigation system.

Digging Holes to Plant Fruit Trees Read More »

Compost and Wood Chips Together Not Needed?

Leave a Comment / compost, Woodchip mulch /

Q. If I use compost around plants and trees, do I still place wood mulch over the compost? Is it needed, or redundant? When the using compost as a fertilizer and soil amendment the compost should be a rich compost full of nutrients. Compost can be a soil amendment, making the soil “fluffier”, but if it’s rich as well then it will add fertilizer or nutrients to the soil. A. Regarding fruit trees, wood chips applied 3 to 4 inches deep on the surface of desert soils is always a good idea. It is also a good idea for many traditional landscape plants, like photinia, mock orange and roses, to have wood mulch or wood chips on top of the soil rather than rock. All these plants are healthiest if rich compost is applied as a fertilizer in the spring. In this demonstration at the University Orchard, compost was added to the soil, the backfill, surrounding the tree roots. The trees were planted the bare root. The woodchip mulch was added to the soil surface in combination with the compost added to the soil. But if compost is added to the top of the soil every year, the woodchip mulch is not necessary for soil improvement. It does a great job however of controlling weeds and conserving moisture around the roots.             Under some circumstances, some plants get by without wood chip mulch or compost applied as fertilizer. Trees and shrubs that are truly “desert adapted”, or suitable for desert landscapes, can get by without wood chip mulch or compost. All they need is a little bit of fertilizer in early spring every year. These are plants such as mesquite, acacia, Texas ranger and palo verde.             In desert landscapes, with the surface of the soil covered with small rocks suitable for walking, your only alternative may be feeding plants with fertilizers applied from bags, a.k.a. mineral fertilizers. These can be applied directly to the surface of the soil near drip emitters and watered in.             Would desert adapted plants be healthier with compost and wood chip mulch? Definitely. But they can tolerate our desert soils without compost and wood chips better than traditional landscape plants.

Compost and Wood Chips Together Not Needed? Read More »

Oak Trees in Illinois Should Stay in Illinois

Leave a Comment / Oak trees, propagating from acorns /

Q. I picked up 10 acorns that were laying on the ground in Illinois. If I were to plant these, would the acorns germinate and produce an oak tree? What are the chances it will survive in the desert climate? A. There are about twenty different kinds of oaks native to Illinois. Two of the more common oaks are northern Red Oak and White Oak. Both of these oaks are not native to the Southwest and you will have trouble growing them here as they get older. A row of live oaks, probably ‘Heritage’ southern Live Oak as a street tree planting in Las Vegas, Nevada.But there is a native oak, gamble Oak, which could be planted and used here. A better choice than importing oaks from northern states.            We have oaks native to the Southwest and you are better off planting those than bringing some from Illinois. But you could have fun with them for a while.             If you found acorns on the ground, then most likely the seed inside the acorn is mature. However, the seed may not be “alive”. Put them in a bowl of water and use the ones that sink and discard the ones that float.            Plant them on the north or east side of a building. Mix compost 50/50 with native soil in an area 3 feet wide and 2 feet deep. Plant the acorns on their side in this amended soil, about 1 inch deep, in mid-November. If the winter is cold enough, the seed inside the acorn will grow when it warms in the spring.            If you missed this November window, put them in a plastic bag with a moist sponge in the refrigerator. Take them out after two months and then plant them in the same way.            Oaks have a very strong taproot. If you move them from this spot, do it when they are very small. They do not move easily to new locations once they establish a taproot. Otherwise, remove extra seedlings and grow the strongest ones the same way you would grow any other landscape tree.

Oak Trees in Illinois Should Stay in Illinois Read More »

Wood Chips and Roses

Leave a Comment / March, roses /

Q. I want to put wood chips around my roses to keep the weeds from returning. Is this a good mulch for the roses? Or might it attract ants or insects I don’t want?  I have not noticed wood mulch at any other homes nearby. Roses love three things when growing in Mohave Desert soils; compost applied to the soil surface, woodchip mulch applied on top of it and exposure to lots of sunlight but avoiding the heat and direct sunlight of the late afternoon. A. Roses, and nearly all plants in the Rose family such as most of our fruit trees, thrive in our desert soils when woodchips are used around them. One of their biggest benefits, besides weed control, is soil improvement. And our desert soils need massive amounts of help in this area. When growing roses in the desert give them plenty of room so that they have air circulation between the plants and through them. This helps to prevent diseases like powdery mildew.             Mulch is applied to the soil surface around plants to assist in controlling weeds, improvement of the soil, reduce the frequency of watering, keep the roots cooler and to improve good “animal life” in the soil. The best mulch is made from shredding and chipping local landscape trees.             The greater diversity in types of trees used to make woodchips, the better the woodchips are for the soil and plants. Personally, I don’t like wood chips made from palms and trees with large thorns like many mesquite trees.             Mulch is made from many sources. Anything applied to the surface of the soil could be referred to as mulch. This includes rock, gravel, sand, plastic, newspaper, old carpet but the best mulch for soil improvement comes from a wide variety of woodchips.             Weeds are suppressed with a 3 to 4-inch layer of woodchips but a few tough weeds will poke through such as Bermudagrass, palm seedlings, nutgrass and well established perennial weeds.

Wood Chips and Roses Read More »

Flowers Produced Late on Pomegranate

1 Comment / Pomegranate flowering /

Q. I have pomegranates a few years old. Every year they don’t produce flowers until late in the season when everyone is harvesting fruit. I am considering every option including removal of the plants. Pomegranate flowers are beautiful in their own right. But some varieties of pomegranate are more “precocious” than others meaning they will produce fruit when they are younger. Expect pomegranate to produce fruit anywhere from their first year in the ground to their third or fourth. Pruning them inappropriately or having some low winter temperature damage can delay the production of fruit. A. Pomegranates produce flowers on new growth in late spring when many other fruit trees have already flowered. Pomegranates are slow starters in the spring but once they start flowering they continue to flower through most of the summer and year after year. The largest fruit, percentage-wise, usually comes from new growth originating on larger diameter, older wood.             The balance between root and top growth affects flowering. The tree adjusts growth above ground to match growth and the size of its roots below ground. This “root to shoot ratio” affects flowering and fruiting. Pomegranates on display at the local open air market in Northern Tajikistan. Like the kiwi and pineapple, they were imported from warmer climates where the plant can survive and produce fruit the next year. Notice only the largest and best looking pomegranates are on display.             If the top of the plant is cut back severely or damaged and the roots stay the same size, the top part of the plant grows rapidly and won’t produce flowers until the growth above ground again matches growth below ground. This ideal “root to shoot ratio” varies among plants, between species of plants, and even among varieties. Many varieties of pomegranate are well-known for producing flowers and fruit very close to each other on new growth. I seldom see any advantage in fruit size by thinning the fruit unless they are growing directly across from each other. If the fruit is separated by 1/2 inch or more I will not thin the fruit.             I believe you are seeing a flush of rapid growth in the spring either because of loss of growth above ground. The top produces a lot of new growth at the expense of flowering. Flowering begins when that ideal “root to shoot ratio” is achieved again.             If you are pruning this pomegranate, do not prune it severely. If you are losing the size of the top because of freezing damage or mechanical injury, try to protect it. If this tree can maintain its root to shoot ratio from one year to the next, this problem will stop. Pomegranate growing and producing no flowers. If top growth has been lost from freezing or pruning, the roots may be large enough to push new top growth at the expense of flowering. Also, fertilizing these plans with lots of nitrogen early in the spring can cause excessive growth with very little flower production             There is a difference in tolerance to freezing temperatures among varieties pomegranate. Some are more cold hardy than others. If winter cold damage occurs, it is possible your pomegranate is a different variety from your neighbors. The pomegranate variety ‘Wonderful’ has been a solid performer in our climate.             Some pomegranates are “precocious” meaning they flower and produce fruit at a young age but all of them should be flowering by the second or third year after planting. Some flower the first year after planting. Some flower possibly as late as the third year after planting.             If you can’t solve this problem through careful pruning, replace it with a fruit tree more cold hardy or suffers less from cold winter temperature damage.

Flowers Produced Late on Pomegranate Read More »

Cane Prune Thompson Seedless Grapes

Leave a Comment / Grape vine cane, Grapevine /

Q. Two years ago I planted Thompson Seedless grapes. The first two years there were no grapes and I did expect any fruit. This year there are leaves and no fruit. They were pruned the same way as my Red seedless grapes which were very prolific. Is there something special that I must do to make the vine produce? When pruning the past years growth on grape, canes (long spurs) are sometimes left instead a very short spurs because the majority of fruiting may not occur on the first eight buds on these varieties. A. If the vine is healthy, it is all in the pruning. Thompson seedless may need to be cane pruned, not spur pruned like many other grapes. When you cut it back, leave about 8-ten inches of last year’s growth and don’t prune it back so hard. Canes are nothing more than long spurs that have at least 10 buds. When pruning spurs, only one bud, possibly two, are left behind.             Thompson Seedless, Black Monukka and Crimson Seedless should be cane pruned.

Cane Prune Thompson Seedless Grapes Read More »