Viragrow Delivers! : How Much "Plant Tonic" Should I Apply to My Bushes...

Viragrow Delivers! : How Much "Plant Tonic" Should I Apply to My Bushes...: Q. We fertilize our bushes early spring and mid fall with a "plant tonic", a 5-10-5 liquid.  Hopefully this isn't too much n...

Viragrow Delivers! : Which Fertilizers Should I Use for My Fruit Trees?...

Viragrow Delivers! : Which Fertilizers Should I Use for My Fruit Trees?...: There are basically three types of fertilizers that you should pick from;  fertilizers with high phosphorus,  fertilizers with high ni...

Viragrow Delivers!

Pruning Roots of Plants Gives Added Control

Did you know that the roots of plants can be pruned? This is called root pruning and dramatically alters the root to shoot ratio of plants.

Root pruning, what is it?
As the name suggests, root pruning is the cutting of roots. It is done for different reasons than pruning the tops of plants. We have total access to the tops of plants. Axis to the roots of plants is much more limited. Roots grow differently from stems. Roots do not have buds. You can virtually cut anywhere on a root and it will "sucker" unlike many of the stems of trees and shrubs.

Why root prune?
The most common reasons for root pruning include controlling the size of the plant, slowing the growth of plants, initiate flowering, keep the roots closer to the trunk, keep the roots out of problem areas or creating problems.

This is a root pruning machine used in nursery practices for undercutting trees growing in the field under production.This machine is driven so that the young trees are undamaged as they pass under and between the tracks. The U-shaped blade is pulled behind this machine and undercuts the roots...root pruning... to make a bare root fruit tree that will transplant to the field with fewer losses. Photo taken by me at Dave Wilson Nursery www.davewilson.com 

Root pruning is commonly done in the nursery operations where trees and shrubs are grown to be transported for planting in a new location. Root pruning is common in bonsai to reduce the growth of plants and keep them small. Root pruning is done in some greenhouse operations for similar reasons to nursery operations.

If root pruning is not done and the top of the plant dies or is severely pruned back, then the top regrows again very quickly to its original size. Once it reaches this size, growth slows again. This is the plants way of reestablishing what we have called the root to shoot ratio of the plant. The plant "recognizes" the difference in size between the top growth and undisturbed root size. The plant directs its growth, the flow of carbohydrates and hormones, to the top of the plant at the expense of growth in the roots.

How can I use Root to shoot ratios?
If a plant is growing too rapidly and you want to slow it down, root prune it. Take a sharp shovel and sever the roots by pushing it through the soil and through the roots as deep as possible.

Do you want to keep the roots of plants from entering the septic tank or other problem areas? Root prune between the plant and the problem area. Root prune every 2 to 3 years.

Some diseases are transmitted from plant to plant when the roots fused together and what are called "root grafts". This commonly occurred in American elm with the transmission of Dutch elm disease. Root pruning can isolate plants from trees that are carrying the disease. If an Apple or Pear tree dies from fire blight, root prune the area around the dead tree to prevent the transmission of the disease through root grafts.

When Retrofitting trees and shrubs from a lawn area to drip irrigation, consider root pruning these trees and shrubs to generate roots closer to the trunk were the emitters are placed.

Having trouble with the tree flowering? Try root pruning to create a new root to shoot ratio that might slow the top growth and induce flowering.

How Many Days between Waterings in the Winter?

Q. I am not sure how long some of my trees can go without water during the winter. I have a mature Pepper, Mesquite and some palms that I have not watered for 10 days because of the cold temperatures. Is 10 days between watering okay?

A. 10 days between waterings should be no problem for trees and large shrubs provided they were given a deep watering prior to this. Deep rooted plants, like most trees and large shrubs, can go without water for a longer period of time than smaller plants. Deep watering means flooding the soil with water to a depth of 2 to 3 feet. If drip is used then making sure enough volume of water is applied to soak to a depth of 2 to 3 feet.

Applying water with drip emitters this close to the trunk is okay for the first couple of years. As this tree gets larger, more emitters will be placed underneath the canopy of this tree and further from the trunk. About half the area under the canopy should receive water. Apply enough water in a single application to wet the soil to a depth of 2 to 3 feet.

Many landscapes have small plants and big plants on the same circuit or valve. This means the small plants cannot be watered separately from the larger plants. The small plants require water more often. This forces the larger plants to be watered frequently even when they don’t require it. 

This twisted Acacia would be considered a desert tree. Putting a tree like this on an irrigation circuitFor desert plants gives greater flexibility when applying water. Applying water more often causes it to grow faster, larger and more dense. Applying water less often keeps it smaller, growing more slowly with fewer leaves.

Secondly, plants that do not originally grow in desert climates must be watered more often than plants which do. The mesquite and California pepper are both desert-type trees where water can be withheld for long periods of time with no problems. Palms are more shallow rooted and require water more often. But ten days is not too long for any of these plants during the winter.

In an ideal world the deeper rooted plants would be on a separate irrigation circuit or valve from shallow rooted plants. Deep rooted desert plants like acacia, palo verde and mesquite would be on a separate circuit from the other non desert deep rooted trees and shrubs. This gives you alot of flexibility in watering. 

Palo Verde is another desert tree whose growth can be managed by applying more or less water. Putting desert trees and shrubs on their own separate irrigation circuit gives you this type of flexibility.

The deep rooted plants would include trees and shrubs and deep-rooted woody perennials that die back each year such as Bougainvillea. The shallow rooted plants would include annuals and flowering perennials that die back each year like Lantana. Lawns should be on a separate circuit but could be tied into vegetables as long as the water could be turned off to vegetables between seasonal plantings. 

When to Harvest Oranges?

Q. My oranges are turning orange. How long should I wait before I harvest them.

Yes, oranges and other tender citrus will grow in Las Vegas but not without some careful considerations.

A. Oranges do not necessarily turn orange before they are ready. Orange color develops due to climate. In the tropics oranges remain green or green/yellow even when  they are ready to eat.

Fully ripe oranges in the Philippines. They do not turn orange because of the warm climate. The fruit above it is rambutan.

Orange color is induced in oranges that don’t develop good color using ethylene gas in closed rooms where orange color is important for marketing and sales. The best way is to pick one and try it. If sufficiently sweet, harvest the others or wait and harvest when needed during cold months but leaving them on the tree too long can reduce the number of flowers in the next cycle of fruit production. When they are ripe start removing them. Cut the stem close to the fruit, don't pull the fruit from the tree, for better storage life.

Handheld refractometer used for measuring total dissolved solids (sugar content) from the juice of fruits and vegetables.

A sophisticated method is to purchase a small handheld device called a refractometer and measure the sugar content. Maturity in fruit is usually a measure of the sugar content which the refractometer will read for you.

How Often to Water Fruit Trees in the Winter?

Q. Do you have any guidelines for watering fruit trees in the winter?  I cant find anything specific to winter watering on your web page. I have apricot, nectarine, apple, fig, pear, plum, cherry, peach, orange - planted spring 2015.  I am not expecting the apple or cherry to make any fruit yet, They are just ornamental. Pomegranite, jujube, lime, grapefruit I planted 3 years ago. Will deep watering once a month suffice for December - February?

Fruit tree with irrigation basin surrounding the trunk. Irrigation bubbler at the top right of the basin that allows 2 gallons of water to flow from it every minute. The basin must be level so that water flows evenly across its surface.Surrounding the trunk is rabbit protection.

A. Once a month is not even often enough for trees established for years in our warm winter desert climate. Once they have been established, trees established for one season might be closer to every two weeks during the winter. If the soil is very sandy, then once a week. Fruit trees surrounded by dry soils should be watered more often than trees in wet soils. Wet soils in the desert might happen if fruit trees are grown close to a lawn area, a wall that has irrigation applied on the other side of it, intercropped between the trees with other plants like vegetables or herbs.

Irrigation basins surrounding newly planted fruit trees that have been staked and mulched with wood chips. The screening around the trees is for rabbit protection which also keeps the wood mulch away from the trunk. If drip emitters were used, two emitters might be enough for the first 2 to 3 years. When they have reached 2 to 3 years old than increase the number of emitters to at least four.

Generally speaking, if there is a surface mulch of at least three inches, add one to two days in the summer and up to one week in the winter. Sandy soils require more frequent watering with smaller amounts applied. Desert soils should contain 50% compost at the time of planting. Fruit trees perform much better with wood mulches applied to the surface and require less frequent watering.

General Watering Schedule for Fruit Trees
Let me run down a general schedule of watering fruit trees that is ignoring rainfall since we only receive an average of 4 inches (10cm) or rain each year.

Newly planted in spring or fall during cool weather....2-3 days; winter 1 to 2 weeks depending on soil and mulch covering. After growing for one season then assume the trees are established.

Fruit trees established at least one season with fruit or nuts on the tree... Summer every three to four days depending on soil and mulch. Spring and fall, weekly. Winter every two weeks. Fruit trees that have been harvested can be watered less often.

How Should I Care for My Fairy Duster Plant?

Q. I'd appreciate some pointers on how to arce for fairy duster plant So it becomes healthier and a better looking shrub. Very little has been done because the bees are usually on it.

Fairy duster and honeybees

A. This plant is native to North and Central America growing in warm desert climates and soils. This tells you a little bit about how to manage it. This should tell you to not water every day. Plants like this are usually very susceptible to root rot so make sure the soil has been amended with compost before planting so that it improves drainage.

Fairy duster in the backyard of reader

It will tolerate desert soils as well as infrequent watering. At planting time I would amend the soil with about 25 to 50% compost and make the whole about three times wider than its container. I realize yours is already in the ground so watering and fertilizer applications are important to mention.

Do not water this plant too often. That will be the biggest mistake people make. Fertilize it lightly once in the very early spring around late January or February with a rose type fertilizer. The plant can get 3 feet wide and 3 feet tall in soils that have been amended with compost.

As long as it's in a sunny location you should see a profusion of blooms in the spring and summer months that attract bees, hummingbirds and night flying moths. Quail like to feed on seed from the seed pods. Rabbits like to browse on new growth.

You can clean up the plant in the early spring by removing dead leaves and stems. You will encourage more blooms if the plant is in a sunny location and flowers are removed before they begin to form seedpods.

Every Potting Soil Contains Fungus Gnats

Q. It seems no matter what brand, no matter where I buy my potting soil I have to bake it before I can use it.  If I don't, I get hundreds of tiny fly that hatch and swarm.  I put out water to catch and drown them. I spray insect oil on top of the soil several times a day. I'm so afraid I'll kill the plants.

A. Yes, fungus gnats are a big problem in potting soils and they can create damage to plant roots. They feed off of both decaying plant parts and soft, succulent living roots as well. Potting soil does not smell very good if you have to put it in your oven at 150° for 15 minutes to kill these nuisance critters.

The larvae can cause damage to new, tender roots of plants. If they are extremely happy in their environment they can multiply very rapidly and cause some severe damage. Besides that, they are pesky and a nuisance inside the house.

This is Garden Gourmet potting soil and I have never seen fungus gnats in this product. However, bagged potting soil that is not been heat treated will carry fungus gnats. This product sells for $5 for one cubic foot.

If potting soil is sterilized with a heat treatment by the manufacturer it should kill all of the fungus gnats. If the soil is introduced into an environment where there are fungus gnats present then it will get reinfested again.

Here is what the University of California says about them

They can be controlled with some organic pest control products; nematodes that go after these larvae and a bacterium which does the same thing. You should be able to find some of these products in your local nursery or garden center. I have never used them so I am reporting only what has been reported on the internet using these methods for fungus gnat control. However, cooking them does work.

Where to get beneficial nematodes
Where to get beneficial bacteria  It says for mosquito control but it is the same product used for fungus gnats and will be included on the label.

Another method is to sterilize this potting soil yourself by placing it moistened into a clear plastic bag in full sunlight and let it bake. Temperatures need to get up to about 160 F for at least 30 minutes for good control. Keep in mind that if you introduce this back in the environment where a fungus gnats are present and they will reinfest this sterilized potting soil. Another option is to apply pyrethrin to the soil and water it in.

When and How to Prune Lantana and Oleander?

Q. How and when should we prune our lantana and oleanders?

This is a Lantana I saw pruned by a local company. Leaving this much wood remaining will make it very "twiggy" at the base. You can actually prune it much closer to the ground in this.

You can see from this close-up that I took last February that suckering can occur much lower on the stems of Lantana. Don't be afraid to cut it close to the ground. Leave about 1 inch for suckering.

A. Both of these plants are pruned during the winter months since they both produce flowers on new growth during the summer months.

After pruning, apply a high nitrogen and high phosphorus fertilizer to push new leaf and stem growth and dark green color. The phosphorus will help to promote flowering. Flowering will not occur until the top growth is large enough and comes into balance with the existing root size. This is sometimes referred to as the root to shoot ratio.

 I would delay pruning them until late winter (late January) unless you don’t mind looking at "dead" space (the space is not occupied by anything). For lantana it normally freezes during winter months and you have a choice whether to leave the dead top of the plant in place or cut it down to the ground, leaving one inch of stems remaining to support the new growth beginning in February.

You can prune oleander close to the ground, just like Lantana. Cut it back to within 2 to 3 inches of the soil surface. This is the time of year to do it up until about the end of January when it begins to push new growth all by itself.

            Because the roots are fully grown, alive and healthy you will see very rapid growth in the spring. Fertilize the pruned plant in late January or early February to encourage new growth and flowers. Use a fertilizer that supports flowering plants such as a rose fertilizer blend or other fertilizer for flowering plants.

You can see from this picture that new growth is beginning to sucker from the base just like Lantana. Apply a fertilizer near the base of the plant close to a source of water. Use the same fertilizer as the Lantana. A rose type fertilizer is fine.

Oleander will regrow very quickly when cut back close to the ground, fertilized and watered. This was one month after pruning. Nitrogen in the fertilizer will push leaf and stem growth along with dark green color. Phosphorus in the fertilizer will push flower growth and flower size.

            Oleander is pruned at the same time of year as lantana because it also blooms on new growth, not older growth. You can chose to remove 1/3 of the plant by cutting these largest stems to the ground for renewed growth at the base or you can cut the entire plant to the ground and let it regrow. Your choice. Either way you will see luxurious growth and lots of flowers next year. Again use a fertilizer that supports flower growth and apply it early in the spring.

This is an example of a fertilizer that will push leaf and stem growth and dark green color. You would apply this immediately after pruning and water it in. A 10 pound bag sells locally for $7.95

This is an example of a fertilizer that it increases the number of flowers and their size. It should be applied about 4 to 6 weeks later. A 10 pound bag also sells for $7.95 .