View the May 2024 Hort Tip articles below.

---

Reverted Plants

Casey Hentges, Associate Extension Specialist

Bailey Singleton, Extension Assistant

 

When installing plants in the landscape, we anticipate them to grow each year. However, that is not always the case. Sometimes this can come in a different way than anticipated. It is always important to know how plants grow in the landscape. 

 

New growth on boxwoods typically is a brighter green color and is softer vegetation as opposed to the woodier tissue below. Often when new growth emerges it may not be the same green color because it is just beginning to photosynthesis and create chlorophyll which is the green pigment in plants. So often when this is seen, it is a sign the plant is healthy and producing new growth that will darken as it continues through the season.  

 

Unfortunately, new green vegetation isn’t always a good thing. On a variegated abelia, it may also produce some branches that do not have any variegation and are just straight green. Now this isn’t too uncommon with variegated plants and may depend on how the plant was developed. Variegated plants are often developed as a result of a natural mutation or can be produced through different breeding practices, making certain variegated plants more stable than others. A plant may revert to its non-variegated form due to stress or not receiving enough sunlight. By producing more green leaves filled with chlorophyll a plant can produce more energy through photosynthesis.  

 

The thing to be aware of is if a plant has reverted back to the traditional color, it should be pruned out of the plant. If allowed to continue to grow, it will only grow stronger and over time it will lose the characteristics of the originally installed plant. It typically isn’t too alarming or too much work, it is just a matter of clipping out a few branches.  

 

Now, sometimes new growth can be a little trickier. Such as with a Canada Red Chokecherry (Prunus virginiana ‘Canada Red’). This cultivar creates a lovely display of burgundy foliage, however, in the spring, it might be alarming to see the new growth is green and one might think it is reverting back to its green form. This is when it is important to know the plant. The cultivar ‘Canada Red’ produces new green growth in the spring. In fact, this contrast between the new green growth and the red leaves on the older branches is part of its appeal. However, if someone was not aware of the cultivar they might accidentally cut the new growth off thinking they were preventing it from reverting. Instead, this one should be left alone.  

 

Another example is Orange Rocket Barberry (Berberis thunbergii 'Orange Rocket'). In this case it is the reverse happening. The new growth is bright red, which is what it is supposed to be, but down in the center of the plant where it gets more shade, the foliage may be less colorful and instead more green. Again, it is simply a matter of the plant trying to compensate for the lack of light and the need to photosynthesize more. There are a number of plants such as coleus and heuchera that often have a range of foliage colors due to the sun or shade exposure.  

 

One more example of reverting plants is on grafted plants. On many Japanese maples the original graft is at the base of the trunk of the tree. This is where they grafted a cultivar such as Dragon Tears that has phenomenal lacy, dark colored leaves onto a plant that gives it a hardier rootstock.  The graft location is a swollen area towards the base the trunk and there is a change in the bark. The vegetation above the graft still has all the desirable characteristics of the Dragon Tears as it should. However, if there are several sprouts that have formed from below the graft, this is vegetation sprouting from the rootstock. So, in essence you have two plants competing for the same resources. If left alone, the often less desirable vegetation from the rootstock would ultimately outcompete the desired Dragon Tears. Therefore, to ensure we keep our intended plant, we again want to make sure to remove any vegetation that originates from below the rootstock.  

 

While we always anticipate new growth on our plants, knowing their habits will allow us to better maintain them for seasons to come.  

 

For more information: New Growth on Plants Video

 

Managing Storm-Damaged Trees

David Hillock

 

Severe weather is a fact of life in Oklahoma, with storm-related damage a major impediment to maintaining healthy trees. Ice and wind have the power to snap limbs and large branches leaving landscapes littered with storm-damaged trees. While we cannot control the weather, we can implement measures to manage storm-damaged trees and minimize risk to people and personal property.  

 

The decision to save or remove a storm-damaged tree is usually a subjective one, with the choice relying more on opinion than fact. Emotions often are the overriding factor in the decision process, especially when the damaged tree is a very large, old, or ‘heirloom’ tree. Here are a few points to keep in mind when deciding whether to rehabilitate or remove your storm-damaged tree:

 

1. Use common sense and ask yourself if the damage has perhaps rendered this tree hazardous? In other words, does it now look vulnerable to any additional wind or ice event that could cause it to fall in its entirety or at least “drop” one or more large branches that could damage nearby property or prove fatal to people and pets?
2. Educate yourself as to the potential growth rate and commercial availability of replacement trees.
3. Even if the tree can be salvaged, assess whether it will ever look “right” again with some semblance of symmetry.
4. If significant bark has been ripped or loosened from the trunk, be realistic about the tree’s potential for attack from opportunistic microorganisms and damaging insects outlined later.

 

If you choose to address the damage to save the tree, it is best to seek out a professional arborist. Hiring an arborist should be like hiring other professionals around the home such as plumbers, electricians, and carpenters. Do your homework–ask your friends and neighbors for recommendations. Additionally, be sure the individual you hire is certified by the International Society of Arboriculture (ISA). 

 

Of course, safety should always come first. Assess the situation and if the size of the job is too big or you don’t feel comfortable with the task, seek out a professional. For more information on dealing with storm damaged trees see OSU fact sheet Managing Storm-Damaged Trees.

 

Repairing Tree Injury

David Hillock

 

Injuries to trees that expose the wood or kill the bark may allow insects or disease organisms to enter the tree. Proper treatment protects the tree and promotes faster sealing of the wound. Few trees reach maturity without receiving one or more wounds from a variety of sources. Yet trees have survived for centuries to become the oldest living creatures on earth despite wounding. Some recent work has involved dissecting trees to understand how they compartmentalize and close an injury. Trees do not heal in the true sense of the word. Injured tree tissue is never repaired and returned to the former state, as is a cut on a person's hand. Trees react by closing the wound and compartmentalizing or isolating the injured tissue from the surrounding tissue. During compartmentalization enclosure, contents from the injured cells leak onto the uninjured surface where they oxidize and form a barrier to prevent further infection. Then the most recently laid down wood is altered, as is the tissue around the injury. This is accompanied by discoloration, the extent of which depends on the kind of tree, the vigor, kind of wound, location of the wound and the time of wounding. New growth rings are laid down the following spring and new tissue begins to grow over the injured tissue. Over a period, the new tissue closes the wound.

 

Homeowners can help the plant compartmentalize the damage more rapidly than it does in nature. If the bark has been crushed or stripped from the trunk, remove the injured bark and shape the wound. Cut away all damaged bark and remove isolated scraps from the wound area. Remove all splintered wood and smooth the surface of the exposed area with a chisel.

 

Some true injuries result in cavities or hollows within the main trunk or large branch of a tree. For many years gardeners have tried to fill these cavities with bricks, concrete and other materials to seal the cavity from rain, insects and diseases. Armed with the knowledge of the plant's ability to compartmentalize any wound it is not recommended to fill tree cavities. If water does not drain easily out of the cavity, many arborists will recommend trimming the cavity opening so that water can drain out. Creating a weep hole by drilling into the bottom of the cavity to allow water to drain freely is not necessary and will create a new wound that may be subject to further decay. Other than these actions, simply keeping the cavity clean of debris and leaves is all that is recommended.

 

In storm-damaged trees, remove all broken branches and reshape the tree as well as possible at the time. Never top or de-horn your tree. Try to encourage new branch development in areas with broken branches. Broken trunks, split crotches or cracked limbs often are mended by restoring the damaged part to its original position and holding it there permanently. Consult professional arborists to install screw rods or cables in trees where this work is necessary.

 

For more information on proper pruning and managing storm-damaged trees see OSU fact sheets Pruning Ornamental Trees, Shrubs, and Vines  and Managing Storm-Damaged Trees.

 

Controlling Caterpillar Pests

David Hillock

 

Caterpillar pests are common on many landscape plants and can cause mild to severe damage depending on plant species and number of caterpillars present. Control of caterpillars may not be necessary in some instances because their numbers are kept in check by numerous natural enemies such as parasitic flies and wasps, disease, predator insects and birds.

 

On shade trees, even if the caterpillars become numerous, a healthy tree can withstand a complete defoliation early in the growing season. New transplants or trees weakened by weather or other factors may require control.

 

Hand-picking caterpillars from flowering plants and vegetables is also an effective method. Most caterpillars are very susceptible to products containing Bacillus thuringiensis, such as Javelin®, Dipel® or Thuricide®. This product is less effective on older larvae because they must consume it for effective control. Young and older caterpillars can also be controlled with the naturalyte ingredient spinosad that is found in Conserve® and some retail insecticide products as well as other insecticides that are labeled for these pests in ornamentals. Control is best achieved before caterpillars become full-grown, and it is essential to get thorough coverage, since they are often slightly protected within their "nest". Of course, it is important to select the right product for the given situation and to always read and follow product labels directions.

 

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.

 

Thrips can Wreak Havoc on Flowers and Plant Foliage

David Hillock

 

A small insect, often showing up in the spring and when present in great numbers, causes problems to flowers in the garden, is the thrips. A thrips has mouth parts like rasps, which is used to scratch the surface of flowers, buds or young leaves and then lap up the plant juices. This causes distorted and discolored flowers or buds and gray or silvery, speckled areas on the leaves. 

 

Thrips are small cylindrical shaped yellowish/orange insects with wings that sort of resemble feathers. They can’t fly very well but move about in the wind. They only live about 40 days, but can have up to 8 generations per year, so they can be present all through the growing season. Thrips may or may not do significant damage in the garden. They may only be present for a period and then blow away. They can do enough damage to warrant control, however. Insecticidal soaps are a good means of treatment. There are several other labeled chemicals, check with your local extension office or garden center professionals for additional recommendations. Sprays may need to be applied 2 to 3 times at 7-day intervals. Thrips have several natural enemies as well. Damsel Bugs, Pirate Bugs and Lacewing Larvae feed on thrips.

 

How to Produce High Quality Tomatoes

David Hillock

 

1. Select or prepare soil high in organic matter and sufficiently loose to allow for extensive vigorous root growth.
2. Apply needed fertilizers and mix into the soil prior to planting.
3. Obtain husky plants of recommended nematode and wilt resistant varieties. Set them into the garden as early as weather and recommended planting dates permit.
4. Water in newly set plants with a starter solution.
5. Provide protection from cutworms and other possible pests of the transplanting season.
6. Use mulching materials around plants within one month following planting.
7. Apply supplemental water as needed, drip irrigation being preferred.
8. Control insects and spider mites as well as leaf and fruit diseases if numbers are increasing week to week.
9. Windbreaks may be especially desirable as hot, dry weather develops.
10. Maintain the identity of different varieties to evaluate their qualities and thus determine the more appropriate kinds for future plantings.

 

For more information on growing tomatoes see OSU Extension Fact Sheet HLA-6012 Growing Tomatoes in the Home Garden.

 

Growing in Raised Garden Beds

David Hillock

 

Raised bed gardens are an ideal way to grow vegetables and small fruit. They are elevated a few inches or more above the soil level, and just wide enough to reach across by hand. Plants can be grouped together in a bed with permanent walkways on either side. The soil does not get compacted, since the soil in which plants are grown is never walked on.

 

The idea of growing plants in single file or “row crops,” started with the use of a horse and plow to cultivate crops on a large scale. The straight rows, far enough apart to drive a horse between, made plowing easier. Wider spaces later accommodated tractors and their implements. Not knowing the reasons behind growing crops in rows, many home gardeners plant single row vegetable gardens. However, foot traffic on each side of a single row can severely compact soil by the end of a growing season. The excessive row spacing also wastes garden space that can be planted with crops.

 

Raised bed gardens can range from a simple rectangular plateau of soil to a more elaborate bed framed in wood, stone and mortar, straw bales or modern snap-together plastic blocks. Although more expensive and time consuming to build, permanent structures will keep soil in place during heavy rains and will look nicer in the landscape. However, for a large garden, several beds of mounded soil are very adequate to achieve desired results. Just make sure plenty of mulch is used on the soil to hold it in place during drenching rains.

 

Benefits of Raised Beds

• Higher Yields. Raised beds allow more garden space for growing plants, with less space utilized for walking paths. Individual plant yields may be slightly less with less space per plant than in traditional rows, but more plants can be grown in a given space.
• Better Soil. Amendments such as compost and fertilizer are only spread on beds and not wasted on pathways. Looser (non-compacted) soil also drains better. Frequent tillage of the garden can be elimination.
• Water Conservation. Plants grown close together shade the soil, decrease evaporation and keep roots cooler. Water is only provided to the beds and not the pathways.
• Fewer Weeds. Closely planted crops keep weeds crowded out. Pathways can be covered in landscape fabric or mulch to choke out weeds.
• Extended Season. Soil in raised beds can be worked earlier in the season, because it warms up faster than soil in traditional in-ground gardens. Rainy weather is less of a hindrance to working in the garden, since mud is not an issue.
• Better Pest Control. Raised bed gardens are easy to cover with insect screening fabric. Crops are easy to rotate from bed to bed — preventing a buildup of pests.

 

For more information about using raised beds see our fact sheet HLA-6033 Raised Bed Gardening.