Landscaping Around a Tree

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This photo shows a good example of landscaping under a tree. Notice the wide, thin mulch rings.

The winter is a great time to start thinking about spring gardens. One of the gardens you might think about for improvement or development is around trees. There are things you can do around trees to help improve the overall look of your landscape, but be careful, some things may be harmful.

Exposed Tree Roots

Exposed tree roots are often a problem in landscapes. Some trees will pop their roots up and out of the ground which makes it difficult to mow around and can be a trip hazard. Unfortunately, there is not a good fix for this problem. If you were to cut the root to remove it from above the ground, you would severely injure the tree and possibly kill it, depending on the size of the root. Adding more soil around the root to try to cover it up is also a bad idea. Adding more soil to the existing grade of a tree can suffocate the roots and kill the tree.

Raised Beds around Trees

One idea many people want to use around their trees is to add a raised bed around an existing tree. Adding the soil necessary to make a raised bed around a tree can kill the tree. If the tree is correctly planted into an established raised bed after the raise in soil grade is complete, that would be fine. However, adding this bed around an existing tree will severely damage the tree and could lead to tree death. Trees are slow to react to these things, so your tree may live just fine for 5-10 years, but then the damage will begin to show up as the canopy starts to thin or die.

Turf under Trees

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Thin turf under a tree, photo from John Fech, Nebraska Extension Educator

Another issue around trees that many people ask about would be thin turf growth or constantly bare soils under a tree. Turf is a sun plant and it will not grow well in shade. There are shade mixes in the market, but those are designed for light shade. Underneath a full grown, healthy tree is often too much shade for the turf to grow in.

A better option instead of thin turf for underneath the tree would be to just mulch the area. Mulch helps to keep the weeds down, retains moisture, keeps the roots cool, and keeps the lawn mower and weed trimmer back away from the tree trunk to reduce the incidence of damage from this machinery. Keep the mulch at a flat layer of 2-3 inches deep and don’t create a volcano of mulch around the tree. The mulch ring should be at least a 3 foot diameter around the tree, but it can be as wide as the dripline.

You can mimic mother nature and provide a nice growing environment for your tree by utilizing mulch and shade plants under the tree. You can plant shade plants into the area around your tree as long as you don’t add soil to put them in. In nature, trees grow great on their own with little input from humans. A big part of that is the growing conditions they are placed in. Trees in nature grow with leaf litter and smaller plants growing all around them. The leaf litter acts as a mulch and the shade plants thrive in the shade of the large trees.

Plant a Tree for Arbor Day

Plant a Tree blog, 2018

One of my favorite holidays is coming up, Arbor Day. As a tree enthusiast, I appreciate any holiday that urges people to plant trees. Arbor Day is always celebrated on the last Friday of April in Nebraska, this year that is April 27th. This holiday is not the same throughout the United States, it is moved around for other states to be in the best planting time for the year.

Deciding what tree to plant is very important and sometimes difficult. Diversity is key when choosing your tree. The general rule is to plant no more than 10% of a tree species, no more than 20% of a tree genus, and no more than 30% of a tree family in a respective urban area. Look around at what types of trees you have and what types of trees your neighbors have before deciding on a new tree, try to avoid everyone planting the same few trees throughout the neighborhood. Look for some unique, underutilized trees such as gingko, Kentucky coffeetree, Ohio buckeye, hornbeam, paw paw, sweetgum, or tulip tree for deciduous trees that do well in southeast Nebraska.

The most important factor to keep in mind when planting trees is how to plant a tree correctly to ensure healthy growth. First of all, remove all of the burlap and any other materials from the root ball before planting. Also remove any tags, twine, or wire from the tree. Remember to remove all the grass and weeds that are within the area you will be planting the tree. Dig a hole that is 2-3 times wider and no deeper than the root ball and loosen up the sides of the hole. Plant the tree so that root flare is at the soil surface. Do not amend the soil that is in the hole, backfill with the existing soil. Make sure that the entire root ball is covered with soil to avoid drying out.

Keep newly planted trees well-watered. Always water newly planted trees, shrubs, or any other plant immediately after planting. Trees should be watered every 10-14 days throughout the growing season and even some during the winter on warmer days. Each watering should give the tree 1-2 inches of water. The best way to determine if a tree needs to be watered is to insert a soil probe or 12-inch-long screwdriver into the ground around the tree. If it goes in easily there is no need to water, if it is difficult at any point then water is necessary for the tree.

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Tree Damaged from Lawn mower blight

A mulch ring should be established and maintained around every tree. Mulch helps to keep the roots cool in the summer and regulated to a uniform temperature through the winter. Mulch will also help keep weeds down and reduce competition from those weeds for water and nutrients. Mulch also reduces damage to the trunk of trees from lawn mowers and trimmers. Finally, organic mulch is a way to hold moisture for use later by the tree. Mulch rings should be only 2-3 inches deep and in a circle around the tree at least 2-3 feet out. Organic mulches are a better choice than inorganic mulches. This mulch will need to be renewed every year to maintain an effective layer because it will break down over the growing season which will improve the soil.

Tree Planting, 2017 (3)Staking a tree is not a mandatory practice. If you do have to stake the tree due to high winds, make sure that the tree has plenty of movement to allow it to build stronger roots. Also be sure that the staking material is removed after the first year to avoid the tree being damaged by the staking materials.

Winter Watering

Winter Watering blog

It’s hard to think about our plants in the winter months. It is even harder to realize that they are still alive and sometimes need care in the winter months. Once plants go dormant for the year many people believe that they need nothing until spring, but that isn’t always the case, especially in years with low or no snow or rain throughout the winter months.

Winter watering is essential in dry winter years. Winter desiccation commonly occurs on evergreen types of trees and shrubs. All trees are still transpiring, or losing water, throughout the winter months, evergreen trees are transpiring at a higher rate than deciduous trees. Winter desiccation occurs when the amount of water lost is greater than the amount of water the evergreen takes in throughout the winter months. The branches and needles of our trees will die. The damage from winter desiccation is brown needles out on the ends of branches. However, the damage from winter desiccation will not usually show up in our trees until early spring, so they will stay green through the winter. Drought effects can damage deciduous trees as well. Especially newly planted deciduous trees need to be watered throughout the winter months if natural moisture is absent.

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Damage to Arborvitae following a dry, windy winter

Ensure adequate watering throughout the entire growing season for all trees and shrubs, especially those recently planted. Make sure that the tree is well watered going into the fall. Also, water throughout the winter when the ground is not frozen to help the trees through a dry winter, if necessary. Winter watering should occur during the day on days when the temperature is 40 degrees Fahrenheit or above and is only necessary 1-2 times per month until spring. It is a good idea to test for soil moisture with a long screwdriver or soil probe prior to watering to determine if watering is necessary. If the screwdriver goes into the soil easily up to 18 inches, watering is not necessary. However, if pushing the screwdriver into the soil becomes very difficult after the first couple of inches or less, watering would be necessary. After watering, apply a light layer of mulch over the roots of the tree, but not up against the trunk to avoid problems with voles.

Turf is another plant to take into consideration regarding winter watering. Winter desiccation can occur on turf when the soil is frozen, making water unavailable to plants. It is more problematic on sunny, dry, windy days when the air temperature is above freezing but the soil is dry or frozen, according to Bill Kreuser, UNL Turfgrass professor. Bill Kreuser states that, a little bit of drought stress prior to winter can actually help prepare the turf for winter conditions, it helps harden off the turf before any severe cold happens. It is actually better for the turf to have drought prior to winter rather than go into the winter with higher precipitation, as has been the case this year.

That being said, home lawns are more tolerant of winter desiccation stress because the Kentucky bluegrass, fescues, and buffalograss have a deeper root system and less overall stress than turf on the golf course. Established lawns may not need winter watering, but newly planted lawns may be more susceptible to winter desiccation. However, if we face a dry winter with little to no snow cover, irrigation may be needed at low amounts. Ensure that winter watering is not through an irrigation system or it will need to be cleared out again so the pipes don’t freeze and burst. It is best to hand water with a hose or bucket in the winter months.

Yard and Garden: June 10, 2016

Yard & Garden for blogThis is the Q&A for the Yard and Garden show for June 10, 2016. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through August 5, 2016. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.

Guest Host: Paul Hay, Gage County Extension

1. The first caller of the day has a small Dwarf Alberta Spruce that is turning brown. What would cause this?

A. This would be from spider mites. This particular tree species is very susceptible to spider mites. They can be controlled with a strong spray of water or insecticidal soaps, horticultural oils, or a general insecticide such as a permethrin product.

2. This caller wanted to know if it was still ok to apply the second fertilizer application for the lawn?

A. Yes, you can do one around Memorial Day. I would suggest waiting until after this heat wave passes through and make sure the lawn is well-watered when you do fertilize, so you don’t fertilize to a drought-stressed plant which can cause leaf burn.

3. What would cause Clematis leaves to turn yellow, the plants still bloomed fine this year?

A. Clematis has a problem with Iron chlorosis. This could be iron chlorosis which can be treated with an iron fertilizer.

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Squash bugs on zucchini

4. A caller wanted to know what the best control for squash bugs in the garden would be?

A. Squash bugs will become active soon. Look on the underside of the leaves of your cucurbit plants such as cucumber, zucchini, squash, pumpkins, and melons. Squash bugs lay their eggs on the underside of the leaves. If you find the eggs, squash the eggs or remove the leaves. You can also spray for them. Spray on a rotation of every 10-14 days throughout the growing season. Switch between at least 2 of the following: sevin, eight, or bifenthrin.

5. This caller has rocks near the lawn and near some trees. There are weeds growing up through the rocks. Can glyphosate, or Roundup, be used around these trees?

A. If the trees are not close enough to be spraying directly on the trunk or leaves, then it will be fine. Glyphosate is not mobile through the soil like some chemicals.

6. This caller wanted to know what to do about the gnats outside? He cannot go outside right now without being attacked by gnats.

A. There is no longterm cure for gnats, much like mosquitoes. Using bug sprays, especially those containing DEET, will help the most. If you have an outdoor event coming up, you can treat the lawn and surrounding plants with sevin or other general insecticide, but these will not last for more than 2-3 days.

7. Is it too late to plant sweet potatoes? What can you do about grasshoppers in the landscape?

A. No, it is not too late to plant sweet potatoes. This is a warm season crop that really doesn’t like the early spring planting. They will do fine if planted in late May to early June. For grasshoppers in the landscape, they can be sprayed with any general insecticide. If in or nearby the vegetable garden use sevin, eight, or bifenthrin for safety of the produce. Be sure to spray the insecticides in the ditch, roadside, and fence rows where grasshoppers are found in high numbers.

8.  This caller has hemlock in the pasture. Is it poisonous? How can he control it so his cattle don’t eat it?

A. Yes, poison hemlock is poisonous if eaten, not if it is touched. Cattle can be poisoned by it, but they typically don’t eat the poison hemlock if there is an alternate food source. Use 2,4-D or Grazon in the pasture to control poison hemlock or dig it out.

*Don’t use 2,4-D this late in the season around landscape plants and never use Grazon or other products that contain Tordon in a landscape setting.

9. A caller has common mullein in his pasture. How can it be controlled?

A. Common mullein is best controlled with 2,4-D or Grazon. Make sure you spray down into the heart of the plant to get the chemical past the hairy leaves. It is best to spray the smaller plants, it would be too late to spray the larger plants that already have a flower stalk on them. Removal of the flower stalks will help reduce seed production from the full grown plants.

10. This caller has a 16 foot river birch that was planted last fall. Now the leaves have turned yellow and are beginning to fall off of the tree. Can it get too much water? What would cause this problem? She hasn’t been watering the tree much yet since it was planted in the fall.

A. Yes, plants can be overwatered to cause death. Newly planted trees need to be watered because they have no root system developed. A tree that was transplanted at this large of a size is going to have a great deal of transplant shock to overcome. Water was sitting in the hole when the tree was planted, so there may be an issue with water draining from the location. Use a probe or long screwdriver to see if the tree needs water. Push the probe into the soil 12-18 inches, if it goes in easy it doesn’t need water, if it is hard to push the probe in very far, the tree needs to be watered.

11. The final caller of the day wanted to install an electronic timer for watering his garden. What would be the best time to set his timer to water his garden?

A. 4 am-10 am is the best time to water any plants. This helps to water the plants while they are already wet from the dew period. It also helps to water early in the day so that the plants will dry out before night. Plants that are wet and cooler overnight introduce a great environment for diseases to occur. To reduce diseases, it is best to water early in the morning.

Yard and Garden: May 13, 2016

Yard & Garden for blog

This is the Q&A for the Yard and Garden show for May 13, 2016. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through August 5, 2016. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.

Guest Host: Fred Baxendale, Horticulture Entomology Specialist, UNL

1. The first caller of the day wanted to know when to transplant Peonies? She also wanted to know if she moved them away from the black walnut tree would that help them grow?

A. It is best to transplant peonies in the fall, but it can be done in the spring as well. It would be fine to move them in the spring as well. It would be beneficial for the plant to be moved away from the black walnut tree to get away from the toxicity produced by the tree as a form of natural weed control for the tree to other plants. Black walnuts produce Juglone which reduces growth and, in some cases, kills the other plants so the black walnuts have less competition for water and nutrients. Planting things 50 yards from the tree will get it out of the zone where damage can occur.

2. A caller has a rose that is old and has grown to 6 feet tall. When can he transplant it? Also, what are the red “ticks” he found around his gardens when he has been working in them recently?

A. Roses are hard to transplant. Do the transplanting in the early spring of the year and take as much of the rootball as can be dug up when it is moved to help the shrub overcome the transplant shock. Maintain adequate water once it is moved. The red “ticks” would be clover mites. These are not damaging to the plants but can leave red marks on house siding and if inside on the walls and curtains. You can treat these with permethrin or insecticidal soap.

3. This caller has Peonies that accidentally got cut back drastically this year. Will they live through this and should she do anything for them?

A. They should be fine but they probably won’t bloom this year. Make sure they are adequately watered and they will regrow by the end of fall. They should be fine again next year.

EAB Damage Collage
Signs of an Emerald Ash Borer Infestation from Boulder Colorado

4. A caller has 2 ash trees in her yard. She has heard about Emerald Ash Borer and wanted to know if there was anything she could do to protect her trees?

A. Emerald Ash Borer (EAB) has not been found in Nebraska and we recommend waiting until EAB has been found within 15 miles of your trees before you begin treating them. It takes 2-4 years for the damage to show up in our trees once it is here, so you will have time to treat them when it does get here. In the meantime, don’t move firewood here from other locations and increase the diversity in your landscape to help fill in holes that may appear when EAB takes out your ash trees. Also, watch your trees for signs of EAB including top dieback, suckering at the base of the tree, increased woodpecker damage, bark falling off, and D-shaped exit holes and alert Nebraska Extension if your trees exhibit any of these signs of damage.

5. This caller has a 10-year-old red maple that has struggled to leaf out the past couple of years. The middle of the tree is entirely void of leaves. Should he remove the center of the tree?

A. Removing the center will not fix the problem. This could be a root issue or it may have been improperly planted which would take around 10 years to show signs of damage. This tree is near the end of its life and removal of the entire tree should be contemplated. There could be borers in the tree but that would be a secondary issue and using an insecticide on them wouldn’t fix the whole problem with this tree.

6. This caller planted a Bradford Pear 2 years ago, it is leaning now. What can be done to correct the leaning?

A. Don’t stake the tree to try to pull it back to the correct position. When we stake a tree to try to pull it back upright, this can cause a girdling issue to the tree and it is very damaging to the tree. Because this tree has only been planted for 2 years, it would be a good idea to try to dig it up and reposition it.

7. A caller has steep hills around his yard and doesn’t want to have to mow it. What groundcover choices would he have to grow instead of grass?

A. Buffalograss, dwarf sumac, crown vetch, or potentilla would all be good choices for this type of growing environment.

8. A caller wanted to know if she could use vinegar for weed control in the flower garden?

A. It is best to use pesticides that are labeled for use in the garden. Pesticides for weed control have been rigorously researched to ensure that they work properly and cause limited harm to the environment if applied correctly. When we use non-gardening products in the garden, there isn’t always research to know how those products will work in the garden and it may cause more problems to our plants or it may cause problems if they get into stormwater. If you want to avoid pesticides, it would be better to use cultural and mechanical methods of weed control such as hand pulling and using mulch for weed control.

9. This lady has ant hills in her lawn, what can she use to control them?

A. Ant colonies would be spreading now. Leave them alone now, but if they start to overrun the lawn or come inside, you can spray them with permethrin or bifenthrin. If they are not taking over the lawn, they are a predator insect so if you don’t need to control them, they can be beneficial for other bad insect management.

10. This caller has a barberry that she wants removed. Should she call Diggers Hotline before digging it up? Also, how can she remove and kill daylilies growing in her landscape?

A. Always call Diggers Hotline before you do any type of digging. It is a free service that will help you before a problem occurs. As for the Daylilies, the best option is to dig them up. Using pesticides on them would need repeated applications over many years. When you dig them up, you can offer them to your friends and family.

11. How can you control bromegrass in flowers and in strawberries?

A. In the flower garden, you can spray a Grass-B-Gon product to control the grass and not harm the flowers. Do not spray this to where it hits your lawn or any ornamental grasses. As for the strawberries, this product is not labeled for use in strawberries or other edible crops, so mulching and hand pulling would be the best option. You can also paint Glyphosate (Roundup) products on the leaves of the grass among the strawberries and not harm the strawberries.

crane fly, David Cappaert, Bugwood
Crane Fly photo by David Cappaert, Bugwood.org

12. What are the giant mosquitoes this caller has been seeing flying around? What do they do? Are they mosquito killers?

A. These would be crane flies. They are not harmful to us. They feed on nectar when they are adults, but can sometimes be a problem in the turf. They are not mosquito killers, they are in the same order as mosquitoes and look like a large mosquito, but do not eat them. The immatures live in moist environments.

13. Would it be ok to spray a 2,4-D product this weekend?

A. Yes, 2,4-D can turn into a gas and spread to non-target plants if the temperatures for 72 hours after spraying is above 80 degrees Fahrenheit. So, with this cool down predicted where the temperatures will be in the 60’s for the weekend, this would be a great time to spray. Just make sure that the wind speeds are very low.

14. This caller has onions that the tops are dying back on. They tops curl up and die, why is that?

A. Onion thrips can cause streaking on leaves, this may be from onion thrips. Onion maggots will feed on developing bulbs as well. It could also be from a root rot issue. Dig up one of the onions that are not looking healthy and inspect the bulb for signs of insects or disease.

15. A caller has a recently planted black oak tree that has all of the leaves stripped off of it.

A. It could be from canker worms. They are a short-lived problem in our oak trees. Using the Eight product will help to control them.

16. This caller transplanted walking/winter onions. The bulbs are developing below ground and on top they are flowering but not developing the bulbs on top of the plant. What would cause that?

A. Try to fertilize the plant to help it with nutrients that may be missing from the growth of the plant.