What Size Container Stock Should I Plant in my Landscape?

By |2019-10-10T12:59:59-07:00October 10th, 2019|Planning, Plant Selection, Trees|

Bigger Plants Are Not Always Better

Because we are coming upon the best planting season of the year, fall, let’s talk about container plant sizes. Plant material comes in a range of container sizes, 1, 5 or 15 gallon, 24″, 36″ 48″ boxes and up, and some species come bare root in the winter.

The natural human instinct of instant gratification leads many clients to ask for larger sized container plant stock at initial installation. I can see why, you get an instant landscape without the wait. Many think, why plant a small tree when I can just get a more mature one installed without having to wait for it to grow?

For sites I consult on, I encourage clients to use the smallest container size possible. Here’s why…

  1. Establishes a supportive root system in native soil early on. Plant roots will leave the initial planting hole and seek water and nutrients in their permanent environment a lot faster and more efficiently from a smaller sized container.
  2. Research has shown that plants and trees from smaller container stock establish quicker and their growth outpaces larger container stock in a matter of 2-3 years.
  3. Less foreign material (potting soil) which is of different texture and moisture holding capacity than native soil.
  4. Less root circling and girdling from growing in a container for too long. These common maladies of container stock often spell a slow, painful decline and eventual death of the plant or tree.
  5. Easy to inspect the root systems in order to accept or reject the plants selected.
  6. Pruning and training plants and trees from a young age to develop a strong form, structure and shape. Nursery pruning of container stock often leads to growth defects and necessitates corrective or restorative pruning.
  7. Initial installation costs are much lower. Plant replacement cost years down the road are much lower from decline and death. And who does not like to save money in both the short and long term?

I have inspected many sites where I can just pull out the plant from the ground, where the roots never left the planting hole. Or sites where the tree just wiggles back and forth in the planting hole, with no structural or supportive roots venturing out into the native soil. These were all plants of large initial container size.

On the other hand, I have also planted bare root and 1 or 5 gallon trees and their growth 3 years after planting is far superior to any larger plant.

So, choose your species wisely to match the soil conditions of your site and plant the smallest plant possible. Be patient, your efforts will be rewarded with healthy, aesthetically pleasing and well shaped landscape trees and shrubs!

Nice Plant Selection #2

By |2019-05-14T19:26:37-07:00May 14th, 2019|Plant Selection, Trees|

A Great Small Tree Selection for Spring Blooms

Tired of seeing the same trees being used over and over again? Tree species diversity is important to the urban forest, so let’s mix up the planting palette. Chionanthus retusus, or Chinese fringe tree, is blooming here in San Diego, and what a show! I took these photos about a week ago when I hit the brakes at the sight of these blooms.

This tree is useful in the landscape because of it’s small size at maturity, less than 25′. Although it is not drought tolerant, it is useful for patios, lawn and garden settings. It’s striking show of fragrant white flowers in spring-summer is followed by yellow fall color and small red berries which attract birds. Chinese fringe tree grows in clay to loam soils in full sun or part afternoon shade in warmer areas. Another tree I love to see growing and being planted!

SelecTree. “Chionanthus retusus Tree Record.” 1995-2019. May 14, 2019.
< https://selectree.calpoly.edu/tree-detail/chionanthus-retusus >

IPM Training for Landscape Professionals

By |2019-05-14T18:19:42-07:00May 14th, 2019|Sustainable Landscape Management, Training and Education, Trees|

Daisy flowers under magnifying glass

University of California Agriculture and Natural Resources is hosting the IPM Training for Landscape Professionals on May 23, 2019. Location is the
Scottish Rite Event Center 1895 Camino del Rio South, San Diego, CA 92108.

Topics of interest for pest management in the landscape setting and CEU’s available. I’ll be speaking on the topic of Diagnosing Landscape Plant Problems, and highlighting the steps and resources useful for an accurate diagnosis.

For information, agenda and registration visit their webpage at: http://cesandiego.ucanr.edu/?calitem=443278&g=98691

Tree Planting

By |2019-06-06T11:09:31-07:00April 30th, 2019|Trees|

Maple tree leaves

When conducting landscape inspections, I commonly see all of these offending practices in regards to trees….poor quality nursery stock, planted too deeply, soil is amended instead of proper species selection, holes dug too large, tree “snorkels” installed, staked improperly and left on too long, hardscape and infrastructure interference, root barriers, the list goes on. None of this has a basis in horticulture or promotes healthy tree establishment and growth. Let’s stop this and promote quality in the landscape so these site assets reach all of their potential for decades to come.

This blog post was written by Jim Downer, and can be found at http://gardenprofessors.com/problems-with-planting-trees/

Problems with Planting Tree

Ok. I admit this blog is going to turn into a rant pretty quick because there seems to be a lot of ways to screw up a fairly simple horticultural practice—tree planting.  Since Arbor days are happening/happened everywhere around now, its a good time to talk about how to plant trees.   First let me state some simple and useful guidelines for a successful tree planting.

-When at all possible, plant trees bare-root. Even washing the container media away. This allows for inspection and removal of root defects.
-Select trees carefully that are free of defect and disease and that are adapted to your climate and soils
-Plant the youngest tree you can
-Take care in choosing the planting site.
-Avoid Root Barriers
-Plant trees so that the root flare is above ground slightly
-Plant trees in a hole only deep enough to contain the root system, no double digging.
-Plant trees in a hole wide enough to contain the root system, no wide holes (unless there is a reason for using one)
-Fill the hole with soil removed to make it. Do not amend the backfill around newly planted trees—Do not put rocks in the bottom of a planting hole!
-Plant trees without staking unless there is a reason to stake them
-Plant trees away from turfgrass or other groundcovers.
-Plant trees under the cover of a fresh layer of arborist chips.

-Irrigate newly planted trees from the surface—Do not install U tubes or tree snorkels to irrigate deeply.

An old planting detail from “a book of trees” . Several myths here: rocks at the bottom of the hole, amended hole, nursery stake still there when it does not need to be, etc.

I guess this rant comes from the variety of tree planting specifications I have seen over the years used by municipalities, landscape architects, nurseries and others. There seems to be a need to use the latest product, method or modification to site soils in order to make a fancy planting detail. Simpler is better and research by Universities has not verified most of the “innovative” approaches seen in planting details.

The first step in planting a tree is to chose the tree you want to plant. While this seems simple there is a lot that goes into tree selection. Setting aside personal choices, it comes down to selecting a tree that is healthy and free of defect. The potential candidate tree should have no signs or symptoms of disease, a naturally developed canopy unfettered by nursery pruning (especially heading cuts), and has few or no root defects. Initial superficial examination of the root collar in the nursery can eliminate some trees with circling or girdling roots. However, when the tree is planted root washing will reveal the entire root system and as Dr. Linda Chalker Scott has shown in this forum, root washing allows for rapid establishment in site soil. When at all possible chose the youngest tree you can for the new site. Young trees have fewer root defects, and we have the advantage of training them (structural pruning) from an early age. Young trees establish rapidly and will often outgrow older, boxed trees. The larger the specimen that you plant, the more chance for establishment problems such as settling, drying out, root rot or just slow growth. Planting trees from seed is ideal but most gardeners don’t have the patience to wait and seedlings, and seedlings do not give the option of using cultivated varieties that impart horticultural value, such as predetermined flower color, disease resistance, and known form (canopy shape and size).

Once the tree is selected, purchased and root washed, it is time for setting it in the ground. The first step is choosing a good planting site. A good site for a tree is somewhere that provides adequate soil volume for its roots to expand and for its canopy to expand. Many trees in urban settings fail to achieve their potential because they have restricted spaces to grow in. Chose a location in full sun. Unless you are planting a species that grows well in shade or needs protection from the environment, most trees will grow best in a sunny location. While trees are forgiving of most soil conditions, they will not grow well in compacted soils. If this is all that is available, break up compacted soils before planting. Consider the ultimate size of the tree you are planting, and imagine it attaining that size in your planting site. Avoid sites that have close proximity to buildings or hardscape. One of the most frequent problems with trees is that as they attain mature size they conflict with the infrastructure at the site.

Dig the hole for your tree so that the roots are very slightly above the grade. Do not double dig! While double digging has its proponents, there is no research-based reason for destroying soil structure– it is a disaster for tree planting. When a hole is dug too deeply soil will always settle after planting and irrigation resulting in the tree being planted too low in the ground. The root collar is buried and this is a predisposing factor for disease. The hole should have undisturbed soil under the roots. The hole only needs to be as wide as the root system. While many planting details show wide holes these are not necessary in most garden sites. If the site is compacted, wide holes can give temporary advantage to a newly planted tree, but the width of the hole will be the size of the “pot” the tree will have to grow in. So it is better to modify the site first to take care of compaction and then you will not need a wide hole.

Root barriers do not function well in most landscapes and lead to the development of landscape trash. They can also create root defects

Root barriers were very popular and are still specified today.  They actually do not usually achieve thier goal of preventing surface roots and protecting infrastructure.  Trees outgrow root barriers and they result in increases of landscape trash/pollution.  Root barriers can also create root defects such as circling and girdling roots.  Do not install root barriers, if you are tempted to do so you are likely not choosing a good site to plant a tree.

Cover the roots with backfill from the hole. Do not modify the backfill. Research does not support adding amendments to planting holes for trees. The native soil is what the tree will be growing in ultimately, and there is no reason to modify it. If the soil at your site is so bad that it needs to be changed, this should be a site-wide soil modification that will cover all the area the tree roots will explore up to its maturity. Most gardeners are not able to do this. Roots rapidly expand beyond the planting hole within months, so the time and benefit derived from an amended planting pit is minimal. Adding amendment, especially organic amendments to backfill can also be disastrous for trees. The organic material may utilize nitrogen in the soil and lead to a deficiency in the newly planted tree, worse, it may break down and cause anaerobic conditions in the bottom of the planting pit. Avoid amending planting holes! Never place rocks in the bottom of the hole—this does not create drainage, but creates an interface that prevents it.

A “lollipop” Tree.  Note the very skinny un-tapered stem, lack of temporary lateral branches and retention of the nursery stake–all bad…. Also note the tree snorkel lurking to the left. Kudos for keeping turf away but not far enough away.

If you have selected a good tree, it will stand without staking. There are three reasons for staking: support; anchorage; and protection. Support is sometimes necessary when a tree is cultivated with a long un-tapered trunk and a lollipop crown. Lollipop trees are often sold in nurseries as they resemble small trees. Trees trained in this manner, will not stand without staking. Loose staking allowing trunk movement will foster development of caliper so the tree can eventually stand without supportive staking. Anchor staking is used for trees that experience high winds and “staked out” with guy wires and a non-constrictive collar. Protective staking is analogous to placing bollards around a tree prevent impact from machinery or cars. Always remove the nursery stake at the time of planting and provide any additional support the tree may need. Many Cooperative Extension services have publications on how to stake a shade tree.

Providing a No Turf Zone around trees will aid in their establishment

Avoid planting trees in lawns. Turfgrass and trees conflict with each other. Trees shade turfgrass which results in a thinning sward and increased disease prevalence. Turfgrass slows the growth of trees in an attempt to limit their shading effects. Turfgrass is a very competitive water user and trees will be deprived of moisture and nutrients if turfgrass is present.  If trees must be planted in lawns, maintain at least a 1 yard radius around them with no turfgrass.

Aeration/Irrigation snorkel tubes do not help trees and result in landscape pollution. Note the original nursery stake still in place and the supportive stakes should have been removed long ago. Mulch needs to be replenished.

It has become a common practice to add irrigation or aeration devices to tree plantings. Sometimes called a tree snorkel these plastic 4 inch U tubes are buried below the root zone. Kits can be purchased from Box stores, and architectural details have been drawn specifying their use. Work by UC researchers showed that oxygen does not diffuse far from aeration tubes. So utilizing tree tubes to increase air flow is suspicious. Some planting details specify adding irrigation to the tubes to force a deep rooted condition in the tree. This places water below the root system, which can dry out and compromise establishment—not a good idea… Worse of all tree snorkels are sometimes installed with no purpose at all other than that was what the planting plan indicated. This is a needless practice and results in landscape pollution. Long term, tree snorkels are ugly, easily broken and provide no useful function to an establishing landscape tree. It is not in the nature of trees to proliferate absorbing roots deep in soil and snorkels will not change a tree’s genetics.

After the tree is set in its hole, and backfill settled in with water, apply a 4 inch layer of arborist chips as far out from the trunk as feasible—at least several feet. The chips will modify the soil improving, chemical, physical and biological properties while conserving moisture from evaporation, preventing runoff, and germination of annual weeds. Generally trees thrive under mulch as it simulates litterfall, or accumulation of organic matter under their canopies. Replenish the mulch as it deteriorates. Finally apply irrigation as needed through the mulch from the surface of the soil. This will help establishing roots, leach salts, and move mulch nutrients into the soil profile.  Avoid companion plantings near the main stem of the tree and avoid piling mulch around the tree stem. Following these guidelines will lead to a healthy and useful shade tree that provides its many services for decades.

PUBLISHED BY

Jim Downer

Dr. Downer has 34 years of experience as a horticulture and plant pathology Advisor with the University of California Cooperative Extension in Ventura County. Dr. Downer’s academic training is from California Polytechnic Univ., Pomona, (BSc. horticulture & botany, 1981; MSc. Biology, 1983;. In 1998 he earned a Ph.D. in plant pathology, from University of California, Riverside. Dr. Downer’s research is focused on mulch, soil microbiology and disease suppression in mulched soils, diseases of shade trees and cultural practices to maintain landscape plants. Dr. Downer is a member of the American Society of Horticultural Science, the American Phytopathological Society, The International Soc. of Arboriculture, and the Western Chapter of the ISA, and the International Society for Horticultural Science. Dr. Downer is an Adjunct professor at California Polytechnic University in Pomona. Dr. Downer serves on the Board of the John Britton Fund for tree Research as the chair of the research advisory committee, and currently chairs the regional conference committee for WCISA. Dr. Downer has a love of shade trees, Shinrin roku (forest bathing/walking) tree work, wood working, horses, gardening, horticulture and the study of plants and their biology.

Celebrate the Benefits of Urban Trees

By |2019-04-09T16:19:01-07:00April 9th, 2019|Trees|

Video Trees Provide Amazing Benefits by Davey Tree

Thank Goodness for Trees!

Arbor Day is April 26, 2019 here in San Diego and across the nation. So look up and around at the valuable assets in your area. Communities would not be the same beautiful, livable spaces without trees.

Statistics on The Benefits of Trees by The Arbor Day Foundation

The net cooling effect of a young, healthy tree is equivalent to ten room-size air conditioners operating 20 hours a day. U.S. Department of Agriculture

The planting of trees means improved water quality, resulting in less runoff and erosion. This allows more recharging of the ground water supply. Wooded areas help prevent the transport of sediment and chemicals into streams. USDA Forest Service

A mature tree can often have an appraised value of between $1,000 and $10,000. Council of Tree and Landscape Appraisers

If you plant a tree today on the west side of your home, in 5 years your energy bills should be 3% less. In 15 years the savings will be nearly 12%. Dr. E. Greg McPherson, Center for Urban Forest Research

Trees properly placed around buildings can reduce air conditioning needs by 30 percent and can save 20–50 percent in energy used for heating. USDA Forest Service

Trees can be a stimulus to economic development, attracting new business and tourism. Commercial retail areas are more attractive to shoppers, apartments rent more quickly, tenants stay longer, and space in a wooded setting is more valuable to sell or rent. The Arbor Day Foundation

Landscaping, especially with trees, can increase property values as much as 20 percent. Management Information Services/ICMA

In laboratory research, visual exposure to settings with trees has produced significant recovery from stress within five minutes, as indicated by changes in blood pressure and muscle tension. Dr. Roger S. Ulrich Texas A&M University