Lawns, Gardens & Trees


Lawns, Gardens & Trees

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Normal fall needle drop in conifers

Conifers - pines, spruces and others - sometimes lose older needles during the fall. This is normal, and does not indicate a pest problem.

During autumn, deciduous trees like green ash and linden change color and lose their leaves. This is normal and expected. It happens every year and people are used to it. When evergreen needles turn brown and die, it’s definitely unexpected, but not necessarily abnormal. 

There are several species of evergreens or conifers that grow in North Dakota. Pines and spruces are most common. Pines have relatively long needles (two to nine inches), which are held in clusters called fascicles. These needles live for two to seven years and then die and drop during the fall. These are the older needles toward the center of the tree. Needles that are going to drop start turning yellow as early as late August. By mid-September these needles turn brown and begin falling from the tree.

Another common group of conifers are the spruces such as Colorado blue spruce and Black Hills spruce. These trees have shorter needles, about three-quarter to an inch long, and are attached to the stem individually, not in bundles. Spruce needles usually live longer than pine needles and may persist for up to 10 years. Just like pines, those spruce needles which are older and more shaded, will turn color and drop during autumn. In the photo, the ponderosa pine (background) is showing normal fall coloration, while the Colorado blue spruce (foreground) is not shedding any of its needles.

Ponderosa pine - fall color

Some needle drop by conifers during the fall is normal. The exception occurs with larch trees (also called tamarack). Larch trees lose all of their needles every year because they are deciduous evergreens. Larch needles are one to two inches long and borne in clusters on short shoots or individually on long shoots. The needles are also very soft. Some larch trees are native to the swamps and bogs of northern Minnesota. A common larch that has been widely planted in North Dakota is the Siberian larch. Larch needles turn bright yellow and provide a golden rain during autumn.

Evergreen needles don’t last forever. Some needle loss toward the center of the tree during autumn is normal. Needle loss at other times of the year is not normal and may be due to an insect or fungal pest or the result of severe environmental stress. Larch trees, the exception to the rule, lose all of their needles every year. Enjoy the colors this fall.

-Joe Zeleznik

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Frost warning

The first frost may strike tonight. Be prepared!

Frozen tomatoFrost may strike parts of our state on Friday morning. This is terrible news—it’s way too early!

This frost might be the end of a disappointing year for many crops. The season started poorly this year due to a cold spring. Most gardens were planted later than usual and never caught up.

As of today, crops in most of our state are a week or two behind. The last thing we need is an early frost.

We cannot stop Jack Frost from coming, but we can be ready for him.

Our first frost is usually a light one (29–32°F). In this case, we can protect our sensitive plants with a blanket or tarp. This will provide a few degrees of protection, which is all we need.

Keep in mind that cold air sinks. Gardens in low spots (frost pockets) are most vulnerable to damage from early frosts.

Cover your most sensitive plants. Tomato, pepper, cucumber, squash and melons are very sensitive to freezing temperatures.

Broccoli, cabbage, carrot and radish can tolerate light frosts and do not require protection. The cool temperatures of fall will actually improve the flavor of these vegetables.

The frost may kill potato vines, but their underground tubers will be safe.

Impatiens, zinnia, celosia, geranium and coleus are among the most sensitive of flowers.

Among the most frost-tolerant flowers are petunia, marigold, cosmos and pansy.

If tonight’s first frost is a light one, we will likely get two or more weeks of gardening season before a hard frost (28°F or colder) strikes. When that killing frost is expected, you need to harvest whatever tender vegetables you can. This includes peppers, cucumbers and squash. Blemish-free tomatoes with a pink blush can ripen off the vine.

Apples on trees tolerate temperatures down to 25°F before suffering damage.

Reprinted from the NDSU Yard & Garden Report for September 8, 2014. Blog entry written by Tom Kalb, Extension Horticulturist, North Dakota State University. Photo was made available under a Creative Commons license by the photographer: Joshua Heyer.

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Iron chlorosis - brief overview

This articles touches on iron chlorosis in trees, including its causes and potential cures. Everything works some of the time, nothing works all the time.

(The following appeared in the ND Forest Service’s ‘Prairie Forester’ publication in 2009.)

-Joe Zeleznik 

Life is tough on trees in North Dakota. They face bitter cold winters, spring floods and summer droughts. One thing they don’t face is nutrient deficiency … usually. Iron chlorosis is the exception. It affects trees throughout the state and it is sometimes fatal.

Iron chlorosis 2

The main symptom of iron chlorosis is yellow leaves with green veins. Iron is used by the trees to make chlorophyll, the green pigment that traps sunlight for photosynthesis. There is no predicting if or when a tree will be affected by iron chlorosis; a tree can be healthy for many years, then suddenly become chlorotic. Iron chlorosis can be the first step in a decline spiral that eventually kills the tree.

Some species are more susceptible than others to reduced iron. Silver maple trees are especially vulnerable. Silver maple is one of the parents of the Freeman maples such as Autumn Blaze® or Sienna Glen®; these hybrids are slightly susceptible to iron chlorosis, but not as much as silver maple. River birch and red oak are less sensitive than silver maple, but more sensitive than most other tree species.

Most of North Dakota’s soils have enough iron in them to support healthy plant growth. But sometimes the iron is in a form that’s not available to plants. The culprit is usually high soil pH. The soil is not acidic enough to keep iron in the available form. Low soil oxygen can also cause iron to be unavailable. Trees are more susceptible to iron chlorosis if they are growing in flooded or compacted soils. Even low temperatures can reduce iron availability.

Can chlorotic trees be “fixed” or “saved”? As with most things, the answer is “it depends.” In the case of iron chlorosis, prevention is more effective than after-the-fact treatment.

Determining the cause of the low iron availability is critical to developing a treatment approach. Obviously, we can’t change the weather – low-temperature induced chlorosis can’t be prevented. However, flooding and compaction – and therefore low soil oxygen – can be mitigated by improving drainage or aerating the soil.

Iron chlorosis 1

For chemical treatment products, there are a lot of manufacturers’ claims. What does the science say? It’s not conclusive. Everything works some of the time, but nothing works all of the time.

If the cause of the chlorosis is high soil pH, then there are two options – lower the pH or add iron in an available form. Soil pH can be lowered by adding elemental sulfur or by adding acid-forming fertilizers. Some experts recommend combining these approaches by applying iron sulfate to the soil. Treatments must be repeated every two-to-three years. Iron can also be added as a chelate. Chelated iron comes in many formulations, so ask your local garden center what formulations are on hand.

Iron can also be added directly to the tree, either as a foliar spray or as a trunk injection into the vascular system. Iron chelate sprayed onto the leaves offers a quick fix to the problem, but the effects are often short-lived. Trunk injections have shown mixed results. Sometimes, injections are effective and trees regain their health and vigor. However, if the damage is too severe, then trees will not recover.

Iron chlorosis can be found in trees throughout the state. But with proper management, it can be prevented, and sometimes, cured.

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A leaf of a different color

Most leaves are green during the growing season. Leaves that are off-color are often showing signs of some type of stress. However, that's not always the case, as seen in these photos.

Leaves normally change color in the fall – we all know this.  If leaves begin to change color in the summer, that’s usually not a good sign.  Insects, diseases, nutrient deficiencies, environmental stresses – or some combination of these – can all cause leaves to turn yellow, brown or other colors during the growing season.

However, some trees and shrubs are supposed to have two-toned leaves during the growing season.  On other trees, you may see individual leaves of one color, and other (individual) leaves of a different color.  In some cases, that’s okay!  See the pics below.

-Joe Zeleznik


‘Schubert’ chokecherry – ‘Schubert’ chokecherry (a.k.a. ‘Canada Red’ chokecherry) is valued for its purple foliage during the growing season and bright red fall color.  The bright green leaves at the tip of this branch are a new flush of growth appearing in mid-season, and they will turn purple in one to two weeks.  This variety of chokecherry is native to North Dakota and is extremely hardy.  Suckering from the roots may cause problems.

Newly formed Schubert chokecherry leaves, showing green color, before changing to a purple tone.

Poplars –This hybrid poplar produces leaves that start off with a purple hue which then change to green – just the opposite of the Schubert chokecherry.  There are many poplar trees that are either native to North Dakota or adapted to the environment here.  Most poplars grow quickly but die young – especially the hybrids.  This can be handy when establishing a windbreak, as the poplars can provide immediate protection while the more-permanent trees establish slowly.

Newly formed leaves of a hybrid poplar show a purple hue, changing later to green.

Ivory Halo dogwood – This species has variegated leaves.  That is, the leaves are naturally two-toned.  There are many other trees and shrubs that are variegated, but finding ones that are tough enough to handle the North Dakota environment can be difficult.  Ivory Halo is hardy to Zone 3, and it does best in protected areas with good soil moisture. 

Two-toned, variegated leaves of Ivory Halo dogwood.

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NDSU Horticulture Field Day Set for July 22

July 22nd from 9:00 a.m. to noon
NDSU Horticulture Field Day Set for July 22


NDSU-Plant Sciences Department will host a horticulture field day on July 22, 2014 from 9:00 a.m. to noon. Festivities will begin at the NDSU Horticulture Research and Demonstration Gardens located at the corner of 12th Avenue North and 18th Street in Fargo. Tours will be conducted of the various gardens and of horticulture faculty research plots.

The NDSU Daylily Garden is an official display garden of the American Hemerocallis Society and features over 1400 daylily cultivars. “This is the largest public daylily collection in the nation,” says Esther McGinnis, Extension Service horticulturist and assistant professor. “The collection is truly a hidden treasure for our state.”

The field day will also feature the All-America Selections bedding plant display garden. “Walking through the gardens is an education and you can see which flowers perform well in our challenging North Dakota climate,” McGinnis says.

New this year, NDSU horticulture faculty will be on hand to offer tours of their campus plots demonstrating their research on raspberries, chokecherries, blackberries, grapes, vegetables, and turfgrass.

Light refreshments will be served.

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Ash anthracnose recently observed.

Ash anthracnose is a recurring problem. This year (2014), it was a little later than normal, but has finally arrived.

Some ash trees have recently lost their leaves because of a problem called ash anthracnose.  We see this in spring, especially following wet weather, as we’ve experienced lately.  Additional symptoms can include black blotches on leaf margins, causing leaf distortion, and small purple-to-brown spots in the middle of leaves. The leaf symptoms may not necessarily be visible on fallen leaves, since the infection that triggered leaf drop is likely on a petiole or other inconspicuous location.Ash anthracnose

Treatment with fungicides is usually not warranted. Fungicides are only effective as a preventative treatment, usually as leaves are expanding.  Treating trees now can prevent mid-season infections, but infection is more common in the wet spring, rather than the drier summer.  For most large trees, fungicide applications aren’t very practical.  However, there are cultural practices you can implement now, such as a light fertilization, to help reduce recurring stress on ash. “Light” fertilization would be 1-3 pounds of nitrogen per 1,000 square feet of soil surface around the tree.  If you already fertilize your lawn, then there should be more than enough to meet the tree’s nutritional needs.

The fungus that causes ash anthracnose overwinters in the upper parts of trees on seeds, on twig cankers, and on any other plant part that remains attached to twigs, so raking and destroying fallen leaves and twigs may only help reduce inoculum rather than completely eliminate it. As a result, ash anthracnose is a recurring problem on ash as long as we have wet, cool weather in the spring. Disease severity varies from one year to the next, and among individual trees.

-Joe Zeleznik

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“Winter Injury” on conifers

Discolored needles on evergreens, noticed in late winter or early spring. Causes are many, true cures are hard to come by.

Every year, starting in late February or early March, I begin to get calls and emails about evergreen trees that aren’t very green.  Some of the needles may be turning brown, red or even a shade of purple.  Generally, we categorize the problem as “winter injury”.  That’s somewhat vague, as the potential causes are many.

The classic example of winter injury is seen in the picture below.  All of the needles that are located above the snow are exposed to harsh winter conditions such as fierce winds and brutal cold.  Additionally, bright sunlight can reflect off the snow and create more problems. 

winter injury, conifer, evergreen, disease

The symptoms of winter injury in spruce trees are often somewhat different (below).  Needles turn different shades of purple or red or brown.  Usually, there is no specific pattern to the damage – the discoloration isn’t above the snowpack, or just on one side of the tree or even worse on one side.  It isn’t necessarily newer needles, or older needles, or needles on the tops of the twigs that are affected.  That makes diagnosis a little difficult – environmental problems usually show some type of pattern.  Nevertheless, if symptoms like these develop over the course of the winter, after January, then it’s almost certain that the problem can be categorized as winter injury. 

 spruce, conifer, evergreen, winter injury, stress, disease

While rough winter conditions can kill needles, the buds that contain next year’s growth often survive.  The trees in the first picture above were damaged in the 2009-2010 winter.  The shoots had new growth in 2010 and the trees recovered well.  Winter injury stresses trees and minimizing stress over the following growing season is important in helping trees recover.  Watch out for pests and treat them as needed.  Spruce trees that have been damaged by spider mites are more susceptible to winter injury than those that haven’t been attacked.  Minimizing drought stress is also important.  Make sure the tree has enough water to meet its needs, but don’t overwater.  A rule-of-thumb for watering is once every 10 days, if there has been no rain.  In the fall, watering up until the ground freezes will help keep the tree hydrated going into winter.  This will help to minimize winter injury, though it won’t completely prevent it.  Helping the tree to build new leaf tissue can also support its recovery.  Adding a small amount of nitrogen fertilizer in the spring – 1 to 3 lbs of nitrogen per 1000 square feet of soil surface – can help the tree to recover. 

Winter injury is common and reveals itself as dead needles during the spring.  Minimizing stress during the growing season can help trees recover from winter injury, and in some cases, can even lower the probability of winter injury from happening in the first place.

Joe Zeleznik

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Youth Gardening Grants Available

Competitive grants available to youth organizations

North Dakota Junior Master Gardener Program logoNorth Dakota State University will make grants up to $1,000 available on a competitive basis to support youth gardening projects. Approximately $30,000 is available.

County Extension offices, 4-H clubs, schools, community organizations, church groups, and other youth organizations are encouraged to apply.

Any project related to youth and gardening is eligible. Examples include the establishment of school gardens and orchards, beautification projects in parks, construction of raised garden beds for the elderly, growing vegetables for local food pantries, and planting trees.

We have curriculum from the national Junior Master Gardener Program available, but projects are not required to use it. This curriculum includes hundreds of programming ideas and you can focus on gardening, nutrition, wildlife and literature.

The application is online and easy to complete. Review of applications will begin February 10, 2014 and continue on a regular basis through April or until available funds are exhausted.

For more information, go to

Please contact Tom Kalb, Dean Aakre or Todd Weinmann if you have any specific questions.

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Best Vegetable Varieties for North Dakota

Recommendations for gardeners

North Dakota Home Garden Variety Trials: Results 2013North Dakota State University and a team of over 500 gardeners have evaluated hundreds of varieties in backyard gardens over the past five years. The team rated the varieties for germination, plant health, earliness, yield and taste. The results of the 2013 trials and our recommendations for 2014 are available for downloading below.

Everyone is welcome to join our team! You will be introduced to new varieties, sharpen your skills in science, and grow healthy vegetables. It is a fun project for the entire family. Our seed catalog for 2014 will be posted in February. For more information, contact Extension Horticulturist Tom Kalb.

North Dakota Home Garden Variety Trials: 2013 Results (PDF, 127 pages, 3.00 MB).

North Dakota Home Garden Variety Trials: 2013 Summary (PDF, 13 pages, 592 KB).

Recommended Vegetable Varieties for North Dakota Gardens - 2014 (PDF, 2 pages, 118 KB).

NDSU Yard & Garden Report for January 2014 (PDF, 8 pages, 672 KB).

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Gift Ideas for Gardeners

Holiday ornamentsThe holidays are here—and these are the busiest shopping days of the year!

Selecting the right gift can be a challenge sometimes. It’s nice to know that many of our friends enjoy gardening. Here are a few gift ideas to consider:

Let’s start with a beautiful flowering houseplant. The delicate blooms of a cactus make it a special gift. Poinsettia and azalea also add dazzling color to the holidays.

Foliage houseplants make a nice gift that can provide for years of pleasure. Put the plant in a colorful ceramic pot to add a special touch. Give them a Norfolk Island pine (which looks like a tiny Christmas tree) and decorate it with ornaments.

A potted amaryllis is fun to grow. Your friend will be amazed on its rapid growth and fabulous flowers.

A dried flower arrangement is another colorful gift idea that provides long-lasting beauty.

A paper pot maker can turn old newspapers into seed starting pots. Soil block makers are another way to make your own plant pots. A heating mat can get the transplants off to a strong start this spring. 

Good pruning tools are always appreciated. A new shovel, spading fork, or quality hoe may not seem like a showy gift, but it will touch the heart of a true gardener.

Consider giving some accessories such as a pocket knife, pair of gloves, or a kneeling pad. Maybe add a set of automatic watering globes—they even look like Christmas ornaments!

Other thoughtful gifts include a rack that dries herbs, a scissors that minces herbs, and crocks for pickling.

Give a subscription to a gardening magazine and they will remember you all year.

Thermometers, soil thermometers, and rain gauges provide valuable information to a gardener.

Hand scrubbing lotions are available that clean and moisturize the best tools of gardeners: their hands.

For the gardener who seems to have everything, wind chimes and spinners can add pleasing sounds and movements to a landscape. Gnomes and other gardening ornaments may be a risky gift, but such gifts can bring the biggest smiles!

Happy holidays!

Photo was made available under a Creative Commons license specified by the photographer: Portrait / Wedding …,

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