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Darrel Koehler

Darrel Koehler is a native of New York Mills, Minn., and is a graduate of the University of Minnesota. After graduation, he worked at the Austin (Minn.) Daily Herald. Later, he was employed for almost 40 years at the Grand Forks (N.D.) Herald, where he was a reporter and wrote a gardening column. He also taught community education gardening classes in East Grand Forks, Minn., and appeared as a regular guest on a local radio gardening show. He and his wife, Peggy, live in East Grand Forks.

DARREL KOEHLER: The Prairie Gardener — New Apples

Regional apple growers are excited to face an avalanche of fruit this fall as the late apples are harvested.

However, some trees didn’t bloom last spring, or the rains were a problem that cut the blooms and the yield.

Many of the apples we enjoyed either fresh or in apple treats were developed right here in Minnesota. Peter Gideon is given credit as the first apple grower in the Gopher State.

He began his apple breeding work in 1853 at his homestead on Lake Minnetonka near Excelsior. He used seed to obtain a healthy, tough apple tree. But with exception of a single Siberian crabapple, they perished in the Minnesota cold.

He bought more seed from a Maine apple grower, and he obtained a successful cross. The apple was called Wealthy, named after his wife. In 1900, this variety was still among the top five apples still grown.

The number of apple varieties is staggering. Some of the recent hits have been the famed Honeycrisp and Telstar.

This year, three apples with distinctive traits have been selected to join honor roll of apples. They are Snow Sweet, Frostbite and SweeTango.

  • Snow Sweet produces savory, sweet fruit with a slight tart balance. An added benefit is how slowly the fruit turn brown when it is cut.

    Frostbite apple was developed at the University of Minnesota.
    Frostbite apple was developed at the University of Minnesota.
  • Frostbite fills a special niche. It is an extremely hardy tree with small fruit that tastes almost like sugarcane. It is very sweet and juicy.
  • SweeTango reflects breeding that is a cross of Honeycrisp and Zestar. The fruit delivers its own unique flavor and crunch.

Honey crisp still takes honors. Since its release in 1991, millions of Honeycrisp trees have been planted and have successfully produced excellent fruit.

Experimental work has also impacted other horticulture crops. And it all started on a pioneer farm in Minnesota.

Winter break

I will be taking a break from mid-October to April. If all goes well, I’ll look forward to seeing you all again in spring.


DARREL KOEHLER: The Prairie Gardener — Fall Lawn Care

Our lawns have had a difficult year. We had a wet, cold spring followed by a hot and dry summer, and while we had scattered rain in late summer, it was not enough to offset the brutal year.

But good lawn care can help alleviate the bad situation.

Here are a few preventative steps you can take:

  • While fall rains can help restock subsoil moisture, you may have to water if the problem doesn’t correct itself.

Controlling weeds also is essential. Usually, a lawn service can apply liquid fertilizer and herbicide to your lawn. Or you can do it yourself. (Herbicides should be applied as soon as Labor Day until late September.)

  • You also can aerate your lawn if the soil is compacted or if thatch is a problem.
  • Lawns require nitrogen to retain their rich, green color. Continue mowing the lawn so that the grass is no higher than 1.5 to 2 inches tall going into the winter.
  • Years ago, gardeners were told to cut their lawns real short to prevent snow mold. They actually did more damage by scalping their lawns. Generally, in places where snow accumulates, you can mow down to 1.5 inches.
  • Most cool season grasses such as Kentucky bluegrass are best maintained at 2 to 3 inches high during the growing season. In October, you can reduce to the overwintering heights best for your lawn.
  • If the grass ceases to grow before all the deciduous foliage has fallen, use the mower as a leaf mulcher or vacuum to keep the leaves from packing down and smothering the grass.

It is getting late to reseed lawns that have bad spots. A good time to reseed would be in early spring after the snow has melted but the soil is still moist to aid germination.

Remember that sunny places are best-suited for Kentucky bluegrass varieties. Red fescue works in shady areas.

Rose care

Final winterizing for roses is usually done in late October after a deep, hard freeze. Cover the roses with plastic foam cones or bushel baskets for protection. Tying the cones loosely beforehand will ease the job. Cut the cones back about 6 to 12 inches and mound the plants with fresh black dirt.

These instructions apply to tender or tea roses. For shrub roses, winter protection is less of a problem. If the top should die, it will grow another in spring.

Many gardeners overwinter their tender roses and other tender perennials by covering with bags of leaves. Also, during the winter, keep tender plants covered with snow, the perfect winter blanket.

DARREL KOEHLER: The Prairie Gardener — Fall Leaves

We are ready to embark on the most colorful time of the year — fall colors. And there is more good news!

Great fall color is dependent on just the right weather conditions, especially moisture, and a spokesperson for the Minnesota Department of Natural Resources says current conditions put us on track for one of the most colorful autumns on record.

With the exception of the Arrowhead region of northeast Minnesota, most of the state has had either average or above-average precipitation, making for healthy trees, which produce the best color. If we continue to get adequate rainfall as nights grow longer, so much the bettter.

Leaf colors reach peak usually between mid-September and early October in the northern region of Minnesota, between late September and early October in the central portion.

The color season comes to an end as Jack Frost heads southward out of Minnesota. The final period of fall color would include the Twin Cities.

According to the DNR, peak fall color lasts for about two weeks. But the period can be shorter if fall rainstorms blow off leaves or heavy rains pound them to the ground.

Trees at higher elevations, such as along the North Shore Drive north of Duluth, are the earliest to show color change. And maples, such as the sugar variety, turn blood red earlier, such as those on gravel hills, where the trees are more stressed.

The DNR provides maps on the weekly progress as the colors move quickly from the northern part of Minnesota down to the southern portions of the state in about a month’s time. Updates are provided Thursdays until the leaves are but a dull brown and the sky takes a gray autumn look. For more information, check the DNR’s website. At this time, leaves are moving from green to red, gold, brown and other hues.

While colorful leaves may be a delight to the eye, you must deal with those that will fall in your yard. Leaves left on lawns over winter can damage the turf, resulting in the need to reseed or re-sod in the spring.

Most people now use a mower attachment for leaves and make several trips over the lawn before the snow comes. If you have real heavy piles of leaves, bag them up the old way and haul to the landfill.

I still hand-rake my entire yard annually. I use some bagged leaves for winter protection around our house’s foundation.

But I still miss the autumns of years ago, when the leaves were raked and burned on a warm, sunny fall day in late October. The rich smell scented the autumn air, and the burning embers were great for roasting hot dogs and marshmallows.

DARREL KOEHLER: The Prairie Gardener — Fall Chores

Labor Day has come and gone.

Already, The Old Farmer’s Almanac predicts a very cold and very snowy winter — not the much milder El Niño scenario many weather predictors are indicating.

In any case, gardeners will have to prepare for winter and readiness means cleanup.

We can start with the vegetable garden. Green beans, peas, sweet corn, melons and squash are done for the season. While a little frost improves the squash and pumpkin flavor, it isn’t necessary.

Leave cabbage, kale, beets, rutabagas and turnips until late September or early October. Most other vegetable crops, with the exception of parsnips, can be cleaned out by mid-October. Parsnips will overwinter just fine and can be enjoyed in early spring the following year.

Many of our houseplants are tropical in origin. So even a little frost can kill poinsettias and Christmas cacti. Geraniums will overwinter if potted or stored in the basement.

Before bringing houseplants indoors, you may have to cut them back if necessary. Also, check for insects and disease.

If possible, bring plants into a cool porch or garage first and then into the house. That way they will avoid drastic temperature shock.

As the weather grows colder, it’s time to pick apples, potatoes and whatever tomatoes remain. If possible, till your garden before winter sets in. The frost will break up the clay balls we have in our gardens. Also, work in well-rotted manure and compost.

Tender bulbs, corms and tubers can be enjoyed right up until a frost. When a frost blackens the tops, it will be time to dig them up carefully and retrieve any offshoots. Cure them for a two- to three-week period by drying them outside or in the garage before putting them into a cool basement. Dahlias, cannas, calla lily and glads are in in this category.

Begonias are handled another way. Don’t cut off foliage but rather let it dry  enough so it will become brittle and break off.

The bulbs will overwinter well in a dark, cool place in the 45- to 50-degree range. You can pack them in peat moss, vermiculite or similar material. Dust with a fungicide and insecticide to curb problems next spring.

Remove dead foliage from peonies or it will harbor disease. Leave mum and asparagus foliage because it will catch winter snow and protect the plants. Keep rotted apples picked up so they won’t harbor disease. Finally, keep lawns mowed and raked and water trees and floral plantings.

DARREL KOEHLER: The Prairie Gardener — Tomatoes And Blight

Despite the prediction this summer would be hot and dry, the opposite was the case, which didn’t bode well for some gardeners who raise tomatoes.

Early summer rains coupled with damp, cloudy weather conditions severely damaged this season’s crop. If your tomatoes were in a dry spot with lots of sunshine, you probably fared better.

According to the Minnesota Extension Service, the most common problem was blight. There are several types of blight, with septoria being the most common.

Septoria causes small, dark spots on leaves. Then, the leaves turn yellow and fall off. It usually starts at the bottom of the plant and works its way upward.

Wet and humid conditions like the kind we’ve been experiencing this summer hasten blight’s development. While you can’t deal with Mother Nature in terms of weather conditions, you can avoid overhead watering.

This disease usually does not cause damage to the fruit, but if the plant loses too many leaves, it can’t supply food to its many tomatoes.

So, we end up with two situations. If conditions have been good, you will end up with a good to bumper crop. If you have a bad blight year, you may have fewer or no tomatoes.

Besides septoria, gardeners also have had to deal with fewer cases of late or early blight. They cause larger spots to develop on leaf steams and fruit.

Protective fungicides containing Daconil can help to control blight. It must be applied at the first sign of the disease — or it will be too late.

Bacterial spot and bacterial speck have also struck tomato plants this summer. Small dark spots form on the fruit and leaves. Unlike the fungal diseases, fungicides will not control bacterial diseases.

In the case of heavy rain, tomatoes may crack. There is no remedy for this.

Here are some tips on how to deal with blight that you can file away for next season.

  • Mulch around plants early to delay onset of the disease. However, once disease is spotted, don’t bother to continue mulching.
  • Space plants a good distance apart, allowing good air circulation.
  • Staking tomato plants or encasing them with cages also helps. Purchase heavy-duty tomato cages as they will have to deal with lots of weight.
  • Don’t allow tomatoes to sit on the ground, since they will be prone to rot as well as attack from slugs.
  • Clear away plants in the fall.
  • When purchasing tomato seedlings, check to see if they are blight resistant.

Good luck!



DARREL KOEHLER: The Prairie Gardener — Mum’s The Word

When I think of fall flowers, immediately the majestic mums come to mind. These are wonderful flowers that can become part of your landscape until the cold and snow arrives in November.

While mums have more frost tolerance than most flowering plants, once the mercury drops to the mid 20s, even the late ones surrender.

Mums come in a rich array of colors, including gold, bronze and mahogany. They also come in white, pink and red. Those plants developed at the University of Minnesota almost always put on a good show.

Chrysanthemums — better known as mums — are unique in that gardeners treat them as annuals or perennials. Early bloomers already are out in late summer while other kinds hit their stride in late fall.

Mums can be purchased at garden centers in either spring or late summer. Those bought in late summer should be treated as annuals. However, those purchased in spring should be treated as perennials.

After they end their season, spring-planted mums can be carried over winter in our gardens and will bloom the following year. If you have mums that you found on discount centers, toss them when they look shabby.

Today’s mums are more hardy than those available in the past. Most varieties that flower early (Sept. 1 through Sept. 25) are worth growing even as annuals if they survive two or more years. Hearty, well-grown plants that have been in full light, watered regularly and fertilized are stronger and are more apt to survive.

Spring mums are best planted in May or early June. Plants purchased at garden centers or greenhouses should not be planted until the danger of frost has passed.

Mums do well in most fertile soils. Plant them in a sunny area that is well-drained and high in organic matter. Plants should be spaced 18 to 24 inches apart and each given 2 tablespoons of 5-10-5 or similar fertilizer. Work the fertilizer well into the ground, and be sure to water if the soil is dry. (If you need to water the plants during the growing season, do it from the bottom, not the top.)

To produce low-growth, sturdy, well-branched mums pinch back the tips of the shoots once or twice during the growing season.

Cool summers will result in earlier blooming, while hot summers may delay blooming by two weeks or more.

Usually, the original plant will die, however small shoots will form at the base and will provide flowers the following year. Cover plants with coarse mulch such as straw but leave tops on plants to catch snow. Don’t use leaves, which mat.



DARREL KOEHLER: The Prairie Gardener — Rhubarb

Even though plants may look ripe for picking in August, most gardeners say you shouldn’t harvest rhubarb after the Fourth of July.

That is good advice, since rhubarb becomes coarse and woody and loses its flavor later in the summer. And continued harvest through the summer months weakens the rhubarb plants and reduces the yield and quality of next year’s crop.

But if you are looking to plant some rhubarb, it’s not too early to start thinking about it now. Spring and early fall (September) are the best times to transplant rhubarb, although potted plants can be placed in the ground anytime.

Rhubarb is a very hardy perennial that does well in Northern states. Sadly, it doesn’t grow in the Sun Belt. It requires a cold treatment before it will grow. (Some is shipped out, but many in the South take it for Swiss chard.)

The rhubarb plant originated in Siberia. It traveled down the old Silk Road to Asia Minor before spreading to northern Europe. Early Europeans ate the root, not the stalk. The stalks are edible, but not the leaves, which are poisonous.

It is said that rhubarb, also known as pie plant, should be in every garden. Plant it somewhere out of the way, in a bright, sunny spot, where the plants will not be disturbed. The area also should be well-drained.

To get started, dig a hole and put in some rotted manure and compost. Then cover the roots with about an inch of soil.

Rhubarb shouldn’t be harvested the first year, and it’s important to give plants a lot of fertilizer and water. The second year, the plants will send out seed pods, which should be removed as they form.

You can either get your rhubarb from a friend or neighbor, purchase by mail order or visit a nursery. The best way is to buy a plant already potted.

Many of the older rhubarb plants that we see around here have a mixture of yellowish-green and reddish stalks. These are known as pineapple rhubarb plants and are an old variety.

The best-known variety of rhubarb is the Canada Red, apply named since the stalks are red all the way the through. They would work well even as an accent to your garden. Other varieties include Valentine and strawberry.

You won’t be disappointed if you decide to plant rhubarb because there is nothing better than a bowl of warm rhubarb sauce in the dead of winter, when the mercury is minus 30 — unless it’s a pie, crisp or jam!

DARREL KOEHLER: The Prairie Gardener — Apples

If the early-fruiting apples are any indications, this year’s crop will be big. That’s unlike the 2014 harvest, which was down due to the awful winter the trees endured. The past winter was very mild, though, and we will have the apples as evidence.

Apples are the most-dependable fruit for this area, which is in Zone 3. A frequent question is when will apple trees bear fruit. Usually, fruiting will occur between three to five years after planting. Standard varieties of apples take longer; dwarf varieties have apples sooner. However, many gardeners don’t plant dwarf apples, as they are said to be less hardy than standard varieties.

A common problem in winter is damage from rabbits, mice or deer. Sunscald also can damage the bark. Check hardware stores for hard plastic protectors, tree wrap or screen.

Worms appear to be somewhat of a problem in an early crop like this year. Clearing all the apples off the ground right after they fall is a good idea. Don’t spray for worms unless you had a problem the previous year.

To prevent wormy apples, apply Sevin spray every two weeks when the apples begin to show a reddish color in the blooms.

Alan Linda of New York Mills, Minn., has a small orchard that he has cared for three decades or longer. Linda grew up on a farm near Riceville, Iowa, and writes a weekly column in the Perham, Minn., newspaper in which he sometimes writes about apples.

He said the most important thing he has learned was never to plant semi-dwarf apple trees.

Here a couple of more tips from Linda:

  • All fruit trees must be watered. Soil type makes no difference.
  • Secure trees with electrical wiring that is attached to steel fence posts that have been driven into the ground on two sides of the tree.
  • Use metal screening to keep varmints at bay as well as manicuring with weed trimmers.
  • It’s not necessary to fertilize.
  • Rather than spray for worms, place red balls with Tanglefoot, a very sticky substance, around your trees.

Linda speaks highly of Haralson and Haralred varieties. These are tart apples that will store well in a root cellar for up to seven months.

Both the Haralson and the Haralred bear heavy crops every other year (apple year) with a sparse harvest in the intervening years. Other varieties such as Honeycrisp provide smaller crops with some apples every year.

For those having problems with Honeycrisp, Linda suggests planting Sweet 16 trees instead. They do better, and they are related to the Honeycrisp. Plan on replanting about 10 percent of the trees each spring.


DARREL KOEHLER: The Prairie Gardener — Giddy Glads, Part 2

Glads are a wonderful addition to any garden as we discussed in a recent column on this wonderful flower. There is so much information, though, so we want to devote a second column to glads.

Glads are more effective and easier to care for if they have their own exclusive bed in the garden. If grown for cutting, the glads can be planted in rows in the vegetable garden where they are easier to care for, including weeding.

Glads begin their growth from an underground stem called a corm. Each summer, the old corm shrivels and dries up. One or more corms are produced during the growing season, which are cured and stored over winter.

The quality of the corms determines the quality of the the blooms. Buy corms from a reputable source. Corms with high centers and that are plump are better than large, flat thin ones. The thicker the corm, the higher the quality of bloom.

Glads can be planted anytime from early May until mid-June. Spacing plantings one to two weeks apart will provide continuous bloom throughout the summer.

Glads can be planted either in rows or informally. For cut flowers, you can have rows 2 to 3 feet apart. For small home gardens, you can plant them 18 inches apart, says former North Dakota State University Extension horticulturalist Ron Smith.

In general, plant deeper in sandy soils and shallower in heavy soils. Deep planting anchors the stem and helps resist wind damage. You also can plant the glads against a chicken wire fence.

A word of caution: Be sure the corms are upright when planted.

Varieties should be labeled as you plant. If you don’t have the correct name, list the color. This will help you keep them separated when digging time arrives in autumn.

Colors such as white, yellow and pink are usually vigorous and may multiply faster than the dark colors such as purple, rose or smoky. If left alone, the lighter, more productive colors will eventually outnumber the darker ones. This may give the impression that the glads have “changed colors” to primary shades.

Lack of moisture can cause shorter spikes, smaller florets and smaller corms for next season. An inch of rain per week is needed. Mulches help conserve moisture and include straw and compost.

If thrips are a problem, dust plants with Sevin or similar powder. Thrips also can overwinter in corms, so dust them prior to storage. Thrips are minute, have wings and might be referred to as thunderflies, storm flies, corn flies and corn lice.


DARREL KOEHLER: The Prairie Gardener — Giddy Glads

August is a wonderful time for gardeners. Much of the heavy lifting is done for another year, and we can claim our rewards.

One of those rewards is the beautiful gladiolus we have in many of our gardens. Few flowers have so much to offer. Every garden should have glads!

According to Steve Sagaser, Grand Forks County horticulturist, glads range from 2 to 5 feet tall with trumpet-shaped blooms. They are formed in a double row along the stem.

Gladiolus come in a wide range of colors from near black to white with just about every shade of the rainbow in between. Besides the large color assortment, many hybrids have ruffled, waved and frilly petals.

Gladiolus are easy grow. First, dig a trench or furrow about 6 inches deep. Then place corms (underground plant stem) in the soil about 6 inches apart and cover. This will keep the plants from tipping in a strong wind. If you fertilize, use an all-purpose fertilizer such as 8-8-8.

If you start with a dozen or so corms in spring, you could have lots in a few years to share with family and friends.

Gladiolus bloom from early August through September — and even later. They need sun, lots of water and well-drained soil. If you space your glads when planting, you can stagger the blooming period. You then will be able to enjoy continuous color all summer long.

Corms must be dug each fall after a killing or hard frost and be stored in a cool, dry spot such as an unheated basement. (They don’t require any special care in winter.) Then, in the spring, you set them back in the garden for another season of beauty.

A popular event at the Minnesota State Fair is the gladiolus show. It takes an hour or more just to make a quiet check of the different arrangements and colors offered by the wonderful flowers.

Next week: More glad tips.