In the Grow - Q & A

Q. My mimosa tree has split down the middle of the trunk. Is there any way to save it? Or should I just take it down?

A. Split trunks are a common problem with multi-trunked species such as mimosa. Split trunk is a significant factor for a "risk tree," if it is sited where damage to humans, pets or property could occur when, or if, the tree falls. Cabling and bracing can be completed by a certified arborist to help provide structural support, but the split will still be a weak point in the tree, susceptible to disease, insect pests, decay and further splitting.  <Read More>

September Home, Yard, and Garden Calendar

HOME (Indoor plants and activities)

Prepare storage areas for overwintering tender flower bulbs and garden produce.

Thanksgiving (or Christmas) cactus can be forced into bloom for the Thanksgiving holidays. Provide 15 hours of complete darkness each day, for instance, from 5 p.m. to 8 a.m., for approximately eight weeks. Keep temperature at about 60 to 65F. Temperatures of 55F will cause flower buds to set without dark treatment.

YARD (Lawns, woody ornamentals and fruits)

Fall is usually a good time to plant many container-grown or balled-and-burlapped nursery stock, but if your area is still suffering from drought, it might be best to wait for better conditions. You do not want new plantings to go into winter in drought condition.

If you do have sufficient rainfall or ability to irrigate new plantings, prepare a hole wider than the plant’s rootball, plant at the same depth it grew in the nursery, and water thoroughly. Mulching will help protect against large fluctuations in soil temperature and moisture. Be sure to stake or guy-wire tall plants during their first season to protect them from strong winds.

GARDEN (Vegetables, small fruits and flowers)

Dig up onions and garlic after tops fall over naturally and necks begin to dry.

Plant radishes, green onion sets, lettuce and spinach for fall harvest.

Thin out fall crops such as lettuce and carrots that were planted earlier.  <Read More>

Stressed Plants May Look Like Early Fall

To state the obvious, many of our landscape plants really show the signs of excessive heat and extreme drought. Some trees are losing leaves already and may be turning color before they drop. Others have turned completely brown while still remaining attached.

Early fall color and/or defoliation is common when plants are under stress and this season has been quite challenging for many trees, both old and young. The intense heat made it difficult for plants to keep up with water and cooling requirements, even in areas where moisture was adequate. Combine extreme heat with drought, and it is a wonder any plants survive.  <Read More>

In the Grow - Q & A

Q. I have been trying, without success, to eliminate the wild violets from my yard. I have tried many different broad leaf weed sprays with no luck. They seem to be invincible! What can I use that is effective?

A. My yard also has a great population of both white- and blue-flowering violets, but I like them! I welcome their presence and look forward to seeing their lovely blossoms each spring. But I realize I may be in the minority on that.  <Read More>

Sap-sucking Bugs Make a Mess of Indiana's State Tree

Tuliptree with scale and
sooty mold (Purdue PPDL)

Across Indiana this week, homeowners with tulip poplar trees could be finding their cars and landscape plants covered in a mysterious sticky film. This time of year tulip poplars are easily recognized by leaves whose shape resembles a tulip and the two inch long lime green and orange flowers in the tree canopy.

The culprit in this sticky mess could be the tulip tree scale insect, a small sap-sucking bug that feeds on the trees’ branches. Declared as the state tree of Indiana in 1931, tulip poplars are well-regarded and widely planted for their beautiful flowers and form, shade, and rapid growth. The tree’s sap carries vital nutrients, and feeding by the insect can cause damage to the trees in addition to the unsightly mess.  <Read More>

June Home, Yard, and Garden Calendar

HOME (Indoor plants and activities)

Indoor plants will require more frequent watering and fertilization as they increase their summer growth.

Houseplants can be moved outdoors to a shady location, but pay close attention to their watering needs.

YARD (Lawns, woody ornamentals and fruits)

Prune spring-flowering shrubs after blooms fade.

Apply fungicide to prevent and control black spot on roses.


GARDEN (Vegetables, small fruits and flowers)

Discontinue harvest of asparagus and rhubarb around mid-June to allow foliage to develop and store food reserves for next year’s harvest. Fertilize and water when dry to promote healthy growth.

Mulch to control weeds and conserve soil moisture after soil has warmed. Many materials such as straw, chopped corncobs, bark chips, shredded paper and grass clippings can be used.  <Read More>

In The Grow - Q & A

Q. What is the best way to eradicate henbit? Would a weed-and-feed in fall or spring be most effective? Would a spray weed killer be most effective in spring or fall? Could you use a pre-emergence like crabgrass preventer in the fall?

A. Henbit is a winter annual, meaning it germinates from seed in the fall, overwinters in a dormant state and then blooms and sets seed to complete its lifecycle in late winter/early spring. By mid- to late spring, the foliage will turn yellow, but if allowed to remain until then, it will have produced a lot of seed to germinate in years to come.  <Read More> 

May Home, Yard, and Garden Calendar

HOME (Indoor plants and activities)

Many indoor plants can be moved to shady locations outdoors but only after danger of frost is past. Plants will dry out more often outdoors, so keep a close eye on soil moisture. Sinking the pots in soil will help slow down moisture loss.

YARD (Lawns, woody ornamentals and fruits)

Prune early spring-flowering trees and shrubs after flowers fade.

Plant balled-and-burlapped or container nursery stock, and water thoroughly.

GARDEN (Vegetables, small fruits and flowers)

Plant frost-tender plants after danger of frost is past for your area. This includes warm-season vegetables, such as tomatoes, peppers, eggplant and vine crops, as well as most annual flowers and tender perennials, such as cannas, gladiolus, dahlias, tuberous begonias and caladiums.

Pinch chrysanthemums and annual flower plants to keep them compact and well branched. <Read More>

In the Grow - Q & A

Q. My rhubarb plant has been blooming and I have been cutting them off, but recently heard that rhubarb leaves are poisonous. Are the flowers poisonous, too? Do I need to wear gloves? What causes them to bloom?

A. The flowers (and the leafy foliage) of rhubarb plant are toxic if ingested, but not generally considered a skin toxin. However, some do find the sap an irritant, so it's always a good idea to wear gloves when gardening.

It does appear that some rhubarb plants are more prone to flowering than others. Old-fashioned varieties, such as Victoria and MacDonald, are heavy seed-stalk producers. Canada Red and Valentine are less likely to bolt. Plant maturity is also a factor, with more mature plants being more likely to bolt than youngsters. Dividing the crowns every 4-5 years should help rejuvenate the planting. And, no doubt, weather also plays a role, as it does seem to be more problematic in some years.  <Read More>

Weird Weather and Pest Predictions

One of the most common questions that has come up in response to this season's winter weather (or lack thereof) is what effect it will have on pest problems this spring or summer, particularly insect populations.  Below are excerpts of responses given by two Extension experts. 

Larry Caplan, Extension Horticulture Educator in Vanderburgh County addressed this question in a recent newspaper column:

I was asked the other day what effect this strange weather will have on our pest problems this year. That is always a very tough topic for me. I don’t like to make predictions, because there are so many variables that can affect future events, rendering my predictions worthless. Still, there are a few things that I expect will happen this season.

First of all, everything will start happening at least 3 weeks earlier than normal because of the long warm-up we’ve had. Crabgrass germination occurs at about the same time as the forsythia shrub blooms. Usually, we can hold off applying our pre-emergent herbicides until mid to late March; this year, though, some parts of the tri-state may already be too late to get the best preventative control.

Dormant oil is applied to fruit trees to prevent later problems with spider mites. The oil needs to be applied before the trees bud out, otherwise the young leaves will be burned by the chemical. It’s already too late in some places. Likewise, the traditional orchard sprays to control disease and insect attacks should begin as the buds open. Normally, gardeners don’t expect to begin this until late March or early April, but I’ve already seen apple and cherry trees in bloom. Be sure to stop spraying while the flowers are open, so that you don’t hurt any bees that may be out.

The repeated storms of the last few weeks have dumped a lot of moisture on the tri-state. With moist conditions and standing water, we can expect increases in biting midges, mosquitoes, and crane flies. This is what we’ve seen for the last couple of years, which have all been pretty wet.

Warm, moist weather is ideal for fire blight, a bacterial disease that attacks apples, crabapples, and pears. The bacteria usually enters the tree through the flowers, but it can also enter twigs damaged by hail storms. Spraying the antibiotic Streptomycin during bloom and after a hail storm may offer some protection.

If warm weather continues, we may see an earlier emergence of Japanese beetles, eastern tent caterpillars, and other pests, but I don’t believe we’ll see increased numbers. Very few of these insects are killed by severe winters, so I don’t think their survival rate will change much.

And from Dr. Rick Foster, Purdue Extension Entomology Specialist, some points focusing specifically on insect populations:

While some insects, such as flea beetles, are directly impacted by cold winter weather and experience greater survival and higher populations as a result of mild winters such as the one we just experienced, many insect species are very well adapted to winter weather and will survive just fine no matter how cold it is.

Most insects have an amazing ability to reproduce in large numbers and, if spring and summer weather is conducive, will be able to develop to serious population levels no matter how many survived the winter.

Finally, some of our pests overwinter indoors and others overwinter in the South, so our winter weather has little effect on their populations.

The bottom line is that for a few insects, we can definitely expect higher populations, but for many others, we just can’t predict.

As you can see, there is no one answer to this seemingly simple question.  While winter weather conditions have little effect on most insect populations, it is the earlier-than-normal emergence of these insects, as well as weeds and diseases, that will be the most likely effect of our mild winter.  And, as Mr. Caplan adds, this is Indiana, so it could snow this weekend and change everything!

Winter Warm Spell Confuses Landscape and Garden Plants

Larry Caplan, Vanderburgh County Extension Horticulture Educator

I knew this warm spell of the past week was going to be a problem. Sometimes, I hate to be right.

Temperatures in the 50s and 60s have caused a lot of bulbs, perennials, and flowering plants to begin to emerge from the soil and bud out. In my garden, I’ve got crocus and daffodil in bloom. The buds on my lilacs are swelling; I’ve had reports of bud swell on peaches and other fruit trees, especially closer to the Ohio River.

According to the Weather Channel website (http://www.weather.com/weather/ ), our overnight temperatures will be dropping below freezing this week. According to the 10 day forecast for Evansville, we can expect overnight temperatures in the 20s starting Wednesday night, and continuing through Sunday night. The most recent prediction on this site is for a low of 20 degrees on Friday night.

Temperatures this low are going to cause damage to any exposed leaves and blooms. Expect to see daffodil foliage killed back to the ground, along with any other perennial plants that started to sprout. Fortunately, the soil is pretty warm, so the bulbs and perennials themselves shouldn’t be killed: they will sprout back out again, and may even bloom this spring.

Shrubs like azalea, lilac, and shadblow are in a very sensitive stage of development, as are crabapples, peaches, and ornamental cherries. As long as the buds haven’t opened, or at least, not show more than a little bit of a green tip, I expect that freeze damage to the blooms will be minor. If peaches, which are probably the most sensitive of our fruit crops, are still in the swollen bud stage, then a temperature of 18 degrees will only kill about 10% of the blooms…hardly noticeable. But if the peach flowers are showing any pink, then the same 18 degree low will wipe out 90% of the blooms.

Strawberries may be badly hurt. It never really got cold this winter, so the plants never really got into full dormancy. Check your garden: if you see any new green leaves, or (worse yet) any blooms, then a drop in temperature below 28 degrees is going to devastate them. If you still have your straw, plan on covering the plants deeply late afternoon, before the temperature drops. Remove the straw in the morning, after the temperature gets above freezing. Looking at the forecast, we’ll be doing this all week.

I’ve seen roses actually leafing out already. Roses produce their flower buds on new growth, so if some of the new shoots get frozen, the plant will simply sprout some more shoots and go on to bloom later in the season. However, a drop to 20 degrees, as predicted, could do more than blast some leaves and shoots: large portions of the plant could be killed back. It is most important to protect the graft union (a swollen section on the lower trunk, where your pretty rose branches, the scion, are grafted onto a root stock). If the graft union is damaged, then the plant will sprout from the roots, giving you a poor quality “wild rose”, which will look nothing like the plant you bought. Mound the base of the plant with wood chips, shredded leaves, or straw to a depth of 18 - 24 inches.

I don’t think you’ll need to cover your shrubs with sheets, but if you do, be sure to use a cloth sheet, and not a plastic tarp. Heat leaches right through the plastic, and any foliage touching it will be frosted. Don’t lay the sheet over your daffodils – you’ll wind up breaking the stems off. The sheets will only protect your plants down to a temperature of 25 to 26 degrees; much below that, and you may still get injury. If the sheet hangs all the way down to the warm ground, you may be able to withstand a colder overnight temperature as all the warm air is kept around the plant.

BTW: Please DO NOT refer to the cold snap this week as a “late frost.” Our average last frost of the year is the first or second week of April for the southwestern corner of Indiana. It’s SUPPOSED to be this cold!

Good luck!

In the Grow - Q & A

Rosie Lerner, Purdue Extension Consumer Horticulture Specialist

shelf fungi (top) and lichens (bottom)

Q. We are enclosing some pictures that we took of some of our trees, which have been attacked by disease. We were wondering if you could tell us what it is and how to treat it. I'm afraid it will spread to our other trees and eventually kill them. The types of trees are maple, apple, oak and poplar. We appreciate any help you can give us.

A. I have good news and bad news. Your trees have two types of growth showing in these photos. The good news is that neither spread to other healthy trees.

More good news is that the flatter, grey-green growth is a colony of lichens - harmless symbiotic (mutually beneficial) organisms composed of a combination of fungi and either algae or cyanobacteria. Together, they live as one organism and are only using the bark of your tree for anchorage; lichens are not parasites. More information on lichens can be found at http://www.ppdl.purdue.edu/PPDL/expert/Lichens.html.

Some not-so-good news is that the creamy-colored growth that protrudes a bit from the trunk is called shelf fungus and lives on old, usually decaying, trees. While this fungus does not cause disease itself, it is an indication of serious decay problems below and can further weaken the tree. The fungus is less serious than the principal cause or causes of decay. Affected branches can be pruned out, but there's nothing that can be done when the decay is on the main trunk. The tree can continue to live for quite a few more years, but eventually it will need to be removed.

  Norfolk Island pine

Q. I've inherited a distressed Norfolk Island pine. It was in an office, which was very dry, and it had been neglected, even as to its watering. It now is in my living room, and I would like to do what I can to get it back to health. It is sparse from the middle on up. I have removed all of the dead branches. It measures approximately 48 inches from the top of the soil to the top of the branches and measures about 48 inches at its widest point. The pot that it is in is 12x16 inches and does not have any drain holes. It is not full but is very wide. Should I prune the tree? I have attached a picture. What is the best course of care?

A. Unlike many other plants the Norfolk Island pine is not able to replace the gaps in the middle. Any branch that has dropped needles or whole branches that have died will remain bare. So there is no way to prune it that would result in desirable regrowth.

The most immediate need is to repot into a container that allows excess water to drain away from the soil. However, given the bare areas in the middle, you might want to consider either starting over with a new plant or, if you really want to save this particular plant, you might try to root the cut top and discard the bottom. Norfolk Island pine cuttings can only be taken from the top of the central leader stem; cuttings from the lateral branches will not form a new leader.

More information on the care of this plant is at http://www.hort.purdue.edu/ext/norfolkislandpine.html and on how to take cuttings at http://www.hort.purdue.edu/ext/HO-37web.html.