Summer faq (26349 bytes)

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Table of Contents

Compiled by Stan Barrett and Connie Rayor, Colorado Master GardenersSM, Colorado State University Cooperative Extension, Denver County.

  1. Flowers: My daylilies seem to be healthy with lush, green foliage so why don't they produce many flowers?
  2. Flowers: I planted some peonies two or three years ago They look very healthy but have never flowered. What causes this?
  3. Flowers: My flower beds seem to be infested with earwigs this summer. Are they harmful to the flowers? If so, how can I get rid of them?
  4. Fruits:  The leaves on my cherry tree are curled and twisted and are spotted with clear, sticky specks and sooty black patches. What is attacking them?
  5. Fruits:  On my grape vine, the new buds have holes chewed in the; the new leaves are almost destroyed and I am getting very few grapes.
  6. Fruits:  Our crabapple tree looks like it's been in a fire. The twigs look scorched and bent over at the tips. The leaves are still on the tree, but a lot of them are shriveled and crispy brown. What happened?
  7. Trees:  My maple tree is already losing a lot of leaves and it's only July! The bottom branches are almost bare, and the few leaves still on those branches are starting to change color. What's going on?
  8. Trees:  The edges of the leaves on my shade tree are turning brown. Is this some sort of disease? What can I do?

 


My daylilies seem to be healthy with lush, green foliage so why don't they produce many flowers?

They may be getting insufficient sun or too much nitrogen. Daylilies need at least six hours of sunshine a day. Also, high-nitrogen fertilizer causes them to produce lots of leaves at the expense of flowers. Apply a balanced (10-10-10) fertilizer in the early summer for best blooming.

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I planted some peonies two or three years ago. They look very healthy, but have never flowered. What causes this?

Peonies planted too deeply may never bloom; make sure the buds at the top of the roots are covered by no more than 1 inch of soil. Plant where they will get full sun--at least 6 hours per day.

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My flower beds seem to be infested with earwigs this summer. Are they harmful to the flowers? If so, how can I get rid of them?

The European earwig is a very common inhabitant of flower beds. They tend to hide during the day in small dark spaces. They often feed on harmful insects and mites, but will also eat flower petals. Their population can increase rapidly as the growing season progresses, causing considerable damage to the ornamental garden.

They can be trapped by placing rolled up dampened newspapers in the flower beds in the morning, then collecting them in the evening. Heavy mulch in frequently irrigated areas provides ideal breeding conditions for earwigs. By reducing mulch thickness and allowing periodic drying of the flower beds, their population can be reduced; this solution is often adequate. In severe cases, insecticide baits containing carbaryl (Sevin) can be applied to the hiding places used by the earwigs during the day.

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The leaves on my cherry tree are curled and twisted and are spotted with clear, sticky specks and sooty black patches. What is attacking them?

Black cherry aphids.  These 1/8-inch long pear shaped insects range in color from pale tan to very dark brown.  In the fall the adult female lays eggs on buds or small branches.  The eggs hatch in the spring when the buds open.  The aphids suck the juices from the plant and excrete "honeydew" which covers the leaves and fruit, creating ideal conditions for the growth of sooty mold (the black patches you saw).

To discourage the aphids, the following steps can be taken:

  • Knock the aphids off the trees, using a strong water spray.  Attack both the tops and the undersides of the leaves.
  • Use insecticidal soap, following label directions, again spraying both sides of the leaves.
  • Attract beneficial insects that prey on the aphids, such as parasitic wasps, by planting small-flowered nectar plants (yarrow and scabiosa are reported to work well) near the tree.
  • Apply dormant oil spray in winter.  This coats the branches and smothers overwintering pests and disease pathogens.

 

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On my grape vine, the new buds have holes chewed in them; the new leaves are almost destroyed and I am getting very few grapes.

The culprit is probably the grape flea beetle.  These are dark shiny insects, about 3/16-inch long.  The adults emerge in spring and lay their eggs in cracks in the bark of grapevines.  Emerging larvae are brown with black spots.  The larvae feed for a month then pupate in the soil for several weeks before reappearing as adults.

What to do:

  • Handpick beetles and larvae.
  • Cultivate the soil around the base of the grapevine.  This kills the pupating larvae or exposes them to birds.
  • Spray the plants with summer oil (a refined horticultural oil) to smother the pests.   All stages will be killed.  Be sure to follow the label instructions carefully.
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Our crabapple tree looks like it's been in a fire. The twigs look scorched and bent over at the tips. The leaves are still on the tree, but a lot of them are shriveled and crispy brown. What happened?


It sounds as though the tree has a bacterial disease called fire blight. If you look closely at the branches, you may also find cankers-- dark, slightly sunken places with a little ooze on them.

For immediate first aid, remove infected twigs as soon as possible–but wait until no rain is predicted for at least two weeks. Make the cuts at least 12 inches below the visible edge of infection. After each cut, sterilize the pruning tool by dipping it in household bleach or spray disinfectant. If branches have cankers, prune them 6 to 12 inches below the edge of visible infection. Be sure to destroy all infected twigs and branches.

There is no cure for fire blight, so prevention is the best solution. Avoid overhead sprinkling of trees; drip or deep root watering are better. Make sure that the soil is well-drained around susceptible trees [apple and pear, as well as crabapple] . Don't fertilize the trees heavily with nitrogen fertilizers or manure. Carefully timed preventive sprays may do some good in future seasons. For details on
sprays and lists of fire blight resistant varieties, see CSU fact sheet #2.907, Fire Blight (link below).

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My maple tree is already losing a lot of leaves and it's only July! The bottom branches are almost bare, and the few leaves still on those branches are starting to change color. What's going on?

It sounds as though your tree is suffering from over-watering that may have occurred earlier this year. Too much water in the soil keeps roots from getting the oxygen they need. Maples, ash, aspen, honeylocust, and birch are among the most susceptible to this drowning condition. The symptoms usually show up first at the bottom and the inside of the tree close to the trunk.

Trees do best when the soil is allowed to drain and dry slightly between watering. Test the soil moisture by using a shovel to check the soil at 10 - 12 inches depth. Don't water if it feels wet. If it feels dry, deep root water around the tree slightly inside the drip line and several feet beyond. See CSU fact sheet #2.932 (link below), Environmental Disorders of Woody Plants.

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The edges of the leaves on my shade tree are turning brown. Is this some sort of disease? What can I do?

If the leaves on the top of the tree and on the outer parts of the branches, were the affected first, it's likely that the problem is drought injury caused our hot, dry summer and dry winter. This environmental disorder occurs on evergreens, as well as on deciduous trees. The damage you see cannot be reversed.

You can lessen or prevent future problems by deep watering to 12 to 18 inches once a month in the summer and every two months in the winter. Organic mulch, such as wood chips, spread under trees reduces moisture loss. Use about 3 inches of mulch around the tree up to a few inches away from
trunk. See CSU fact sheets 2.932 and 2.926, HealthyRoots/Healthy Trees.

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Date last revised: 01/05/2010