Hort Update for November 24, 2014

Hort Update for November 24, 2014

Hostas ready for cutting back in Fall. Photo by Jack Pearce, flickr.com
In This Issue: Major Symptom:
1. Stop fertilization Wait until spring if final fall application was missed
2. Broadleaf weed control Apply herbicides if conditions right and weed leaves green
3. Dormant seeding Prime time, especially if some soil preparation can still be done
4. Snow mold not a concern Short period of snow cover reduces risk
5. Buffalograss weed control Round up can still be applied if conditions are right
6. Sudden temperature drop effects Difficult to predict but potential for some
7. No mulch volcanos Keep mulch six inches from tree trunks
8. Cutting back herbaceous perennials Considerations for cutting back perennials
9. Potato, onion and other vegetable storage Check stored produce during winter
10. In garden vegetable storage Heavy straw mulch may delay soil freezing
11. Tree and small fruit bud damage Extreme winter temperatures may cause bud damage
12. Drying gourds Surface mold during drying is common
13. Firewood insects Do not store firewood indoors to avoid nuisance insects
14. Care of holiday plants Needed when transporting plants as well as in the home

1. Stop fertilization

Soil temperatures are too cold for plant roots to take up nitrogen. If fertilizer is applied now, there is a high risk of nitrogen leaching out of the soil during winter and spring before roots can absorb the nutrient. Wait until mid to late April before fertilizing turfgrass.


2. Broadleaf weed control

Broadleef weed control could still take place if weather conditions are right and temperatures are not too cold. Weed leaves must still show some green color for herbicides to be effective this late in the season. Read and follow label directions to determine conditions for which a herbcide can be applied. Control will not be seen this fall but perennial or winter annual broadleaf weeds will die over the winter. 


3. Dormant seeding

Dormant seeding can take place now that soil temperatures have dropped below 40 degrees F. Although broadcasting seed and allowing it to work into the soil naturally through frost heaving can work, it is much better to prepare soils using aerification, power raking or tillage or to power-seed to improve seed to soil contact. Seeding rates should also be increased by 10 to be safe when accounting for seed loss due to erosion, animal feeding, etc.

Improve Success of Dormant Seeding, Nebraska Extension


4. Snow mold not a concern

Snow molds are fungal diseases that can infect turfgrass when areas of a turf remain covered with snow for long periods. The risk of infection increases if snow falls before turfgrass is fully dormant or before the soil is frozen. Gray and pink snow mold can infect Nebraska turfgrass but neither should not be a concern due to our recent November snowfall as the snow melted fairly rapidly.


5. Weed control in dormant buffalograss

Weed control in dormant buffalograss with glyphosate (RoundUp™ ) could still be done if temperatures for applying the herbicide are warm enough and weed leaves are still showing some green color. Glyphosate can be applied over the top of dormant buffalograss to control cool-season grasses and broadleaf weeds while not affecting the dormant buffalograss. Late fall (Nov-Dec) is the best timing for this application. The key is there is no green in the leaves of buffalograss at the time of application. It is safest to treat late in the fall when the target cool-season weeds are still green.


6. Sudden temperature drop

The recent sudden drop in temperature can injure plants.  The effects on landscape plants are hard to predict as factors ranging from plant hardiness to microclimates and late summer care  affect how a plant might be impacted, if at all. Plants not fully hardy to Nebraska were most susceptible to injury. These include plants with hardiness zones of 6 or higher, but even zone 5 farther north. Plants hardy to zone 5 or lower could still be injured if they were not fully dormant, were stressed, or had improper fall care.

Trees and shrubs prepare for winter through a hardening off process. Typically, a woody plant does not reach peak hardiness until mid-winter. Temperature extremes during fall are likely to cause more harm than during winter.

The care woody plants receive in late summer affects cold temperature susceptibility. Plants that were pruned, fertilized with nitrogen, or overwatered within the six weeks prior to the cold snap were more likely to be injured. These practices can interfere with the hardening off process.

Next spring we may see plants that fail to grow at all. This will be more rare than common. There may be some dieback on the tips of plant branches or stems. Because woody plants already have leaf buds for next year, we could see sparse or late leafing on some plants but only if leaf buds were injured. Healthy plants will develop a second set of buds. Leaf buds are hardier than flower buds. On plants where the flower buds were already developed, we might see less flowering and fruiting next spring.


7. No mulch volcanos

Mulch piled against tree trunks is harmful. It holds moisture against the trunk that can lead to infection by fungal disease. During winter, voles and other wildlife will use deep layers of mulch for protection leading to gnawing and girdling of tender barked trees. Mulch is an important tree care practice; however, keep mulch about six inches away from tree trunks and only use a two to three inch deep layer. Deeper layers attract wildlife and tree roots will also grow up into deep mulch layers, exposing them to cold temperature injury since roots are less hardy than the trunk or tree branches.


8. Cutting back herbaceous perennials

When weather warms and snow melts away perennial gardens can still be worked. Plants with winter interest may be left and cut back in early spring. Perennial seeds (Echinacea, Heliopsis, Rudbeckia) are a food sources for a variety of birds. Ornamental grasses, Eupatorium, Buddleia, hardy hibiscus and many others provide winter interest.

Plant foliage killed by recent cold temperatures, such as hosta and daylily, can be cut back to the ground. Cut plants to a few inches above the plant crown or growing point to avoid injuring dormant plant crowns. Leave the tops on less hardy perennials for added winter protection. Plants such as chrysanthemum, tender ferns and Carypoteris benefit from standing foliage that catches winter snow and provides moisture for the plant crowns.

Evergreen perennials such as Geum, which maintain green foliage throughout winter, should also be left standing.


9. Potato, onion, and other vegetable storage

Periodically check stored produce during winter and remove any that have started to mold or rot.  For proper storage temperatures and methods for fruit and vegetables, refer to:

Storing Fruits and Vegetables, University of Nebraska-Lincoln


10. In garden vegetable storage

Root crops such as beets, carrots, rutabagas, parsnips and turnips can be left in the garden into late fall and early winter. A heavy mulch of straw will help prevent the ground from freezing so the roots can be dug when needed. The mulch will also maintain the quality of the roots, as it will reduce repeated freezing and thawing of the vegetables. Many people prefer the taste of these root crops after they have been frosted because their flavors become sweeter and milder. When temperatures drop low enough to freeze the ground under the mulch, finish harvesting the roots. Cut offall but one-half inch of the top and store at 32° to 40°F in high humidity to reduce shriveling.


11. Tree and small fruit bud damage

Extremely cold winter temperatures can cause damage to flower buds.  Bud development stage determines how susceptible it is to damage.  Refer to Critical Spring Temperatures for Tree Fruit Development Stages for the amount of potential damage at specific temperatures. Tree and small fruits may have a significant reduction in crop production if many buds are killed.  The most critical time fruit buds is spring when they begin to lose winter dormancy.


12. Drying gourds

Drying goards can take several months, especially large gourds. During the process, the outside skin of the gourd may start to mold. This is normal, so don't throw them away. If the shell is still firm and hard, then continue to periodically turn the gourds and let them continue to dry. Providing warmth during the internal curing process will accelerate drying and discourage decay. Leave the mold until the gourd is completely dry; it usually will wash off then or can be rubbed off with a rough cloth or fine sandpaper. If the shell becomes soft, the gourd is rotting and should be discarded.

Gourds, Purdue Extension


13. Firewood insects

Most insects emerging from firewood, even tree borers and subterranean termites, are only considered nuisance pests when brought into the home in firewood. This is because most insects cannot survive in the home when introduced via firewood. For example, subterranean termites quickly die without their underground colony and emerging adult tree borers will not attack or damage aged or finished wood inside the home. To avoid nuisance pests emerging indoors, only bring firewood inside as needed. Do not store firewood indoors. If firewood is held below 50 degrees Fahrenheit, insects in the wood will remain dormant. If brought indoors and allowed to warm, insect activity resumes and insects may emerge from the wood inside the home.

Insects in Firewood, Purdue Extension


14. Care of holiday plants

Care of holiday plants begins when the wholesale truck delivers the plants to the store and at the point of purchase. Avoid chilling injury when unloading the truck; and when transporting plants from the store home. Once unloaded off the truck and brought home, promptly remove the paper or plastic sleeve placed around the plant. If a plant sleeve remains around a plant for more than 24 hours, ethylene gas produced by the plant will cause leaves to begin dropping. Check the potting mix to be sure it is moist. Inspect plants closely for signs of insect pests; treat and quarantine any found to be infested. Display most plants where they receive fairly bright light and away from warm or cold air drafts. Soilless mixes dry out quickly in dry indoor air. Check plants daily for watering needs. When plants are purchased, they need to be wrapped in a plastic bag to protect them from chilling injury while transported from the store home. For information on specific plants, see link below.

Selection and Care of Holiday Plants, Iowa State University