1712 Claflin, 2021 Throckmorton Plant Science Center
Manhattan, KS 66506 (785) 532-6173
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Horticulture Newsletter
The Horticulture Newsletter page from Kansas State University offers valuable insights and resources for gardeners and horticulture enthusiasts. It features articles on plant care, pest management, and seasonal gardening tips, as well as updates on horticultural research and community gardening initiatives. Subscribers can access past newsletters, providing a wealth of information to enhance their gardening experience. The newsletter serves as a hub for education and support in horticulture.
hnr.k-state.edu
ANNOUNCEMENTS
K-State Garden Hour: Shrubs that Thrive in Kansas
Wednesday, September 3, 2025 Noon to 1:00 PM CST
Register here.
Join Dr. Jason Griffin, Woody Ornamentals Horticulture Extension Specialist and Director of the John C. Pair Horticulture Center, as he highlights some great shrubs to incorporate into your landscape. Learn the best shrub varieties suited for our state’s unique climate challenges during this free webinar.
GARDEN TO-DO
- Avoid fertilizing ornamentals so they harden off before winter
- Take cuttings from annuals for over-wintering indoors. See: Cuttings to Grow Inside for Winter
- Turn compost pile and add water when dry
- Harvest winter squash when skin is hard enough that it isn’t easily punctured with your thumbnail
- Plant garden chrysanthemums for fall color
- Fertilize cool-season lawn (KY bluegrass or tall fescue)
- Dig gladiolus when foliage begins to yellow & air dry before storing
- Buy spring-flowering bulbs. Plant in late September through October
VEGETABLES
- Asparagus and Rhubarb in the Fall
Asparagus and rhubarb need to be maintained even though harvesting is finished.
- Add water as needed to prevent plants from drying out. Control weeds by using mulch and cultivation.
- Wait to fertilize until early spring.
- Asparagus foliage can be left intact or removed when it turns brown.
Harvesting Sweet Potatoes
Cold soil negatively affects the quality of taste and shelf life of sweet potatoes. To prevent this, harvest prior to the first fall freeze. Sweet potatoes are typically ready for harvest three to four months after planting.
Gently unearth the sweet potatoes in one mound to check for readiness. You may notice die-back of the above ground growth as harvest time approaches. After digging, sweet potatoes need to be cured for several days. This process increases the shelf-life and flavor of the sweet potatoes. Curing should be done in a warm, humid location. Ideally the temperature should be between 85- and 90-degrees F with a relative humidity between 85 and 95%.
Store sweet potatoes for several weeks before consuming. During this time starches are converting to sugars which improves the flavor. Protect sweet potatoes during storage by keeping temperatures above 55 degrees F.
Vegetable Crop Rotation
Success in the garden requires planning. To give your plants a healthy start next year, rotate crops within the same family to a different location than where they’re growing this year. This is known as crop rotation and offers several benefits.
Plants in the same family are typically susceptible to similar pests. Some pests overwinter in the soil; some are able to survive on debris. If the same host is available when the pests emerge in the spring, they will be able to continue feeding and multiply the problem. Crop rotation breaks the cycle of these pests.
Plants in the same families have similar nutrient requirements. Rotating crops prevents the soil from becoming depleted of those nutrients. Also, the varied root system depths from one plant family to the next contributes to the health of the soil.
Now is the perfect time to make a map of the vegetable garden so you can switch things up when you plant next year. For example, in the location where tomatoes are growing now, avoid planting anything from the Solanacaeae family (eggplant, pepper, potato) next year.
The Kansas Garden Guide has a helpful table of common vegetable crop families and an example of how to rotate these crops. You can access a digital copy of the Kansas Garden Guide here: https://bookstore.ksre.ksu.edu/pubs/kansas-garden-guide_S51.pdf
FLOWERS
Drought Tolerant Plants
Fall is a great time to plant perennials but selecting the right plants is important. If you’re planting this fall here are some options that can tolerate drought once established.
Perennials
Herbs
Ornamental Grasses
Shrubs
Aster
Artemisia
Big Blue Stem
Lilac
Monarda
Basil
Blue Fescue
Forsythia
Butterfly Weed
Lavender
Fountain Grass
Rose of Sharon
Coreopsis
Lemon Balm
Switchgrass
Cotoneaster
Dianthus
Marjoram
Porcupine Grass
Viburnum
Gaillardia
Oregano
Ninebark
Garden Phlox
Sage
Mockorange
Black-eyed Susan
Thyme
Juniper
Gaillardia Coreopsis
Japanese Flowering Quince
For fall planting, it is best to wait until the weather is cool but still enough time for roots to establish before the ground freezes. Though the above plants will be tolerant of drought once established, they will need supplemental water initially, especially during hot periods.
Dividing Daylilies
September is an ideal time to divide daylilies, a task that should be completed every three to five years to promote flowering. Because of the extensive root system, a sharp knife may be required. However, cutting the roots with a knife can cause more stress to the plant and should only be done if necessary.
Alternatively, use a shovel to dig up the entire daylily clump. Remove the soil from the roots by shaking it or spraying the roots with water. Separate the plants into clumps of two or three. Cut the leaves to about half their height. This will enable the roots to better support the plant without falling over and reduce the water lost through transpiration.
Replant the divided clumps at the same depth 24 to 36 inches apart. Flowering will be limited next year but will become more vigorous until it is time for dividing again.
PESTS
Mimosa Webworm
Are your trees suffering from Mimosa Webworm? Symptoms of this pest include leaves matted together with webs. The larvae typically make these web nests on the tips of branches. From a distance infested trees look brown. Larvae can cause severe tree defoliation.
The second-generation larvae are active now and though treatments can be applied, for best control, efforts should begin in late May to early June. Repeated treatments are often necessary due to overlapping generations. If you’re seeing webs now, mark your calendars to scout for larvae next year. You may also be able to selectively prune out webs if they are minimal and not too high in the tree.
When selecting plants for your landscape recognize the susceptibility of certain varieties to pests. Sunburst is a variety of honeylocust that tends to be most attractive to Mimosa webworm. Avoid large groupings of thornless honeylocust varieties unless you plan to use appropriate control measures.
To read more and learn about control options check out: Mimosa Webworm (KSRE Publication).
Lace bugs
Description: Adult lace bugs are 1/8 to 1/3-inch long with lace-like wings. Their bodies are lightly colored and have dark markings. Nymphs do not have wings, are darker than adults and have an oval-shaped body. Nymphs leave behind exoskeletons when they molt. These can be seen attached to plant foliage. Small, dark droppings are deposited on undersides of leaves by adults and nymphs. Eggs are small and black and can also be found on the underside of leaves.
Life Cycle: Lace bugs have two generations each year. Adults overwinter under tree bark or in plant debris on the ground. As plants leaf out in the spring the adults begin feeding and lay eggs which hatch within two weeks. The nymphs feed for several weeks as they molt, mature into adults and lay the next generation of eggs. This generation feeds through summer and into fall.
Damage: Lace bug damage is often seen on oak and sycamore trees in our area. Some other hosts include: hawthorn, pyracantha and cotoneaster. Adults feed on leaves using a piercing mouthpart. This creates a stippled look on the leaf which can result in discoloration and premature drop if the infestation is heavy.
Control: Control measures are not recommended at this time of year. Trees and shrubs have adequately stored food for the winter so lace bugs will not negatively affect an otherwise healthy tree/shrub at this point in the season. Natural predators, such as green lacewings, spiders and others, prey on lace bugs as well so any treatment used should be carefully selected to avoid harming this population. Spraying infested plants with a strong force of water can dislodge lace bugs.
Read more: Lace bugs (KSRE Publication)
TURF
Timing Lawn Seeding
September is the time to reseed cool-season lawns, such as tall fescue and Kentucky bluegrass. For Kentucky bluegrass, finish reseeding by early October. The last day to safely reseed tall fescue is considered October 15.
With a late seeding, take special care not to allow plants to dry out. Anything that slows growth will make it less likely that plants will mature enough to survive the winter. Seeding after the cut-off date can work, but the success rate goes down the later the planting date. Late plantings often fail as a result of poorly rooted plants being heaved from the soil after repeated freezing and thawing. Roots are then exposed and quickly dry out. Help the seedlings establish a healthy root system prior to freezing weather by keeping them watered well.
QUESTION of the WEEK
What should I do about bagworms right now?
My junipers are covered in bagworms. What do I need to do?
Right now, make a reminder in your calendar for May. This is when bagworms begin to emerge. If you have adult bagworms now, you will likely have a new round of larvae next year as well. Scouting for bagworms needs to be done from mid-May through early June to time treatment for best control. Unfortunately, the only thing you can do to prevent damage from the bagworms now is manually remove them from your plants and destroy the bags. The worms are mature by now and most have stopped feeding. Males will be emerging soon (if not already) as moths for mating. Treating with insecticides at this point in the season is not recommended nor is it effective.
If you’d like to learn more about bagworm control you can find information here:
Bagworms (KSRE Publication)
Contributors:
Cynthia Domenghini, Horticulture Instructor
K-State Turfgrass Blog
K-State Extension Entomology
K-State Wildlife and Outdoor Enterprise Management
Division of Horticulture
1712 Claflin, 2021 Throckmorton
Manhattan, KS 66506
(785) 532-6173
For questions or further information, contact: [email protected].
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K-State Research and Extension is committed to making its services, activities and programs accessible to all participants. If you have special requirements due to a physical, vision or hearing disability, or a dietary restriction please contact Extension Horticulture at (785) 532-6173.
Cynthia Domenghini, Ph.D.
Instructor, Horticulture and Natural Resources
Kansas State University
[email protected]
