Blog Posts - K-State Research and Extension Horticulture Newsletter

Reblooming Poinsettias

9/15/2023

Photoperiodism, the amount of light or dark a plant is exposed to, affects the bloom of most plants. Some plants need longer periods of darkness and are known as “short-day” plants. Others require fewer dark hours, “long-day” plants.

Many summer flowers and vegetables are in the long-day category. Chrysanthemums, Christmas cactus and poinsettias fall in the short-day category. These plants require at least 12 hours of darkness every 24 hours in order to bloom. Growers can force blooming by controlling the light and dark periods.

If you have poinsettias from last year, follow these steps to encourage blooms in time for the holidays.

For no more than 12 hours each day, keep poinsettias in an area where they will receive the brightest light possible. Temperatures should be kept between 65- and 75-degrees F.
Provide at least 12 hours of uninterrupted darkness to the plants every 24 hours. If a completely dark room or closet is not available, place a cardboard box over the top of the poinsettias. Be sure to seal the openings of the box with duct tape to prevent light from entering. 60- to 65-degrees F is the ideal nighttime temperature to promote blooming.

Continue the dark treatment for six weeks until buds have set. Within another two to five weeks poinsettias should be blooming. (Cynthia Domenghini)

Planting Trees in the Fall

9/15/2023

Fall can be a great time to plant trees and take advantage of the root growth that can occur while the soil is still warm before freezing begins. This gives trees a head start enabling them to endure spring growth and summer stress. Early September to late October is the ideal planting time for most trees. Some trees are not good candidates for fall planting such as beech, birch, redbud, magnolia, tulip poplar, willow oak, scarlet oak, black oak, willows and dogwood. These trees will not be able to establish roots in time to survive the winter.

Newly planted trees require some care even when the above-ground growth is dormant. The soil should remain moist so roots do not dry out. A layer of mulch can be beneficial for regulating soil temperature and reducing water loss. (Cynthia Domenghini)

Moving Houseplants Inside for the Winter

9/15/2023

With some relief from hot weather this week and colder temps on the way, it’s time to turn our attention to protecting cold-sensitive plants. Some gardeners move houseplants outdoors to bask in the summer heat and recover from the stress of an indoor environment. Planning for their reentry to the house is important so houseplants have time to adjust to the changes in growing conditions.

Before bringing any plants indoors, check thoroughly for pests. Small populations of insects, such as mites and aphids, can be dislodged by spraying the foliage with a hose. If the insects are found in the soil, soak the entire container in lukewarm water for 15 minutes. Plants with a heavy infestation may be better off discarded.

Once moved indoors, continue to monitor for pests to prevent spreading throughout the house. Plant growth will slow substantially indoors and will therefore require less water and fertilization. Most houseplants will benefit from receiving water only when the soil surface is dry. Fertilization will likely not be necessary until spring.

It is best to help plants adjust to the lower light conditions indoors gradually to prevent leaf drop. Initially, place plants near windows with the brightest light. Over several weeks move the plants further away until they’ve reached the desired location. Supplemental lighting can be provided with grow lights. Avoid cold drafts from doors and windows and heat from air vents. These extremes can put plants under stress.

Many houseplants come from tropical locations and favor humid conditions. Kitchens and bathrooms tend to be more humid areas inside the home. If space and lighting permits, this may be a good location for your plants. You can increase humidity for your plants by using a humidifier or grouping multiple plants together creating a microclimate. (Cynthia Domenghini)

Root Cellars

9/15/2023

Root cellars are a time-tested solution for storing the harvest surplus through winter. The temperature and humidity underground can provide favorable conditions for certain vegetables. Traditionally, onions, garlic, turnips, carrots and potatoes are stored in cellars. However, many types of fruits, squash, nuts and other vegetables can successfully be stored as well. Here are a few tips to increase the shelf-life of your harvest.

Store fruits separate from vegetables to avoid ethylene exposure to vegetables.
Turnips, cabbage and other vegetables with a strong odor may transmit this to nearby produce
See the chart below for recommended storage conditions for specific produce.

(Cynthia Domenghini)

Temperature (degrees F)	Humidity (%)	Produce
32-35	60-70	garlic, onions
32-40	80-90	apples, grapes, oranges, pears
32-40	90-95	beets, Brussels sprouts, cabbage, carrots, cauliflower, celery, horseradish, artichoke, kale, kohlrabi, leeks, parsnips, radish, rutabaga, turnips
32-50	60-70	dry beans and peas
38-40	80-90	potatoes
50-55	60-75	pumpkins, winter squash
above 50	80-90	sweet potatoes, tomatoes

Video of the Week: Cuttings to Grow Inside for the Winter

9/8/2023

Lawn Seeding Timing

9/8/2023

Although September is typically the preferred month to reseed cool-season lawns, such as tall fescue and Kentucky bluegrass, with the heat we have been experiencing throughout the state, postponing may be a good idea. When temperatures are elevated as they have been recently, newly-planted seeds need additional water. Homeowners who put down seed during the heat may find themselves watering several times a day. By middle to late September, we should have relief from triple digits allowing homeowners time to re-seed.

Our usual recommendation is don’t plant Kentucky bluegrass past early October. However, you can get by with an early to mid-October planting for tall fescue. October 15 is generally considered the last day for safely planting or overseeding a tall fescue lawn in the fall. 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 well-watered. See the August 29th newsletter for information on how to seed or overseed a lawn. (Cynthia Domenghini)

Harvesting Sweet Potatoes

9/8/2023

Cold soil negatively affects the quality of sweet potatoes in taste and shelf-life. 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 also 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. (Cynthia Domenghini)

Vegetable Crop Rotation

9/8/2023

Crop rotation is the recommended practice of changing the location of plants within the same family each growing season. Plants within the same family are often susceptible to similar pests. They also have similar nutrient requirements. By planting crop families in different areas of the garden each season, a common host plant is removed. Pests that overwinter in the soil or debris are not able to continue their life cycle which prevents the population from growing exponentially. Additionally, the varied root system depths and nutrient requirements prevents nutrient depletion in the soil. Often, cabbage, peas, lettuce, onions and other cool-season crops have more shallow roots. Warm-season crops tend to have a more extensive root system.

To plan your crop rotation draw a diagram of your vegetable garden now while you remember where everything is. Next year, as you making your planting plan, reference this sketch and alternate locations for each plant family. For example, in the area where you have tomatoes this year avoid planting anything from the Solanacaeae family (eggplant, pepper, potato) next year. If you planted bush beans this year, be sure to avoid planting anything from the fabaceae family (lima beans, peas, pole beans, etc.) in the same location next year. (Cynthia Domenghini)

Ornamental Sweet Potatoes

9/8/2023

Ornamental sweet potatoes are mostly valued for their attractive foliage as it drapes down the sides of containers and spreads over the ground within planters. As with other ornamental vegetable varieties, though ornamental sweet potatoes are edible, they are grown for their aesthetic value. Consequently, the flavor quality of ornamental varieties is often lacking. In the case of ornamental sweet potatoes, the tuberous roots are much more bitter than the edible counterpart. If you choose to consume them, follow the curing instructions in this newsletter.

Ornamental sweet potatoes can be overwintered by digging them just before the first frost and storing until it’s safe to plant in the spring. Remove the above ground growth and keep the roots in moist peat moss in a cool, dark room. Alternatively, the entire plant can be moved indoors and kept as a houseplant during the winter. Check the plant first for signs of disease or pests. Cut the vines back to about one-foot and carefully transplant into the desired container. Keep the plant in a space with plenty of natural light until warmer weather returns in the spring.
(Cynthia Domenghini)

Garden Spiders

9/8/2023

Though some consider spiders to be unwelcomed, they are a valuable resource for pest control.
The yellow garden spider is commonly found in our Kansas gardens. The body is one-inch long and has yellow markings on the dark-colored abdomen. Legs of the garden spider are black with a yellow or reddish band.

The banded garden spider is similar in size with yellow and white bands marking the legs and abdomen. The legs have black and orange bands.

These two varieties of spiders are types of orb weavers and construct large, circular webs often in bushes, tall grasses and other areas with high insect populations. These spiders are not dangerous to humans and should be left alone to allow them to continue feeding on pests in the garden. (Cynthia Domenghini)