Kansas gardeners will soon be harvesting fresh tomatoes and onions.
It’s an important time to care for tomatoes, onions
K-State horticulture expert shares some tips for success
May 28, 2020
MANHATTAN, Kan. – Rain across much of Kansas during Memorial Day weekend was certainly welcome, but it did cause a bit of a delay in a timely task for the state’s gardeners.
“Soils are warm enough now that tomatoes can benefit from mulching, as long as the soils are not saturated with water,” said Kansas State University horticulture specialist Ward Upham.
Garden beds should allow water to filtrate, he noted, so that plants are not sitting in flooded soils.
“Tomatoes prefer even levels of soil moisture, and mulches provide that by preventing excessive evaporation,” said Upham, noting that mulch also suppresses weeds, moderates soil temperatures and prevents the formation of a hard crust on the soil, which restricts air movement and slows the water infiltration rate.
“Hay and straw mulches are popular for tomatoes, but may contain weed or volunteer grain seeds,” Upham said. “Grass clippings can also be used but should be applied as a relatively thin layer – only 2 to 3 inches thick. Clippings should be dry because wet clippings can mold and become so hard that water can’t pass through.”
Upham cautioned that clippings from lawns that have been treated with weed killer should not be used until at least the fourth mowing after the chemical has been applied. If the lawn has been treated with a product containing quinclorac, a common ingredient in many crabgrass killers, the clippings should not be used as mulch.
Onions
Upham notes this is the time of year that another of Kansans’ favorite vegetables is growing and developing rapidly: onions.
“If the soil ever dries out, water onions regularly and fertilize lightly to maximize their growth,” he said.
“If your soil tends to be alkaline, use ammonium sulfate (21-0-0, referring to the percentage of nitrogen, phosphorus and potassium in the product) at the rate of one-half cup per 10 feet of row. Or, you can use a lawn fertilizer – such as 29-5-5 or 27-3-3 and similar products – but use only one-third cup per 10 feet of row.”
Upham again cautioned against products that contain weed preventers or killers.
“Sprinkle the fertilizer two to three inches alongside the row and water it in,” he said. “Do not fertilize after the onions start to bulb.”
Upham noted that as much as two-thirds of the bulb may remain out of the soil as onions develop. He said that is normal and there is no need to cover the bulb with soil.
Upham and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for keeping yards and gardens healthy and beautiful year-round. The newsletter is available to view online or can be delivered by email each week.
Interested persons can also send their yard and garden-related questions to Upham at wupham@ksu.edu.
