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Gardener’s almanac for May 14, 2016: black spot on roses, cabbage worms, longer corn harvest

Stagger your corn plantings for a longer harvest.
Stagger your corn plantings for a longer harvest. Tribune

Black spot on roses — High humidity, warm weather and extended wetness on the leaves contribute to black-spot disease on roses, Ward Upham of K-State says. Black spot is self-descriptive: It causes black spots on rose leaves, and also raised purple spots on young rose canes, Upham says. The leaves often turn yellow and fall off. Splashing water spreads black spot.

To help prevent it, Upham says, plant resistant varieties of roses, water on the ground rather than getting it on leaves, plant roses in sun and give them room for air movement so leaves dry faster, pick up diseased leaves that have fallen and prune out affected canes.

If a rose has black spot, it may require a fungicide, which should be sprayed regularly, every 10 to 14 days, Upham says. Recommended products include tebuconazole (Bayer Disease Control for Roses, Flowers and Shrubs), myclobutanil (Immunox, Immunox Plus), triticonazole (Ortho Rose & Flower Disease Control) and chlorothalonil (Broad Spectrum Fungicide, Garden Disease Control and others), Upham says.

Plant — Beans, cucumbers, eggplant, melons, peppers, okra, pumpkins (plant closer to July 4 for a Halloween harvest), sweet corn, tomatoes, squash, salsify.

Lengthen corn harvest — Sweet corn is only good for a few days when it’s ready to harvest, so it’s best to stagger plantings of it, Upham says. Plant a small block of corn and then follow up with another one when the first planting is 1/2 to 1 inch tall. You can continue to do these staggered plantings through around mid-June.

Cabbage worms — Keep an eye out for green worms on your cabbage, broccoli, cauliflower, turnips, Chinese cabbage, Napa cabbage and bok choy. Cabbage worms should be dispatched early before they do too much damage, Upham says. Organic sprays include BT (Bacillus thuringiensis) and spinosad (Borer, Bagworm, Leafminer and Tent Caterpillar Spray; Captain Jack’s Dead Bug Brew) are effective organic products that are labeled for this pest. “Direct sunlight deactivates BT quickly so it is helpful to spray late in the day or on a cloudy day,” Upham writes in the Horticulture 2016 newsletter. You must hit the undersides of leaves, something that’s easier when using a dust applied with a duster rather than a liquid spray, he says.

Moving houseplants outside — It’s hard to believe that temperatures are forecast to be in the upper 40s at night again. However, in general, they have been above the 55-degree consistency for moving houseplants outside. When you introduce indoor plants to the outdoors, don’t put them in full sun, or their leaves will sunburn. Instead choose a spot that has dappled shade, protection from wind and close proximity to water, Upham says. When soil is dry half an inch down, it’s time to water, he says.

Garden events

Visit to Prairie Pride Plants — The Herb Society of South Central Kansas will meet at Prairie Pride Plants, a native-plant nursery at 504 W. Hendryx south of Delano. The meeting will be at 6:30 p.m. Tuesday. The public is welcome. Bring a chair and snack to share. For more information, call Lisa at 316-461-3638.

“My Tomatoes Are Planted: Now What?” — A class on how to grow tomatoes will be from 6 to 8 p.m. Tuesday at the Extension Center at 21st and Ridge Road. The cost is $5. The class is part of the Extension’s Grow Good Food Gardening series. Register online at sedgwick.ksu.edu or call 316-660-0100.

Talk about master gardeners and tour — Master gardener Cindy McWilliams will be at Botanica on Wednesday to talk about what master gardeners do and to preview their garden tour that will be June 3 to 5. The lunchtime lecture, at 12:15, is included in Botanica admission. Truffles will have lunch for sale for $8 between 11 a.m. and 12:15 p.m.

Project Beauty May luncheon — Project Beauty will have a luncheon at 12:30 p.m. Thursday at the Double Tree by Hilton, 2098 Airport Road. Wayne Bryan of Music Theatre Wichita will present the program. The cost is $18; send a check to Jean Wellshear, 6411 Marjorie, 67206 by Monday.

Kansas City-area garden tour — The Johnson County Extension Master Gardeners have a garden tour every other year, and this is the year. Six gardens in Overland Park and Lenexa will be on the tour May 20 and May 21. Hours will be 9 a.m. to 5 p.m.; tickets are $15. For more information, go to the websitewww.johnson.k-state.edu or call 913-715-7000.

The Sedgwick County Master Gardeners’ annual tour will be June 3 to June 5 in Wichita.

“History and Folklore of the Flint Hills” — Jim Hoy will give a talk about the Flint Hills at the Summer Soiree at Dyck Arboretum of the Plains in Hesston on June 12. The event also will feature dinner, music and a silent auction to benefit the arboretum. Tickets are $80; reserve by June 1 online at dyckarboretum.org or by calling 620-327-8127.

Annie Calovich