HortusScope, a checklist of garden and nature related things to do in Central Indiana has been posted. This calendar is compiled by Wendy Ford of Landscape Fancies as a pubic service.

The September checklist for the garden has been posted.

A garden spider spins a silky tomb for a bumble bee. © Jo Ellen Meyers Sharp

This time of year, garden spiders spin their orbs in the landscape.

The yellow and black females are larger than the males, more colorful and usually more visible, especially this time of year. The females make the large webs, some up to two feet across, and the males spin smaller orbs around the fringes, each with a zigzag in the center.

The garden spider (Argiope aurantia) is native throughout the United States and is considered a beneficial.

The female garden spider is about one inch long, but is not harmful to humans. She hangs upside down on her web, spun between two plants in a sunny spot protected from wind. The male is narrower and may be brownish. It is about one-fourth to one-third inch long.

When bees, flies, butterflies and other insects become ensnared in the web, the spider shoots them full of venom and quickly wraps them into silky tombs. Some are stored for dinner later, but many are eaten as soon as they are encapsulated. Each day, the female garden spider eats the entire center section of the web and spins a new one. Speculation is she cleans out her pantry of bugs to make way for the new catch of the day.

Late summer is the annual mating and egg-laying season. So risky is his journey into her web that he frequently has a silken tether at his belly that allows him to drop to the ground if she says no. The males die after mating and sometimes make a meal for the female.

She lays her eggs and wraps them into round bundles of silk, with the last layer a brownish color for better camouflage. She hangs the egg sacs on the web where she can guard them against predators. She usually dies by the first frost.

Eventually, the eggs hatch, but stay in their cocoon until spring when they emerge and go their way.

The Fairfax County (Va.) Public School’s Web site has more lifecycle details and other interesting tidbits about this spider.

From Scott Kunst, Old House Gardens Friends of Old Bulbs Gazette

Rain lilies, which open pink then fade as they age, like to be crowded in the pot. © Jo Ellen Meyers Sharp

High heat has plagued much of the country this summer. Some bulbs like it, but others suffer. Dahlias, for example, have struggled or failed in many gardens where they usually thrive. That’s because they come originally from the mountain plateaus of Mexico where days are hot but nights are dramatically cooler. When nights are too warm, dahlias just can’t grow well. Some varieties are more sensitive than others and can even die. The good news is that if you can keep them going till temperatures cool (which has to happen sometime, right?), they’ll kick back into gear and bloom gloriously till frost.

Glads may develop kinked stems in unusually hot weather as they sag a bit during the day, unable to fully replenish the water evaporating from them, and then grow upright at night when evaporation slows. This is most often a problem with glads like ‘Atom’ that have thin, wiry stems. To help, keep your glads well-watered and protect their shallow, wide-spreading roots from disturbance. Tiny sucking insects called thrips proliferate when it’s hot, too, and can leave glad leaves and blossoms mottled, or even prevent buds from opening. Here are tips on control of thrips.

Heat affects flower color, too. Deep-colored lilies such as ‘African Queen’ may be paler in high heat, bicolor dahlias such as ’Deuil du Roi Albert’ may bloom temporarily as solids, and the rosy tones of ’Kaiser Wilhelm’ and others won’t develop fully until the weather cools.

Of course some bulbs love the heat. In many gardens this summer, cannas, tuberoses and rain lilies have been especially happy — and we hope you’ve been enjoying them.

Many lawns have crabgrass this year because of the rain, hot weather and other factors. (C) Jo Ellen Meyers Sharp

Crabgrass is sprouting all over the lawn. And, it’s probably worse this year than in years past, even though you applied a pre-emergent herbicide this spring to keep the weed from sprouting.

There are several factors that caused this bumper crop, not the least of which is the weather. It did nothing but rain in central Indiana during crabgrass’ key germination period in late April and early May. After that, the temps turned hot and stayed there, nourishing tiny seedlings into full-grown weeds.

The weather also contributed to several grass fungus diseases, such as pythium blight and red thread. Like most weeds, crabgrass (Digitaria) is opportunistic and will take advantage of thin, weakened spots in the lawn.

Timing of herbicide applications is also a contributor. Many consumers apply lawn fertilizers with pre-emergent herbicides in March, which is too early. Most pre-emergent herbicides are effective in keeping crabgrass seeds from germinating for about eight weeks. Waiting until April and May to apply the pre-emergent extends protection well into summer.

It’s too late to apply a post-emergent herbicide on crabgrass now, because the weeds are so large and the weed killer is much less effective. Hand pull or hoe out crabgrass from garden beds.

Fortunately, crabgrass is an annual weed, which will be killed by cold temperatures. Draw a sketch of the landscape and indicate which areas were infested so you’ll know where to apply the pre-emergent herbicides next spring.

Other tips:

• Mow grass to 3 ½ high.
• Apply two-thirds of the annual lawn fertilizer in fall, preferably in September and November.
• Irrigate the lawn during extremely hot periods with no rain to keep the grass from going dormant. A dormant lawn is an invitation for weeds to move in.

The Hoosier Gardener talks about crabgrass and offers tips for controlling it Aug. 25 on Indianapolis’ Fox59 Morning News.

For more information, download Purdue University’s Control of Crabgrass in Home Lawns.

The Marion County Extension's City Gardener program covers plants' roots and other details to help you succeed in all of your gardening efforts. (C) Jo Ellen Meyers Sharp

If you are a new or inexperienced gardener or a first-time homebuyer and have questions about what to do when in the landscape, the City Gardener program offered by the Marion County Extension Office, will provide the answers.

Topics in the 12-hour program include: how a plant grows; soil and fertilizers; pests and pest management; tree and shrub selection and care; weed identification and control; lawn care; vegeteable gardening; animal damage management; annuals and perennial flowers.

Participants receive a reference notebook, which contains outlines of the presentation and supporting publications. The two Saturday sessions, Aug. 28 and Sept. 11, 2010, will be at Keep Indianapolis Beautiful, Inc.’s headquarters, 1029 Fletcher Ave., near Fountain Square. There’s plenty of free parking.

The fee is $20. A  $10 scholarships may be available to those with financial need, said Steve Mayer, an extension educator who teaches the program.

Here’s the registration form.

Hendricks County Master Gardener, Adventures in Gardening, features Irvin Etienne, Indianapolis Museum of Art as the keynote on growing vegetables in the flower garden.  Other topics:  The Winter Garden with conifer specialist Terri Park; Going Native in Suburbia — how to your subdivision into a beautiful wildflower habitat with Dan McCord; and Water Ponds Made Easy with Steve Wicker.

Fee: $30, includes lunch. Call (371) 75409260, or visit the Web site.

Where: Hendricks County Fairgrounds Auditorium, 1900 E. Main St., (Old U.S. 36) in Danville.

Hendricks County Master Gardeners, Perennial Plant Exchange,  with planting tips from Colletta Kosiba. Bring four to six identified plants to the Plainfield Library, 1120 Strafford Road. Free, but registration is required, (317)  839-6602.

Hendricks County Master Gardeners, Putting Your Garden to Bed for the Winter, by Colletta Kosiba.  Learn about clean up, adding soil nutrients and more fall chores.  Brownsburg Library, 450 S. Jefferson St. Free, but registration is required, (317) 852-3167.