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posted: 8/23/2013 1:00 AM

Time to break out the cool-season crops

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  • Seeds for lettuces, mesclun mixes and other greens can be sowed again this month.

    Seeds for lettuces, mesclun mixes and other greens can be sowed again this month.

By Tim Johnson
Chicago Botanic Garden

Fall is on the way, meaning it's time for cool-season crops. Seeds for lettuces, mesclun mixes and other greens that were sowed in early spring can be sowed again this month.

If the weather is unusually hot, plant these greens in partial shade or wait a few days until there is a cooler forecast.

The best quality and best tasting salad greens come from plants that are watered frequently and lightly rather than infrequently but deeply. This advice is the exact opposite to what is recommended for watering trees, shrubs, perennials, grass and other plants.

Holes in the lawn dug by raccoons and skunks may indicate the presence of grubs -- insect larvae that feed on grass roots. Check for areas of the lawn that are browning or where the grass can be lifted like a piece of sod. If there are more than 12 grubs per square foot and you are seeing extensive damage to the turf, you may consider using a product designed to kill grubs quickly.

Be sure to read the bag carefully to ensure that you are buying the right chemical for grub control at this time of year. It is important to follow the instructions for application.

If the new growth at the tips of your pine's branches has turned brown, a disease called Diplodia tip blight may be the problem. It is too late to spray fungicides now, as infection occurs in the spring.

Prune out dead tips in dry weather to reduce the spread of infection. Remove all infected needles from the base of the tree and discard them off-site, such as in brown bags of landscape waste for pickup.

Some crab apples are very susceptible to apple scab and those not treated with fungicides in spring may have lost many of their leaves. Their remaining leaves may have black and yellow spots.

Spraying at this point will not help combat this disease, but you can help the trees withstand the stress by giving them extra care. Water them as needed for the remainder of this year and fertilize them in fall or next spring. Remove all infected leaves and do not add them to your compost pile.

Consider replacing disease-prone trees with a cultivar that has been bred to be resistant to apple scab.

Look in your hedges for woody plant weeds such as mulberries, buckthorns and boxelders that grow up among the shrubs.

These weeds tend to be hard to spot when they are young sprouts, but are easier to see by late summer because their leaves usually are very different from the surrounding shrubs. Remove these weedy plant seedlings with their roots if you can or cut them off at ground level.

• Tim Johnson is director of horticulture at Chicago Botanic Garden,

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