Can I harvest rhubarb in August? 

Gardeners should stop harvesting well-established rhubarb plants by mid-June. Continued harvest through the summer months weakens the rhubarb plants and reduces the yield and quality of next year’s crop. The rhubarb stalks do become somewhat woody by mid-summer, but they don’t become poisonous. 

Would a late summer fertilizer application harm a brown, dormant lawn? 

Fertilizing a dormant lawn will not harm it. However, the turfgrass may not receive the full benefit of the fertilizer application. If the granular fertilizer remains on the soil surface because of a lack of rain, some of the material may actually volatilize into the air. It would be best to wait until growing conditions improve before fertilizing the lawn.  September is an excellent time to fertilize lawns in Iowa.  Lawns can also be fertilized in late October/early November. 

Why are my tomatoes cracking? 

Fruit cracking is a common problem on tomatoes. Cracks usually appear at the top or stem end of the fruit. Cracks radiate out from the stem (radial cracks) or circle the fruit in concentric rings (concentric cracks). Fruit cracking is associated with wide fluctuations in soil moisture levels. A heavy rain or deep watering after a long, dry period results in rapid water uptake by the plant. The sudden uptake of water results in cracking of ripening fruit. Generally, fruit cracking is most common on the large, beefsteak-type tomatoes. 

Fruit cracking can be prevented by supplying the tomato plants with a consistent supply of moisture during the summer months. During dry periods, a thorough soaking once every seven days should be adequate for most tomato plants.  Conserve soil moisture by mulching the area around tomato plants with dried grass clippings, straw, shredded leaves or other materials. Also, plant tomato varieties that possess good crack resistance. Tomato varieties that possess good to excellent crack resistance include Jetstar, Mountain Spring and Mountain Fresh. 

When should I harvest my potatoes? 

Potatoes can be harvested when the tubers are small and immature (“new” potatoes) or when the crop is fully mature. 

“New” potatoes are dug when the plants are still green and the tubers are greater than 1 inch in diameter. New potatoes should be used immediately as they do not store well. 

Potatoes grown for storage should be harvested after the vines have died and the crop is mature. To check crop maturity, dig up one or two hills after the plants have died. If the skins on the tubers are thin and rub off easily, the crop is not fully mature. Allow the crop to mature for several more days before harvesting the potatoes. When harvesting potatoes, avoid bruising, skinning or cutting the tubers. Damaged potatoes should be used as soon as possible. 

Before placing the potatoes in storage, cure the tubers at a temperature of 50 to 60 degrees F and high relative humidity (85 to 90 percent) for two weeks. The curing period allows minor cuts and bruises to heal. Thickening of the skin also occurs during the curing process. 

Once cured, store potatoes at a temperature of 40 degrees F and relative humidity of 90 to 95 percent. Store the crop in a dark location as potatoes turn green when exposed to light. If storage temperatures are above 50 degrees F, the tubers may begin to sprout in two or three months. When stored below 40 degrees F, potatoes develop a sugary, sweet taste. Sugary potatoes can be restored to their natural flavor by placing them at room temperature for a few days prior to use. Do not store potatoes with apples or other fruit. Ripening fruit give off ethylene gas, which promotes sprouting of tubers.

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