Today’s the first day of spring, but anxious Iowans should hold off leaping into lawn work for a couple of weeks yet in their quest for green grass. Iowa State University horticulture professor Nick Christians says it’s still too cold to plant grass seed or apply chemicals. He says some lawn care companies might apply fertilizer now, but he says they have thousands of customers to get done. He says you don’t need to think about it till mid April.While it’s warm today, the forecast over the next several days calls for very cold weather and the chance of snow. Professor Christians says in mid-April, Iowans who want to start reviving their lawns may want to fill in bare patches by matching the seed with their current grass.Christians says one way to keep a lawn looking lush is to apply weed-killing chemicals, but those have to be sprayed at certain times too. They have to be put down before the weeds germinate in the spring.He says flower planting, too, can wait several weeks, in fact, until May.