Where lawn and garden care is concerned, where do we spend the most money -- on flowers, lawn seed, plant food, compost? Today we'll discuss how much "green" we spend on gardening, and exactly what we're spending it on. The largest single expenditure is for lawn care, with homeowners spending on average $220. Next is landscaping ($174), followed by care for existing trees ($97). Flower gardening ranks next with $88 per home (18 percent of all flowers sold are impatiens; then come petunias and pansies). After flowers, we spend $60 on insect control and $58 planting vegetables (one-fourth are tomato plants). Flower bulbs account for $40, and we spend another $40 on green houseplants. For more tips, visit our Web site at onthehouse.com. And that's the On The House tip for today.