PLATTSBURGH — Knowing when and how to use conventional and organic fertilizers can make all the difference between success and failure with your flowers, vegetables, shrubs and lawns.Fertilizer, a broad subject, begins with how plants make their own food through photosynthesis."They have been surviving just fine without people fertilizing them for a long time," said Amy Ivy of the Cornell Cooperative Extension. She presented "Feed Me Seymour!" a lecture on fertilizers at the recent Cooperative Extension Spring Garden Day held at Clinton Community College."It's more when we put a demand on the plant that we have to think about feeding it. For example, vegetable crops, fruit crops and lawns because we're forever mowing lawns. The plant grows, and we cut it down."Trees and shrubs in the landscape don't need fertilizer. Fertilizer gets a bad rep when it is used in excess and at the wrong time."When that happens, it can get in ground water and surface water. It can contribute to algae in the lake and things like that. When used properly, it can be a helpful tool that will actually make the plant stronger and more able to tolerate problems."A healthy plant can coexist with some insects and is more resistant to disease than one that is not as healthy. The right use of fertilizer contributes to a hardy plant that will need less pesticides and other intervention.Fertilizer is comprised of nitrogen, phosphorous and potassium. It is a tool for growing healthy plants."Whether they come from organic or conventional sources, you want to get nutrients to your plant. When you make a decision, you need to think about how that plant grows and what is the best time to fertilize that particular crop."The most common fertilizer misuse is putting on too much at one time. If the product calls for a teaspoon per gallon, many people add two teaspoons. If the product calls for sprinkling a cup on the ground, people up it to two cups.Fertilizer used at the wrong time doesn't match a plant's needs."For example, vegetables have a lot of growing to do to produce a crop in a short season. They benefit from fertilizer at the beginning of the season. Strawberries, you fertilize after you pick them. If you fertilize before the crop, it makes the fruit soft and mushy and it won't hold up well. That's an example of why it's so hard to give one standard statement for all plants."Before you think fertilizer, think soil."Think about feeding the soil and let the soil feed the plant. Let the soil become a reservoir. The best thing you can do for your soil is to add organic matter. Any soil benefits from organic matter such as manure, compost, rotted leaves and grass clippings."Many people err in relying on fertilizer for everything."Fertilizer is not a cure-all. You have to have good quality soil. Match the plant to the site. If you take a sun-loving plant and put it in the shade, it will not grow well. Dumping on more fertilizer will not make it grow better."Fertilizer can enhance plants anchored in good soil. Gardeners also err in using fertilizer to help a stressed plant get healthy."You shouldn't fertilize a plant that is stressed. Whether that is from drought or a bad site or an infestation. Giving it fertilizer does not help. You want to figure out what the stress is and solve that. When the plant is growing again, then consider if fertilizer is appropriate. That would depend where the plant is on its life cycle, if it's about to bear crops."Conventional fertilizers come in granular and liquid form. They contain the basic nutrients that are readily available to the plant."If you use them correctly, they are not harmful but their drawback is they go directly to the plant. They skip that step from feeding the soil and letting the soil feed the plant."Organic or natural fertilizers such as manure and compost are delivered more slowly to the plant."They need warm temperatures. They count on micro-organisms to make the nutrients available to the plants."Organic fertilizers build a reservoir of nutrients in the soil. A good organic base is optimum for every gardener."It's a personal choice. Gardeners may feel they need a short-term supplement with a conventional product. Everyone should be working at getting a good quality base of good healthy soil."Gardeners should learn as much as possible about improving their soil quality and adding natural minerals through composting."That's why gardening is fun," Ivy said. "It's an ongoing learning process. People should keep reading and learning and get more and more ideas from people and try things out and see how it works for them. Keeping your own observations can be helpful to see how things are responding. A book can only tell you so much."