Gardeners can't always do things by the book. Sometimes we're out of time, money or patience to do a job correctly - or we just don't have the tools. So we do what we can and hope for the best.

The question is: Why do some gardeners get away with it? Their plants live, and their gardens look great, while others don't do well.

The "green thumb" concept has existed for centuries in various forms. The French refer to "the green hand"; the Brits say someone "has green fingers." Whatever the digits, we understand it to refer to those mythical gardeners who ?can grow every plant their green thumbs touch.

Nonsense, I used to say. A green thumb isn't a mysterious gift. ?It simply describes a person who ?has gardened for many years ?and who has a great deal of knowledge, whether it was learned formally or informally. Sometimes that person also happens to have really good soil, or really good indoor conditions, such as plenty ?of light and decent humidity. The right site certainly makes one's thumbs greener.

Now I would like to modify my opinion: Some people, with the same information or experience as other gardeners, are more intuitive; they are more tuned in and sensitive to the needs and state of their plants.

This intuition, or intangible sense, is often the guiding light ?that leads to gardening decisions . ?Must I water now? Does it need fertilizer, or a larger container? Surely that intangible gardener's intuition is a large component of so-called green thumbs.

When it might rain: This ?is what I was thinking last Friday as I watered some recently planted shrubs and container plants, ?even though three respected meteorologists had predicted rain later that day:

"Why am I watering when it's going to rain?" I asked myself. I had other things to do. And it wasn't that I doubted that rain would come. I watered before the predicted rains, in case the rain didn't fall on my garden, because the consequences of no rainfall felt like serious jeopardy for a few of my plants. There was no downside to being wrong - a good long soaking wouldn't hurt anything this season.

As it turned out, the rainfall was spotty. I'm glad I watered.

Imperfect planting: This happens for every plant lover: You have brought home a plant that you couldn't resist, that was so exciting to find, that you've wanted for years. And now its needs don't quite match the available spots in your garden. It's a dilemma:

. The tag says "Full to part sun," and your site offers dappled shade at best.

. The tag indicates "Hardiness Zone 6 - needs winter protection," and the spot faces the west wind.

. The tag says "Requires evenly moist soil," and your garden has competing tree roots sucking up the water.

Do you hold the plant over winter in its container, tucked against the house, and prepare a new bed next spring? Do you plant it in the imperfect location and hope to move it later? Or do you think you can make that location work despite the recommendations?

Gardeners make decisions like these every day. Some plants live, and some don't.

To weed, tolerate or overhaul: Even experienced gardeners who know perfectly well that there is no such thing as "just a little goutweed (or mint or wild morning glory)" don't get after the weeds on time. Sometimes part of the garden feels overrun, and we have to decide: What must we absolutely tackle now? Can we win the battle weed by weed, digging or pulling or smothering them? Or must we overhaul the whole area before the problem spreads?

It's easy for a garden writer to write words like "always remove the surrounding soil to 18 inches to remove all the root pieces." But the advice isn't always realistic. So when must you wage a battle, and when can you and the plants live with the situation?

Sometimes it's experience that informs the decision; you remember the time the Japanese knotweed took over the Japanese anemones. Sometimes you're limited by time or strength, no matter what your judgment tells you. But sometimes it's intuition that says "this time the weeds are getting ahead of these plants; it can't wait any longer."

Earlier this week in my garden I finally took on a 10-square-foot patch where goose grass and quack grass had been commingling with lambs' ears and Astrantia clumps for years. The soil was right for easy pulling and digging; the plants had strong root clumps and could be lifted without risk; I'll have time this month to watch for stragglers to return.

Decisions, decisions: When you decide how much compost to put in a planting hole, whether to divide the day lilies this year or next, when to move a lilac that isn't getting enough sun, and how far to cut back that Itea . are these decisions based on learned horticulture principles, on experience, or on your feeling for what to do next? Do you have an innate or long-developed gardener's intuition? Maybe you were just born with a green thumb, but more likely the greenness of your thumb is in direct proportion to your attention to the garden. If your thumb is anything like mine, it took a long time for it to turn green.

Sally Cunningham is a garden writer, lecturer and consultant.