What "Full Sun" on the Plant Tag Actually Means
Full sun means six or more hours of direct sunlight a day. Part sun or part shade means roughly four to six. Full shade means under four, and even that usually assumes bright open sky overhead, not a dark corner behind a fence. Those are the industry conventions, and the tag writer assumed you knew them.
Direct matters more than the number. Direct means nothing is between the sun and the leaf. Not a tree canopy, not a screen porch, not a patio cover, not a pane of glass with a film on it. Light bouncing off a white wall is real light and the plant will use some of it, but it is a fraction of the beam and it never adds up to full sun.
The tag also has no idea where you live. It does not know about your neighbor's oak, your west-facing brick wall, or the fact that your six hours all arrive between noon and six in a place that hits triple digits. Treat the number as a minimum, not a goal. A tomato in five hours does not drop dead. It grows slower, makes fewer fruit, and never builds enough leaf to handle the first stretch of hot weather. Then it fails in August and you blame the water.
The Hard Shadow Test You Can Run in Sixty Seconds
Go stand where the pot would sit. Hold your hand about a foot above that surface and look at the shadow. A dark shadow with a crisp edge means direct sun is hitting that spot right now. A soft grey smudge means filtered light through leaves or a cover. No shadow at all means ambient light only, and a fruiting plant will sulk there forever.
The reason you need the shadow is that your eyes lie like hell about brightness. Your pupil opens, your brain rebalances the exposure, and open shade under a north wall looks perfectly bright to you while delivering nowhere near the intensity of the direct beam. Your phone camera does the same trick. The shadow does not adjust to anything. It is either there or it is not.
One shadow check is a screening test, not an answer. It tells you about this minute. But it takes less time than reading this paragraph, and it will disqualify a bad spot on the spot.
How to Count Your Sun Hours Without Buying Anything
Pick a clear day you will mostly be home. Set an alarm for every hour from early morning to evening. Each time it goes off, step outside, look at the spot, and type sun or shade into your notes. Ten or eleven checks and you have a real number for that spot in that season. Cost is zero. No meter, no app, no kit.
If you are gone all day, prop your phone somewhere it can see the spot and use a time lapse or a repeating timer. Or do the cheap version and check three times, once mid-morning, once at noon, once mid-afternoon. Most spots are obviously in the six-hour club or the three-hour club and three checks will settle it. The ones that fool people are the dappled spots under a tree, where sun and shade trade places every few minutes. Those you actually have to count, and when you do, they usually come in lower than they feel.
Count in the season you plan to grow in. The sun rides lower in the sky in spring and fall, so building and fence shadows stretch longer. Deciduous trees go from bare to full canopy in about three weeks, and a spot can drop from six hours to two in that window without you noticing a thing. That is why last year's good corner betrayed you and you thought you had gotten worse at this.
When "Needs Full Sun" Is Bad Advice
In a hot climate, afternoon sun past the mid-nineties is not food, it is punishment. Tomatoes and peppers commonly drop their flowers when it stays brutally hot, so the plant can be in eight hours of sun and still give you nothing. Six hours of morning sun with shade from three o'clock on will usually beat all-day blast in the south. Morning hours are worth more, and no tag will tell you that.
Containers make it worse. The ground is a giant heat sink and it buffers root temperature all day. A bucket does not. A dark pot sitting in direct afternoon sun can get the root zone far hotter than the surrounding soil, and hot roots stop moving water properly. The leaves wilt at 2pm even though the mix is damp. You water again, the mix stays soggy overnight, the roots start suffocating, and now you have a sun problem wearing a water costume.
The reverse mistake is just as common. People blame shade for problems that are actually drainage or soil. If your pot has no hole in the bottom, if it is packed with garden soil, if it is a plastic nursery pot sitting in a saucer full of standing water, no amount of sun will save it. Check the free stuff first. Tip the pot, look for a hole, stick a finger two inches into the mix. Then argue about sun.
Pick the Plant to Fit the Light You Actually Have
Here is the rule that makes shopping easy. If you eat the leaf or the root, the plant needs less sun. If you eat the fruit, it needs more. Building a fruit full of sugar and seeds is expensive, and that energy comes from one place.
- Under four hours: mint, chives, parsley, and loose leaf lettuce will still give you something
- Four to six hours: spinach, kale, chard, bush beans, radish
- Six to eight hours: tomato, pepper, cucumber, squash, eggplant, basil
- Reflected light off a pale wall helps a little and never counts as a sun hour
- Too little sun means smaller, slower, fewer, not a fast dramatic death
If you counted three hours, buy herbs and greens and quit fighting it. Buying a tomato for a three-hour spot is buying a slow disappointment with a receipt attached. A pot of leaf lettuce you actually cut from twice a week will teach you more than a leggy tomato that never sets fruit, and it will not make you feel like a failure every time you walk past it.
What to Set Up Today
Do the shadow check before you do anything else. Then run one day of hourly notes on the two best candidate spots. Write the numbers down somewhere you will find them again. That is the whole assessment, and it costs you nothing but a day of alarms.
Then set the thing up so it has a chance. A five gallon bucket with four or five half inch holes drilled in the bottom is a legitimate garden. Fill it with potting mix, not garden soil. Garden soil in a container packs into a brick, the air pockets collapse under watering, and roots that cannot get air quit working even while sitting in moisture. Potting mix is built light and chunky for exactly that reason, which is why the bag says what it says. The other advantage of a bucket is that it moves. You can chase the sun in spring and drag it into afternoon shade during a heat wave. A raised bed and the ground cannot do that.
Start with two or three plants, not ten. Some of them will die anyway, and that is not a verdict on your character. Note where each one sat, what its sun count was, and what happened to it. Do that for one season and you stop buying on hope and start buying on information, which is the only thing that separates people with food on the step from people with a pile of dead pots and a grudge.