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Aug 16, 2010 07:12 PM

Determining sunlight

I've been in an energetic mood lately and decided I wanted to step up my garden a little. My tomatoes in my double dug garden bed are wilting today, a cloudy day. The tomatoes got rain from clouds and the container tomatoes are doing way better. The major difference between the containers and beds is the containers get much more sun. Therefore, I've started the process of evaluating how much sun I get.

Today, I helped cut the top off the tree in the perimeter of my garden. Most of the tree branches were over top of my tomatoes. I can see more light hitting my tomatoes now. My question is how much sunlight is enough? I don't want to cut down every tree in my backyard. The sun rises in the east so I'm assuming priority would be as follows.

1. Branches over head or in close proximity to the garden.
2. Tree branches blocking the eastern or morning sun.
3. Tree branches blocking the western sun
4. Tree branches blocking the after noon sun.

I'm not even sure cutting down every tree would be good for the garden. I've read in Starter Vegetable Gardens by Barbara Pleasant that "leafy vegetables need shade to protect from the scorching sun." My quote might not be exact. I'm just not sure what a leafy vegetable is, are tomatoes a leafy vegetable?

I've read 10 hours or more of direct sunlight for tomatoes, but the above words have no meaning to me. What is direct sunlight? How do you determine how many hours of sunlight my tomatoes get vs veggies that are adjacent?

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  1. Hmm, I'm a pretty novice gardener, but my gut is that the amount of sunlight should be proportional to where you live and thus the heat and the directness of the sun. So if you live, say in AZ, then less sun may be better, whereas someone in, say MN, probably wants the max amount of sun.
    So, friend, where do you live?

    1 Reply
    1. Leafy vegetables: lettuce, spinach, cabbage, kale, collards, etc.
      Lettuces will do well in partial shade. They do fine in full sun but they are prone to scorching if it's particularly hot and dry and will become bitter and go to seed faster.

      Direct sunlight is full, unadulterated sun. 10 hours or more is prime, 7-10 is good, 6 or less will still get you a few tomatoes.

      Before you go cutting down your trees make a rough map of your garden on paper. Observe and note down the times when your beds come into the sun, have partial shade, go into complete shade. Note which beds have full sun all the time, which ones are always partially shaded, which ones are always fully shaded. Do this for spring, summer, and fall, and winter too if you want to try growing crops under cover. You'll want your full sun beds for that.

      As you get to know plants better you'll be able to take advantage of the way the sun hits your garden by matching plants' light requirements to the various areas of your garden. Seed and nursery catalogs usually have symbols next to a plant's description indicating it's needs. A good gardening encyclopedia will have that and much more detail.

      As you get to know your garden site better, you'll also discover it has micro-climates which may allow you to push the limits on plants not zoned to your area.

      A bit of patience and observation of how the light hits your garden may save you from having to cut down much, if any, of your trees and shrubs and pinpoint where removal is necessary. Maybe just thinning and pruning will be enough. Trees and shrubs provide habitat for birds (and other critters) that help greatly with pest control and pollinating.

      8 Replies
      1. re: morwen

        From my understanding direct sun is when the you can see the sun beam directly on the plants/grounds. If the sun beam is blocked by leaves its not direct sun. At around 2:30ish only one bed is receiving almost full sun, the zucchini bed. The yellow squash bed receives considerably less sun, and the beans/tomatoes are hardly hit by the sun at all. In fact, when I looked only a few beans were being hit by the sun.

        My tomatoes in the raised bed are wilting further despite all the natural rain. My potted tomatoes seems to be doing well, about 4 green tomatoes on the early girl and 3 green tomatoes on the other 2. I've only gotten two tomatoes so far both from the early girl.

        Btw, I discovered a third tomato in the raised bed. A thick stem has emerged and is already 4 feet high. I didn't know tomatoes could reproduce that way. I also notice that the tomatoes try to grow towards the sun. My bedded tomatoes try to grow towards my bush beans, which receive slightly more sun. Meanwhile, my potted tomatoes try to grow over top of the zucchini.

        I have lots of zucchini and yellow squash flowers and blossoms but no fruit. I'm wondering what the cause is, and if the cause is a lack of light. I know I failed to double dig the yellow squash bed. The zucchini bed wasn't getting enough water and mold was growing. There was a moderate number of weeds in the garden, I pulled most. Finally, I didn't thin my zucchini nor yellow squash, I didn't know what the instructions meant, and my dad said it would be ok to skip thinning.

        "Before you go cutting down your trees make a rough map of your garden on paper." Can you give me a sample map? I'll map my garden, scan the map, and post the image once I know what to do.

        I have several rectangle bed and one almost square bed. The square bed is 48 x 51 inches if you count the end boards. My rectangle beds are 99.5 by 48 inches.

        Here's the link of my diagram:

        The squares are the posts that rise up three feet or so, I didn't even try to make my diagram 3D. Image shack distored the image slighly, I scanned at 600 dpi, grayscale, and saved as a .jpg. The scanned image looked notiably better than the online version.

        1. re: Bottomless_Pit

          Your image didn't load. Try cutting down the image to 100 dpi or rescan at 100 dpi. Then reduce the image proportionately to a 4" width. You should be able to upload it directly to CH.

          Here's the image that we work off of for the garden immediately around the house

          1. re: morwen

            Ok I'm posting both the 100 dpi scan and 600 dpi scan of my garden bed. I finished cutting off the branches of the ash tree hanging over my garden. Some of the branches fell on the tomatoes a little, but the tomatoes were and still are wilting.

            1. re: Bottomless_Pit

              Maybe what's affecting your tomatoes isn't a lack of sunshine. It could be fusarium wilt, septoria leaf spot, early blight, or verticillium wilt to name a few infections that cause leaf wilt. Go to this link: and scroll down and click on the pdf file: ISU Tomato Diseases and Disorders and see if what you've got looks like anything in the photos there.

              This link about tomato wilt might be helpful to:

              1. re: morwen

                I just looked at the photos of the first, the leaves look wilted, though some seemed to have recovered while the sun was shining on the plants around 6 pm. The tomatoes are fairly big compared to the containers and keep growing, so no dwarfing. The worse leaves looked fairy yellow or dying. No oddness about the leaves like in the photos.

                I do have one black walnut tree about 50 feet away, but the tree is an older tree which have reduced toxicity on top of that the tomatoes are in a raised bed.

                "The initial symptoms of Verticillium and Fusarium wilts are wilting of the plant leaves during the heat of the day. Affected plants often recover in the evening or overnight. Gradually, however, the wilting becomes progressively worse and many plants eventually die. " I'll see how the tomatoes are doing during the heat of day tommorow.

                1. re: Bottomless_Pit

                  Here's a video of the sunlight in my garden:


                  the video also includes a look at my tomato plants.

                  1. re: Bottomless_Pit

                    BP, you really need to get involved with local gardeners who can help you with such specific problems like the amount of sunlight in your garden. Someone on the ground there will be able to provide you with much more information than those of us here trying to do it blind. Your local extension probably has a list of gardening groups and organizations in your area but a simple internet search should turn a lot of them up too.

                    1. re: morwen

                      I wasn't sure how to get in touch, my local extension lacks a head of committee, because of lack of funds. I guess I could try calling anyways. I'm not sure what I would google, gah typed in local gardening groups clicked on first result, and found a group not related to gardening over 10 miles away. Just tried another search, google can be so frustrating sometimes. You know exactly what you want but instead businesses come up and unrelated.

                      I even asked the manager the premier nursery in our area and the manager had nothing for me.

      2. Don't worry if you are not able to get the 6-9 hours of sun recommended for tomatoes in your whole garden. Cherry and grape tomatoes and some early varieties (as well as beans and many leafy vegetables) seem to do well in an area of my CT garden with less than 6 hrs direct sun. Try to put the ones with the longer growing seasons in the sunniest areas.

        B-Pit, my zucchini and squash are also setting few fruit this year (in both sunny and shaded locations). Never had this trouble before, especially with zucchini!

        1 Reply
        1. re: DonShirer

          Don, do you think the problems with the Zucchini has to deal with temperatures over 90 degrees? My dad said he grew Zucchini in the shadiest part of the garden about 10 years ago. I'm surprised about the Zucchini since I gave the Zucchini the sunniest bed, the container tomatoes adjacent have given me 4 green tomatoes + each!

          "Cherry and grape tomatoes and some early varieties (as well as beans and many leafy vegetables) seem to do well in an area of my CT garden with less than 6 hrs direct sun." What do you mean by CT, my only guess is container tomato. I'm going to look into grape and cherry tomatoes. Next year I plan to grow some tomatoes from seeds or seedlings.