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Last year my wife and I were veggie gardening rookies: I built a 4'x8' raised garden bed out of cedar, we planted, and actually didn't do half bad. At the end of the season we spoke with a "master gardener" at a county fair who told us why we lost half of our harvest: our irrigation method. I had, in my ignorance, been watering our plants via sprinkler at the end of the day. According to this gardener, this "top-down" irrigation method was leaving moisture on the leaves, allowing mildew/rot/disease to creep in. Apparently it also makes it harder to get the water directly to the roots, and so its inefficient as well.

This year I wanted us to learn from our mistakes. We went out and bought all our seeds and transplants, some extra top soil and compost, etc. Last weekend I got the soil/compost in the garden, and I thought we would be planting everything together this coming weekend.

Turns out my wife couldn't wait. She went ahead without me and planted everything in the garden basically according to the space each plant needs around it as well as by aesthetic appeal:

enter image description here

I was planning on doing soaker hose-based irrigation this year, that is:

  • Putting everything (essentially) into an (x,y) grid
  • Snaking a soaker hose back and forth betweeen the "axes" on the grid

But as you can see, we now have a hot, unstructured mess where instead of a neat, easily-irrigatable grid, we have "plant clusters". So I ask: is there any way for us to stay with soaker hose irrigation? If so, what might it look like and what special hardware would I need to snake around all of these "plant clusters"? If not, what is our best option for irrigation here?

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I prefer drip emitter tubing over soaker hoses. They deliver more even and consistent watering throughout the length. You can get them with various emitter spacings from 6" to 18" or so. If you lay rows of tubes spaced the same distance apart as the emitter spacing you can get good watering over the entire bed. For example with 12" emitter spacing, place rows of drip line 12" apart. Cover with mulch to help retain moisture. See an example with 6" drip tubes in a raised bed on my site. You can do the same with soaker hoses under mulch as well. The lines don't need to be directly next to a plant. With slow watering the water will spread out with through capillary action and the roots will eventually be everywhere under the soil.

May not be the most effective way to water seeds though as drip irrigation is intended for slow, deep watering. You can water from the top without killing your plants following these tips.

  • Don't over water your plants. It's better to water less often but deeper
  • Water from plant to plant, watering a little at a time and then repeating until you provide the desired amount of water. That way the water soaks in before you hit it again.
  • Water in the morning so if any moisture gets on the leaves it will dry out before the evening
  • Use a wand instead of a standard trigger sprayer so you can water at the base of the plants. I like the Dramm wands with their breaker heads, they even have a mister for seedlings. They have wands with triggers but I like the one with a ball valve you twist because it's more reliable. Can still be operated with one hand.
  • mulch around the base of your plants to prevent water/mud from splashing up to your plants and to keep the soil moist between waterings.
  • for tomatoes, as the plant grows trim off the lower branches so they don't touch the soil.
  • Thanks @OrganicLawnDIY (+1) - I like your suggestion about the mulch - is it OK to just go ahead and mulch my entire bed, or is there a reason why I would just want to mulch around the base of my plants? I would think covering the entire bed (though a wee bit more expensive) would help distribute soil temp/moisture evenly and keep weeds out. Thoughts? Thanks again! – smeeb May 27 '15 at 11:59
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    Mulch around the entire bed. It doesn't have to be expensive. A thick layer of mulch can help suppress weeds. For the vegetable garden I normally use a few layers of newspaper I know use soy based inks or more frequently cardboard then cover with some organic mulch like grass clippings, thatch, any leftover uncomposted fall leaves, compost, straw etc. I don't like wood chips or bark here. I'm going to try some coir mulch this year because I prefer to keep my grass clippings in the lawn and I've always wanted to try it. You don't want to cover the seeded areas until they get big. – OrganicLawnDIY May 27 '15 at 15:23
  • Thanks again @OrganicLawnDIY (+1) - one last quick followup question (I promise): if I go with straw as the mulch is there a realistic risk of introducing weeds to the bed? Of the options you listed straw is the likely viable mulch option for me (I don't really have any newspapers, especially with ink that I'm certain is soy based; same for cardboard, thatch, leaves, etc.). Thoughts? Thanks again! – smeeb May 27 '15 at 15:35
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    Straw is the stalks of plants after seeds have been harvested. It may contain some weed seeds but it is frequently recommended because it has less seeds than hay. See extension.umd.edu/sites/default/files/_docs/locations/… Plastic sheeting as mulch, also works well and can increase yields on certain plants but it's easier to put it down before you plant. I'm trying red plastic mulch for the first time this year. – OrganicLawnDIY May 27 '15 at 16:28
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You've mentioned seeds as well as transplants, so I'm assuming the bed has seeds planted in it already? If that's the case, trying to put in a soaker hose will be next to impossible without disrupting what's been planted already. I think I'd stick to sprinkler watering, but do it in the early morning instead - that way, any moisture lurking on any leaves dries out better. It is true that sprinkling at the end of the day MIGHT increase the risk of fungal infection because the plants are sitting damp in the cool of the night, so doing it first thing should get round this possible problem.

UPDATED ANSWER;

In response to your comment - my apologies, when you said soaker hose, I imagined leaky pipe, which does go under the soil, whereas a soaker hose does not, sorry! That's assuming the terminology is the same in both our home countries, I'm not where you are.

  • Thanks @Bamboo (+1) - great advice, and I will likely do just that. Just for my own edification though, I'm not understanding what you mean when you say "If that's the case, trying to put in a soaker hose will be next to impossible without disrupting what's been planted already." My question is: why? Doesn't the soaker hose just sit on top of the soil? (And yes, to confirm your suspicions, we do have a mixture of planted seeds and transplants.) Thanks again! – smeeb May 27 '15 at 11:52
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I started square foot gardening in 4 X 4 beds this year, and merely installed a soaker hose that surrounds the center 4 squares; after agonizing over several designs that just did not word well in that planting scheme. What I have found out so far is this: you have to water a lot more than "1 inch per week", and you still have to water with a can while seeds are germinating and for about a week after transplanting. The reason for this is that the drip goes straight down into the soil and then spreads out, so to reach all the plants you have to have a lot of spreading, which takes a lot of water. I discovered this when my broccoli and brussels sprouts started to wilt even though I had watered "sufficiently", even according to a moisture meter; and it hasn't consistently gotten into the 70s here yet. Also, the dry areas on the surface never soak up the water from down below, so you have to prime those spots from above, because the drip water will not reach the shallow seeds and roots. Once everything is established, in a couple weeks, I will switch to just the soaker hoses, adjusting the watering budget for the temperature. Some recommendations are as much as .5 inch per 10 degrees over 60F. Water from above in the morning so the sun will evaporate it off the leaves. It is also my belief that plants need more water as they get bigger; and more fertilizer as well. The once size fits all approach given on most fertilizers of "the same amount every week" doesn't fit any. I put balanced fertilizer in the soil at time of seeding and transplanting, and will then deep root fertilize for each vegetable per its needs through the growing season. When I was a weekend gardener I got sporadic results. No, retired, I am trying hard to turn my black thumb green.

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