How Much Water for the Garden?

Water is essential for plants to absorb nutrients from the soil. The weekly water requirements of plants varies by temperature and by type of soil. At temperatures of 70°-75°F (21-24 C), plants use 0.15″-0.20″ (0.4-0.5 cm) of water per day, or 1.05″-1.40″ (2.7-3.6 cm) per week. At temperatures of 80°-90°F (27-32 C), plants use 0.25″-0.35″ (0.64-0.9 cm) of water per day, or 1.75″-2.45″ (4.44-6.0 cm) per week. Use the lower rates for clay soil and the higher rates for sandy soil. For every day that temperatures exceed 90°F, add 0.25″ (0.64 cm) of water per day.

Water infiltrates the soil more quickly on lighter soils than on heavier soils. Whether you use a drip irrigation system (greatly preferred to minimize both atmospheric water loss and fungal leaf diseases) or an overhead watering system, adjust the flow rate as follows:

  • Sand                  2.0″ (4.9 cm) per hour  (Needs a faster drip rate)
  • Sandy Loam     1.8″ (4.6 cm) per hour
  • Silt and Clay     0.5″  (1.3 cm) per hour
  • Clay                   0.2″ (0.5 cm) per hour   (Needs a slow  rate or else water will puddle)

Jumbo EZ Read Rain Gauge image courtesy of hardwareandtools.com

Since watering the lawn or garden plants can be expensive, a rain gauge is a useful tool for seeing how much water needs to be supplied to make up for any rain deficiencies during the week. The Jumbo EZ Read Rain Gauge is my favorite tool for determining how much extra water is required each week. Some hardware stores may carry this item, or else search the internet for a preferred supplier.

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4 Responses to How Much Water for the Garden?

  1. HT says:

    Thanks for the tips – really appreciated. I use a sprinkler hose in the front – once a week for a half hour, and a soaker hose in the back – same duration, but I check the ground every couple of days during hot dry spells. It seems to work for me, however, I’ll look into that rain guage. P.S. the sprinkler hose in the front is great – the wisteria, dwarf lilac and holly seem to like getting wet, as do the perenials that I’ve planted in the garden (townhouse, small lot – 9’by 30′) but in the back, the many clematis I have climbing the fence don’t seem to like their leaves getting wet, hence the soaker.
    Thanks again for this great site!

    • grayslady says:

      Clematis love having cool soil at the root zone, so your soaker hose is just right for them. If your plants in the front yard are well established, they are probably fairly drought-tolerant at this point; an inch of water per week may be just fine for them.

  2. HT says:

    oops, I should have stipulated, the front is 9 by 30, and I don’t have a lawn, it’s all garden. The back is 25X45, and I live in zone 6a on an ancient river bed, so clay base. I’ve dug down 3 feet, front and back, over the years, and replaced the surface clay with a variety of soils – loam, sand, peat and compost mixed in, but mainly triple mix, which is just more topsoil, peat and compost. Works for me.

    • grayslady says:

      Our property sizes sound similar, except I’m in Zone 5a. I’m really impressed with the “double-digging” you’ve done with your soil. It’s a tremendous amount of work, but so much better for the plants. Good for you!

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