One of the lessons I learned after installing a drip irrigation system the first time is how easy it is to overwater and underwater the plants in a raised garden bed. The key to watering raised gardens correctly is to get the timing right.
You should drip irrigate a raised garden for 15 – 45 minutes every other day, providing about 1 inch of water per week, depending on the season, soil type, bed size, and the number of emitters on the drip lines. The flow, plant size, and mulching will also influence the watering duration.
The plants’ response will guide you on whether to leave the drip lines running for longer or shorten the time and frequency. I’ll discuss factors influencing your decisions when drip irrigating the raised garden bed.
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How Long To Run Drip Irrigation in Your Raised Garden Bed
Raised garden beds differ from in-ground gardens. They have limited or no soil compaction, better drainage, and a longer growing season. They also have different watering requirements (source).
When you use a watering can or garden hose, you can tell how much water your plants are getting. It is easy for you to underwater or overwater your plants when drip irrigating your raised garden because you cannot estimate the amount of water released.
How long you run the drip irrigation system in the raised garden bed depends on the following factors.
Size and Type of the Raised Bed
The size of the raised bed and how you space the drip lines will determine how long you water the raised garden. The ½ inch (1.27cm) and ¼ inch (0.63cm) drip tubings are the most common for raised gardens.
The ¼-inch (0.63cm) tubes are best for small gardens, while the ½-inch (1.27cm) tubing is excellent for large raised garden beds.
The 1/2-inch (1.27cm) drip tubes release a maximum of 200 GPH (gallons per hour), while the ¼-inch (0.63cm) tubes produce a maximum of 30 GPH. If you use the smaller line on a large raised garden bed, you’ll need to run it for a longer time than if you were using the ½-inch tubes (source).
It is important to note that ¼-inch tubes are best not used in gardens that require more than 17 feet (5.2m) of piping. In this case, a ½-inch tubing is ideal.
You need to run your drip lines for a long time during summer than in the cooler seasons because water evaporates faster when it is hot. You also need to give plants a little more water when it is windy and dry.
The plants will lose some of the water in the soil through evaporation. They will also lose some of the absorbed water through transpiration (source).
During the cooler months, the soil retains moisture for longer, and evapotranspiration rates are lower. You risk having soggy soil if you maintain the summer watering schedule in the fall and spring seasons.
This YouTube video sheds light on how long to water plants and the factors influencing the watering duration:
The Number of Emitters
The ½ inch (1.27cm) tubing has in-line emitters spaced 9 – 12 inches (22.86cm – 30.48cm) apart, while the ¼ inch (0.63cm) has emitters spaced every 6 – 12 inches (15.24cm – 30.48cm).
The spacing between emitters is influenced by;
- The type of soil.
- The plant’s thirst.
- Soil exposure to the sun.
Well-draining soils absorb water faster, so the space between emitters should be wider than those in drip lines in raised gardens with dense soils.
Plants with more than one emitter feeding it will not need the line to run as long as plants with one emitter. If you have thirsty plants, it is best to have more emitters on the drip lines (source).
Most people prefer using CARPATHEN 100 1/4 Tubing Drip Emitters (link to Amazon) for raised beds.
The Type of Plants in Your Garden
The plants in your raised garden play a critical role in your decision on the duration you will run your drip lines. Plants have different water needs. For example, tomatoes have deep roots and require more water than green leafy vegetables.
Have plants with similar watering needs planted together in the raised garden bed whenever possible. If this is impossible, you’ll need to find a balance when watering plants with different water needs.
|Moisture Loving Plants||Plants that require little water|
|Tomatoes||Herbs (rosemary, sage, marjoram)|
If your raised garden bed has plants with high and low water needs, you should consider mulching to reduce moisture loss. You should also set the timer to a duration that doesn’t harm the plants.
The Plant’s Size
The watering duration may not be as long for new plants as for established plants, but the frequency is higher. Older plants will benefit more from deep but infrequent watering.
Most plant roots are 6 – 12 inches (15.24cm – 30.48cm) deep into the soil in raised gardens. These plants need at least an inch (2.54cm) of water weekly. Deeper roots may need more water (source).
New plants usually need more water because some water becomes lost through evaporation. As they grow taller, the leaves shield the soil from the sun, so most of the moisture is retained in the ground.
If the raised bed is moist, you will run the drip lines for a shorter time. However, when it’s hot, established plants lose more water through transpiration, so you will need to water them for longer.
There is no standard watering duration for drip irrigation in raised beds. To avoid overwatering or underwatering your plants, check the raised bed to see how wet or dry the bed is before setting the timer.
If the soil is slightly moist, water the plants for a shorter time. Likewise, if the soil is dry, run the drip lines for a longer time.
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