Run drip lines about 12 in apart for closely planted crops, which is four lines on a 4-ft bed, and use three lines on a 4-ft bed for larger crops such as broccoli, cabbage, and squash. For tomatoes and other big plants, run one line per row of plants, about 24 in apart.
Open this example in the Drip Irrigation Planner
How the number of lines is set
Water spreads sideways from a drip line, but only so far. Lines too far apart leave dry strips between them; the crop decides how far apart is close enough. Extension guides run drip lines 12 in apart, four lines on a 4-ft bed, for closely planted crops, and three lines on a 4-ft bed for larger crops such as corn, squash, and the cabbage family (Irrigating the Vegetable Garden).
The planner turns that into one rule: divide the bed's width by the line spacing and round to the nearest whole line.
lines per bed = round(bed width in inches ÷ line spacing in inches)
Lines per bed by width and crop
| Crop spacing | Line spacing | 3 ft bed | 4 ft bed | 5 ft bed |
|---|---|---|---|---|
| Close: greens, carrots, onions, beets | 12 in | 3 | 4 | 5 |
| Medium: broccoli, cabbage, kale, corn, bush squash | 16 in | 2 | 3 | 4 |
| Wide: tomatoes, peppers, vining squash | 24 in | 2 | 2 | 3 |
The 12 in and 16 in spacings follow extension guidance. The 24 in spacing for tomatoes, peppers, and vining squash is the planner's own default (one line per row of large plants), not an extension figure. Extension guides run two lines down a 2-ft-wide tomato bed, so add a line if your soil is sandy and water doesn't spread far.
Example: three 4 × 8 ft beds of broccoli
Broccoli is in the medium group. Three 4 × 8 ft beds with drip tape:
round(48 in ÷ 16 in) = round(3.00) = 3 lines
Plant the same beds with lettuce or carrots instead and you need 4 lines per bed: 96 ft of tape, or 106 ft to buy. That's a third more tape for the same beds, so pick the spacing for what you'll actually grow.
More lines also put water on faster. The standard drip-rate formula divides by the line spacing (Water Recommendations for Vegetables), so the broccoli beds get 0.25 in of water an hour and need 4 h 4 min a week for 1 in, while the lettuce beds get 0.33 in an hour and need 3 h 3 min. Set the timer for the spacing you chose.
Laying out the lines
- Space the lines evenly across the bed, with the outer lines about half a spacing in from each edge.
- Run them the long way, down the length of the bed, all starting from the header at one end.
- If one bed mixes crops, set the spacing for the most closely planted one, or give that crop its own bed.
Run your own numbers
The free BedMath Drip Irrigation Planner works this out for your beds, spigot, crops, and tubing, and shows every formula and source. This link opens it with the example above filled in.
Sources
Published 2026-11-03. The numbers in the examples come straight from the planner.