Lavender needs little water after established, but young lavender needs to be watered every four to five days in the first month if there is not regular rainfall. Where lavender thrives in Grand Haven, Michigan and the Provence region of southern France, the average annual rainfall is 36” and 24” respectfully. Both areas receive enough rainfall and there is no need to supplement with irrigation even in the summer months. The rainfall at our farm averages 56” annually. Quite a bit more which can be detrimental especially if drainage is not right [hence the mounds and added gravel]. And our rainfall can be heavy one day, sometimes for days at a time in some months, and little or no rain in other months. Since we planted in the summer with 90 degrees+ and the cost of irrigation for our test field was relatively low, we decided to install irrigation. The recommended irrigation for lavender is 5/8” Drip Tape 15 mil with 36” emitter spacing, averaging .33 GPH and can be put over or under weed cloth.
Several months before planting, we purchased our system online from Drip Depot, a DIY Irrigation Superstore. An online store that was easy to navigate with great customer service. After reading lots of information on the Drip Depot’s website and emailing customer service, we configured/ordered a $165 drip tape system for the test field. We also decided that we would put the drip tape over the weed cloth. Our bed mulch layer that we used to make our mounds with weed cloth can also install drip tape at the same time underneath. Since we wanted emitters positioned at the base of each plant, and this was the first time bedding with heavy [5 oz] weed cloth on a slope, it seemed better and easier to install on top after making our mounds and planting.
On July 6th, the day after we finished planting our test field, it was time to set up our irrigation. We rolled out our drip tape on one of our lavender rows to straighten out in the sun for a few hours before installing. We noticed that the emitters did not lined up at the base of the plant. Were our holes not 36” center? Even though we double checked prior to burning holes, we checked our spacing again, and confirmed all of our holes were 36” center. We then checked the drip tape, and found that most were not 36” between emitters, and the spacing varied on the same roll. This irregular spacing after 5 or 6 holes would result in the emitters completely missing most of the holes of our 29 plant rows. We also were not convinced the water would penetrate if the emitter was on top of the heavy weed cloth and definitely did not seem the most efficient or economical way to water.
We contacted and sent pictures to Drip Depot’s customer service to see if we received a defective roll or if this was the norm [although no indication that it would be anything but 36” on their website]. The rep sent an email to the manufacturer, Irritec to find out more. We also contacted Irritec directly as time was of the essence. The first Irritec customer service rep said it was supposed to be 36” spacing, but would give our information to their technical rep to confirm. Even though the Irritec technician was on vacation, he called later that day to let us know that the “acceptable 36” production spacing has a range of 35.2 to 36.9”. After discussing that it would not work for our lavender 8” holes and heavy weed cloth, the technical rep recommended tubing and manually punching holes at the plant base and attaching low flow emitters. We ordered this system from Drip Depot, and respectfully asked them to update their website with the 36” drip tape acceptable variance so others would be aware of this possible issue.
Still not sure why 36” drip tape is recommended for lavender. Have to assume it’s installed underneath to be successful. As we wait on the new irrigation system to arrive, I ordered a small battery powered sprayer from Amazon for less than $50. After checking moisture of each plant with a soil moisture meter, I watered the plants as needed. Not ideal with frequent trips to refilling the small tank, but overall worked well for a small test field and the plants in front of our shed.
On July 15th, we finally installed our new tubing and low flow emitter irrigation system. We also put a rain gauge in the middle of our test field to monitor/log rainfall, but still used the soil moisture meter before watering. Thankful that our irrigation system was finally installed!
Added note: But wait, there’s more to the tale. We only used the irrigation system twice. The days of no rain ended July 26th with heavy rainfall, and it continued to rain consistently so we did not need to supplement with irrigation. Mother Nature, you got to love her. We plan to add 1000+ lavender plants in the Spring 2023, not sure with the typical rainfall at our farm during this time of year, if we will install an irrigation system...
