How much should I water my lavender plants?

Hi, I am a new gardener (if you can call what I do gardening, because I seem to be much better at killing plants :). I live in Houston, TX (Zone 8B) and am trying to grow potted lavender outdoors (my plants are still small, I bought them at a local nursery in 4in pots recently). I’ve read several books and forums on the subject, so I guess I’m reasonably well informed about the obvious facts concerning the care of lavender.

Rule #1: Don’t over-water!

So here is my problem. I’m a number-loving chemical engineer who is very detail-oriented, so I need specific numbers concerning exactly how much water lavender needs. I killed a couple of plants recently, I’m pretty certain, due to over-watering. I was watering them with the mist setting on the garden hose every two days for approximately 45-60 seconds. I learned recently to try not to get the leaves of the lavender wet and it’s better to water in the morning.

So, should I get a moisture meter? Any brand recommendations? Is there a rule of thumb I can use, like if the plant is indoors water ½ cup every 8 days, if the plant is outdoors, water 1 cup every 4 days?
The manager at the nursery suggested I water the lavender only when the plant shows signs of wilting, but we’re up to 100 deg F just about every day now, so I’m thinking that’s not good advice. Should I move my plants under growing lights indoors (we keep our thermostat on 76 deg F, so it’s relatively warm indoors)? If so, how much should I water them then?

Any suggestions/ideas would be most appreciated.

Happy Gardening!!

Well, Arizona's a whole lot drier than Texas, but I would be concerned that the plants were being underwatered at the root level. I wouldn't use a mist setting, I'd use a soaker or other gentle, higher-volume delivery method in order to soak the root ball and surrounding soil thoroughly.

I'd also get a moisture meter (only I already have one). That will tell you what you really need to know, and keep you from under-or-overwatering them. Test the root ball as well as a couple of surrounding soil areas close by. The roots need to be able to grow out into soil that isn't dried out and acting like a pot.

Please keep us posted on your experiences and success with lavender. I've tried unsuccessfully for a while to grow it outdoors. And will try, try again. What cultivar are you growing?

I had read years ago that it was successfully grown in Baton Rouge in a raised bed with good drainage and white crushed rock mulch to keep the ground temps cooler.

I do think soaking the soil rather than misting is good when needed. I'd also use a mulch to retain moisture and require less watering as well as keep cooler ground temps. But then you are also in danger of those toad strangler rains that occur.

But then what do I know? I've killed my share of lavender. As I said, please let us follow your successes.

The herb nursery here suggests planting it about 6" deep in crushed rock. The roots will make their way to the soil below. She has one completely filling a circle about 4-5 feet in diameter, in all white crushed stone. Remember, they are Mediterraneum plants. Hers are huge, and gorgeous! The quart-size plants I bought from her languished in soil, and the one that survived is now in a pot that's half sand, half soil and doing better since it now drains well. (I'll either bury the pot before winter or put it in the root cellar.)