Many, many of the most drought-tolerant plants have adapted to long periods of heat without water. That's why we love them! And want them in our gardens. Because they can deal with the conditions are water supplies sometimes can't. 

But this means that if *most* low-water plants sit in water or get too much of it - especially when it's hot - they get sick and die very quickly. I mean you barely knew they were there quick (see end of article of a list of drought-tolerant plants not so water sensitive). 

Hence, the be all end all of drought tolerant plants is....great soil drainage

I didn't believe until I saw it, but TONS of low-water plants are extremely content growing in near sand. Or rock piles with clay or sand on top. In fact they love it. (Like the mountain of wildflowers in the picture below going out of a semi-arid mountain). Not that they don't need some light amendments and irrigation to make the most of it. But let me tell you, they can live their best life on a gravelly mountainside or near the dunes. 

Read on to know what to do to your soil structure for the best results. 

NOTE ON SLOPES: if you've got a good slope then you've got good drainage. While it may take a little something to get the water to actually penetrate at the outset (like gypsum) you don't have to stress about amending the soil for drainage too much if it's showing signs of clay.  

Know Your Soil

There's a million tutorials on how to test your soil's structural balance. From the mason jar shake to drainage pits. A quick google will give you all the geeking out you could ever desire. But the quick and dirty is:

• If your soil cracks after being wet for awhile and then drying, it's clay. 
• If your soil is hard as a rock when you try to stick a shovel or hand trowel in it when it's dry it's clay (or overly compacted)
• If you stick your finger in the dirt when it's damp and you can't wipe the mud off without washing it under water, it's a decently clay.

To be clear clay isn't all bad, it's actually a great and nutrient supporting thing to have in the soil. Sand is the hardest to grow fruits and vegetables in for example, because it leeches nutrients extremely fast. We just need to make clay soil drought-tolerant plant friendly so your new garden doesn't pay the price or poor drainage. 

Soil Type Fixes 

QUICK CLAY SOIL FIX

If you have intensely compacted or high clay content soil. You will need to make significant improvements to your soil to guarantee your low-water plant's success.

1. Temporary modifications like gypsum help
2. Even better is to put a minimum of 2" deep of lava rock in the bottom of every drought-tolerant planting hole. 

Alternatively you can mulch the top of your soil (up to 2-3" deep) with gravel, decorative rock or Decomposed Granite (DG). 

Most Sensitive Plants to poor drainage: Ceanothus, Penstemon, Eriogonum (buckwheats), Manzanita, Atriplex, Jojoba, Mimulus auranticus (monkey flower), Cactus  

CLAY SOIL CURE-ALL

The full monty would be to actually till or mix sharp draining gravel into your soil's top foot. You can also add 4-12" deep of decomposed granite to give your plant's top roots the best possible drainage. If you really want to go the full monty you can mix fast draining material and a bit of compost into the top foot. BUT ensure the blend is close to or over 1:1 to the clay so you don't accidentally create concrete. 

COMMON SANDY SOIL MISTAKE

Amending this soil with compost in the planting holes will cause plants to rot once their roots venture outside of them. Compost and fertilizers are always best top-dressed - or spread on the soil's surface for a trickle down effect. 

MEDIUM SOIL MOD

Let's say you've magically got the prairie dirt in a suburban California stretch. Well that nice loamy blend might do just fine. But a nice topping of DG or gravel mulch wouldn't hurt as some California native plants are sensitive to too much fertility too. 

DROUGHT TOLERANT PLANT WATERING BASICS

We've all heard it, but it's just as true with landscaping plants as it is with house plants!! Over watering is the most common cause of death. Drought tolerant plants like to be watered deeply and infrequently. And they HATE being watered when it's super hot out (though most, except the most sensitive ones listed above) still need a little to get by. Just make sure you wait for the slightly cooler days or irrigate gently at night. 

Times plants want or need regular water: first 6 weeks of establishment

Plants that can take extra water: Mexican Sages, Grasses, Some succulents, Mint family plants & their relatives (agastache, nepeta, etc.)