Cultivation - Updated 4/25



Geoscape Desert Nursery
Cold hardy cactus, succulents & perennials for the rock gardening enthusiast.
1-208-884-1251 ( voice mail )
geodesert@yahoo.com
Selection & Planting Guide
Step 1of 3: Determine your zone hardiness. Remember this includes both heat as well as cold tolerance. If your not sure what your zone is I've provided a link to the USDA Zone Hardiness map. This will open a separate window.

Click Here for USDA Zone Hardiness Map link

Once there, enter your zip code to determine your zone. On all plant list pages, each plant description will list the compatible zones for that plant, such as Z4a-7a. The further the plants are grown outside of these parameters, the more likely the plant can be lost from excessive heat or cold exposure. Also keep in mind if your growing in containers to shave one full zone off the hardiness scale. This is because the whole plant (roots and all) are fully exposed above the ground level and are less protected from extreme weather unless taken indoors.

Step 2 of 3; Determine your best soil mixture based on your average annual rainfall. In basic terms the higher the average rainfall goes the more you'll have to lean out the mixture with regards to the ratio of large rock pieces to the finer sizes to increase the sharpness of drainage, allowing it to dry out faster after rainfall has occurred. In desert regions the native soil can be fairly rich which allows for more moisture retention with very low average rainfall. On the other end of the spectrum, in high rainfall regions, dry loving plants are restricted to vertical cliffs or rock fractures in exposed bedrock that have extreme drainage and dry out quickly after rainfall.

The following are recommended formulas for different levels of average rainfall. In many cases you'll have to experiment to get just the right drainage requirements if your at the extreme ends of the spectrum or are marginal between the different categories. The average annual rainfall can vary greatly depending on regional weather patterns, nearby lake/ocean effects, or elevation differences with mountain ranges that capture more rain on their upwind side and rain shadow effects on their downwind side. See Rainfall Map further down the page as an example of diversity of the Continental USA. If your not sure what your average annual rainfall is, contact one of your local weather forecasters and they should have that information. Local garden clubs and organizations specializing in cactus or succulents are also helpful in determining good mixes for your area.

Latest revision updated April 2020:










Less than 15 inches per year: For arid areas of the western USA, Lava fines is the ideal medium for open desert plants with porous air pockets that provide both good drainage but also allow for some moisture retention. In addition it adds anti compaction properties that keeps a good percentage of air pockets in the root zone critical for plant health. Lava (also called cinder) fines are commonly found in most western states where many natural sources are readily available at most nurseries. In addition to lava fines, a small amount of riverbed sand and active soil mix (garden compost) help balance out mineral composition and natural fertilizer properties to the overall mix. Only small amounts of additional trace minerals are needed for a fully optimized recipe. Decomposed granite is another commonly used mix for desert plants in the Desert Southwest but is not as good as it has a tendency to compact down over time unless used on a sloping angle and would only recommend if lava fines are not available.

16-30 inches per year:  For this formula, lava fines can still be incorporated on the lower end of the spectrum but should be avoided with 20+ inches and should be replaced entirely with a hard gravel mix with a good percentage (at least 50%) of one inch stone to provide larger air pockets and minimize compaction. Also the trace minerals become more important as rainfall increases which can wash away minerals and acidify the pH level.

30+ inches per year: Extreme drainage becomes critical for this amount of rainfall and will be the most challenging for adapting dry loving plants. Larger 1 inch crushed gravel will have to be a high percentage of the mix (up to 80% above 40 inches per year) to have enough drainage. Planting on hillsides, raised beds or large containers will help greatly. Trace minerals, especially limestone are critical in balancing the pH to avoid becoming too acidic.

Washed Sand: When purchasing sand, make sure that it's a "washed" (no dirt) product where water is used in the screening process verses a dry screen. Dry screened sand (including road mixes) contain too much dirt fines and can become tacky and harden after rainfall which can suffocate areas in the root zone.

Active Soil (garden) Mix: Pretty much any organic brand will do for adding active beneficial microbes and natural fertilizer. For desert plants (except for desert riparian plants) use very sparingly in your mix. Too much can increase the risk of root rot and, or fungus.

* Trace Minerals : A product called Azomite is a good quality trace mineral blend that helps balance out any mineral deficiencies that may be missing in your mix that encourages more rigid growth and improved disease & cold resistance. This product is not common in most local stores but is widely available online. Recommended additional mineral products to purchase are Gypsum (for vigor and & cold resistance), Superphosphate (to stimulate flowering and strong root growth), and Dolomite Limestone (mostly calcium based also for more rigid growth and disease resistance). A blend of these ingredients lightly dusted over the surface at the time of planting is recommended then repeated at least twice per year (spring & fall) for low rainfall areas. For higher rainfall areas this may have be done every 2-3 months. If you can find time release, especially limestone, pellets this will minimize the effort.

Amazon links here:
Azomite - Here
Gypsum - Here
Superphosphate - Here
Dolomite Limestone - Here

Step 3 of 3: Transplanting prep & procedure.

Cactus plants: Best transplanting temperature is above 80+ degrees F as daytime highs. Rooting can still be done below these temperatures but can take much longer and is not advised below 60 F as daytime highs.  Make sure the cactus soil mix is mostly dry with just a hint of dust separating when dropping a handful into the air. If no dust separates, then the mix is too wet and more dry mix should be added. Stir up and allow to dry out more if your out of extra dry mix. Once a little dust begins to separate out, then proceed with planting.

Important Note: Cacti are water sensitive and should not be watered immediately after planting. Avoid planting if any steady or heavy rain is in the forecast unless covered.  Allow the mix to dry completely to a depth of 3 or more inches before lightly watering. After 6-8 weeks, the new roots should be formed and a deeper watering can be done if necessary to compensate for summer heat. If rooting cuttings, they can be gently nudged out of the ground every 2-3 weeks to check for progress. Once established (usually after the first full year) regular watering is only necessary if natural conditions are abnormally hot or dry while the plants are actively growing, typically between the end of March until about mid August for most areas. When watering, use what I call "The 3 Inch Rule" to allow the soil to dry completely to a depth of 3 or more inches between watering if the plants are showing signs of drought (shrinking, wrinkling) distress. Discontinue any watering in late summer to harden off for winter. Many plants will normally shrink and, or lay down flat as winter approaches. This is normal as plants prepare to endure the freezing temperatures. The plants will literally "spring" back to life as the temperatures warm again the following spring just before producing flower buds and new growth.

Succulents & Perennials: Best transplanting temperature is between 50-70 degrees F as daytime highs. Plants need the cooler temps of early spring or fall (or winter for more southern climates ) to minimize dehydration of the leaves and stems from the heat of summer. Unlike cacti, succulents and perennials should be lightly watered in immediately after planting. Use the same "3 Inch Rule" strategy by allowing to dry to a depth of 3 or more inches between watering. This is critical during the first one to two years to get the plants established. Once established, watering should only be necessary if natural conditions are abnormally hot or dry. Discontinue any watering in late summer to harden off for winter.

Soil mix for higher water demanding (semi-riparian to riparian) desert perennial plants:
Note: On the Perennials Page, this refers to most plants with a "Sandy Loam" soil mix description. This group of desert plants like their roots damp to moist at all times during the heat of summer to maintain hydration or flowering and are adapted (or adaptable) to richer soils than their open desert counterparts. For these plants mix equal parts washed sand and good quality garden compost to retain more moisture. Also for this reason the plants don't need to be elevated above the ground level like true desert plants that demand sharp drainage unless you have more than 40 (rough threshold) inches of annual rainfall.

In drier areas below 20 inches per year, a deeper, wider planting hole is recommended to 1 1/2 to 2 feet deep (keep mature plant size in mind for width) so that the plants are placed into a slight depression slightly below the average ground level when finished backfilled and topped off with a top dressing of potting soil. This will minimize evaporation in the root zone and keep the water confined to the planting hole when watering.
Quick Reference Maps:
Less than 15 in. per year
10 parts lava fines
2 parts washed sand
1 part active soil mix
*trace minerals
16-30 inches per year
8 parts 1 inch crushed gravel
8 parts crushed pea gravel
2 parts washed sand
1 part active soil mix
*trace minerals
30+ inches per year
15 parts 1 inch crushed gravel
5 parts crushed pea gravel
2 parts washed sand
1 part active soil mix
*trace minerals