How to Propagate Joshua Trees

Joshua Tree in Bloom

Joshua Tree in Bloom

Joshua Trees (Yucca brevifolia) sprout readily from fresh seed. Joshua Tree seeds are most viable when they are fresh and fully matured; that is, harvested from the current year’s seed production and black in color. If you collect seeds, try to grow them as soon as possible.

When to Collect Seeds

The Joshua Tree plant flowers in the Mojave Desert from February to late April, depending on the elevation and temperatures (snow conditions) each year. Most important for blooming is rainfall at the right time of the year. Seeds need to mature for months and dry out somewhat in the pod.

Joshua Tree seed pod

By late summer they are generally ready to harvest and propagate. The pods should be dry (not green as in the picture) and at least a little difficult to open. Seeds inside should be black!

Break open the dried pods and clean the seed before the pod dries out to a rock-like texture that is difficult to open and larvae of the yucca moth have eaten even many seeds.

Growing Joshua Trees from Seed (Propagating)

In many pods, you will find both flat, black seeds and tan seeds. The tan seeds are not fully mature and most will not grow. The black seeds are ripe and ready to sow.

Cluster of Joshua Tree Seeds

Check the black seeds over carefully for evidence of holes. The yucca moth pollinates the flower while laying its eggs in the flowers, and the larvae eat some of the seeds as they mature. Many more seeds are produced than are eaten, so you can usually find seeds that are chewed and many that are untouched inside the same pod.

Discard any seeds that have holes in them. They are no longer viable.

Breaking Dormancy

Most seeds sprout readily unless they have been left to dry out for a long time (many months to years). When the seeds has dried out, it will take longer to get them to sprout, but many still do, so be mindful of that fact when you follow the directions below. In most cases, you get the best results when you plant mature and freshly harvested seed promptly.

Here’s how to get your seeds growing:

Select the black Joshua seeds with no holes in them.
Lay them out in one layer between two paper towels in a shallow dish or pot bottom.
Spray the paper towels heavily to moisten them. The paper towels can be soggy but seeds should not sit immersed in water.
Place the dish indoors in room temperature (away from sources of cold drafts which would delay germination).
Spray them again as the paper towels begin to dry out. Check them every day and make sure they are continually moist but not immersed in water. Keep them warm (indoor temperatures). Watch for changes.
After about 10 days to two weeks, small white stems will emerge from one end of the seed. Keep spraying so the paper towels are just moist to provide moisture to the newly emerging sprout. They don’t all sprout at once, so you may just want to plant up those whose white shoot is longest and keep spraying the remaining seeds in hopes of getting more to sprout. Oftentimes you will get many more to sprout.
At this point, the seeds may be planted in soil, so ready a container with “clean” soil; that is, planting mixture that is new and unused, with less chance of harmful bacteria being present. If you re-use older soil, you can moisten it and microwave it for 1-2 minutes on high to sterilize it. Get a clean start so your plants will not succumb for fungi or bacteria while so young and tender.
Although the seeds can be transplanted into small containers if space is a problem, it is better to choose at least a gallon container that will allow a seedling to grow undisturbed for some time (years). You will be increasing the chances of survival in a gallon can both by not having to transplant for a year and because more soil holds more moisture for the plant.
Plant the white stems pointing up. They will emerge from the soil and, amazingly, arch back into the soil to establish the permanent plant from which the roots will grow and the tree will emerge.