Ask Mr. Smarty Plants

This USDA Plant Profile for Castilleja latifolia (Monterey Indian paintbrush) shows it as being endemic to one coastal area in central south California. We have no reference to ssp. mendocinensis in our Native Plant Database, but this ITIS report has a reference to Castilleja latifolia ssp mendocinensis, identifying it as a synonym for Castilleja mendocinensis, which is shown in this Calflora Taxon Report as in the range of Mendocino County. The upshot of all this is that we have no information on the propagation and placement of this plant, but did find a reference saying it was regarded as endangered. About the best we can do for you is give you the Propagation and Growing Conditions for Texas native Castilleja indivisa (entireleaf Indian paintbrush). You will note that in the Growing Conditions, the Castilleja is hemi-parasitic, its roots growing until they touch the roots of other plants to obtain a portion of their nutrients. Transplanting paintbrush may kill it. Since we can give you no definitive information on the specific plant you are dealing with, we would suggest you do some experimentation, using all of your suggested techniques, hopefully determining which would be the most beneficial to the plant.

Propagation Material: Seeds
Description: Seed in open, sunny sites for best results. Indian paintbrush seed may require a cold wet period in the winter to germinate. Plant the seed in the fall and rake it into loose topsoil to ensure good seed/soil contact. Seeds are exceptionally small (4 million seeds per pound), commercially available, depending on the previous year’s seed crop and can be expensive. The recommended seeding rate in 1/4 pound per acre.
Seed Collection: Seeds are formed in capsules at the base of each flower. Seed capsules may be carefully collected by hand April – May when the capsules are dry and brown.

Water Use: Medium
Light Requirement: Sun
Soil Moisture: Dry
Soil pH: Acidic (pH<6.8)
Soil Description: Sandy soils. Sandy Loam, Sandy, Medium Loam, Clay Loam, Clay
Conditions Comments: The roots of this plant will grow until they touch the roots of other plants, frequently grasses, penetrating these host roots to obtain a portion of their nutrients. Transplanting paintbrush may kill it.