Now imagine you’re a commercial citrus grower - Your incentive is to grow as many big, pretty citrus trees for sale as quickly as possible. In spite of all its other positive attributes trifoliate is very slow growing, and on average it takes approximately one year longer to grow a tree to market size compared to other more vigorous rootstocks. If your business is growing big trees fast, trifoliate is a losing proposition, especially when there are alternative rootstocks like Carrizo and Kuharske citrange that will.
The two main citrus tree producers I see around town are Brazos Citrus Nursery (many reputable nurseries like ArborGate and RCW) and Saxon Becnel (commonly found at Home Depot, Lowes, etc). Brazos citrus uses trifoliate for kumquats (graft compatibility reasons), Carrizo citrange for most other things, and maybe Swingle citrumelo for pummelos. In the past they have also produced trees labeled ‘Dwarf’, which I’ve bee told means they’re grafted onto either trifoliate, or and even more dwarfing trifoliate variant called Flying Dragon. The last time I called Saxon Becnel I was told they produce trees on Kuharske citrange, and claim their experience has showed them it is the best rootstock for the Gulf Coast.
I completely understand why they use the rootstocks they use, and both rootstocks can work here if given the right conditions (good drainage, cold protection). But I have also been through hard freezes that killed all of my citrus trees that weren’t on trifoliate. What we need is a rootstock that is well suited for the greater Houston area, but grows quickly enough to be competitive with Carrizo and Kuharske citrange. Turns out the University of Florida may have found it as part of their search for rootstocks resistant to citrus greening disease. It’s called US-802, and is a trifoliate x pummelo hybrid (botanically a citrumelo). In field trials it has proven to be well adapted to wet and clay soils, more cold hardy than Swingle citrumelo, resistant to citrus greening, and very vigorous! (https://www.growingproduce.com/citrus/varieties-rootstocks/taking-stock-of-new-citrus-rootstocks/)
The Texas A&M Citrus Center now offers budwood from the UFL program, so I decided to trial this new rootstock for Houston. Who knows? It could be the win-win solution for commercial producers and home citrus growers! The only way to find out is to try it..... but how? Budwood is just, well, budwood. What I really needed was a rootstock, or at least seeds, but it looked like my only option was going to be trying to root the budwood cuttings. While researching this, I stumbled across Dan Willey’s website FruitMentor.com, where he documented how citrus is grafted and rooted from cuttings in a single step by commercial growers. He also detailed his attempts to copy the process. I decided to try it myself, using US-802 budwood from the Citrus Center, and Dancy tangerine budwood I cut from my tree.
First I Z-grafted the Dancy and US-802 together, and wrapped it with parafilm and a rubber band. Then I dipped it in Dip-n-Grow rooting hormone, and stuck it in a half-soda bottle filled with coconut coir. I placed the top half of the bottle back on to keep the humidity high, and placed it on a heat mat under LED plant lights. After about a week I started to see growth! I knew that this didn’t mean it was growing roots yet, but I was still amazed. I continued to watch every day, until the leaves were pressing against the sides of the bottle. I couldn’t leave it like that, so I decided to separate the two attempts. When I did, I was sad to see no evidence of rooting. I placed them each in their own bottles, and re-sealed them. I’ll have to wait another month or so to see if my experiment will be a success or not. With any luck, I’ll be planting the first trial tree on US-802 soon!