Shalom Kavod HaRav. I asked the original question in 5772 about grafted citrus trees and kilayim and would like to ask a follow-up question. One of our grafted Kumquat trees has almost died off and the rootstock below the grafting point has started growing strong branches on its own. It seems from the appearance of the new leaves that the rootstock is a "Palestinian Sweet Lime" (Citrus limettioides), a rootstock that’s frequently used in Israel. However, on the old, almost dead Kumquat trunk there are still a few Kumquat leaves left. Can I leave these two citrus types growing together, coming out of the same trunk at different heights? Or should I chop off one variety? If I want to keep the rootstock Sweet Lime, does it have to start a new Orlah count because it’s different from the original Kumquat tree and sprouted up less than a Tefach from the ground? (Actually it even seems to come up from below the ground, but I can’t tell for sure because of dense grass and weeds around it). Is it a problem if it started sprouting during Shmitta? Thanks for your consideration.

Great questions! I conferred with Rav Yehuda Amichai, one of the world specialists in agricultural mitzvot from the Machon HaTorah v’haAretz, and the answers are as follows: As I wrote in the previous response, the Chazon Ish is of the lenient opinion that all citrus fruits are considered 1 species regarding Kilayim. Even though there are those who disagree with him and take a more stringent stand, but regarding our question, where there is an additional doubt or disagreement whether one is allowed to keep a prohibited grafted tree or not (see Pitchei Tshuva, on Y.D. 295, 7) we can surely say it’s a “sfeik sfeika” (a double-doubt: maybe there's no prohibition, and even if there is, maybe your'e allowed to keep it) and it’s therefore allowed. On the other hand, being that the kumquat and lime fruits look significantly different, it’s a problem that it “looks” prohibited (“mar’it ayin”) and others may mistakenly learn from you that grafting 2 species is allowed. Accordingly, you must take off the kumquat fruits (which you say its branches are almost dead anyway). Regarding orlah, on a large adult tree, where it’s obvious that at least 3 years have past, we need not worry that lower branches look like a new tree, and you need not count anew.