Question: My gardener comes every month to mow the lawn and trim the hedges, etc. Can he come during the nine days?
Answer: The Mishna (Taanis 26b) tells us that when the month of Av enters, we decrease our rejoicing. The Gemara (Yevamos 43a) writes that among other things, one shouldn’t build or plant during these nine days. Tosafos writes that the Gemara Yerushalmi qualifies this prohibition as building or planting for joyous purposes such as building a house for a wedding and planting a royal garden. Thus, the Shulchan Aruch (OC 551:2) only forbids building or planting for joyous purposes. The poskim, however, extend these restrictions to anything done for beauty (See Mishna Berura 551:12). Thus, one should avoid planting new plants and herbs.
R’ Ephraim Greenblatt (Rivevos Ephraim 1:374) writes that one may, however, mow their lawn and maintain their garden during this time. It doesn’t matter whether one has their gardener do it for them or one does it themselves. On Tisha B’av itself, however, one mustn’t do any gardening.