Our Lawson Cypress has died. Diagnosis is Phytophthora. We have 2 quotes to have the tree removed but there appears to be varying opinions regarding what we do prior to replanting. One guy says to treat the soil to reduce the Phytophthora and to 'deter' reinfection of new planting. The other guy says it's in the water table, we will not get rid of it, and so long as we're not planting the same tree in it's place we should be all right. Will cost almost $300 extra to treat the soil which I don't want to pay unless we have to. Any thoughts? If it makes any difference, the tree we would like to replace the Cypress with is a Siberian Spruce. Thank you for any insight you might be able to offer.
Second person is right; Lawson's Cypress is usually killed by Phytophthora lateralis, which is only damaging to that species, and also correct that you can't realistically get rid of it from the soil. Siberian Spruce Picea obovata isn't a very interesting tree, and not well adapted to your climate. Are you sure you didn't mean Serbian Spruce Picea omorika? That's much nicer and a good choice.
Thank you Michael. I believe you are correct, it looks like the Serbian Spruce is the one we're looking at. It had beautiful purple pine cones if I remember correctly. The loss of our Cypress will leave a large hole in our front landscape, so we're looking another evergreen for the privacy. We'll skip the fungus/chemical treatment. Sounds like it would not be a good use of our money. Thanks for your reply!!
Row of failing 'Alumii' street trees in Tacoma were determined by a world authority on the topic to be infested with several species of water molds including genera other than Phytophthora. Maybe if you leave the planting spot empty for a few years the lack of a host will cause the water molds to diminish significantly. Unless they are living on other specimens around the spot where the cypress was. Where there is concern about people looking in a solid fence might be adequate, a replacement tree will not immediately fill the same space as the cypress did anyway. Unless it arrives on a trailer, is lowered into place with a crane.
Thank you Ron. I want to replace the tree asap. The sooner we plant it, the sooner it gives us privacy. There are other plants in the garden bed and there will be more to come. If the fungus only affects Lawson's Cypress then I'm assuming other species are more resistant to it ??
My point was that other water molds have been found on the tree here, which will of course attack other kinds of plants as well - some water molds infest a huge range of species. Declining big-leaf maples in the Seattle arboretum were also found to be hosting an assortment rather than one or two kinds. By the way, you know your tree had Phytophthora by what method? Experts take samples of infested plant parts and use these to identify the water molds present under laboratory conditions. If you just had somebody come out and look at the carcass, go "Yep" - well, they might happen to be right and they might not.
An arborist came out and gave us the diagnosis however he did not take any samples. He looked at it and we gave him some details regarding when it started to look bad and that's really it...
So general circumstances imply water mold infestation but in fact that is not known with certainty. If adjacent plants aren't declining maybe just remove the stump and dig out a pit, refill with soil from elsewhere, plant in that. If you hit mud you will know you may need to improve the drainage.
