Here is a guide for which wood to choose, some design ideas, and a few tips that will make your beds keep their form and last longer. In this case, long lasting means a lifetime or over 100 years. The hemlock tree comes from Canada, and is a traditional evergreen tree. Hemlock lumber is produced from trees in the genus Tsuga. I looked at pottery planters that are glazed the the outside, but they all have glaze running into the inside, and to me the glazes look like they are lead based. Western hemlock (Tsuga heterophylla), sometimes called Pacific hemlock, thrives in the moist coastal ranges from Alaska to northern California, and also climbs mountain slopes in Idaho and Montana. What’s in them. Aluminum siding-- The InterNACHI report projects that aluminum siding should last for 25 to 40 years. How wet will they get. These plants can grow up to 80 feet high, and amateur gardeners can make a few mistakes in growing these trees which affect the health and growth of the hemlock tree. The length of time they stay alive has a lot to do with environmental factors and how fast they dry up. Last Modified Date: October 25, 2020 . How long your boxes will last can be influenced by a number of factors. If hemlock lumber will be used in an outdoor setting, it needs to be treated to protect it, and periodic re-treatments are advised to keep the wood in good condition. What’s around them. While the plant grows undamaged, it emits a chemical warning which grazing animals recognise and avoid. In some cases it may remain in good shape for even longer. There are two species of Hemlock, Cicuta (Water hemlock) and Conium (Poison hemlock). How active is your soil. If I leave cedar bare outside, not touching the ground, and not being walked on, just exposed to the weather, how long will it last? Outside of the body, sperm may die quickly when they’re exposed to the air. In fact both plants are poisonous, but it is the Conium which is the most toxic, most common and most often responsible for poisoning. Now you need to decide what lumber to use, and get some tips on just how to construct your beds. So you’ve done some research and decided that raised garden beds are for you. Brick veneer-- Both the NAHB and the InterNACHI indicate that brick is a good choice for a long lasting exterior veneer.