Poplar Trees

Question: Are these Poplar Trees planted too close together? They were planted 4 years ago.

responder: Thank you for your question!  Replied June 07, 2023, 1:51 PM EDT
response: Hello Mangala They very likely are planted too closely together; it depends on the species and variety of poplar. At 7 feet you have allowed 3.5 feet of width on that side of one tree, or a total of 7 feet wide of crown for one tree. Trees should be planted for good air circulation and sunlight at mature size— spaced at least at their mature width plus a couple feet. For mature trees that are 20 feet wide, you would plant them 21-25 feet apart.  However, moving them now may not be a good idea. It will take 2-4 years for them to recover from being transplanted, and the root ball required would require heavy equipment to lift the tree. Removing one to allow the neighboring trees room may be helpful if you see one tree starting to decline. Do you know which variety of poplar you planted? The variety and the mature height and width should be on the plant label. There are a few poplars that are considered columnar and have a narrower width than the species. Here are some references with some varieties: https://campustrees.umn.edu/white-poplar https://www.uwgb.edu/biodiversity-old/herbarium/trees/popnig01.htm https://www.ag.ndsu.edu/trees/handbook/th-3-133.pdf

responder: The Question Asker Replied June 07, 2023, 2:49 PM EDT
response: Thank you for your response.  The trees are Tulip poplars and they were planted four years ago in our yard by a reputable landscape company in town, so we didn't question it.  Can you give us more information from the pictures of the leaf and bark from the tree?  We had to take down a tall tree (originally there in the open space you see in the picture because it died) and we wanted to replace it.   Now, we are at a loss as to what we can do based on your earlier response.  Thank you for any help you can offer.

responder: The Question Asker Replied June 07, 2023, 3:02 PM EDT
response: I am re-posting the pictures. Thank you.

responder: Thank you for your question!  Replied June 07, 2023, 3:53 PM EDT
response: Hello again, Well, a tulip poplar, scientific name Liriodendron tulipifera, is not a ‘poplar’ – scientific name Populus species. So please disregard the information on Populus that I sent you. There are cultivars of Liriodendron that are considered dwarf or compact. I am hoping you have one of those. The species, i.e. the typical Liriodendron, grows to to 70+ feet tall and 35+ feet wide: https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a878 The more compact form known as L. tulipifera ‘Ardis’ grows about 15 feet tall and wide, according to one reference. The tree called L. tulipifera ‘Fastigiatum’’ grows about 50 feet tall and 15 feet wide. https://extension.usu.edu/botanicalcenter/trees-of-varga-arboretum/columnar-tuliptree There may be new compact cultivars as well. If you do not have the plant label, contact the nursery you purchased from and ask them which cultivar they sold you.  If you have one of the compact forms that is only about 15 feet wide at maturity, your planting should be fine, even though they are a little closely planted.The picture of the damge on the trunk looks like an old frost crack that is closing . It takes years for thes wound to close. If you remove one or more trees, choose the ones with the least number of injuries.  I do see some signs of chlorosis in the picture of leaves you sent. This could be a soil pH issue, or something else. If you decide to keep the trees I recommend you have these off-color leaves diagnosed.  There are two ways you may get a diagnosis: Firstly, Email all your pictures to MSU Plant and Pest Diagnostic lab. That is <personal data hidden>   They will advise you of what it is and what action to take, if any. They may need plant or soil samples to diagnose the problem, and there is a fee for doing that. Heir email to you will indicate if further tests are necessary. Secondly, you may hire a certified arborist to come on site, check the soil, check for diseases, and give you a complete diagnosis and plant care plan. To find these tested and certified professionals, search by zip code here – www.treesaregood.org Best of luck with your tulip poplars. If it turns out the trees are too big, perhaps you can remove two and let the third one grow? They are beautiful trees. Regards, Laura