Poplar, known botanically as Populus, is a species of fast-growing trees with more than a dozen cultivars and hybrids including Aspen trees. Poplars are medium to large trees with straight trunks and an upright growth habit. Many cultivars reach up to 100 feet in height at maturity with foliage that is roughly spade or maple leaf-shaped with lightly to deeply toothed margins. The poplar species is tolerant of a wide range of soil conditions, but there are a few parameters that must be heeded to keep the trees healthy and problem free.
Poplar is not terribly fussy about its soil conditions and will tolerate a wide range of textures provided there is good drainage and no pooling of stagnant water in the soil. Light clay, sand, loam and humus soils are all acceptable for poplar. Heavy clay soils or those with poor drainage should be amended with coarse sand, small aggregate, peat and or perlite to improve drainage and oxygenation at the root zone.
Soil Acidity and Alkalinity
Poplar will thrive in both slightly acidic as well as slightly alkaline soil pH. The ideal range to provide is between 6.0 and 8.0 pH. Soils higher than 8.0 and very alkaline should be amended with sulfur or other acidifiers to lower the pH. When soil is lower in pH than 6.0, very acidic soils should be amended with lime or other base amendments to raise the pH. Planting soil should be amended and topdressings of amendments can keep the pH in the proper zone if needed.
Poplars are highly adaptive to varying levels of moisture in the soil. The preference is for easy draining soil that is consistently very moist but does not remain soaking wet for extended periods. Poplar will tolerate wet to flooded soil conditions temporarily without much harm. It will also tolerate dry soil and drought conditions for short intervals but may drop its leaves prematurely to cope with extended periods of drought, particularly in summer when heat exacerbates the lack of soil moisture.
Poplar is a fast growing species and nutrient rich soils help to ensure healthy and strong tissue growth. When grown in nutrient deficient soils, generous amendments of well aged livestock manure and quality compost should be added to the planting soil. For established plantings of poplar, the trees should be top dressed once or twice a year with several inches each of organic materials. The manure and compost will boost the soil quality and provide nutrients for the poplar roots. Slow-release tree fertilizers with a guaranteed analysis of 4-1-4 or 3-1-2 will also help to boost soil fertility gently over time and will not harm the tree.