Three years ago I cleared an area that had been infested with buckthorn for decades. I have replanted with native shrubs and native forbs. I have managed this planting well, planted appropriate vegetation, yet, the vegetation has barely grown. The forbs are as I planted them three years ago. I think the soil, which is loam, suffers from the allelopathic tendencies of buckthorn. I have done searches for this answer but do not find a good one: how long does it take, on average, for the soil to recover after having been infested with buckthorn vegetation?
Dakota County Minnesota
I cannot find any reference which states Buckthorn has allelopathic tendencies. It is aggressive due to the prolific seeds it produces and birds eating the berries with their diuretic properties. It could be that the soil is compacted, there isn't enough sun or moisture or other reasons for the lack of growth. You may have to till the soil, add compost and then replant your vegetation next spring.
http://www.botany.wisc.edu/waller/PDFs/KlionskyAmatWaller_2010_RestorEcol.pdf There is much emerging research that points to all kinds of soil issues in areas long infested with buckthorn. Soil composition/pH is changed in many ways that makes it difficult for native plantings to establish and thrive. Allelopathic chemicals such as emodin are implicated as one reason for this failure. The soil in this area is not compacted, has good soil texture, and vegetation replanted suits part sun conditions. I was hoping you would have access to information regarding longevity of allelopathic residue in soils. Regardless, compromised soil quality after longstanding buckthorn infestation is important in understanding revegetation efforts. See conclusions above for a good summary of this complex issue.
You apparently have different information than I have at my sites. I cannot give you the answer you requested.