Should I be concerned with planting fruit trees or vegetables near pine trees?

Asked March 1, 2013, 1:00 PM EST

I live on 5 acres of Ponderosa Pines. Should I be concerned with planting fruit trees or vegetables near pine trees? I heard the pines can make the soil toxic. Is there a 'safe' distance to plant?

El Paso County Colorado

1 Response

Yes, that's a valid concern. Ponderosa and other pines produce and emit allelopahic compounds, biochemicals that act like herbicides to limit the growth of some nearby competing plants. There is some ongoing research that looks into using various plant extracts and allelopaths as "natural" herbicides
The best-known example of allelopathy by a tree is the juglone produced by black walnuts, which inhibits growth and interferes with some but not all plants growing nearby, providing the walnut with a competetive advantage..

Assuming that some of these allelopathic compounds are emitted by ponderosa pine roots into the surrounding soil, it would be best to exercise caution in planting fruit trees or vegs within the rootzone of a ponderosa pine. Rootzones extend well beyond the area under branch extremities..

Most allelopathic compounds do not last long in soils, so large areas where ponderosas have been removed could be considered. Suggest you choose an area (perhaps close to your house?).well away from any ponderosa pines for your veg garden.
And keep in mind that only some plants are likely to be affected. Unlike the case for black walnut, there aren't research-based, well-defined lists of plants known to be intolerant and tolerant of allelopathic compounds produced by ponderosa pine.
Through trial and error, you may find, for example, that radishes grow well near a ponderosa but sweet corn won't. Also keep in mind that there are many other possible reasons why a particular plant fares poorly near a ponderosa pine.
Good Luck ,