I’ve recently cleared some sloped land and have tilled in minerals to the soil as prescribed by a soil test. The orchard will be irrigated. The soil is clay loam. I’m in the Pacific Northwest (8b) and in between mountain ranges where it can be wet / rainy.
As a complete orchard neophyte, I’ve learned mostly from this forum and am highly grateful for all of your knowledge sharing. One of the things commonly mentioned is that planting bare root trees on top of mounds can be very helpful - especially where wet and poor drainage conditions exist.
I’ll most likely need to bring in non-native soil to help create the mounds. This non-native soil would be a blend of Mushroom Compost, Composted Bark and Sand - but fill dirt is also a possibility and much cheaper.
My question is which type soil should best be used above and below the trees
A) Create mounds using native soil, and then cover tree roots with non-native soil
B) Create mounds using non-native soil, and then cover with native soil
C) Till both native and non-native together and use above and below tree roots.
I’m thinking option B would be the easiest, but perhaps C would be best. As all options require a substantial effort I’d like to do this in a way most beneficial.
I would appreciate your comments and learning from your experience.
Rick, what types of trees do you intend to plant? Seems like stone fruits are very sensitive to having their feet wet and pome fruits are more tolerant. You might not have to do a ton of work for apples, but might need more for peaches. Usually, if your native soil is ok, you are best to go with it. If you can’t do that, then option C is probably best so there is not a sharp transition from one soil type to another which might encourage your trees to avoid pushing roots out into the native soil.
I’m on a hill with 9 to 12 inches of hard pan and clay over fractured basalt. Not much choice but to build mounds with purchased dirt. All I have is stone fruit, so good drainage is important to me. Mounds have worked out well.
my rocky clay soil has killed most trees I’ve put in it directly. i used cheap unfertilized bag soil for all my tress and they have done well. i always keep 3-4in. of mulch around them so i find planting in 4’ x4’ raised boxes made of cedar helps keep the chips in place and actually looks pretty good. also doesn’t require as much soil. i just put a square of cardboard right on the sod, position the box, place a stake thru the cardboard into the native soil, then plant your tree. the stake holds it in place until the roots can anchor into the native soil.
I think the cherry, asian plum, and pluots will be a little more sensitive to wet feet than the rest of your list. As you mentioned, having a slope is really helpful. It would be interesting to get someone else’s thoughts on euro plums. I belive they are more tolerant.
With the slope it sounds like you should not have any drainage problems. If you are putting some trees not on the slope or at its bottom they may need some help. So, unless your soil is known bad for some reason I would just plant them directly.
A slope only takes you so far, over the years I’ve work many excessively wet sites that have sloping terrain. For instance, when a finer top-soil is layered over coarse sand. Mounds can help partially by changing the textural order.
A slope may also be inadequate for creating drainage in very clay soils, particularly for peach roots. I believe the mounding may simply increase the “slope”, but certainly if you make the mound with a coarser mix it is a lot easier than changing the total soil. It doesn’t take all that much well-drained soil to support a good-sized fruit tree. Without the mound the water would pool up in a small amount of improved soil.