Herb garden needs better drainage to thrive

Some plants seem to do just fine in clay soil, but for others you will need to provide much better drainage. Here's a question from a reader who is faced with that problem.
QUESTION: "My hosta/herb garden is located directly behind my newly constructed home of 3 years on 7 open acres that used to be farm fields. The back of the house and garden face mostly eastward.
"The topography of the land is sloped with the house positioned at the top. When we built the home we added soil (clay) from the neighbor who just started building (as we were finishing), on "plastic" soil at the bottom of the hill which used to be a pond many years ago. I am assuming "plastic" and "clay" soils are the same or close.
"The hostas really don't seem to mind the soil, but I am finding out that as I add lavender and other herbs, they just don't like it. I put a rhododendron in as an accent but it too croaked.
"I thought about removing the soil and starting over, but that would be costly as the area is about 25 foot square, sits on top of the plumbing to the septic tank, and I do have some plants already established that would have to be temporarily removed....is there an amending solution that would be less expensive and stressful for my plants?" - Donna Hrenak
ANSWER: I can certainly relate to this question! We have an area beside our home where we built a garden area using fill from a pond we were digging at the time. So, basically, we used all fill and mostly clay.
For lavender we dug a trench about one foot deep, took out that soil and replaced it with a mixture of concrete sand and small amounts of soil. This allowed good drainage for the lavender. Lavender is a Mediterranean plant that does not need a lot of water. Most herbs will also need to be done the same way. In other parts of the garden I raised the soil level to about 4 foot creating berms. Most of the herbs that do well in our garden are planted there.
I did have drainage tiles put in around the garden about 2 foot into the soil that are exactly like drainage tiles for septic lines that move a lot of the runoff from hard rains to outside the garden area. However, the tile thing may not work for you because you are sitting on the septic line.
I can suggest a product that is organic that I use in compacted soil but needs to be done more then once a year. It's called Prosper Soil Conditioner and it increases friability, resists crusting, allowing water and air to permeate soil However, this would be for general use. For the herbs and lavender and plants like that, I would suggest that you do what we did in the similar situation as described above.
QUESTION: "We have just built a new home and are trying to do the landscaping ourselves. We planted two dappled willows in the front on either side of a set of windows with a boxwood in the middle.
"Can we keep the dappled willows trimmed and shaped to where they will not overpower the boxwood and stay a medium sized shrub, or should we move them to the side of the house where they can get bigger? They look beautiful now but I heard they can get huge. I love the color and if at all possible would like them to be in the front." - Lisa Minnick
ANSWER: You are correct in that it can reach a height of 15 to 20 feet, but if you keep it shaped and trimmed you should be able to manage it for quite a number of years.
The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to snipped-for-privacy@landstewrd.org and for resources and additional information, or to subscribe to Steve's free e-mailed newsletter, visit www.landsteward.org
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