Gardening Planting

No Need to Dig a Deep Planting Hole

Planting showing root ball placed directly on soil at bottom of hole.

By Larry Hodgson

Only dig a planting hole as deep as the root ball is high.

When I started gardening over 50 years ago (I started very young!), the recommendation for planting was to dig a hole deeper than the root ball so you could add a nice, thick layer of good soil to the bottom of the hole … and that bit of misinformation is still being repeated to this day. In fact, however, studies on plant growth show that plants do better when their root ball is set on a solid base, not on fresh or loosened soil. So, the best advice for planting is to dig a hole wider than the root ball (you need that to give you room for planting), but no deeper than it is high.

The problem with amending the soil under the plant is that loosened soil tends to compact downwards over time, with the result that root ball drops deeper (or starts to slant if the ground settles unevenly). If you make a hole only as deep as the root ball is high, though, the plant will not move, but will stay put … and you really don’t want a plant to move when it’s supposed be settling in and producing new roots.

If you’re concerned that the soil at the bottom of the planting hole might be very heavy and drain poorly, rather than breaking it up, simply punch a few holes in it with a garden fork to allow any excess water to drain through.

But what about adding good soil to the planting hole? There is no need to put it under the plant: fill in around it if you feel it needs better soil. Better yet, mulch all around the plant, out to 3 times the width of the original root ball, with a rich organic mulch like chopped leaves. As the mulch decomposes, it will supply all the nutrients the plant needs.

Adapted from an article that first appeared in this blog on May 21, 2016.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

6 comments on “No Need to Dig a Deep Planting Hole

  1. In some cases, like azalea & blueberry plants, shadow rooted plants can have a root ball a few inches above ground level, if mulched heavy, even cold winters will not harm it.
    A plant that is to deep will slowly die over a few years at most.

  2. As always you did a great job, I just had to say something.

  3. OH MY! This should be SO obvious! Yet, no one believes me! When I was still working for one of those ‘reputable’ ‘landscape’ companies (with all those pretty brochures full of buzz words), we provided our clients with diagrams of how new plant material would be planted, clearly showing that the planting holes were to be significantly deeper than the root balls. It was embarrassing. Fortunately, no one actually did that. Heck we sometimes (often) cut the tops of root barriers to partially bury on the edges of pavement near new trees so that we could charge for the installation of full depth root barriers. It was too much work to dig the trench.

  4. Margaret

    Once again, you have destroyed on of my long-held gardening truisms. Thank you! 🙏

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