Eucalyptus Trees and Vegetable Gardening

sitenum=205

Seasonal observations of the UCCE Master Gardeners

Author: Bill R. Reed

Published on: August 9, 2018

Over the last several years, my wife and I have been setting up a raised bed garden on the west side of our home. There are about 10 Eucalyptus trees on the west edge of the garden that provides some shade from the very hot late afternoon sun. These trees are about 35 years old and well established. However, they have invaded all the raised beds with a dense root mat that is essentially stopping the production of vegetables.

To document this I purchased tomatoes plants (Ace variety, from a 4 pack), and utilized three of the plants to run a trial to see if I could determine how significantly the eucalyptus roots affected the tomato plants' growth.

First, I planted one tomato plant directly into the root-infested raised bed. The second tomato plant was planted in a 5-gallon container which I filled using the raised bed root materials, cut up into chunks, and planted the tomato directly into this mixture. This planting was to test to see if the dead Eucalyptus roots had any phytotoxic effects on the tomatoes. The third tomato was essentially my control, with the tomato planted in a 5-gallon container in the new potting mix. All were fertilized bi-weekly with low nitrogen organic fertilizer and watered every other day.

The experiment was run for about 5 weeks. I found that the tomato planted directly into the root-infested raised bed grew very little, and seemed to struggle to get enough water, so I gave it extra water. The tomato planted in the chopped Eucalyptus roots with the raised bed potting mix actually did quite well and has the best set of tomatoes. There does not seem to be any phytotoxic effects from the dead Eucalyptus roots. The tomato in the new potting mix is growing fine and has set some tomatoes but fewer than the tomato plant in the dead roots. My belief is that this might be due to more nitrogen in the fresh potting mix.

Other garden vegetables such as vine crops, beans, and some other plants do not tolerate the root competition. We have found that carrots do okay, asparagus does moderately well, and potatoes are marginal. However, all these crops grow during the spring months when there is more free water in the soil.

The Australian Department of Agriculture and Water Resources recommends that farmers stay 50 feet away from Eucalyptus, we are within 30 feet. We have shifted to above ground containers after excavating several raised beds and lining them with double landscape fabric to no avail.

Four photos are attached separately, as well:

Photo 1: Initial photo of the three tomato plants

Tomato-start-May1-600

Photo 2: Tomato plant growing in the raised bed with matted roots

tomato-in-raised-bed-375

Photo 3: Tomato plant in the pot filled with chunked up soil and matted roots

tomato-in-cut-roots-and-pot

Photo 4: Tomato plant in pot with the fresh potting mix

Tomato-in-fresh-potting-mix

Comments: 2

Comments:

by Glanz

on April 30, 2019 at 9:04 AM

We have SAME problem. We were thinking about lining the beds and placing gravel ontop of the lining, do you think that would work? If not can we put bottoms on the beds but put them back on the ground with bottoms or do they need to be raised an inch off ground too? We don't want to go through this work ever again, we threw out all the rooted soil and are going to buy all new soil so if this happens again, we will have wasted a lot of time/money. Please advise the way that will work.

by Rhonda Keelin

on February 28, 2024 at 8:53 AM

I was able to grow cauliflower in my flower bed but they were small heads,very tasty. I did loosen up the soil and added some fresh mixed up dirt. Plus Gazania grows really well among the roots and cosmos among other flowers directly under the Eucalyptus trees.