Fruit Tree Site Selection (cont)
By: National Gardening Association Editors
Have your soil tested, preferably the season before you intend to plant your trees. If necessary, add lime or sulphur to correct the pH to a range of 5.5 to 7.0, suitable for most trees. Add phosphate or potash fertilizers if phosphorus or potassium levels are low. All fruit plants will be healthier if the soil contains high levels of organic matter, so turning under a green manure crop or two before planting helps a great deal.
Plant nematode-susceptible stone fruits (peaches, plums, cherries, and apricots) where a grass cover crop or lawn grew for the previous 2 years. Two years without broad-leaved plants almost completely eliminates the most troublesome nematodes, root knot, and lesion, as well as verticillium wilt. Nematode- or verticillium-infected fruit trees are stunted and unproductive, and once infected, there is no cure. Many vegetables and small fruits are susceptible to verticillium wilt. Try not to plant fruit trees where susceptible plants have grown in the last 2 years. If you must plant stone fruits where vegetables grew recently, choose an area where corn has grown.
Have the soil tested for nematodes before planting. If high levels of root knot or lesion nematodes are found, plant the ground with a trap crop of marigolds, which will attract nematodes to their roots, the season before planting the fruit trees. Don't bother planting marigolds around the trees once they're set out to get rid of nematodes; you need to get nematode levels down before tree-planting time. Choose a marigold variety proven to be a good trap crop, such as 'Tangerine' or 'Nemagold' blend. Plant them 6 to 7 inches apart so they form a solid stand, and keep them weeded. In early fall, pull up the marigolds--roots included--and destroy them. Then plant a winter rye cover crop for additional protection against nematodes, and till it in early the next spring before planting trees.
Planting Trees in Lawns
Planting fruit trees in a lawn is fine; just remove the sod in a circle 3 or 4 feet out from each fruit tree, and mix some compost or other organic matter into the whole area. If the lawn contained many broad-leaved weeds, test the soil for nematodes and follow the instructions above for planting marigolds. Eliminate any noxious perennial weeds such as quack grass. Remove competitive grasses such as Bermuda or zoysia from the entire area that the fruit trees will ultimately occupy, and replace them with less competitive groundcovers. Do not replace an old fruit tree with the same or a closely related type of fruit. Not only have nematodes and other soil-borne diseases built up, but the roots of certain fruit trees, such as peaches, exude a toxin that inhibits the growth of new peach roots. Don't place new stone fruit trees right next to older ones, to prevent the spread of non-curable diseases such as X-disease or cherry yellows.