Juglone in black and white walnut trees can cause some gardening problems. Don’t despair if walnut trees are killing your other plants, especially Juglan nigra varieties. Here are some ways to help your plants survive the terrors of juglone. Juglone is a toxic chemical found in the roots of walnut trees which affects the growth of other organisms and plants nearby. If you want to avoid the juglone problem altogether, choose from the list of tree and shrubs that are resistant to juglone.
Steps to help with juglone
1. Try to clean up any debris immediately as these trees may shed a massive leaf or two intermittently throughout the growing season. Don’t wait until fall foliage drops to pick them up. Any contact that the parts of the tree make with the soil, will affect the plants growing nearby. You should also gather the nuts as soon as they fall as the toxins in the husks increase as the nuts ripen.
2. Try to make sure that your soil contains a lot of organic matter to improve its health, aeration, and drainage. Micro-organisms in compost may also consume some of the leached juglone for energy and somewhat neutralizes the substance. You can also regularly add a top layer of compost to increase your soil’s organic matter, Make sure that you do not use walnut debris in any form as a mulch until it has thoroughly decomposed in a hot compost pile.
3. Avoid plants like apple trees, mountain laurels, rhododendrons, blueberries, and white birches that can die from the effects of juglone. Instead, you should learn which plants are resistant to juglone.
Trees and shrubs resistant to Juglone:
American arborvitae, Thuja occidentalis
American holly, Ilex opaca
Carolina silverberry, Halesia carolina
Dogwood, Cornus species
Eastern redbud, Cercis species
Golden raintree, Koelreuteria paniculata
Hawthorn, Crataegus species
Japanese maple, Acer palmatum
River birch,Betula nigra
Serviceberry, Amelanchier x grandiflora
Blackhaw viburnum, viburnum prunifolium
Daphne, Daphne species
Forsythia, Forsythia species
Juniper, Juniperus species
Lilac, Syringa species
Ninebark, Physocarpus opulifolius
Rose of sharon, Hibiscus syriacus
Spicebush, Lindera benzoin
Wild hydrangea, Hydrangea arborescens
Witch hazel, Hamamelis species