Italian Cypress Oil? - Knowledgebase Question

Costa Mesa, Ca
Question by annabrewingt
February 8, 2006
I heard that Italian Cypresses produce an oil that inhibits the growth of


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Answer from NGA
February 8, 2006

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Although some plants (walnut trees and sunflowers for example) exude chemicals to suppress the growth of plants in the vicinity of their roots, I can find no reference to Italian cypresses having this quality. The major challenge in planting beneath an established evergreen such as Italian cypress is that the soil beneath them are typically dry and the site is shady. The roots of established trees will compete with other plants for moisture and nutrients and the tree usually wins the competition. So, to successfully garden beneath your Italian Cypress, you'll need to use only plants that will adapt to dry shade.

There is an extensive list compiled by the Berkeley Horticultural Nursery which I have included here:

Before planting in dry shade, try to improve your soil's water-holding capacity by adding organic matter such as compost, leaf mold, manure, coconut coir, etc. Don't expect to achieve fantastic lushness; most of the plants will tolerate, not necessarily thrive, in dry shade and will probably flower and fruit more sparingly.

Bulbs:

Amaryllis belladonna
Convallaria majalis
Cyclamen hederifolium
Freesia
Iris japonica
Lapeirousia
Narcissus
Scilla

Ferns:

Dryopteris
Polypodium
Polystichum munitum

Groundcovers:

Aegopodium podograria
Bergenia crassifolia
Cerastium tomentosum
Erigeron karvinskianus
Hedera helix
Hypericum calycinum
Pachysandra terminalis
Rubus calycinoides
Stachys byzantina
Vinca major
Vinca minor
Viola labradorica
Viola odorata

Perennials:

Aeonium
Agapanthus orientalis
Aloe
Alstroemeria ligtu
A. pulchella
A. aurantiaca
Anaphalis
Anemone x hybrida
Arum italicum
Aspidistra elatior
Campanula latifolia
Campanula primulifolia
Ceratostigma plumbaginoides
Chrysanthemum ptarmicifolium
Corydalis lutea
Dierama
Dietes vegeta
Digitalis purpurea
Epimedium
Eucomis
Euphorbia cyparissias
E. robbiae
E. epithymoides
E. perralderianum
E. pinnatum colchicum
E. x warleyense
Festuca ovina glauca
Francoa ramosa
F. sonchifolia
Galium odoratum
Gasteria
Geranium macrorrhizum
G. palmatum
Helichrysum petiolatum
H. 'Limelight'
Helleborus argutifolius
H. foetidus
H. orientalis
Hemerocallis
Heuchera maxima
Iris foetidissima
Kniphofia
Libertia formosa
Limonium perezii
Liriope spicata
Mimulus (Diplacus) hybrids
Modiolastrum lateritum
Origanum dictamnus
Oxalis oregana
Polygonatum commutatum
Polygonum capitatum
Sedum spathulifolium
Sedum spectabile
Sedum spurium
Tiarella
Tolmeia menziesii
Tulbaghia violacea
Vancouveria hexandra
Vancouveria planipetala
Zauschneria californica

Shrubs:

Abutilon megapotamicum
A. hybridum
Amelanchier alnifolia
Arctostaphylos bakeri 'Louis Edmunds'
Arctostaphylos nummularia
Aucuba japonica
Berberis darwinii
Berberis thunbergii
Budddleia davidii
Buxus
Ceanothus griseus var. horizontalis
Ceanothus thyrsiflorus
Cercis occidentalis
Chaenomeles
Correa 'Dusky Bells'
Correa reflexa
Corylus
Cotinus coggygria
Cotoneaster
Daphne odora
Dendromecon harfordii
Elaeagnus
Escallonia
Euonymus fortunei
Forsythia x intermedia
Garrya elliptica
Hibbertia cuneiformis
Hibbertia dentata
Ilex aquifolium
Ilex cornuta
Ilex vomitoria
Iochroma cyaneum
Kerria japonica
Ligustrum japonicum
Ligustrum ovalifolium
Mahonia aquifolium
Mahonia pinnata
Myrica californica
Myrtus communis
Nandina domestica
Olearia insignis
Philadelphus virginalis
Phyllostachys aurea
Protea cynaroides
Prunus ilicifolia
Rhamnus alaternus
Rhaphiolepis indica
Ribes viburnifolium
Ruscus aculeatus
Ruscus hypoglossum
Sarcococca ruscifolia
Symphoricarpus albus laevigatus
Symphoricarpus orbiculatus
Vaccinium ovatum
Xylosma congestum

With all of these choices, I know your garden will be lovely. Enjoy!

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