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JACOBSON CONIFER GARDEN

What is a conifer?

Conifers are a group of woody plants that produce cones with scales that contain their seeds. Many of these plants produce needles instead of leaves and many are also evergreen. Contrary to popular belief, some conifers do in fact lose their leaves or needles in the winter. Some conifers even produce cones that resemble fleshy fruit! Most conifers are wind pollinated, so the pollen floats on the wind and hopefully finds a receptive female cone. Seeds are usually hard with a strong seed coat and are often called a “nut” despite not being closely related to true nuts. Some common conifers include pines, spruces, firs, ginkgo, junipers, cedars, larches, and redwoods.

With its proximity to the Hughes Education Building and year round interest, this is one of the most visited areas at the Iowa Arboretum and Gardens. The collection was established in 1982 as the Dwarf Conifer Collection but many of the specimens fall instead into the intermediate or even large conifer category. Many cultivars were so new to commerce that their ultimate sizes were unknown when planted.  The collection became more prominent when the Jones Memorial Gazebo was added in 1991. In 2005, the collection was renamed for Craig Jacobson of Marshalltown, a Board Member with a specialty conifer nursery. Craig and his wife Deb donated many specimens over several years.

This garden has evolved quite a bit since it was first planted 40 years ago. The now mature conifers make a perfect structural back drop and specimens for further garden design. A naturalistic style perennial border is being added a few species at a time throughout the garden. Many charismatic native prairie and woodland species are a part of the palette, and stunning cultivars to compliment existing plants are being added. This garden will grow and change over time, providing beautiful vignettes. 

American Conifer Society Reference Garden

The combination of the extensive collection of dwarf conifers planted in the Alpine Garden and Jacobson Conifer Garden led to the Iowa Arboretum & Gardens receiving the distinction of an American Conifer Society Reference Garden. This program allows us to continue our mission of educating the public about plants while helping provide funding for projects related to conifers.

Conifer Conservation

Spurred by a seed exchange with Steven Roesch of New Berlin, WI in 2022, the Iowa Arboretum & Gardens started a special conservation project working specifically with the genus Hesperocyparis. Now in partnership with the California Botanic Garden Seed Conservation Program, the arboretum is working to evaluate the hardiness of several species in the genus in the hopes to conserve them through horticulture.

Listed with International Union for Conservation of Nature (IUCN) as endangered or vulnerable, members of the genus Hesperocyparis need some help. Their reproductive cycle is completely dependent on low-intensity fire to open ripe cones and disperse seed. With decades of fire suppression in their native ecosystems, they have lost the ability to reproduce and subsequent fires are too intense, killing trees and burning seed. These species also have an extremely low germination rate and have little success in long-term seed storage.

So far, the arboretum has successfully grown from seed and overwintered four species: Hesperocyparis arizonica (Arizona cypress), H. bakeri (Modoc cypress), H. glabra (smooth Arizona cypress), and H. nevadensis (Paiute cypress). Our hope is that they prove to be totally hardy and eventually grow large enough to set seed, preserving their genetics for further conservation efforts. 

If any particular plant proves to be a handsome specimen, propagation and distribution will keep the genetics alive in gardens for many years into the future! Native to high elevations from Arizona, California, and Oregon, these plants regularly experience temperatures below freezing and snowfall. While we are most optimistic about the species from the northern Sierra Nevada mountains, species from further south have surprised us with their hardiness. Foliage color can range from fresh green, to pewter silver, to even a cool blue, providing ample potential in the landscape. Many varieties of H. glabra (smooth Arizona cypress) and H. arizonica (Arizona cypress) are readily available on the market, others are on the way. Native historical distribution maps below are provided by the Biota of North America Program (BONAP).

The arboretum’s Hesperocyparis trees can be found in the Jacobson Conifer Garden, Perennial Garden, and Shrub Border.

Click the image below for a gallery of photographs from the garden:

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Plant Lists:

Firs:
Abies koreana ‘Horstmann’s Silberlocke’ – Horstmann’s silberlocke Korean fir
Abies koreana ‘Silver Show’ – Silver show Korean fir
Abies nordmanniana subsp. equi-trojani – Turkish fir
Abies nordmanniana subsp. equi-trojani – Turkish fir

False cypress/Sawara cypress:
Chamaecyparis pisifera ‘Filifera’ – Threadbranch false-cypress
Chamaecyparis pisifera ‘Filifera’ – Threadbranch false-cypress
Chamaecyparis pisifera ‘Squarrosa Minima’ – Dwarf Sawara cypress
Chamaecyparis pisifera filifera ‘Golden Charm’ – Golden charm thread-branched false cypress
Chamaecyparis pisifera filifera ‘Sungold’ – Sungold thread-branched false cypress

Ginkgo:
Ginkgo biloba ‘Jade Butterflies’ – Jade butterflies ginkgo
Ginkgo biloba ‘Spring Grove’ – Spring Grove ginkgo
Ginkgo biloba – Ginkgo

New World cypress:
Hesperocyparis glabra – Smooth Arizona cypress
Hesperocyparis nevadensis – Paiute cypress

Junipers:
Juniperus chinensis ‘Torulosa Variegata’– Variegated Hollywood juniper
Juniperus rigida ‘Pendula’– Weeping temple juniper
Juniperus scopulorum ‘Blue Arrow’ – Blue arrow juniper
Juniperus scopulorum ‘Moonglow’ – Moonglow juniper
Juniperus scopulorum ‘Skyrocket’ – Skyrocket juniper

Larches:
Larix decidua ‘Pendula’ – Weeping European larch
Larix kaempferi ‘Blue Rabbit’ – Blue Rabbit Japanese larch
Larix x ‘Varied Directions’ – Varied directions larch

Spruces:
Picea abies ‘Acrocona’ – Red cone Norway spruce
Picea abies ‘Little Gem’ – Little Gem Norway spruce
Picea abies ‘Maxwellii’ – Maxwell Norway spruce
Picea abies ‘Nidiformis’ – Bird’s nest spruce
Picea abies ‘Pendula’ – Weeping Norway spruce
Picea abies ‘Tabuliformis’ – Table-top Norway spruce
Picea abies ‘Wingle’s Pendula’ – Wingle’s weeping Norway spruce
Picea abies – Norway spruce
Picea abies – Golden Norway spruce
Picea glauca ‘Pendula’ – Weeping white spruce
Picea glauca – White spruce
Picea koyamae – Koyama spruce
Picea obovata ‘Arctos’ – Arctos Siberian spruce
Picea orientalis ‘Atrovirens’ – Atrovirens Oriental spruce
Picea pungens ‘Compacta’ – Dwarf blue spruce
Picea pungens ‘Globosa’ – Globe Blue Spruce
Picea pungens ‘Sester Dwarf’ Sester’s dwarf blue spruce
Picea sp. – Spruce
Picea pungens ‘Golden Ghost’ – Golden ghost blue spruce
Picea pungens ‘Montgomery’ – Montgomery blue spruce
Picea purpurea – Purple cone spruce
Picea wilsonii – Wilson spruce

Pines:
Pinus echinata – Shortleaf pine
Pinus heldreichii var. leucodermis – Bosnian pine
Pinus koraiensis ‘Silveray’ – Silveray Korean pine
Pinus koraiensis ‘Variegata’ – Variegated Korean pine
Pinus koraiensis – Korean pine
Pinus parviflora ‘Fukai’ – Fukai Japanese white pine
Pinus peuce – Macedonian pine
Pinus rigida x taeda – Pitlolly pine
Pinus strobus ‘Bennett’s Fastigiate’ – Bennett’s fastigiate white pine
Pinus strobus ‘Lovable Fuzz Ball’ – Lovable fuzz ball white pine
Pinus strobus ‘Pendula’ – Weeping white pine
Pinus strobus ‘Torulosa’ – Twisted needle white pine
Pinus sylvestris ‘Gold Coin’ – Gold coin Scots pine
Pinus sylvestris ‘Hillside Creeper’ – Hillside creeper Scots pine
Pinus virginiana ‘Wate’s Golden’ – Wate’s golden Virginia pine

 

Bald cypress:
Taxodium distichum ‘Peve Minaret’ – Peve minaret bald cypress
Taxodium distichum – Bald cypress

Yew:
Taxus x media ‘Maureen’ – Maureen yew

Arborvitae:
Thuja occidentalis ‘Bobozam’ – Mr. bowling ball arborvitae
Thuja occidentalis ‘ex Brandon’ – ex. Brandon arborvitae

Hemlocks:
Tsuga canadensis ‘Horsford Contorted’ – Horsford contorted Canadian hemlock
Tsuga canadensis ‘Pendula’ – Weeping Canadian hemlock

Other woodies:
Acer miyabei – Miyabe maple
Acer x pseudosieboldianum ‘North Wind’ – North Wind Korean maple
Aesculus glabra – Ohio buckeye
Fagus sylvatica ‘Rohan Weeping’ – Rohan Weeping purpleleaf beech
Hamamelis sp. – Witchhazel
Juglans x quadrangulata ‘White’s Hybrid’ – White’s hybrid walnut
Magnolia x ‘Little Bird’ – Little Bird magnolia
Nyssa sylvatica ‘Carolyn’ – Carolyn bluck tupelo
Nyssa sylvatica ‘Penwood Weeper’ – Penwood Weeper bluck tupelo
Phellodendron amurense – Amur cork tree
Zelkova serrata ‘Village Green’ – Village Green Japanese zelkova

Herbacious plants:
Amsonia x ‘Seventh Inning Stretch’ – Seventh Inning Stretch bluestar
Asclepias tuberosa – Butterfly milkweed
Brickellia eupatorioides – Fakse boneset
Euphorbia polychroma ‘Bonfire’ – Bonfire spurge
Geranium x ‘Rozanne’ – Rozanne geranium
Hemerocallis x ‘Blue Arb’ – Blue Arb daylily
Lespedeza bicolor ‘Yakushima’ – Yakushima bush clover
Monarda luteola ‘AMES 34204’ – Yellow bee balm

Narcissus x ‘Minnow’ – Minnow Daffodil
Panicum virgatum – Switchgrass
Penstemon digitalis ‘IAArbo Strain’ – IAArbo strain foxglove penstemon
Rudbeckia hirta – Black-eyed Susan
Schizachyrium scoparium ‘Aldous’ – Aldous little bluestem
Schizachyrium scoparium ‘Blaze’ – Blaze little bluestem
Schizachyrium scoparium ‘Prairie Blues’ – Prairie Blues little bluestem
Schizachyrium scoparium ‘Puccoon Prairie’ – Puccoon Prairie little bluestem

Symphyotrichum oblongifolium ‘Lalla’ – Lalla aromatic aster