H
- Hackelia deflexa var. americana (N)
- Hackelia virginiana (N)
- Halesia tetraptera var. tetraptera (N)
- Hamamelis virginiana (N)
- Hasteola suaveolens (N)
- Hedeoma hispida (N)
- Hedeoma pulegioides (N)
- Hedera helix (I)
- Helenium amarum var. amarum (N)
- Helenium autumnale var. autumnale (N)
- Helenium flexuosum (N)
- Helianthemum bicknellii (N)
- Helianthemum canadense (N)
- Helianthus × ambiguus (N)
- Helianthus angustifolius (N)
- Helianthus annuus (N)
- Helianthus × brevifolius (N)
- Helianthus × cinereus (N)
- Helianthus decapetalus (N)
- Helianthus divaricatus (N)
- Helianthus × divariserratus (N)
- Helianthus × doronicoides (N)
- Helianthus giganteus (N)
- Helianthus × glaucus (N)
- Helianthus grosseserratus (N)
- Helianthus hirsutus (N)
- Helianthus × intermedius (N)
- Helianthus × kellermanii (N)
- Helianthus × laetiflorus (N)
- Helianthus × luxurians (N)
- Helianthus maximiliani (N)
- Helianthus microcephalus (N)
- Helianthus mollis (N)
- Helianthus × multiflorus (N)
- Helianthus occidentalis ssp. occidentalis (N)
- Helianthus petiolaris ssp. petiolaris (N)
- Helianthus salicifolius (N)
- Helianthus strumosus (N)
- Helianthus tuberosus (N)
- Heliopsis helianthoides var. helianthoides (N)
- Heliopsis helianthoides var. occidentalis (N)
- Heliotropium europaeum (I)
- Heliotropium indicum (I)
- Helleborus viridis (I)
- Hemerocallis fulva (I)
- Hemerocallis lilioasphodelus (I)
- Hepatica nobilis var. acuta (N)
- Hepatica nobilis var. obtusa (N)
- Heracleum maximum (N)
- Hesperis matronalis (I)
- Hesperostipa spartea (N)
- Heteranthera dubia (N)
- Heteranthera reniformis (N)
- Heterotheca camporum var. camporum (N)
- Heuchera americana var. americana (N)
- Heuchera americana var. hirsuticaulis (N)
- Heuchera americana var. hispida (N)
- Heuchera longiflora (N)
- Heuchera parviflora var. parviflora (N)
- Heuchera villosa var. villosa (N)
- Hexalectris spicata var. spicata (N)
- Hibiscus laevis (N)
- Hibiscus moscheutos (N)
- Hibiscus syriacus (I)
- Hibiscus trionum (I)
- Hieracium aurantiacum (I)
- Hieracium caespitosum (I)
- Hieracium × flagellare var. flagellare (I)
- Hieracium × floribundum (I)
- Hieracium greenii (N)
- Hieracium gronovii (N)
- Hieracium kalmii var. fasciculatum (N)
- Hieracium kalmii var. kalmii (N)
- Hieracium longipilum (N)
- Hieracium paniculatum (N)
- Hieracium pilosella var. pilosella (I)
- Hieracium piloselloides (I)
- Hieracium scabrum var. scabrum (N)
- Hieracium venosum (N)
- Hierochloe hirta ssp. arctica (N)
- Holcus lanatus (I)
- Holosteum umbellatum (I)
- Hordeum brachyantherum ssp. brachyantherum (N)
- Hordeum jubatum ssp. jubatum (N)
- Hordeum marinum ssp. gussonianum (I)
- Hordeum pusillum (N)
- Hordeum vulgare (I)
- Hosta lancifolia (I)
- Hosta ventricosa (I)
- Hottonia inflata (N)
- Houstonia caerulea (N)
- Houstonia canadensis (N)
- Houstonia longifolia (N)
- Houstonia purpurea var. calycosa (N)
- Houstonia purpurea var. purpurea (N)
- Hudsonia tomentosa var. tomentosa (N)
- Humulus japonicus (I)
- Humulus lupulus var. lupuloides (N)
- Humulus lupulus var. pubescens (N)
- Humulus lupulus var. lupulus (I)
- Huperzia × bartleyi (N)
- Huperzia × buttersii (N)
- Huperzia lucidula (N)
- Huperzia porophila (N)
- Hyacinthoides non-scripta (I)
- Hybanthus concolor (N)
- Hydrangea arborescens (N)
- Hydrastis canadensis (N)
- Hydrocotyle americana (N)
- Hydrocotyle ranunculoides (N)
- Hydrocotyle sibthorpioides (I)
- Hydrocotyle umbellata (N)
- Hydrophyllum appendiculatum (N)
- Hydrophyllum canadense (N)
- Hydrophyllum macrophyllum (N)
- Hydrophyllum virginianum var. virginianum (N)
- Hylotelephium telephioides (N)
- Hylotelephium telephium ssp. telephium (I)
- Hypericum ascyron (N)
- Hypericum boreale (N)
- Hypericum canadense (N)
- Hypericum drummondii (N)
- Hypericum ellipticum (N)
- Hypericum gentianoides (N)
- Hypericum gymnanthum (N)
- Hypericum hypericoides ssp. multicaule (N)
- Hypericum kalmianum (N)
- Hypericum majus (N)
- Hypericum mutilum (N)
- Hypericum perforatum (I)
- Hypericum prolificum (N)
- Hypericum punctatum (N)
- Hypericum sphaerocarpum (N)
- Hypericum virgatum (N)
- Hypochaeris glabra (I)
- Hypochaeris radicata (I)
- Hypoxis hirsuta (N)
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