• Hydrocotyle vulgaris Marsh Pennywort
  
• Hyoscyamus niger Henbane
  
• Hypericum androsaemum Tutsan
  
• Hypericum elodes Marsh St. John's-wort
  
• Hypericum humifusum Trailing St. John's-wort
  
• Hypericum maculatum St. John's-wort, Imperforate
  
• Hypericum perforatum Perforate St. John's-wort
  
• Hypericum pulchrum Slender St. John's-wort
  
• Hypericum tetrapterum Square-stalked St. John's-wort
  
• Hypochaeris radicata Cat's Ear
  
• Ilex aquifolium Holly
  
• Impatiens glandulifera Indian Balsam
  
• Inula helenium Elecampane
  
• Iris foetidissima Stinking Iris
  
• Iris pseudacorus Yellow flag
  
• Jasione montana Sheep's Scabious
  
• Juncus articulatus Jointed Rush
  
• Juncus bufonius Toad Rush
  
• Juncus bulbosus Bulbous Rush
  
• Juncus gerardii Rush, Saltmarsh
  
• Juncus maritimus Sea Rush
  
• Juncus planifolius Broad-leaved Rush
  
• Juncus squarrosus Heath Rush
  
• Juncus subnodulosus Rush, Blunt-flowered
  
• Juncus tenuis Slender Rush
  
• Knautia arvensis Field Scabious
  
• Lactuca tatarica
• Lamium album Dead-nettle, White
  
• Lamium hybridum Cut-leaved Dead-nettle
  
• Lamium purpureum Red Dead-nettle
  
• Lapsana communis Nipplewort
  
• Lathraea squamaria Toothwort
  
• Lathyrus linifolius Vetch, Bitter
  
• Lathyrus pratensis Meadow Vetchling
  
• Lavatera arborea Tree-mallow
  
• Lemna minor Duckweed
  
• Lemna trisulca Duckweed, Ivy-leaved
  
• Leontodon autumnalis Autumn Hawkbit
  
• Leontodon hispidus Rough Hawkbit
  
• Leontodon saxatilis Lesser Hawkbit
  
• Leucanthemum vulgare Dog Daisy
  
• Leycesteria formosa Himalayan Honeysuckle
  
• Ligustrum vulgare Wild Privet
  
• Limonium humile Lax-flowered Sea-lavender
  
• Limonium recurvum Sea Lavender
  
• Limosella aquatica Mudwort
  
• Linum catharticum Fairy Flax
  
• Listera cordata Lesser twayblade
  
• Listera ovata Common twayblade
  
• Lithospermum officinale Common Gromwell