Seeds to Sow in Mid-May

The Sower, Kew Gardens, London

The growing season is picking up speed! Nights are generally still cool, although warming up… and frost is far from impossible in much of North America! The soil too is warming up, more so in drier parts of the garden than in moister areas, meaning conditions are great for sowing many seeds outdoors.

Before we get to that, though, there is still one annual I like to sow indoors in mid-May: the nasturtium (Tropaeolum majus). Yes, you can sow it outdoors (I like to wait until the soil is well warmed up, usually at the end of May), but if you give it a head-start indoors – just 2 or 3 weeks of extra warmth! – it will give much better results, yet won’t have time to get leggy (as happens so easily when you start it indoors too early).

When it comes to sowing outdoors, this is the time to sow seeds that actually prefer things “just a bit chilly” and that includes the vast majority of perennials (at least, those that don’t need a cold treatment: the others should be sown in the fall). Of course, there are also annuals, herbs and vegetables that don’t mind cool nights. Here are some suggestions:

  1. Agastache (Agastache foeniculum and others)
  2. Ageratum (Ageratum houstonianum)
  3. Annual Chrysanthemum (Glebionis carinatum, formerly Chrysanthemum carinatum)
  4. Annual Phlox (Phlox drummondii)
  5. Aster (Aster including Symphtrichon, Eurybia and others)
  6. Astilbe (Astilbe )
  7. Avens (Geum )
  8. Baby Blue Eyes (Nemophila )
  9. Baby’s Breath (Gypsophila paniculata, repens, G. muralis, etc.)
  10. Bachelor’s Button (Centaurea cyanus , montana, C. macrocephala and others)
  11. Balloon Flower (Platycodon grandiflorum)
  12. Baptisia (Baptisia )
  13. Beebalm (Monarda )
  14. Bellflower (Campanula )
  15. Bergenia (Bergenia )
  16. Blazing Star (Liatris )
  17. Blue Fescue (Festuca ovina glauca and others)
  18. Blue Poppy (Meconopsis)
  19. Bluestar (Amsonia )
  20. Broccoli (Brassica oleracea italica)
  21. Burning Bush (Bassia scoparia, syn. Kochia scoparia)
  22. Butterfly Weed (Asclepias )
  23. California Poppy (Eschscholzia californica)
  24. Camomille romaine (Chamaemelum nobile, syn. Anthemis nobile)
  25. Campion (Lychnis x haageana)
  26. Candytuft (Iberis )
  27. Carolina Lupin (Thermopsis )
  28. Chamomile (Matricaria recutita, syn. Matricaria chamomilla)
  29. China Aster (Callistephus chinensis)
  30. Chinese Forget-Me-Not (Cynoglossum amabile)
  31. Chinese Lantern (Physalis alkekengi)
  32. Chinese Pink (Dianthus chinensis)
  33. Chives (Allium schoenoprasum)
  34. Cinquefoil (Potentilla )
  35. Clarkia (Clarkia unguiculata, syn. elegans)
  36. Clematis (Clematis )
  37. Cleome or Spiderflower (Cleome )
  38. Columbine (Aquilegia )
  39. Common Sage (Salvia officinalis)
  40. Coreopsis (Coreopsis )
  41. Corn-Cockle (Agrostemma githago)
  42. Cosmos (Cosmos bipinnatus and sulphureus)
  43. Creeping Zinnia (Sanivitalia procumbens)
  44. Culver’s Root (Veronicastum virginicum, formerly Veronica virginica)
  45. Dahlberg Daisy (Thymophylla tenuiloba, syn. Dyssodia tenuiloba)
  46. Dahlia (Dahlia x)
  47. Daisy (Leucanthemum x superbum, syn. Chrysanthemum maximum)
  48. Daylily (Hemerocallis
  49. Delphinium (Delphinim x elatum, syn. x cultorum)
  50. Echinacea (Echinacea )
  51. Edelweiss (Leontopodium alpinum)
  52. Elecampane (Inula )
  53. Euphorbia (Euphorbia myrsinites, polychroma, etc.)
  54. Evening Primrose (Oenothera )
  55. Evening-scented Stock (Matthiola incana)
  56. False Sunflower (Heliopsis helianthoides)
  57. Fennel (Foeniculum vulgare)
  58. Feverfew (Tanacetum parthenium, syn. Matricaria parthenium, Chrysanthemum parthenium)
  59. Fleabane (Erigeron speciosus and others)
  60. Four O’clock (Mirabilis jalapa)
  61. Gaillardia (Gaillardia x grandiflora and others)
  62. Garden Mum (Chrysanthemum x morifolium, formerly Dendranthema x grandiflorum)
  63. Globe-Thistle (Echinops )
  64. Goat’s Beard (Aruncus )
  65. Godetia(Clarkia amoena, formerly Godetia amoena)
  66. Gold Basket (Aurinia saxatilis, syn. Alyssum saxatile)
  67. Golden Marguerite (Anthemis tinctoria)
  68. Heuchera (Heuchera )
  69. Hosta (Hosta )
  70. Houseleek or Hen and Chicks (Sempervivum )
  71. Hyssop (Hyssopus officinalis)
  72. Iris (Iris)
  73. Italian Bugloss (Anchusa azurea and others)
  74. Jacob’s Ladder (Polemonium caeruleum, reptans, etc.)
  75. Knautia (Knautia macedonica, arvensis, etc.)
  76. Knotweed (Persicaria , syn. Polygonum spp.)
  77. Lamb’s Ears (Stachys byzantina, syn. lanata)
  78. Lemon Balm (Melissa officinalis)
  79. Leopard’s Bane (Doronicum )
  80. Lettuce (Lactuca sativus)
  81. Lewisia (Lewisia cotyledon and others)
  82. Lily (Lilium )
  83. Lobelia (Lobelia cardinalis, siphilitica and others)
  84. Love-in-a-Mist (Nigella damascena and others)
  85. Lungwort (Pulmonaria )
  86. Lyre-Leaf Sage (Salvia lyrata)
  87. Maltese Cross (Lychnis chalcedonica, L. x arkwrightii)
  88. Masterwort (Astrance major and others)
  89. Mauve (Malva )
  90. Mexican Hat (Rabitida )
  91. Mexican Poppy (Argemone )
  92. Mignonette (Reseda odorata)
  93. Monkshood (Aconitum )
  94. Nepeta, Catmint or Catnip (Nepeta x faassenii and others)
  95. Nicandra (Nicandra physaloides)
  96. Nicotiana or Flowering Tabacco (Nicotiana alata, sylvestris and others)
  97. Obedience Plangt (Physostegia virginiana)
  98. Onion (Allium cepa)
  99. Oriental Poppy (Papaver orientale)
  100. Ox-Eye (Buphthalmum salicifolium)
  101. Painted Daisy (Tanacetum coccineum, formerly Pyrethrum coccineum and Chrysanthemum coccineum)
  102. Painted Sage (Salvia viridis, syn. horminus)
  103. Parsley (Petroselinum crispum)
  104. Parsnip (Pastinaca sativa)
  105. Pasque Flower (Pulsatilla vulgaris, Anemone pulastilla)
  106. Pea (Pisum sativum)
  107. Penstemon (Penstemon)
  108. Peony (Paeonia lactiflora, officinalis, etc.)
  109. Perennial Everlasting (Anaphalis margaritacea and others)
  110. Perennial Flax (Linum perenne, flavum, etc.)
  111. Perennial Pea (Lathyrus latifolius)
  112. Perennial Sage (Salvia x superba and nemorosa)
  113. Phacelia (Phacelia campanularia, tanacetifolia and others)
  114. Pincushion Flower (Scabiosa atropurpurea and caucasica)
  115. Pink (Dianthus deltoides, gratianopolitanus and others)
  116. Pot Marigold (Calendula officinalis)
  117. Primrose (Primula)
  118. Red Valerian(Centranthus ruber)
  119. Rhubarb (Rheum )
  120. Rock Cress (Arabis and Aubrieta spp.)
  121. Rudbeckia (Rudbeckia )
  122. Sandwort (Arenaria montana)
  123. Saxifrage (Saxifraga )
  124. Sclary Sage (Salvia sclarea)
  125. Sea-Holly (Eryngium)
  126. Self-Heal (Prunella)
  127. Sheep’s Bit (Jasione laevis, syn. perennis)
  128. Shirley Poppy (Papaver rhoeas and commutatum)
  129. Silene (Silene )
  130. Sneezeweed (Helenium )
  131. Snow-in-Summer (Cerastium tomentosum)
  132. Snow-on-the-Mountain (Euphorbia marginata)
  133. Soapwort (Saponaria )
  134. Spanish Poppy (Papaver rupifragum)
  135. Spiderwort (Tradescantia x andersoniana, ohioensis)
  136. Spring Radish (Raphanus sativus)
  137. Statice (Limonium sinuatum, platyphyllum and others)
  138. Strawflower (Xerochrysum bracteatum, syn. Helichrysum bracteatum)
  139. Sunflower (Helianthus annuus and others)
  140. Sweet Alyssum (Lobularia maritima)
  141. Sweet Pea (Lathyrus odoratus)
  142. Tansy (Tanacetum vulgare)
  143. Thrift (Armeria maritima and others)
  144. Tree-Mallow (Lavatera)
  145. Tuberous Jerusalem Sage (Phlomis tuberosa)
  146. Tulip Poppy (Hunnemannia fumariifolia)
  147. Turnip(Brassica rapa rapifera)
  148. Turtlehead (Chelone )
  149. Veronica (Veronica )
  150. Winged Everlasting (Ammobium alataum)
  151. Zinnia (Zinnia elegans, Z. haageana, Z. angustifolia, etc.)

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

1 comment on “Seeds to Sow in Mid-May

  1. Pingback: Seeds to Sow Indoors in Early March* – Laidback Gardener

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