Seeds to Sow in Mid-May

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 latter 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:

• Agastache (Agastache foeniculum and others)
• Ageratum (Ageratum houstonianum)
• Annual Chrysanthemum (Glebionis carinatum, formerly Chrysanthemum carinatum)
• Annual Phlox (Phlox drummondii)
• Aster (Aster spp. including Symphtrichon, Eurybia and others)
• Astilbe (Astilbe spp.)
• Avens (Geum spp.)
• Baby Blue Eyes (Nemophila spp.)
• Baby’s Breath (Gypsophila paniculata, G. repens, G. muralis, etc.)
• Bachelor’s Button (Centaurea cyanus , C. montana, C. macrocephala and others)
• Balloon Flower (Platycodon grandiflorum)
• Baptisia (Baptisia spp.)
• Beebalm (Monarda spp.)
• Bellflower (Campanula spp.)
• Bergenia (Bergenia spp.)
• Blazing Star (Liatris spp.)
• Blue Fescue (Festuca ovina glauca and others)
• Blue Poppy (Meconopsis spp.)
• Bluestar (Amsonia spp.)
• Broccoli (Brassica oleracea italica)
• Burning Bush (Bassia scoparia, syn. Kochia scoparia)
• Butterfly Weed (Asclepias spp.)
• California Poppy (Eschscholzia californica)
• Camomille romaine (Chamaemelum nobile, syn. Anthemis nobile)
• Campion (Lychnis x haageana)
• Candytuft (Iberis spp.)
• Carolina Lupin (Thermopsis spp.)
• Chamomile (Matricaria recutita, syn. Matricaria chamomilla)
• China Aster (Callistephus chinensis)
• Chinese Forget-Me-Not (Cynoglossum amabile)
• Chinese Lantern (Physalis alkekengi)
• Chinese Pink (Dianthus chinensis)
• Chives (Allium schoenoprasum)
• Cinquefoil (Potentilla spp.)
• Clarkia (Clarkia unguiculata, syn. C. elegans)
• Clematis (Clematis spp.)
• Cleome or Spiderflower (Cleome spp.)
• Columbine (Aquilegia spp.)
• Common Sage (Salvia officinalis)
• Coreopsis (Coreopsis spp.)
• Corn-Cockle (Agrostemma githago)
• Cosmos (Cosmos bipinnatus and C. sulphureus)
• Creeping Zinnia (Sanivitalia procumbens)
• Culver’s Root (Veronicastum virginicum, formerly Veronica virginica)
• Dahlberg Daisy (Thymophylla tenuiloba, syn. Dyssodia tenuiloba)
• Dahlia (Dahlia x)
• Daisy (Leucanthemum x superbum, syn. Chrysanthemum maximum)
• Daylily (Hemerocallis spp.
• Delphinium (Delphinim x elatum, syn. D. x cultorum)
• Echinacea (Echinacea spp.)
• Edelweiss (Leontopodium alpinum)
• Elecampane (Inula spp.)
• Euphorbia (Euphorbia myrsinites, E. polychroma, etc.)
• Evening Primrose (Oenothera spp.)
• Evening-scented Stock (Matthiola incana)
• False Sunflower (Heliopsis helianthoides)
• Fennel (Foeniculum vulgare)
• Feverfew (Tanacetum parthenium, syn. Matricaria parthenium, Chrysanthemum parthenium)
• Fleabane (Erigeron speciosus and others)
• Four O’clock (Mirabilis jalapa)
• Gaillardia (Gaillardia x grandiflora and others)
• Garden Mum (Chrysanthemum x morifolium, formerly Dendranthema x grandiflorum)
• Globe-Thistle (Echinops spp.)
• Goat’s Beard (Aruncus spp.)
• Godetia(Clarkia amoena, formerly Godetia amoena)
• Gold Basket (Aurinia saxatilis, syn. Alyssum saxatile)
• Golden Marguerite (Anthemis tinctoria)
• Heuchera (Heuchera spp.)
• Hosta (Hosta spp.)
• Houseleek or Hen and Chicks (Sempervivum spp.)
• Hyssop (Hyssopus officinalis)
• Iris (Iris)
• Italian Bugloss (Anchusa azurea and others)
• Jacob’s Ladder (Polemonium caeruleum, P. reptans, etc.)
• Knautia (Knautia macedonica, K. arvensis, etc.)
• Knotweed (Persicaria spp., syn. Polygonum spp.)
• Lamb’s Ears (Stachys byzantina, syn. S. lanata)
• Lemon Balm (Melissa officinalis)
• Leopard’s Bane (Doronicum spp.)
• Lettuce (Lactuca sativus)
• Lewisia (Lewisia cotyledon and others)
• Lily (Lilium spp.)
• Lobelia (Lobelia cardinalis, L. siphilitica and others)
• Love-in-a-Mist (Nigella damascena and others)
• Lungwort (Pulmonaria spp.)
• Lyre-Leaf Sage (Salvia lyrata)
• Maltese Cross (Lychnis chalcedonica, L. x arkwrightii)
• Masterwort (Astrance major and others)
• Mauve (Malva spp.)
• Mexican Hat (Rabitida spp.)
• Mexican Poppy (Argemone spp.)
• Mignonette (Reseda odorata)
• Monkshood (Aconitum spp.)
• Nepeta, Catmint or Catnip (Nepeta x faassenii and others)
• Nicandra (Nicandra physaloides)
• Nicotiana or Flowering Tabacco (Nicotiana alata, N. sylvestris and others)
• Obedience Plangt (Physostegia virginiana)
• Onion (Allium cepa)
• Oriental Poppy (Papaver orientale)
• Ox-Eye (Buphthalmum salicifolium)
• Painted Daisy (Tanacetum coccineum, formerly Pyrethrum coccineum and Chrysanthemum coccineum)
• Painted Sage (Salvia viridis, syn. S. horminus)
• Parsley (Petroselinum crispum)
• Parsnip (Pastinaca sativa)
• Pasque Flower (Pulsatilla vulgaris, syn. Anemone pulastilla)
• Pea (Pisum sativum)
• Penstemon (Penstemon spp.)
• Peony (Paeonia lactiflora, P. officinalis, etc.)
• Perennial Everlasting (Anaphalis margaritacea and others)
• Perennial Flax (Linum perenne, L. flavum, etc.)
• Perennial Pea (Lathyrus latifolius)
• Perennial Sage (Salvia x superba and S. nemorosa)
• Phacelia (Phacelia campanularia, P. tanacetifolia and others)
• Pincushion Flower (Scabiosa atropurpurea and S. caucasica)
• Pink (Dianthus deltoides, D. gratianopolitanus and others)
• Pot Marigold (Calendula officinalis)
• Primrose (Primula spp.)
• Red Valerian(Centranthus ruber)
• Rhubarb (Rheum spp.)
• Rock Cress (Arabis spp. and Aubrieta spp.)
• Rudbeckia (Rudbeckia spp.)
• Sandwort (Arenaria montana)
• Saxifrage (Saxifraga spp.)
• Sclary Sage (Salvia sclarea)
• Sea-Holly (Eryngium spp.)
• Self-Heal (Prunella spp.)
• Sheep’s Bit (Jasione laevis, syn. J. perennis)
• Shirley Poppy (Papaver rhoeas and P. commutatum)
• Silene (Silene spp.)
• Sneezeweed (Helenium spp.)
• Snow-in-Summer (Cerastium tomentosum)
• Snow-on-the-Mountain (Euphorbia marginata)
• Soapwort (Saponaria spp.)
• Spanish Poppy (Papaver rupifragum)
• Spiderwort (Tradescantia x andersoniana, T. ohioensis)
• Spring Radish (Raphanus sativus)
• Statice (Limonium sinuatum, L. platyphyllum and others)
• Strawflower (Xerochrysum bracteatum, syn. Helichrysum bracteatum)
• Sunflower (Helianthus annuus and others)
• Sweet Alyssum (Lobularia maritima)
• Sweet Pea (Lathyrus odoratus)
• Tansy (Tanacetum vulgare)
• Thrift (Armeria maritima and others)
• Tree-Mallow (Lavatera spp.)
• Tuberous Jerusalem Sage (Phlomis tuberosa)
• Tulip Poppy (Hunnemannia fumariifolia)
• Turnip(Brassica rapa rapifera)
• Turtlehead (Chelone spp.)
• Veronica (Veronica spp.)
• Winged Everlasting (Ammobium alataum)
• Zinnia (Zinnia elegans, Z. haageana, Z. angustifolia, etc.)