Only January, Yet Already Time to Sow Seeds?



20180103 ENG, &

It’s only January! Surely it’s too soon to sow seeds? Source:, & mzayat. com

The new year has barely begun, yet now and over the coming month it’s already time to start certain seeds indoors.

This is a very select group of especially slow-to-mature plants. January is far too early for most seeds (think March or April instead), but you need about four to five months of indoor culture to bring the following plants to the right state of growth for outdoor planting.

  1. Agastache (Agastache foeniculum)
  2. Datura (Datura metel)
  3. Fairy Snapdragon (Chaenorrhinum origanifolium, syn. glaerosum)
  4. Lisianthus (Eustoma grandiflora)
  5. Spike dracaena or cabbage palm (Cordyline australis, syn. indivisa)
  6. Tritome (Kniphofia )
  7. Tuberous Begonia (Begonia × tuberhybrida)

No Easy Feat!


Artificial light is almost essential for seeds started in January. Source: laidbackgardener. blog

Starting seed in January in the Northern Hemisphere is not simple. The days are short, the sun is weak and, in many areas, the weather is gray more often than sunny, meaning light is seriously lacking. Also, temperatures in front of the average windowsill are cool, yet almost all seeds need warmth—and fairly even temperatures—to germinate well. As a result, you pretty much have to start these under artificial lights, such as fluorescent or LED plant lights, and in the warmest part of your home.


Germinate the seedlings under glass, possibly over a heating pad, as above. Source:

Always start winter-sown seeds “under glass” (under some sort of transparent covering) to maintain high humidity and stable temperatures and in a room that is at least moderately warm (72 to 75˚ F/21 to 24˚ C) or place the seed containers on a heating pad (one specifically designed for plants). Use a timer to set the day length of your lamp at 14 hours to simulate the long days of summer and place the containers of freshly sown seeds about 6 to 12 inches (15 to 30 cm) below the lamp. Now, wait patiently for germination to occur. (One reason that certain seeds need early sowing is that they are slow to germinate.)

Seeds That Require a Cold Treatment


Many tree, shrub and perennial seeds need a cold treatment before they will germinate. Source: laidbackgardener. blog

January (or December or February) is also a good time to start seeds that need a cold treatment (cold stratification) to germinate well. This group includes most trees and shrubs from cold and temperate climates, but also many perennials and even a few annuals.

These seeds will not germinate until they have received a given number of days of cool, moist conditions, from as little as one or two weeks to four months or more, information you would (hopefully) find on the seed pack.

The number of weeks given is the minimum requirement for that species, but there is no maximum. So, if you keep seeds that need, say, a two-week treatment in the cold for two months, that’s not a problem. That’s nice to know, because the information on the minimum cold treatment for seed X is not always available, especially for seed you harvested yourself. If you don’t know, I suggest giving seeds of perennials a six to eight-week cold treatment: that’s usually enough. For trees and shrubs, I’d recommend three months.

Simply sow these seeds in a container as you would any other, then seal them inside a clear plastic bag and pop them into the refrigerator or cold room for at least the minimum number of weeks. Afterwards, move them to a warm, well-lit spot, on a windowsill or under lights, for germination to start.

100 Seeds That Need a Cold Treatment

Here are 100 plants that germinate best with a cold treatment (there are thousands of others!). Check the seed envelope or the seed supplier’s web site for more information.

  1. Abies (fir)
  2. Acer (maple, mosts species)
  3. Aconitum (aconite)
  4. Alchemilla (lady’s mantle)
  5. Allium (ornemental onion)
  6. Amelanchier (serviceberry)
  7. Aquilegia (columbine)
  8. Asclepias (milkweed, some species)
  9. Astrantia (masterwort)
  10. Baptisia (false indigo)
  11. Buddleia (butterfly bush)
  12. Caltha (marsh marigold)
  13. Caryopteris (bluebeard)
  14. Cercis canadensis (redbud)
  15. Chelone (turtlehead)
  16. Cimicifuga (bugbane)
  17. Clematis (clematis)
  18. Cornus (dogwood)
  19. Corydalis (fumitory)
  20. Delphinium (delphinium)
  21. Dicentra spectabilis, now Lamprocapnos spectabilis (bleeding heart)
  22. Dictamnus (gas plant)
  23. Dodecatheon (shooting star)
  24. Echinacea (purple coneflower)
  25. Eremurus (foxtail lily)
  26. Eryngium (sea holly)
  27. Eupatorium (Joe Pye weed)
  28. Filipendula (meadowsweet)
  29. Forsythia (forsythia)
  30. Fragaria (strawberry)
  31. Fuchsia (fuchsia)
  32. Gentiana (gentian)
  33. Geranium (perennial geranium, cranesbill)
  34. Goniolimon (German statice)
  35. Helianthemum (rock rose)
  36. Helianthus (perennial sunflower)
  37. Heliopsis (false sunflower)
  38. Helleborus (Christmas rose)
  39. Hemerocallis (daylily)
  40. Heuchera (coral bells)
  41. Hibiscus moscheutos (perennial hibiscus)
  42. Hypericum (St. John’s wort)
  43. Iberis (perennial candytuft)
  44. Ilex* (holly)
  45. Incarvillea (hardy gloxinia)
  46. Iris (iris, many species)
  47. Kirengeshoma (waxbells)
  48. Knautia (knautia)
  49. Lathyrus (perennial sweet pea)
  50. Lavandula (lavender)
  51. Leontopodium (edelweiss)
  52. Lobelia (hardy lobelia)
  53. Lonicera (honeysuckle)
  54. Macleaya (plume poppy)
  55. Magnolia* (magnolia)
  56. Malus (apple, crabapple)
  57. Mazus (creeping mazus)
  58. Mertensia (Virginia bluebells)
  59. Muscari (grape hyacinth)
  60. Myrrhis odorata (sweet cicely)
  61. Nepeta (catmint)
  62. Oenothera (evening Primrose)
  63. Opuntia* (beavertail cactus)
  64. Paeonia* (pivoine)
  65. Penstemon (beard-tongue)
  66. Persicaria (fleeceflower)
  67. Persicaria orientalis, syn. Polygonum orientale (kiss-me-over-the-garden-gate)
  68. Phlox (phlox)
  69. Physalis (Chinese lantern)
  70. Picea (spruce)
  71. Platycodon (balloon flower)
  72. Primula (primrose)
  73. Pulsatilla (pasque flower)
  74. Quercus (red and black oaks)
  75. Ranunculus (buttercup)
  76. Ratibida (prairie coneflower)
  77. Rosa (rose)
  78. Rudbeckia (black-eyed Susan)
  79. Sambucus (elderberry)
  80. Sanguinaria (bloodroot)
  81. Sanguisorba (burnet)
  82. Saponaria (soapwort)
  83. Saxifraga (saxifrage)
  84. Scabiosa (pincushion flower)
  85. Sedum (stonecrop)
  86. Sempervivum (houseleek)
  87. Sidalcea (prairie mallow)
  88. Staphylea* (bladdernut)
  89. Stokesia (Stokes’ aster)
  90. Syringa (lilac)
  91. Thalictrum (meadow-rue)
  92. Tiarella (foamflower)
  93. Tricyrtis (toad-lily)
  94. Trillium* (trillium)
  95. Trollius (globeflower)
  96. Tsuga (hemlock)
  97. Vernonia (ironweed)
  98. Veronica (speedwell)
  99. Viola (violets)
  100. Vitis (grape, some species)
*Some species in this genus require a double cold stratification: that is, two cold treatments separated by warm one, to germinate well. Try two to three months of cold followed by two months of warmth, then again two to three months of cold. When you expose them to warmth after these repeated treatments, most will germinate quite readily.

Good growing!20180103 ENG, &

What Was I Thinking When I Planted That!


20161119iWhen it comes to gardening, my own insatiable curiosity is often my worst enemy. I keep trying new plants, either new hybrids or simply plants I’d never seen before. Of course, most of the time the worst that happens is I spend money for nothing on a dud plant, but still, I often do discover some really great varieties. But sometimes the result is much worse.

You see, most of the worst weeds in my yard are ornamentals I planted without having checked them out adequately. Had I looked into them a bit more, I never would have planted them.

Here are a few examples:

The Euphorbia that Ate my Flowerbed


‘Fen’s Ruby’ cypress spurge (Euphorbia cyparissias ‘Fen’s Ruby’)

I planted ‘Fen’s Ruby’ cypress spurge (Euphorbia cyparissias ‘Fen’s Ruby’) because it just looked so cute in the nursery, almost like a little purple conifer with contrasting chartreuse flowers. But what was I thinking when I planted it? I knew that several (but not all) spurges (euphorbias) were invasive, but this one was so tiny and dense, how could it possibly do any damage?

12 years later, I’m still fighting it. The plant spreads thanks to underground stolons that head off in all directions. And to be honest, it’s not even all that attractive, because its pretty spring coloration doesn’t last, the leaves turning a more boring glaucous green for the rest of the summer. Worse, when I yank it, it releases a sticky, poisonous latex you must not get into your eyes. In spite of my efforts, every year its spreads further and further. I may have lost the war against this one!

Self-Sowing by the Thousands


‘Ravenswing’ cow parsley (Anthriscus sylvestris ‘Ravenswing’).

‘Ravenswing’ cow parsley (Anthriscus sylvestris ‘Ravenswing’) is in itself totally charming. And I see it mentioned recommended on lots of Websites as a great garden plant. With its glossy, deeply cut foliage in a superb dark purple, almost black, it looks like a black fern… when it’s not in bloom, at least. Of course, the umbels of tiny white flowers, reminiscent of those of its cousin, the wild carrot (Daucus carota), prove it isn’t a fern (ferns don’t bloom), but they do make a nice contrast with the foliage.

It didn’t take me long to realize I’d made a mistake in planting this one. The following spring, hundreds of seedlings popped up in my garden, about half with the same shiny dark purple leaves as the cultivar, the other half with plain green foliage. (Obviously it does not come totally true to type from seed).

Subsequently I learned that the secret to keeping ‘Ravenswing’ under control is to remove the flowerheads before they go to seed, because the plant itself never suckers: it only spreads by seeds. Besides, removing the flower stalks before they go to seed helps extend the life of this plant which is essentially a biennial. If it doesn’t produce seed, it will tend to sprout anew the following season.

But it’s too late for that now. Pretty clearly, the seeds can live for many years, because even if I pull out or cut back the seedlings as soon as I see them and never let them bloom, new seedlings grow back every year.

I intend to keep fighting this one: I don’t want to be accused of having introduced this invader to my region (the green form is known to be a noxious weed!)… and self-sowing plants get around much faster than stoloniferous ones!

An Aggressive Invader


Plume poppy (Macleaya cordata).

I must admit that I was still a young and naive gardener when I planted my first plume poppy (Macleaya cordata). I don’t think I was yet 25, so that would have been nearly 40 years ago. I simply assumed that garden centers would never sell weedy plants, that if it was being sold, it had to be something desirable. I’ve since learned otherwise.

Some people actually like plume poppy. Its proponents claim it’s not all that invasive and that it’s easy to control. If so, how come every time I see it in a garden, it seems to have pretty much taken over? And it’s a big bruiser of a plant, too, about 8 feet (2.5 m) high, big enough to crowd out the competition.

Part of the difference in attitude might be that it is less invasive in heavy soils. Well, I planted mine in practically pure sand. The plant spread from one end of the flower bed to the other, about 20 feet (6 m) in just two years. The whole bed turned into a macleaya jungle, and it would have taken over the lawn too if I didn’t mow it regularly, chopping off the sprouts as I went. When you try to pull it up, it covers you in sticky orange sap that stains everything. Worse yet, all that effort is for a plant I honestly don’t even find all that attractive.

I solved this problem quite promptly: I moved and left it to the new owner to handle.



Common false spirea (Sorbaria sorbifolia): beautiful, but what a garden thug!

I knew that common false spirea (Sorbaria sorbifolia) was invasive and I would never have planted it on purpose, but I was done in by a lying label.

You see, I was looking for Kashmir false spirea (S. tomentosa angustifolia, syn. S. aitchisonii), common false spirea’s more restrained cousin. This species doesn’t sucker and is not invasive. In fact, that’s its main selling point: it’s just as pretty as common false spirea, but it stays put! The two species pretty much resemble each other (Kasmir false spirea has somewhat finer leaves, though), and before I realized the error, the damage was done. I’d let the devil loose in my backyard!

The problem wasn’t obvious at first: like many woody plants, the mislabeled common false spirea took a few years to settle in. Then suckers began popping up… everywhere. This shrub made a beeline for the fence and moved into my neighbor’s yard from which it now  regularly makes forays into my garden. It follows the fence for a good 50 feet (15 m) and every year I cut back and pull out hundreds of suckers that dare cross the fence back into my yard.

The phenomenon of mislabeled plants is unfortunately very common in the horticultural world. Some nurseries just don’t seem to give a damn about what the label says as long as the plant sells. You can see where you could make a lot more money selling the prolific common false spirea labeled as the slow-to-multiple Kashmir false spirea. But I don’t want to make it sound like all nurseries do this: many take the correct identification of their plants very seriously.

I really don’t have a solution for this problem except to always complain when you find a mistake. It’s not your local garden center that is to blame (usually), but the wholesale nursery that shipped out the plants with the wrong labels. I like to think that if enough people complain about getting the wrong plant, it will make a difference.

Sold the Wrong Knotweed

The false spirea incident was not the only time I got into a pickle because of a mislabeled plant. There was also the case of the mislabeled Japanese knotweed and that could have been much, much worse!


The wild, unselected Japanese knotweed (Fallopia japonica): exactly what I didn’t want in my garden.

Japanese knotweed (Fallopia japonica) has such a bad reputation as an invasive plant that the species itself is rarely seen in plant nurseries. It’s considered one of the worst weeds in the world! But if the species itself is highly invasive, there are a few ornamental cultivars that don’t sucker or only do so to a very limited degree. The variegated cultivar, F. japonica compacta ‘Milk Boy’ (apparently the correct name for ‘Variegata’), for example, is easy to control and fairly widely available.


‘Crimson Beauty’ Japanese knotweed (Fallopia japonica ‘Crimson Beauty’) is a beauty and totally non-invasive… if you can find it!

But I wasn’t looking for ‘Milk Boy’. I wanted ‘Crimson Beauty’, an extraordinary giant perennial with bright mossy red flowers I first saw at Longwood Garden decades ago. It is non-suckering and produces a huge shrublike plant with flowers that last 3 months. Really, I have rarely seen such a beautiful perennial! But I never seemed to be able to find it in nurseries, not even in catalogs, at least, not in Canada (for me, ordering from the US is a major complication). Then, in 2003, I finally saw one in the mail order catalog of an Ontario nursery and of course of course sent for it.

It didn’t bloom the first year, but when the second year came around, the flowers were not red, but white. I thought maybe they’d turn red over time, but no such luck. Then I figured (wishful thinking!) that maybe the red flowers only appeared when the plant was mature. But by the third summer, I realized that I had made a huge mistake, that my plant was not the non-suckering ‘Crimson Beauty’, but the species. I knew this for sure not just because of the still-white flowers, but because suckers started popping up everywhere, even 3 or 4 feet away from the mother plant.

I’ve been known to put things off, but my entire yard was at stake here, and I didn’t hesitate. I dug up the mother plant (quite a struggle, as the roots were incredibly deep), then hacked out all the thick rhizomes I could see as well, pretty much trashing a huge section of garden. Soon new shoots appeared: strong, dominant shoots as thick as my thumb that seemed to be saying “you’ll never be able to stop us”. But I cut them to the ground. And cut back the new sprouts that followed as well. And their replacements. Each time I cut them back, the next generation had thinner, shorter stems. By year 3, the invasion was nearly over. Still, the occasional stray sucker came up in year 4 and even a few in year 5. None appeared in year 6: I had succeeded in eliminating Japanese knotweed from my yard: not many gardeners can make that claim.

I did contact the nursery that sold me the plant and they apologized. It wasn’t one of their plants, but a plant they’d bought in under the name ‘Crimson Beauty’. I know that sort of thing happens, but it’s annoying to have had to put 5 years of efforts into correcting someone else’s mistake.

Caveat Emptor


Check before you plant!

Anyone can make the mistake of buying an invasive plant by accident. After all, the fact that the plant is a weed is not the kind of detail that the seller ever mentions on the label! But don’t do as I did and plant an unknown plant without checking into it. The Internet can be a great tool for that sort of thing and it takes only minutes to do a reasonable search. You won’t want to be struggling today to control a plant you put in years before.