Sowing advice for springtime

With the first snowdrops in bloom spring is undeniably in the air. It is an exciting time with renewed hope and we all think about new plants to add in the garden.
Some people plan well ahead about what to grow from seeds, but others maybe purchase seeds and plants on the impulse of the moment. Then, there are always seeds arriving late from seeds exchanges.

Because all the latest orders had in common a combination of species, warm and cold germinators, I feel obliged to repeat how to proceed at this time in order to obtain the best results with minimum effort. Good timing for sowing is important!
If you don’t need advice, jump to the end of the post to see a few ‘green things’ from the garden :) (2020) All grown from seeds, except the snowdrops.

For those in the Northern Hemisphere
Species that are indicated to germinate at warm (15-20C) can be sown right away if you use indoor lighting for growing seedlings or later (April/early May) if you intend to keep the pots outdoor.

*Species indicated to have double dormancy that require first a slightly warm cycle, followed by a cold one in order to germinate (Hydrophyllum, Euonymus, Actaea…) – can be sowed later, in the summer. Most Peonies are also in this category; sowing in late June to August gives them more than enough time to develop the roots until late fall. Same goes for two stage warm germinating Lilium species (L. michiganense, L. monadelphum…).

Most Fabaceae can be treated with the ‘hot water treatment’ and considered warm germinators. Last year tests gave excellent results (Hedysarum, Oxytropis, Astragalus, Baptisia, Thermopsis, Lupinus*).

Species that can be sowed ‘in situ’ & indicated warm germinators (Papaver, Erinus, various Campanula, Capnoides, Arisaema tryphyllum, some Viola spp.…) – wait until April/early May and cast the seeds in place, incorporating lightly (most such seeds are fine and need light to germinate), keep the area moist and if there are too many critters around consider placing a mesh on top of the sowing location.

Species indicated as: sow in the fall or with cold/moist stratification – I advise you to keep the seeds packets in the fridge until fall, and then proceed with sowing at the right time (in pots or ‘in situ’).

You can of course try to provide cold/moist stratification in the fridge, but don’t expect the same good results; it doesn’t work very well for all species. Also, you may end up with seeds germinating in June/July and with young seedlings by late fall – too young to withstanding the winter cold.

 Moist packed seeds: are only sold spring – summer to late fall. The exception are the two years germinators  like Caulophyllum and Medeola; when stock supply and temperatures allow sometimes seeds are offered in late spring. Sow them outdoors.

Cypripedium and other orchids and mycorrhizals: if not using ‘in vitro’ equipment, as discussed already, there is a slight chance that by incorporating the seeds in the garden, usually in late fall, close to where other orchids thrive, to be successful. Note the ‘slight chance’.

Those in the Southern Hemisphere: reverse the timings, sow the cold germinators, keep the warm ones in the fridge.