Timing the sowing in springtime

The Crocuses, snowdrops, the first Hepatica in bloom and others announce that spring is in the air, a bit too early this year. It is an exciting time with renewed hope when we all think about new plants to add to the garden and new ones to start from seeds.

Some people plan well ahead about what to grow from seeds; others purchase seeds and plants on the impulse of the moment or after they see nice spring flowering pictures. Then, there are always seeds arriving late from seed exchanges.

Usually late spring orders have in common a combination of species, warm and cold germinators, so 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 because seeds can also enter sometimes a second dormancy if not handled improperly.

This is a repeat of an older post with some updates. If you don’t need advice, jump to the end of the post for the first flowers of spring 2024 :-)

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 outdoors, or to sow the seeds directly on the ground (‘in situ’).
Species that can be sowed ‘in situ’ (Papaver, Lobelia, Campanulastrum, some Viola species.…) – 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 you have to place a mesh on top of the sowing location.

Various Fabaceae can be treated with the ‘hot water treatment’ and considered warm germinators. Testing gave good to excellent results  for Hedysarum, Oxytropis, Astragalus, Baptisia, Thermopsis, Lupinus*. It seems that Anthyllis and Lespedeza violacea seeds also reacts to this treatment, only that it has to be repeated many times.
See in the pictures below, how large the Lespedeza seeds that imbibe with water look like; only one seed from that batch is ready to be sown. The roots appear in about a week after that.

The alternative to the HWT is of course the old fashioned method of scarification using sheets of sandpaper.

Species indicated: sow in the fall/winter or as cold/moist stratification – I advise you to keep the seeds packets in the fridge until fall, and then proceed with sowing (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. Also, you may end up with seeds germinating in June/July and young seedlings by late fall which will withstand poorly the winter cold.

Species indicated to have double dormancy which require first a slightly warm cycle, followed by a cold one in order to germinate (like Hydrophyllum, Euonymus, Actaea and most peonies species) should be sown later in the summer (late June/July/August). This will give them more than enough time to develop the roots until late fall, before the cold cycle begins in the winter. The same goes for two stage warm germinating Lilium species (L. michiganense, L. canadense, L. kesselringianum…).
Again, these cycles can be provided in the house + fridge, but it is too late now to obtain good seedlings by late fall. It is of course anyone’s choice, I can only recommend the best method.

Moist packed seeds: are not sold at this time of the year, with the exception of two years germinators (Caulophyllum, Medeola, when stock supply and temperatures allow). When to sow and how to handle them has been outlined in other posts.

Orchids and other mycorrhizals (Chimaphila, Conopholis): if not using ‘in vitro’ equipment, there is a slight chance that by incorporating the seeds in the garden close to where other orchids/preferred hosts thrive will be successful. This method gave good results also for Castilleja but with the seeds sowed in late fall.

An early March garden walk dedicated to the Women’s Day!