This article was written by One of Our Members, Mike Dysinger to share with the rest of the members. I found it so valuable I asked if I could share it here. Learn more about Mike at the end of the article.
Tips and Tricks for Growing Plants from Seed
Growing plants from seed is by far the cheapest way to expand your plant inventory. I’ve been growing plants from seed for almost 30 years now and have picked up a few pointers along the way that others might find helpful. Some things may be obvious while others may not be.
- Use a good soil-less mix, in other words, peat or perhaps coir (from coconuts). The finely milled commercial seed starting mix is great but expensive; a bale of peat is much cheaper but usually has some bigger chunks of roots or sticks that can be easily sifted or removed. (While I love compost, humus, etc., these soil components can carry many soil pathogens detrimental to seed growing and are best avoided as seed starter mix.)
- I always add perlite to my mix, even if it’s pre-bagged as a seed starting mix. The perlite makes your mix go much further, provides aeration and drainage, and helps hold moisture. (Pro-tip: buy large bags of perlite from a horticultural/farm supply store. The small bags at big-box stores are very expensive!)
- Wet your perlite before adding to your dry peat. This moistens your mix much faster than just trying to add water to dry peat. Huge timesaver!
- You want your mix to be moist before sowing your seeds, however, not soaking wet. Your mix should be similar to a wrung out sponge.
- Commercial mixes usually have vermiculate as well as perlite added. That’s fine, but I find vermiculite an unnecessary addition and expense when making my own. Perlite is much more effective.
- The larger the seed, the deeper you plant it in the mix, but not too deep! Almost no seeds should be deeper than about a ¼” inch. It’s probably a little better to go a little too shallow than too deep. Experience is a great teacher here. If it is too shallow when it germinates – you can see the roots perhaps – it easy enough to sprinkle a little more mix on top.
- If you cannot easily grasp individual seeds they are just best sprinkled on top of the mix. Smaller seeds generally need light to help germinate.
- With surface sown seeds I typically press them down to make sure they have good contact with the mix.
- For larger seeds, like trees and shrubs, for instance, I will water from above. With most smaller seeds, however, I water from the bottom to avoid disrupting the seed placement. I set my flats in a larger shallow pan / flat for an hour or more, or even overnight. (I use something called ‘Perma-nest’ trays which I think are still being sold.)
- Cover your seed tray with clear plastic cover to keep seeds moist. Once your seeds have been exposed to moisture and warm temps they will begin the germination process. This can take weeks or even months so be patient! (Annuals may germinate much quicker.) Re-moisten the mix as needed when it dries on top. Remove the cover when you see the first green peeking through the soil.
- The clear plastic salad / bakery ‘clamshell’ containers make great mini-greenhouses for seed starting. Don’t forget to put holes in the bottom for drainage and bottom watering.
- Don’t forget to label your seed trays! I like to put as much info as I can on the label: name, date sown, number of days to germination, seed source, etc. More info is better than less! We also use paper logs to track things (and do a similar thing with cuttings, as well.).
Many seeds require a period of cold and / or warm moist stratification which can seem a bit daunting to novice seed growers. There are several strategies to address this issue.
- While it’s not always the case, if a plant normally goes through a cold winter (in other words, a non-tropical plant), there is a good chance it needs a period of cold, moist stratification for best germination.
- The simplest way to deal with this is to sow your seeds outside in a garden bed in the fall just like Mother Nature would do. You may need to cover the bed with screening, hardware cloth, or some other permeable material to keep the critters from eating your seeds, and / or leaves to hold in moisture. The down side of this method is lack of control, and you may get fewer plants, as well. Plants with long tap roots like poppies can be done this way.
- Method 2 is to sow your seeds in a flat (or plug trays which I generally prefer) and place them in a cool to cold area outside such as the north side of a structure to minimize the yo-yo temp swings many of us endure. Cover the flats with screen or mesh to keep critters out. Check them periodically to keep the mix moist. Wind can dry out flats quickly which may ruin germination success. I’m doing this more this year than in previous years when I typically cold stratify my flats in an open, unheated greenhouse. I sometimes stack flats in totes to preserve moisture and as a barrier to critters. (BTW, stacking flats is a good way to conserve space over the winter, but don’t forget to check them periodically for early germinators. Some things germinate in cooler temps!)
- Finally, you’ll see a lot of references to the baggie method of stratification where seeds are placed in a sealable sandwich baggie with moist vermiculite or sand. Again, barely moist – think a wrung-out sponge – is preferable to wet and soggy. Label your baggies ahead of time with the name, sowing date, length of time for stratifying, and any other information you might need. Then place your baggie in the produce tray of your refrigerator. Don’t forget to check them periodically for germination, dryness, or fungus/mold breakout, a sign it’s too wet. (In this case, open the baggie for a day or two to let some of the excess moisture escape. Then place back in the fridge. In general, your seeds will not be harmed so don’t panic. If the seeds have become mushy, though, they are probably doomed.)
- Some seeds need a period of warm, moist stratification before or after the cold treatment to induce germination. Others are what’s known as double dormant, meaning they need a cold- warm –cold treatment to germinate. This emulates the seed going through two winters. I typically do these types of seed using the baggie method as you can shorten the germination time from two years to less than one. Again, note on your baggie how long the seed needs to experience the cold – warm –cold cycle. (Note: some things need a warm – cold – warm cycle.)
- There are plenty of references in books and online that give you good information on the stratification needs of various seeds. If I’m unsure of length of time, a 90 day period of time for each stratification period is generally sufficient.
- With some things, I will start with a warm, moist stratification period first prior to the cold. I’ve found this to be helpful germinating double dormant seeds quicker.
- Some seeds have a very hard seed coat which needs to be scarified to allow the seed to imbibe water prior to germination. Things like redbud tree, baptisias, and other legumes generally require this, as well as others. There are many ways to scarify seeds mechanically – a file, nail clippers, sandpaper, etc. – I’ve found the best way to do a large number of seeds is to boil a pot of water, let cool for a few minutes, then pour over the seeds and let them soak overnight. You should see seeds swell up with water. Any that don’t, give a second hot water bath. Sow the swollen seeds and give them the necessary stratification treatment.
- You can let Mother Nature do the scarification for you, if you prefer. The freeze / thaw cycle of winter is often enough to break the hard seed coat, however, it can be somewhat inconsistent and may take a second year to germinate.
- Some propagators use sulfuric acid to scarify seeds but this requires expert knowledge and extreme safety precautions!
- Some seeds have other chemical germination inhibitors or require a period of after-ripening, however, most do not. Southern Magnolia (Magnolia grandiflora) falls in this category.
- A small number of seeds are what is known as ‘hydrophylic’ (water loving) and cannot be stored dry. These seeds should be planted immediately upon maturity. Many of our woodland plants, trillium, for example, fall into this category. (Ants carry ripe trillium seeds to their nests to feed on the outer coating, leaving the seed to germinate over the next year or two!)
- Seeds mature and scatter at different times of year, not just late summer or fall. If nothing else, follow Mother Nature’s example and sow your seeds when they’re ripe and provide the same conditions they would naturally experience (For example, spring seeders experience a warm summer prior to a cold winter.).
- Once seeds have germinated, allow your mix to dry a little between waterings. Small seedlings are susceptible to ‘damping off’, a group of fungal diseases that are certain death to small seedlings. A small fan in your propagation area might help, in this regard, also.
- If you’re growing in a greenhouse, a flat of seeds can be perfectly moist in the morning, but quite dry in the evening. I typically check my flats on a daily basis, sometimes twice daily, by a simple lift test of the flat. Over time you’ll learn to feel the weight of a fully moist flat vs one that needs water.
- Fungus gnats can be another problem developing with too much moisture in your flats. While the adult gnats are harmless, the larval stage gnats in the soil can feed on your developing plant roots. There are many ways to combat this annoying pest including a 4:1 water to hydrogen peroxide treatment, Bt, an organic insecticide, and other methods. You can also use yellow sticky traps to capture / monitor outbreaks, or use the ‘jar’ method many use for fruit fly control. If you see these annoying pests flying above your flats, don’t panic. Adjust your watering, provide a little ventilation, and do a search for the control method of your choice.
- A white layer of mold or fungus may develop on the surface of your mix, again, generally an indicator of too much moisture. The most important thing to know is this outbreak will not generally harm your seeds. You can treat with a similar 4:1 water to hydrogen peroxide treatment as above, put your flat in the sun for a few hours (not recommended if your seeds have newly sprouted, you can burn them up!), and adjust your moisture levels and provide better air circulation..
Finally, don’t be afraid to try your hand at seed propagation, and don’t be afraid to fail! That is how we learn best, by trial and error. Trust me, I’ve failed a lot! Most seeds are fairly easy to germinate, however. You might start with annuals or vegetables which are generally easy to germinate and grow. Even after nearly 30 years I still get excited when I see those first little leaves pop up!!
Mike Dysinger is a past president of Gardening Partners, an educational and volunteer gardening organization in Middle Tennessee, a garden and landscape designer, and owner of Native Plants Plus nursery, focusing on North American native plants, heirlooms, and select eco-friendly plants from around the world. [email protected] plants,
Thank you Mike Dysinger for sharing this valuable information!
Questions, comments, mean things to say? Post them below and I will respond. Until then, by any and all means stay inspired! -Mike McGroarty