Starting your Seeds, why are some seeds so tricky to grow?
Have you ever wondered why some seeds never seem to come up while others can't be stopped?
Different seeds need different conditions, but some are fussier than others. Here are a few things to consider to improve your odds and get good germination rates.
What do seed need to germinate?
Several conditions have to be met for seeds to germinate and grow.
- Do you have a viable healthy seed?
- Is the temperature right?
- Does the seed need stratification? (cold treatment)
- Is there enough or too much moisture?
- Is the seed getting enough air/oxygen?
- Does the seed need light to germinate or must it be in the dark?
- Is the seed so tough that it could benefit from scarification?
- Some seeds have very specific requirements.
Is your seed even alive?
Do you have a good fresh seeds. Some plants don't really make viable seeds and prefer to reproduce by extending their roots of by cuttings. Hybrids sometimes do not make seeds or make non viable seeds.
If the mother plant was infected with fungus then the seeds might not germinate well. This happens with zinnias for example. Here is an article about The Effects of hydrogen peroxide treatment on the germination, vigour, and health of Zinnia elegans seeds
Sometimes the seeds were collected before they were ripe, or kept too long. Some plants such as parsnips, leek and onion need very fresh seeds. You can expect most seeds to last a couple of years. Corn, parsley, Okra, and peppers don't do well if kept longer than this. Beans, tomatoes, peas, carrots age better and can last 4 or more years. I planted 25 year old tomatoes last year and 2 out of 10 came up. Cucumber, cabbages, celery, eggplant, kale, rutabaga, melons, radishes and lettuce can stay alive for 5-6 years. Seeds need to be stored in cool dark places to stay viable. Some seeds such as Perilla barely make it to the one year mark and a large number of seeds sold will never germinate. As the seeds ages, fewer will germinate so if you are planting older seeds allow for a lower germination rate and plant more seeds. You can always thin out extras.
If you manage to get an old seed to come up the plant will be as nutritious and healthy as any other plant.
There is usually a lot of information on the back of a seed packet. Here lettuce is to be planted at a depth of .6 cm, this is just about a quarter inch. This tells me that the seed probably likes a bit of light to germinate. At the bottom there is a date. Check this if you find really cheap seeds, they may be well past their prime.
Sometimes old seeds can be helped by a soak in a dilute hydrogen peroxide solution, more on this later.
When choosing your seeds consider seeds that are suitable for your area. It's no use growing nice little seedlings then putting them out in completely unsuited area for them. If a plant needs 130 days to mature, for example, you want a frost free period of at least 130 days! The seed packet will tell you how long it takes to get a harvest, for my lettuce here it's 45-50 days.
Hybrids, are they GMO? What about Heirloom seeds?
A hybrid is simply a cross between 2 different varieties of plants to produce a better offspring. These offsprings are often more vigorous, grow faster, look nicer, produce better fruit and more of it. Gardeners have been making hybrids for hundred's of years. If you let your hybrid plants go to seed then the seeds will revert back to parent characteristics. They will not breed true and keeping seeds is not very useful since they will show a whole range of characteristics, you never know what they will be like. Hybrids don't always produce seeds and when they do the seeds are not always fertile.
The little leek seedlings are only a couple of weeks since planting. On the left the F1 hybrid seed has come up with great enthusiasm, on the right the heirloom variety is just starting to show. I'm running an experiment to see if the hybrid is better than the heirloom. So far the hybrid is much more vigorous, time will tell if it's as tasty. To be continued...
A GMO plant has had it's genetic material actually modified using sophisticated techniques. GMO seeds breed true and are permanently changed.
Heirloom is a loosely applied term for seeds that have been around for a longish time (at least 50 years) and that have developed qualities that make them work very well in the area they were developed. Although these heirloom varieties will breed true and often taste better they are not necessarily well adapted to your area unless they developed there.
Here is a link to my page on Hybrids.
Temperature of the soil makes a huge difference to germination.
Temperature is probably the most important factor to influence germination.
Some plants like beans will not germinate very well if the soil is too cold. If you are planting them directly outside it's best to wait till the soil warms up.
Beans that sit in cold damp conditions while they wait for warmer days run the risk of rotting, or in my case of being eaten by eager squirrels that watch my garden and help themselves to pea and bean seeds as I plant them.
At the other end of the spectrum many plants like cool conditions. These plants often have instructions such as "plant as soon as the soil can be worked."
I have found that using a heating pad almost halves the time seedlings come up. My house is quite cold so it makes a huge difference. I had an old lizard heating mat and started by using that. It worked well. I also tried a low wattage battery heater. It was covered in plastic and it also worked well. It was only about 5 watts. I had some plastic over it so it would not get wet. Better to get a proper plant mat though, there is a danger of wetting the wires and being quite dangerous, don't try this at home. Amazon has several: VIVOSUN 2 Pack Durable Waterproof Seedling Heat Mat Warm Hydroponic Heating Pad 10" x 20.75" MET Standard
It's a good bet, if you can't find any instructions as to proper germination temperature, to plant seeds that come from warm countries with some bottom heat, and to plant early season seeds in cooler soil. Seed packets often have instructions.
Here is a table of germinating temperature.
Min: Minimum temperature; Op-Ra: Optimum Range; Op: Optimum Temperature; Max: Maximum Temperature.
Alberta Agriculture and Forestry has a page on soil temperature and field vegetable germination.
In order to interpret such tables you have to understand that if you wait till your soil outside has reached this temperature, your plants will often either not have enough time to mature, or will be exposed to searing summer heat. Realistically, you plant outside when the soil has gone up ABOVE the minimum temperature but the absolute ideal germinating temperature has not been reached. This article from Texas Agricultural Extension Service, The Texas A&M University sums it up nicely
IF you are starting your plants inside then you can happily warm up your soil to ideal temperature and get quick enthusiastic germination. You can then put out your plants to enjoy the best of the summer weather.
Note: A table such as this is only a rough guideline. Different varieties will vary. Many plants have been developed for cold short season areas, or alternatively for hot conditions.
Bottom line: if you are starting the plant indoors then aim for optimum temperatures, If you are planting outside directly, then plant when the ground is above the minimum temperature so you get a realistic season length.
Gardeners have developed any number of strategies, such as warming mulches and black plastic, or row covers and cloches to increase the temperature of the soil for earlier direct planting and improved germination rates.
Does your seed need stratification?
Some seeds will categorically refuse to grow unless they are subjected to a period of cold. This is particularly true of plants that are native to areas that get a winter. In nature these plants would drop their seeds and these would stay dormant all through the winter, in the spring, having had their stratification period, they are eager and able to get on to the business of germinating and growing.
Stratification can be as simple as just throwing the seed packet in the fridge and forgetting about it till spring. Usually 12 weeks is required. I once had ginseng seeds that I had put in a baggie in peat and tried to grow the next spring. The plants never came up but a year later, I noticed that the few seeds I still had, forgotten in the fridge for 2 years, had germinated. They went on to grow and flower. Don't ask about my fridge ok.
Often seeds like to be put to bed in moist but not wet peat then seeds and peat go in a bag then in the refrigerator for a nice long sleep, 12 weeks is often recommended. Some plants like to be planted out in the fall and left outside in a protected spot till the spring.
Milkweed, Lupine, Coneflowers, Helianthus, perrennial Hybiscus, and many more, all like a nice stratification period. Most seeds from fruit trees require stratification. If you have the patience you can pick out blueberry seeds and they will grow after their cold treatment.
Many tree seeds will not germinate without being cold stratified. Link to my page on how to grow Tulip Trees
Many plants can be coaxed to grow even though they have not had their full stratification period using a hydrogen peroxide solution bath.
Seed vendors often sell seeds that need a cold treatment. Some will already have had their winter sleep, other will need to be kept in the fridge until you plant them. Check the packet.
Using Hydrogen Peroxide bath can speed up stratification and increase germination
There has been lots of research that has shown that a bath in a dilute solution of hydrogen peroxide speeds up germination, reduces the need for stratification and as an added benefit, helps kill pathogens that might infect a plant. Hydrogen Peroxide helps break down the seed coat allowing water and oxygen into the seed. It is though to act as a signaling chemical that helps encourage the breaking of dormancy. It's not entirely clear why it works but it does. Different modes of Hydrogen Peroxide Action During Seed Germination article in Frontiers in Plant Science.
Older not as viable seeds show a higher germination rate after a H2O2 treatment.
Many recipes and length of soaking have been tried and have worked.1 fluid ounce (30ml) of 3-percent hydrogen peroxide to 1 pint (475 ml) of water with a soak period of 12 to 18 hours has been successful. Various experiments suggest that a solution of between 6% to 9% is effective and soak periods of a half hour to 24 hours have worked. I guess it depends on the seed, how old it is, how tough the seed coat is, temperature and type of plant. Shorter soak for higher concentrations work.
After soaking, rinse your seed and plant.
Other research has tested regular bleach solution and found that it was also effective in improving germination. It also had the effect of killing disease organisms that infected the seed. They were using 50% household bleach. (Be careful, bleach is nasty.)
Is there enough or too much moisture?
The title says it all. If there is not enough moisture, the seeds will not germinate. If there is too much then the seeds might suffocate, and drown, or rot, or they will come up but the seedlings will damp off and rot. Most plants unless they are water plants, don't want saturated ground. It's ok while you are watering but the ground should be able to drain nicely, leaving the roots moist but not wet, and allowing air to come into the soil.
Some plants that live in water or in swampy conditions actually like to be wet. In this case the low oxygen level of the water is not a problem but a requirement. If you are trying to grow them then try to imitate their natural environment.
Desert plants however like to have nice moist conditions to start off. That's why deserts seem to instantly come in bloom after a rain. After the seedling are established of course they should be kept dryer.
Is the seed getting enough air/oxygen?
Seeds need oxygen to change their chemical composition in the process of germinating and respiration. In saturated soils, or soil that has compacted, seeds don't get enough oxygen and germination is slower, or completely inhibited. Carbon dioxide is a by product of seed respiration and must be dispersed out. If it accumulates then the seed does not do as well.
If you plant your seeds in a nice fluffy soil but over water, you might cause your soil to compact and even though you started with nice texture, you quickly end up with a dense mass that does not easily allow for gas exchange, oxygen to get in and Carbon Dioxide to get out.
This is one of the reasons professional growers will often start their seeds in a mostly peat soil. It drains well but retains moisture, does not compact so the seed and little plant gets lots of air, and can be pasteurized to help prevent damping off. The nice texture allows the little roots to spread easily. It is not fertile and can be quite acid so this needs to be considered but peat growing medium is a very successful material in which to start your seeds.
Sand used to be quite a popular starting medium for similar reasons. It does not hold water very well but seeds will come up nicely in it.An article from Gardening Know How on soil-less seed mixes
Does the seed need light to germinate or must it be in the dark?
It took me years to figure out why coleus did not want to germinate for me. I would plant them and a few might germinate but mostly they were a total failure. Eventually I got around to reading the back of the packet. The seed needs light before it germinates and I was very diligently and carefully covering my seeds.
If you look at seed packets, the instructions will direct you to press the seeds onto the ground, or cover very lightly. In those cases the seeds need light to germinate.
When seeds need light to germinate the issue becomes one of keeping the seeds moist enough for it to germinate without shading too much. Often a loose piece of plastic or a cloche or small enclosed plastic container works well. The bags used for produce in the grocery store work well to enclose small pots as long as there is some holes punched in them. I used bamboo skewers to keep the plastic supported. Seeds needs to be kept moist but not wet and there is the danger your seed will get mouldy so there must be some ventilation. Otherwise no great difficulty once you've figured this out.
Often plants that self sow will want light to germinate.
Many plants need light to germinate: Ageratum, Anise Hyssop, Balloon Flower, Begonia, Browallia, Coleus, Columbine, Gailardia, Geranium, Impatiens, Lettuce, Lobelia, Nicotiana, Nigella, Osteospermum, Petunias, Poppies, Savory, Shasta Daisies, Shiso (perilla), Snapdragons, Sweet Alyssum
Some plants that are listed as requiring light to germinate are quite tolerant and even though they prefer light, they will still come up in the dark, but not as well.
When I don't know, I plant some seeds covered and some just pushed onto the soil and let them figure it out. It's easy to pinch off the extra plants if too many come up.
Some plants will not come up if they are planted in the light. Onions are touchy this way, other plants that prefer to germinate in the dark are Calendula, Cannabis, Delphinium, Gazania, Pansy, Phacelia, Phlox, Salpiglossis, Sweet Pea, Vinca, Viola, Coriander, Parsley.
A seed's need for light is related to a pigment called phytochrome. Phytochrome, which exist in most plants, reacts in the presence of ligt. Phytochrome chemistry is what makes a plant grow towards light. Seeds are sensitive to light and it's this reaction to phytochromes that either makes the seed break its dormancy or steadfastly refuse to germinate.
Phytochromes are a class of photoreceptor in plants, bacteria and fungi use to detect light. (according to Wikipedia) They regulate the germination of seeds (photoblasty), the synthesis of chlorophyll, the elongation of seedlings, the size, shape and number and movement of leaves and the timing of flowering in adult plantsLink to Youtube Video about how Giant Sequoia needs fire to grow.
Is the seed covering really tough
Some plants make really tough waterproof coatings. This is useful if you live in an area where you need to make sure the conditions will last long enough for your seed to grow but it slows down germination a great deal.
Canna lily seeds will sprout much faster if you cut a little notch in the seed. You can also use a bit of sandpaper to abrade the covering instead. Moonflowers, Nasturtium, and any other tough seed can benefit from scarification. It's often done on peach or other nut seeds to speed up the gemination by getting water and air inside the seed faster.
If you use a knife, watch your fingers, it's easy to slip and notch your finger instead. I have a pair of wire cutter with quite a sharp point that works well to nick seeds. I also use sandpaper. These seeds also often benefit from being soaked in water overnight before planting.
In the photos you can see moonflower seeds which have had their tips nipped off to allow water and air to enter. Doing this makes the seed germinate in only a few days. If I don't scarify, it can take weeks and the germination rate is much reduced. I usually place the seeds between wet paper towels until they have started to sprout. They they go in soil. They grow quickly and can be set out permanently after only a couple of weeks if the weather is good.
Honey Locust seeds
I picked these unpromising tough dried out Honey Locust pods one spring walking along the sidewalk and decided to try and grow a tree. It's about 8 inches long.
Since they had spent the winter outside they did not need any cold treatment but I rubbed the seed with sandpaper till the very tough seed coat was abraded and I could see the inside. I soaked the seeds overnight and kept them between moist paper towels for a few days. They soon germinated and I ended up with several happy little seedlings that I planted in the yard.
Chemical scarification, also works for some plants. It occurs naturally when a bird or other animal eats a seed. The digestive chemicals including concentrated hydrochloric acid and strong bases in the gut weaken the seed coating allowing it to germinate more quickly. Horticulturist have successfully tried various chemical to duplicate this effect.
See hydrogen peroxide bath procedure above for an example.
Thermal scarification can also work. Sometimes a hot water treatment will encourage germination as will exposure to fire or to chemicals created during a fire. Lodgepole pine, Eucalyptus, and Banksia, Sandplain gerardia and Wood lily need fire to germinate or to release the seeds from the tough cones.Article by the US National Forest.org about how plants regenerate or sprout after a fire.
Some seeds are very particular about conditions.
In this page I have already mentioned some examples, such as plants that need fire or hot water to either activate or break dormancy of the seeds. Or seeds that need to go through a bird or animal to germinate. Some seeds are really fussy about being exposed to light or not. Some seeds need to be exposed to chemicals made from fires, it's not the heat but rather the chemicals that trigger the seed. Others will not think about coming out unless they have had a specific number of days below freezing.
Many elements have been tried to see if they affect germination. Cerium improve germination and growth of seedling
Luckily most garden plants are not so fussy and when all else fails you often can get seedlings ready for planting from your garden stores.
This article is for information only, I don't claim to be an expert on anything. If you try pre treating your seeds keep in mind that chemicals like hydrogen peroxide or bleach can be dangerous and be careful.