Many garden plants start out as seeds. You could look at these tiny plants wrapped in hard shells as presents waiting for spring to unwrap themselves.
Primitive plants like mosses and ferns don’t make seeds; they reproduce by releasing small parts of themselves called spores. When one of these spores is introduced into an environment that is conducive to growth, it develops into a thallus and then grows reproductive organs—the reproductive organs fertilize and a new plant develops.
In more advanced plants with seeds, though, the male and female flowers develop on the plant (or on nearby plants) and fertilization takes place in the female flowers when they are exposed to male pollen. The pollinated egg is a zygote, which grows into a tiny plant (embryo) encased in a shell.
The shell helps to protect the small plant and allows it to stay in stasis until it finds itself in conditions that allow it to continue to grow. When separated from the parent plant and put in a suitable environment, the shell will break open and the tiny plant will resume growth.
These shell-encased small plants are known as seeds. Each seed has three elements: the plant, a supply of nutrients and a seed coat. The encased plant will already have seed leaves (cotyledons), stems (hypoctyl) and a root (radicle). The seed nutrient stores of some plants develop outside of the seed coat and are known as fruit. The seed coat is the protective outer layer of the seed and can be soft or rigid.
Some seeds—like tomatoes—require special handling before they can be planted. Tomato seeds must be ‘fermented’ in a jar with some water. To prepare tomato seeds, scoop the inside of the tomato into a jar with a little water. Loosely cover with plastic wrap and keep in a warm location for two to three days, stirring daily.
On the last day, scoop off the floating material, then rinse with plain water and dry. Other seeds, such as some kinds of fruit and certain forest plants, might require a cold period or have other special requirements to sprout.
To help the tiny plants inside seeds stay in a state of suspended animation, excess moisture should be allowed to evaporate as the seeds dry out. Depending on the type of plant and the conditions, the seeds might last through the winter months to sprout in the spring, or they might last for several years, awaiting conditions that will allow them to sprout.
Seeds kept too wet might sprout prematurely and then die, so seeds should be stored in a dry container at cool temperatures for best results.
Germination starts with the reintroduction of moisture to the seed and finishes when the plant ends its reliance on its food stores and can begin to draw nutrition from the environment. In nature this is one of the most vulnerable times for a plant—which is why so many seeds are generated by parent plants in order to ensure at least a small number of surviving plants in the next generation. The requirements for germination are moisture, oxygen, an appropriate temperature and—for some plants—light.
The seeds of most plants have a low moisture content, which helps give them a long ‘shelf life.’ Before a seed will sprout, it must first be rehydrated. When the seed comes into contact with moisture, it draws in the water through a small hole, or micropyle.
This moisture will cause the plant to swell and will soften the seed coat, allowing the radicle to break through and seek more moisture. The seed leaves will also begin to swell and will open to seek out light. To help with getting moisture through the micropyle, some gardeners will soak seeds in water for 24 hours. Scarification practices such as nicking the seed coats with a sharp object or rubbing the seeds on sandpaper or an emery board are also sometimes used to help weaken the seed coat and allow the plant easier access to moisture.
Moistening a paper towel, wringing it out and putting it with seeds in a plastic bag in a warm location to sprout is another way of getting moisture to saturate your seeds. If you’re using this method you should change the paper towel every few days to keep it fresh, as an environment conducive to germinating plant seeds is congenial to mold spores as well—if a seed becomes waterlogged, fungus can set in and ruin it.
The amount of oxygen needed by a particular type of plant varies. Some plants will not germinate even in the presence of moisture unless air is also present. For this reason, most seeds should not be soaked directly in water for days on end, but transferred to a better-aerated environment after a day or so.
Moist seeds will germinate at temperatures between 68 and 86°F, with 75°F being ideal for many plants. In cold settings a heating pad might be used to raise the temperature of seed trays. Some seeds germinate better in light, while others prefer dark conditions—research the type of seed to learn which it prefers.
Seeds can be started directly in the pots that they will be grown in, but care must be taken to ensure proper moisture levels are maintained. One drawback to using final pots to start seeds in is that each seedling will take up a fair amount of space, which can be a pretty dramatic limiting factor when you’re starting seeds indoors in the early spring for spring plantings.
One solution to this dilemma is to first start your plants in smaller pots and then transplant them into larger containers once the plants have grown to fill the smaller pot—this allows for more seeds to be started in the same area. Treat the roots gently while transplanting, as they are easily damaged.
To start even more plants in a given area, they can be planted in ‘starter plugs’, which are commonly made with rockwool, foam, coco or compost. Inserts are available to allow seeds started in plugs to be kept neatly in standard 1020 trays. A crochet hook can be very handy as a probe, or to make a hole in your medium for a seed or cutting. With care it can even be used to seat sprouts in starter plugs.
Many seeds can be sprouted by simply burying them at a depth three to four times their width and keeping them moist—but not soggy—until sprouting. To prevent the medium from drying out too quickly, sometimes domes or plastic sheets are used to keep humidity high while the seeds sprout.
Do not allow your seedlings to stay too wet for too long, however, or fungus might start to grow on the plant near the medium, causing the fatal condition known as ‘dampening off,’ where infected sprouts will wilt and rot. To prevent root rot, make sure the seedling medium is allowed to dry out slightly between waterings. Media should be moist, not wet. Don’t allow the media to dry out too much, however—once the plant has germinated it loses its ability to survive without water and with such a small root system it can dry out and die quickly.
Seeds are not only essential to the survival of many types of plants, but they are an important food source. Corn, wheat and rice are seeds commonly used for food. Quality harvests depend on quality seeds—whether purchased, exchanged or gathered. Seeds from many plants can be collected and used the following a year.
If you’re planning to collect and use seeds, for predictable results open-pollinated varieties should be employed—these will tend to produce similar plants from one year to the next. If consistency isn’t that important to you, seeds from hybrid plants can be used, with potentially surprising results that will demonstrate much greater variation.
In late winter to early spring, it is common to start seeds indoors to be prepared for spring planting. To determine when to start your outdoor garden seeds indoors, find out the date of the last frost in your area. Then read the seed packet, which should tell you how many weeks before the last frost date to start them. If the information is not available on the seed packet itself, look up the information online.
There is an additional concern with some plants when calculating their planting dates because of something called photoperiodism—which means that these plants use the duration of their dark periods to determine when to flower. These plants bulk up during the summer until the longer nights of fall trigger flower or fruit set. The reason that this can be a concern is that if these plants are set outside in the early spring months when the nights are still long they can immediately begin flowering.
This summer I want to try growing loofahs (a plant sponge that can be used in a variety of ways) on the top of my patio porch and in my backyard. Loofahs need a very long growing season (160 to 220 days) to produce sponges.
Since the last frost in my area is March 23, I know I can start my seeds on March 1 and they will have time to sprout and get in a couple of weeks of growth before getting moved outside. Depending on your area, it is common to start seeds indoors six to eight weeks before the last frost date.
Plants started indoors should be ‘hardened’ by moving to a sheltered location or by gradually increasing the time the plant spends outdoors—this will allow the plant to become used to its new conditions over time and minimizes shock from the change.
Starting plants from seeds can be very rewarding and much cheaper than purchasing established plants. You’ll get a real feeling of accomplishment from growing a big, beautiful plant from a tiny seed—and as a bonus, starting your seeds indoors will extend your active gardening season as well.