Category: 6. Germination

#1: Read the seed packet.

The purpose of a seed packet isn’t just so you can look at a pretty picture of the vegetable you’re growing. There’s also a lot of useful information on the back!

Before you start sowing seeds, slow down and take a minute to read over the seed packet. The most critical things to note at seed starting time are the following:

Temperature: If there are any soil temperature considerations for a particular vegetable the company will print that on the seed packet.

My Jalapeno seed packet has a tip that says, “Peppers germinate best in warm soil, so gentle bottom heat may be helpful until seedlings emerge.” (I’ll talk more about this in #4.)

Timing: You should be using a custom seed starting calendar that maps out what seeds to start when based on your average last frost date.

The back of the seed packet will often list the best timeline for starting those particular seeds and can be a handy double check on your timing.

For example, on the back of my Lively Orange Pepper seeds from High Mowing it states, “Start transplants 6-8 weeks before planting date.” I can double check my calendar to make sure I’m starting those seeds at the appropriate time.

Days to germination: This will give you an idea of when you can expect the seeds to start poking up through the soil. Most vegetables germinate between 7-14 days.

How quickly they do so is often dependent upon whether you’re giving them the optimal conditions.

Seed planting depth: Most seeds will need to be covered in soil to aid germination. But, some seeds, like flowers, should only be lightly covered because they need light in order to germinate.

#2: Don’t try to plant old seeds.

The first step before you sit down in front of your computer to order new seeds is to sort through your existing seed stash and look at the dates on all of the packets.

Stored under optimal conditions, seeds can last up to five years. But, optimal conditions are often cited as around 42 degrees F and low humidity.

I store my seeds in this neat plastic storage case in my office closet, so they’re definitely not getting those conditions. It would be like working in a refrigerator if my office was that cold!

You could store your seeds in your refrigerator. Most recommendations I’ve read suggest using glass jars with desiccant packets placed in them.

Personally, I have a lot of seeds and I don’t want to give up valuable storage space in my fridge.

So, back to the office closet they go.

I err on the side of getting rid of old seeds instead of keeping them. For me, it’s not worth it to take the chance that seeds I’m planting won’t germinate well. 

When this happens, I often don’t realize it for several weeks after planting, and that means I’ve already lost a lot of time. My garden season is too short and I’d rather spend the few extra dollars on new seeds to ensure I’ll have more success.

There’s also a concern about plant vigor or viability. As a seed ages, its ability to produce a healthy and vigorous seedling declines. So, a seed might germinate, but the plant might not grow very well.

Again, not worth the chance in my opinion.

If you look around at different sources for seed storage life, there is some conflicting data. But, here’s a basic guideline:

One Year Only
Onions

Up to 2 Years
Fennel
Parsley

Up to 3 Years
Sweet Corn
Leeks
Okra
Parnips
Sage

Up to 4 Years
Beans
Carrots
Peas
Chamomile
Cilantro
Dill
Lavender
Marjoram
Mint
Oregano
Rosemary
Thyme

Up to 5 Years
Beets
Broccoli
Brussels Sprouts
Cabbage
Cauliflower
Celery
Collards
Eggplant
Kale
Kohlrabi
Peppers
Radish
Rutabaga
Soybean
Spinach
Swiss Chard
Turnip
Watermelon
Basil

Over 5 Years
Arugula
Cucumber
Lettuce
Melon
Pumpkins
Squash
Tomato

Print out this chart from Johnny’s Selected Seeds to keep with your seed supply.

You can always do a home germination test with seeds you’re not sure about. Wet a paper towel until it’s damp, spread some seeds on the towel, and insert it into a plastic bag. Seal the plastic bag and put it somewhere warm.

After 7-14 days you should be able to see how many of the seeds have germinated. This will help you decide whether you want to replace them with a new packet.

#3: Understand what temperature each seed needs to germinate well.

Soil temperature is one of the most critical factors in determining whether your seeds germinate evenly. If the soil is too warm, cool weather vegetables like lettuce may not germinate at all.

If the temperature is too cold, pepper and tomato seeds may take up to three weeks or more to germinate. (Happened to me!)

You likely already know that some vegetable plants prefer the cooler temperatures of spring and fall and others thrive in the long, hot days of summer.

Seeds also have their ideal temperatures, and during seed starting season it has more to do with the temperature of the soil you’re starting them in as opposed to what the weather is like outside.

The vegetables we often think of in spring, like onions, lettuce, and kale, like cooler soil temperatures for germination. Their optimal temperature is 65-70 degrees F. 

In contrast, pepper, tomato, and eggplant seeds prefer warmer soil temperatures of 85 degrees F.

It’s usually not a problem to provide seeds with cooler temperatures during the seed starting process since most of our homes will be on the chillier side in late winter.

But, if you’re starting cool weather seeds in an unheated greenhouse outside in cold weather, or in a basement that’s damp and cold, you might want to think about providing some supplemental heat. (We’ll talk about that below.)

In general, I’ve never had much of a problem getting my onions, kale, lettuce, broccoli and other spring planted vegetables to evenly germinate in my living room or office without any extra heat.

It’s the other end of the spectrum where you’re more likely to experience problems. Peppers, tomatoes, and eggplant can be the most tricky seeds to coax into germination because they like it hot!

If you want to track your soil temperature more closely you can purchase a soil thermometer.

This chart lists the optimal soil temperature for each vegetable.

#4 – Provide consistent heat.

As I wrote above, at my house most of my seeds germinate just fine on my seedling rack in the ambient temperature of my home.

But, I have had difficulty getting peppers and eggplant to germinate in the past since they prefer such high soil temperatures.

Without supplemental heat, you might have spotty pepper germination. Over the years I’ve had the best success with using either a seedling heat mat underneath newly planted seeds or an electric soil warming cable buried in the soil of the tray.

After observing how much better my pepper, eggplant, and tomato germination is with extra heat I would never plant these seeds without using one of those two tools.

In the past, peppers especially would sometimes take up to three weeks to germinate! With a supplemental heat source, they often germinate in less than 10 days.

Don’t use this mat with seeds like lettuce or onions because you may make the soil too hot for them to germinate well. (Been there, done that…)

If you’re feeling like you want some extra guidance with seed starting, my how-to video series, Super Easy Seed Starting, walks you through the entire process of starting seeds from start to finish. You’ll avoid lots of mistakes and have a fun and successful experience!

#5 – Provide consistent moisture.

Besides warmth, seeds also need consistent moisture in order to germinate properly.  If you allow the soil to dry out after planting your seeds you could delay or even prevent germination.

Over the years I’ve found that using a “germination chamber” greatly increases the humidity around my seedlings and ensures even and successful germination.

What is a germination chamber?

It’s pretty fancy… it’s a plastic bag! After seeding and watering my containers or pots, I slide them into a plastic bag and seal it shut. 

My seedling rack is in front of a south-facing window, so I place the flat on the rack so it picks up some heat from the sun.

You can see in the photo above that there is a lot of moisture built up in the bag. I usually don’t have to water the soil again until after the seeds have germinated.

Warning: You must check your germination chamber frequently.  Once most of the seeds in a tray or pot have “popped” (broken through the soil with the first leaves) you need to take the plants out of the chamber and put them under the lights.

The new seedlings will not be happy being trapped in a plastic bag and will become leggy (tall and spindly) quickly.

When you take the time to understand the needs of the seeds you’re planting at home you can greatly increase your success, and greatly decrease the potential frustration that can accompany the seed starting process.  

Starting seeds at home can be an extremely exciting and enjoyable part of your gardening experience. After ordering seeds from various catalogues, setting up your seed starting rack and lights, and gathering all of your supplies, it’s time to finally plant.

When you first break open those seeds packets it feels like a miracle to hold tiny, new seeds in your hands. And it’s exciting to imagine the day when they’ll grow big enough to provide you and your family with harvests of beautiful vegetables.

Growing your own food from seed is quite an amazing process!

Unfortunately, it can also be frustrating when you have trouble getting those stubborn seeds to germinate into the plants that will eventually provide you with the food you’re so eagerly anticipating.

If you’ve been foiled by your seeds in the past because you don’t quite understand how to germinate seeds evenly and quickly, I have good news!

There are a few simple tricks you can incorporate into your seed starting process that will help you increase your success rate and avoid seed starting disappointments.

Let’s get started in learning five tips for how to germinate seeds successfully every time.

Using the appearance of the coleorhiza and root emergence as indicators, germination was monitored over a 46-h period of the seedling development (Figure ). Caryopsis covering structures, i.e., seed coat and fruit coat, were disrupted at 6 h after imbibition (HAI) in most of the seeds (Figure A). In the majority of the seeds, the coleorhiza appeared at 8 HAI, while at 10 HAI, almost all of the seeds had a coleorhiza that was already visible.

The primary root emergence and coleoptile growth were the next steps in the Brachypodium seedling development. Primary roots appeared at 20 HAI (Figure A) in some seedlings, while at 24 HAI, almost all of the seedlings had visible roots. The measurements of the embryo length during germination and growth at various time points are presented in FigureB. The embryo size in dry seeds was estimated to be approx. 0.2 cm in length. During the first 16 h of imbibition, the size of the Brachypodium embryo increased only slightly. Intense embryo growth began at 18 HAI, and at 24 HAI, the Brachypodium embryos had doubled their length.

Brachypodium distachyon (Brachypodium) grains at key time points of imbibition (A) and the progress of Brachypodium embryo size growth during 46 h of imbibition (B), data are means ± SE. Abbreviations: Cr—coleorhiza, R—radicle, Cl—coleoptile. Scale bar represents 1 mm.

Active growth in the embryo, other than swelling resulting from imbibition, usually begins with the emergence of the primary root, known as the radicle, from the seed, although in some species (e.g., the coconut) the shoot, or plumule, emerges first. Early growth is dependent mainly upon cell expansion, but within a short time cell division begins in the radicle and young shoot, and thereafter growth and further organ formation (organogenesis) are based upon the usual combination of increase in cell number and enlargement of individual cells.

Until it becomes nutritionally self-supporting, the seedling depends upon reserves provided by the parent sporophyte. In angiosperms these reserves are found in the endosperm, in residual tissues of the ovule, or in the body of the embryo, usually in the cotyledons. In gymnosperms food materials are contained mainly in the female gametophyte.

Since reserve materials are partly in insoluble form—as starch grains, protein granules, lipid droplets, and the like—much of the early metabolism of the seedling is concerned with mobilizing these materials and delivering, or translocating, the products to active areas. Reserves outside the embryo are digested by enzymes secreted by the embryo and, in some instances, also by special cells of the endosperm.

In some seeds (e.g., castor beans) absorption of nutrients from reserves is through the cotyledons, which later expand in the light to become the first organs active in photosynthesis. When the reserves are stored in the cotyledons themselves, these organs may shrink after germination and die or develop chlorophyll and become photosynthetic.

Environmental factors play an important part not only in determining the orientation of the seedling during its establishment as a rooted plant but also in controlling some aspects of its development. The response of the seedling to gravity is important. The radicle, which normally grows downward into the soil, is said to be positively geotropic.

The young shoot, or plumule, is said to be negatively geotropic because it moves away from the soil; it rises by the extension of either the hypocotyl, the region between the radicle and the cotyledons, or the epicotyl, the segment above the level of the cotyledons. If the hypocotyl is extended, the cotyledons are carried out of the soil. If the epicotyl elongates, the cotyledons remain in the soil.

Light affects both the orientation of the seedling and its form. When a seed germinates below the soil surface, the plumule may emerge bent over, thus protecting its delicate tip, only to straighten out when exposed to light (the curvature is retained if the shoot emerges into darkness). Correspondingly, the young leaves of the plumule in such plants as the bean do not expand and become green except after exposure to light. These adaptative responses are known to be governed by reactions in which the light-sensitive pigment phytochrome plays a part.

In most seedlings, the shoot shows a strong attraction to light, or a positive phototropism, which is most evident when the source of light is from one direction. Combined with the response to gravity, this positive phototropism maximizes the likelihood that the aerial parts of the plant will reach the environment most favourable for photosynthesis.

Dormancy is brief for some seeds—for example, those of certain short-lived annual plants. After dispersal and under appropriate environmental conditions, such as suitable temperature and access to water and oxygen, the seed germinates, and the embryo resumes growth.

The seeds of many species do not germinate immediately after exposure to conditions generally favourable for plant growth but require a “breaking” of dormancy, which may be associated with change in the seed coats or with the state of the embryo itself. Commonly, the embryo has no innate dormancy and will develop after the seed coat is removed or sufficiently damaged to allow water to enter.

Germination in such cases depends upon rotting or abrasion of the seed coat in the gut of an animal or in the soil. Inhibitors of germination must be either leached away by water or the tissues containing them destroyed before germination can occur. Mechanical restriction of the growth of the embryo is common only in species that have thick, tough seed coats. Germination then depends upon weakening of the coat by abrasion or decomposition.

In many seeds the embryo cannot germinate even under suitable conditions until a certain period of time has lapsed. The time may be required for continued embryonic development in the seed or for some necessary finishing process—known as afterripening—the nature of which remains obscure.

The seeds of many plants that endure cold winters will not germinate unless they experience a period of low temperature, usually somewhat above freezing. Otherwise, germination fails or is much delayed, with the early growth of the seedling often abnormal. (This response of seeds to chilling has a parallel in the temperature control of dormancy in buds.) In some species, germination is promoted by exposure to light of appropriate wavelengths.

In others, light inhibits germination. For the seeds of certain plants, germination is promoted by red light and inhibited by light of longer wavelength, in the “far red” range of the spectrum. The precise significance of this response is as yet unknown, but it may be a means of adjusting germination time to the season of the year or of detecting the depth of the seed in the soil. Light sensitivity and temperature requirements often interact, the light requirement being entirely lost at certain temperatures.

germination, the sprouting of a seed, spore, or other reproductive body, usually after a period of dormancy. The absorption of water, the passage of time, chilling, warming, oxygen availability, and light exposure may all operate in initiating the process.

In the process of seed germination, water is absorbed by the embryo, which results in the rehydration and expansion of the cells. Shortly after the beginning of water uptake, or imbibition, the rate of respiration increases, and various metabolic processes, suspended or much reduced during dormancy, resume. These events are associated with structural changes in the organelles (membranous bodies concerned with metabolism), in the cells of the embryo.

Germination sometimes occurs early in the development process; the mangrove (Rhizophora) embryo develops within the ovule, pushing out a swollen rudimentary root through the still-attached flower. In peas and corn (maize) the cotyledons (seed leaves) remain underground (e.g., hypogeal germination), while in other species (beans, sunflowers, etc.) the hypocotyl (embryonic stem) grows several inches above the ground, carrying the cotyledons into the light, in which they become green and often leaflike (e.g., epigeal germination).