Growing your own vegetable garden from seeds is a lot more hands-on than you might initially think. It takes patience, dedication, and the right amount of knowledge to successfully germinate a seed. Luckily, you’re in the right place to find answers.
This article answers some essential questions regarding seed germination. How long does it take for a seed to germinate? What are the most common germination problems? What’s the best way to calculate seed germination rates? So, let’s get started.
What Is Germination?
With plants, germination is the process through which a dormant seed sprouts into a seedling. It’s the initial and most vital stage of plant development, as it determines the plant’s rate of survival and productivity later on.
During the germination process, the seedling undergoes biochemical, physiological, and morphological changes, all of which dictate the plant’s vegetative yield and quality.
In general, plant germination consists of three main stages:
- Phase I: Water imbibition
- Phase II: Metabolism reactivation
- Phase III: Radicle protrusion
Germination begins with imbibition, a term used to describe the uptake of water by the dry seed.
As water stimulates the seed’s embryo, its enzymes and food supplies expand and hydrate. The activation process of water imbibition allows the seed to increase its metabolic activities, so it can produce energy all throughout its growth process.
The second step occurs when the seed is thoroughly hydrated. In the initial stages of metabolic reactivation, the seed’s respiration process goes through an anaerobic phase before turning aerobic as oxygen enters the seed.
The seed then grows a root (radicle protrusion) to access water underground, before shooting upwards towards the sun to begin photomorphogenesis.
Seed Germination – Whole Process
The germination process, in and of itself, is relatively straightforward, although there is a lot of technical vocabulary involved.
At most, it takes one to two weeks for a seed to germinate.
Gibberellins – also known as plant hormones – are produced upon the activation of a dormant seed through water absorption. Reawakening the seed’s metabolic activity also triggers the synthesis of amylase, which then breaks into maltose.
From here, the seed is either polymerized to cellulose (for cell wall formation) or hydrolyzed to glucose (for energy). In both cases, the promotion of cell division and growth is achieved.
Once the seed is fully metabolized, the seed’s outer coat ruptures. Then, slowly, the embryonic root (radicle) begins to protrude into the ground. The root absorbs vital nutrients and minerals from the soil, eventually leading to the growth of a young plant.
Of course, there are several other technical aspects to consider when germinating a seed. Unfortunately, germination doesn’t start merely upon the contact of sufficient soil and water.
To initiate germination, three conditions must be fulfilled:
Germination Temperature
Temperature and the seed’s surrounding environment determine the success of a seed’s germination. If it’s not the right temperature, the seed will remain dormant.
If the temperature is too high, the seed may suffer from heat stress and seed aging. This prevents it from metabolizing. With a temperature that’s too low, the seed won’t respond and will remain dormant. Even if germination was successful, the plant will likely grow weak and yield poor harvests.
For most plants, the ideal germination temperature is between 68ºF (20ºC) and 85ºF (30ºC). However, every seed has its unique germination temperature. For example:
- Asparagus, broccoli, cabbage, cauliflower: 60 to 85°F
- Garlic, onion, parsley: 65 to 85°F
- Corn, cucumber: 65 to 95°F
- Eggplant: 75 to 85°F
- Squash: 85 to 95°F
- Watermelon: 70 to 95°F
The Effect of Moisture on Seed Germination
Another main factor to consider when germinating is the seed’s level of water absorption.
When simulating natural conditions (i.e., manually watering the seed), ensure you don’t overwater or underwater your seed. Keep it damp but not too wet. It should feel moist an inch or half an inch below the soil’s surface.
For best results, water the seed once a day. If you’re using a seed starting tray, cover the container with transparent plastic wrap to keep the soil moist for more extended periods.
Regardless of where you plant your seed, you should store it in soil that has a moisture content above 30% for optimal growth. If the seed’s moisture content falls below the 25% mark, it may lose its viability.
The Effect of Lighting on Seed Germination
Most seeds germinate best with controlled amounts of light. Without sufficient light, seedlings may not sprout from the seeds. However, it isn’t rare to find seeds that germinate in total darkness. Some seeds can even grow in both light and dark environments.
Here are some examples:
Plant Seeds That Need Light to Germinate
- Celery
- Dill
- Lettuce
- Petunia
- Poppies
- Snapdragons
- Geranium
Plant Seeds That Don’t Need Light to Germinate
- Gazania
- Nemesia
- Delphinium
- Calendula
- Schizanthus
Plant Seeds That Germinate With or Without Light
- Celosia
- Cucumber
- Balsam
- Broccoli
- Cabbage
- Pumpkin
- Squash
Seeds that need light shouldn’t be fully covered under the soil, so they can easily access the light they need to support their germination process. Seeds that need darkness should be burrowed deeper into the ground to block out UV rays that stop their germination.
With that said, the light requirements of seeds pre-germination differ from the light requirements of seedlings. Not all seeds need sunlight, but all seedlings do. Without sunlight, seedlings will deteriorate. The amount of light a seedling requires depends on the type of seed you planted.
Germination Rate
Germination rate determines the number of seeds that are likely to germinate over a given period. It’s usually measured in percentages. For example, a 70% germination rate indicates that 7 out of 10 seeds are likely to germinate in appropriate conditions. Usually, anything higher than a 50% success rate is acceptable.
Here is an easy-to-follow guide that we found online, which can help you determine germination rate. After planting, you’ll simply need to calculate the rate at different time intervals.
- Obtain a filter paper and petri dish. If these aren’t available, use a paper towel and a small transparent plastic bag.
- Soak your seeds in water for about an hour.
- Arrange the seeds on the filter paper in the dish.
- Moisten them with several drops of water (about 10 ml).
- Cover the container and place the seeds in a dark environment. If you’re using seeds from different plants, be sure to label them appropriately.
- On a table, record the number of seeds that germinate. Do this every day to determine the germination rate. Typically, it takes no more than one to two weeks for seeds to germinate.
Common Germination Problems
Weeks have passed, and your seeds have yet to germinate. What went wrong? Here are some of the most common germination problems you’re likely to encounter.
Old Seeds
Like produce, seeds have an expiration date. They go bad over time. Seeds stored in good conditions may last anywhere from one to five years. The older the seed, the less likely it’ll germinate.
Incorrect Temperature
As discussed above, different seeds need different temperatures. Summer seeds won’t properly germinate during winter and vice versa.
Check the seed’s packet to determine the proper planting temperature and make sure it’s planted in a suitable condition.
If you’re trying to germinate summer seeds in winter, you should consider using heat mats and/or propagators to raise the soil’s temperature.
Too Much (or Too Little) Water
If you don’t water your seeds enough, they’ll remain dormant. If you overwater them, they’ll drown and rot before they’ve had the chance to germinate.
Before sowing your seeds, moisten them for 8 to 12 hours, but no more than 24 hours. Then, transfer the seeds into a moist environment.
Developing seeds should be watered consistently with a handheld pump sprayer.
Improper Seed Depth
Seed depth requirements directly coincide with light conditions. Some seeds only grow in the presence of light, while others need to be stored in complete darkness. Some plants, like cucumber, broccoli, and pumpkin, are okay with both.
If your seeds require light to germinate, simply press them into your soil rather than digging them down. If they don’t need light, burrow them deeply. Read the seed packets for depth information.
Good Tips For Germination
To improve seed germination and increase your chance of success, check out the following tips and tricks:
- Soak your seeds before planting.
- Avoid overcrowding by planting your seeds in broad, flat containers.
- Prevent fungal infections by adding a drainage system to the seed pots.
- Regularly turn the seedings to keep their stems strong.
- Gradually acclimate the seedlings to direct sunlight over a three-day period to avoid environmental shock.
- Encourage germination by placing the seeds in a warm environment.
- Evenly incorporate a seed-starting mix into the soil using a kitchen sieve.
- Plant your seeds in sterile or pasteurized soil.
- Aerate the ground with a garden fork to promote airflow.
- Store your seeds in an airtight container for later use.
Conclusion
Usually, seeds germinate anywhere between one to two weeks, with some taking up to three weeks at most.
To successfully germinate your seeds, make sure they’re placed in optimal growing environments. If your germination rate is below 50% despite appropriate conditions, consider changing your seed sources.
Good luck, and happy gardening!