Free Guide to Growing Plants from Seeds

Understanding Seeds and How Plants Grow From Them

Seeds are nature's way of spreading plants to new locations. Inside each seed is an embryo—a tiny plant waiting to grow—along with stored food that helps it survive until it can make its own nutrition through photosynthesis. Understanding what's inside a seed helps you provide the right conditions for growth.

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Seeds vary greatly in size, shape, and structure. A tomato seed is tiny and flat, while a sunflower seed is large and striped. An avocado pit is massive, while an orchid seed is nearly invisible to the naked eye. Despite these differences, all seeds follow the same basic process: they need water, oxygen, and proper temperature to germinate, which is when the embryo wakes up and begins growing roots and shoots.

The germination process typically takes anywhere from a few days to several weeks, depending on the plant species. Cool-season crops like lettuce and spinach germinate within 5-10 days. Warm-season plants like peppers and eggplants may take 2-3 weeks. Some seeds, like those from trees, require months of cold exposure before they'll sprout—a process called stratification that mimics winter conditions.

Different plants have different dormancy requirements. A tomato seed will sprout quickly in warm soil, but a peony seed needs a cold period before it's ready to grow. This is why some seeds need to be stored in a refrigerator before planting. Reading seed packets carefully tells you what each plant requires for successful germination.

Practical Takeaway: Before you buy seeds, research the specific plant's germination needs. Check the seed packet for information about how long germination typically takes and what temperature range works best. This knowledge helps you choose appropriate seeds for your climate and available space.

Selecting Seeds and Reading Seed Packets

Quality seeds are the foundation of successful gardening. When selecting seeds, you have several options: buying from garden centers, ordering from seed catalogs, or collecting seeds from existing plants. Each option has advantages. Garden center seeds are convenient and immediate. Seed catalogs offer wider variety and detailed descriptions. Saved seeds from your own plants cost nothing but require knowledge about which plants produce viable seeds.

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Seed packets contain valuable information that guides your planting decisions. The front typically shows a picture of the mature plant and variety name. The back includes germination time (how many days until sprouting), days to maturity (how long until harvest or bloom), temperature requirements, light preferences, and planting depth. Some packets note whether seeds need stratification, light for germination, or soaking before planting.

Look for the date on the packet. Seeds have different lifespans depending on the plant type. Lettuce and onion seeds typically last 3-4 years. Tomato and cabbage seeds last 4-5 years. Peppers and beans last 3-4 years. Asparagus seeds last only 2-3 years. Seeds stored in cool, dry conditions last longer than those stored in warm, humid environments. Seeds purchased from the current year are most likely to germinate successfully.

Seed companies typically provide germination rates on their packets—the percentage of seeds expected to sprout under ideal conditions. A 95% germination rate is excellent. An 80% rate is still acceptable but means you might plant more seeds than you need to account for potential failures. Starting with more seeds than needed gives you a safety margin in case some don't germinate.

Practical Takeaway: Always read the entire seed packet before planting. Write the planting date and expected germination time on your calendar or keep the packet in a garden journal. This helps you monitor progress and know when to expect sprouts.

Preparing Your Growing Environment and Materials

Seeds need the right environment to germinate and develop into healthy seedlings. Three essential factors are moisture, temperature, and air circulation. Creating the proper conditions doesn't require expensive equipment—many gardeners start seeds successfully using household items and basic materials.

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Seed-starting medium is different from regular garden soil. Garden soil is too dense and heavy for seedlings; it compacts around delicate roots and can harbor diseases. Seed-starting mix is light and fluffy, usually made from combinations of peat moss, coconut coir, perlite, and vermiculite. This mix drains well while retaining enough moisture for germination. You can purchase pre-made mixes or make your own by combining equal parts peat moss (or coir), perlite, and vermiculite.

Containers for starting seeds range from seed trays and peat pots to recycled items like yogurt cups, egg cartons, and toilet paper tubes. The only requirements are that containers have drainage holes (or you poke them in) and are clean. Dirty containers can harbor fungal spores that cause damping off, a disease that kills seedlings at soil level. Wash reused containers with hot soapy water before filling them with fresh seed-starting mix.

Temperature control is crucial for germination. Most vegetable and flower seeds germinate best in soil temperatures of 65-75°F (18-24°C). Warm-season crops like peppers, eggplants, and basil prefer temperatures around 70-80°F (21-27°C). Cool-season crops like lettuce, cabbage, and spinach prefer 60-70°F (15-21°C). In cold climates, placing seed trays on top of a refrigerator or using a heat mat under the containers maintains proper temperature. In warm climates, simply placing trays in a warm location works well.

Light becomes important once seedlings sprout. Seedlings need 14-16 hours of bright light daily to grow stocky and strong. A south-facing window provides natural light, but seedlings in north or east-facing windows may become leggy and weak. Fluorescent shop lights positioned 2-3 inches above seedling tops provide excellent growth. LED grow lights work even better and use less electricity. Rotate trays under lights regularly so all seedlings receive equal light exposure.

Practical Takeaway: Start with what you have available. A clean jar with seed-starting mix, placed on a sunny windowsill, successfully starts many plants. Invest in grow lights only if you're starting large quantities of seeds or your windows don't provide adequate natural light.

Planting Seeds and Managing Moisture

Proper planting depth is critical for seed germination. A general rule is to plant seeds at a depth equal to two to three times their thickness. Tiny seeds like petunias and snapdragons are barely covered with soil or pressed lightly onto the surface—light is needed for their germination. Small seeds like tomatoes and lettuce are planted about 1/4 inch deep. Medium seeds like beans and corn go 1/2 to 1 inch deep. Large seeds like squash and melon seeds are planted 1 to 1.5 inches deep.

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To plant seeds, fill your container with moist seed-starting mix. Gently press down without compacting. Make shallow holes or furrows at the correct depth using your finger, a pencil, or the seed packet's edge. Place seeds in the holes and cover gently with mix. Press the soil lightly to ensure seed-to-soil contact, which is essential for proper moisture absorption. Water gently with a fine spray or by placing the container in a larger container of water and letting the mix absorb moisture from below.

Moisture management is the most common mistake beginners make. Seeds need consistent moisture but not waterlogged soil. Soggy conditions promote rot and fungal disease. Overly dry conditions prevent germination. The soil should feel like a wrung-out sponge—moist but not dripping wet. Check soil moisture daily by touching it with your finger. Water when the top feels dry, using a spray bottle or fine mister to avoid disturbing seeds.

Many gardeners cover seed trays with plastic domes or plastic wrap to maintain humidity during germination. This is especially helpful in dry climates or heated homes. Once seedlings emerge, remove the cover immediately. Too much humidity after germination encourages damping off and mold growth. Provide good air circulation by running a small fan on low speed near seedlings for a few hours each day.

Labels are crucial. Within days, you may not remember which container holds tomatoes and which holds peppers. Write the plant type, variety, and planting date on waterproof