How to Grow Plants from Seeds

Choose Seeds Carefully. Garden stores often recommend seed varieties that are easy to grow in your local climate and the right season. Excellent vegetable choices for beginner gardeners include: green beans, lettuce, and basil. Sunflowers, dragonfly chrysanthemums, and poppies are some of the easiest flowers to grow from seeds.

• Fresh seeds tend to have a higher germination rate than older ones.
• Collecting seeds from your own plants or fruits can be risky but fun. Due to cross-pollination or grafting (joining a branch from one plant to the root of another), the new plants may not resemble the parent plant.

Determine the Right Planting Time. In most cases, it's best to start sowing seeds indoors. However, this can vary depending on the type of plant. For example, lettuce and green beans grow better when directly sowed in outdoor soil. You can plant them before the last spring frost. Cold-hardy plants can be planted outdoors at the end of winter or early spring. Plants that thrive in warm weather require a later sowing time (mid to late spring) so they are ready to go outside once the weather warms up.

• Typically, it takes about three to six weeks for seeds to germinate, grow into healthy plants, and be ready for outdoor transplanting, but some plants may take up to 15 weeks.

Select a Seed Tray. Outdoor seeds are more vulnerable to pests and harsh weather, so the survival rate is often higher when seedlings are cared for indoors. While seed trays from garden stores are convenient, small containers with drainage holes will also work well.

• Before reusing old containers, thoroughly wash them with soap and water. Soak the containers in a solution of one part bleach and nine parts hot water, then allow them to dry. This step helps eliminate harmful microorganisms that could affect the seeds.
• Certain plants like lettuce, cucumbers, watermelon, and sunflowers can be damaged if their roots are disturbed. Instead, sow these plants outdoors after the last spring frost, or sow each seed in a separate compartment of a seed tray and transplant the entire clump of soil when planting outside.

Mix Seed-Starting Soil. Making your own soil mix is simple and much more cost-effective than buying pre-made soil. Combine perlite, vermiculite, and coconut coir (or peat moss) in equal parts. This mixture is light and drains quickly, preventing root rot and allowing plant shoots to emerge from the soil. Moisten the seed-starting mix and fill the tray, leaving about 0.6 cm from the top. Use a clean tool to press the soil down firmly and level it. Allow excess water to drain before moving to the next step.

• If using store-bought soil, check if it contains compost. If so, you won’t need to fertilize the seedlings. (Don’t add extra compost to your homemade mix for the first planting – this could create more problems than benefits.)
• If you use peat moss instead of coconut coir, add some hot water to make it easier to mix. Since peat moss is acidic, you can balance the pH by adding lime (calcium carbonate) to the garden. Try mixing ¼ teaspoon of lime for every 4 liters of soil mixture.

Sow the Seeds. If the seed-starting mix is dry, water it lightly before sowing. Follow the instructions on the seed packet for the correct spacing and depth, or follow these general guidelines:

• Single Tray, One Type of Seed: Spread the seeds evenly across the tray.
• Single Tray, Multiple Seed Types: Use a clean ruler to mark rows spaced 2.5–5 cm apart. Drop the seeds of each type into separate rows and label each row.
• Individual Pots or Seed Trays with Holes: Sow one large seed (like cucumber or watermelon) or two smaller seeds (like most sunflower seeds) in each pot.

Cover Seeds According to Their Size. The rule of thumb is to plant seeds at a depth twice their diameter. Most tiny seeds need light to germinate, including plants like lobelia, lettuce, and snapdragons. Simply sprinkle these seeds on the soil surface.

• Dry vermiculite or crushed sphagnum moss (not peat moss) is ideal for covering seeds, but you can also use your seed-starting mix as a substitute.
• Lightly cover the seeds with soil. If you pack the soil too tightly, the plant shoots may have difficulty breaking through the compacted surface.

Seal in moisture using plastic wrap. Seeds are highly sensitive to either excessive or insufficient moisture. Covering the soil with a layer of plastic wrap or a plastic bag will help retain moisture until the seeds sprout.

• Most seed trays sold at garden centers come with plastic wrap to help retain moisture inside. If not, you can create a tiny greenhouse effect by covering the tray or using an old fish tank and sealing it with a lid.

Place the seed tray in a warm area with indirect sunlight. If there are no specific temperature instructions on the seed packet, aim to keep daytime temperatures around 18-24ºC, and no lower than 13ºC at night. If the room temperature is lower than this range, you can place a heat mat underneath the seed tray. Most seeds thrive with plenty of light, but avoid direct sunlight if the tray is covered in plastic.

• Some seeds, like tomato, impatiens, calendula, and cilantro, germinate best in darkness. You can block light using black plastic wrap or cardboard.
• If you want to increase your chances of success, research the specific temperature for the plant variety you're growing. However, be aware that some seeds might fail due to unfavorable temperatures or take longer to germinate.

Check moisture daily or every other day. If the soil mixture looks dry, place the seed tray in another tray of water. The soil will absorb moisture from the bottom of the seed tray. This method is safer than watering from above, as it prevents seeds from washing away or being oversaturated.

• As mentioned earlier, plastic wrap is sufficient to maintain moisture during the germination period. This step is just an additional measure to support it.

Remove the plastic wrap after the seeds have sprouted. Most seeds sprout within about two weeks. Once the seedlings appear above the soil, you should remove the plastic covering (if used).

• If you planted multiple rows of seeds in one tray, consider cutting strips of plastic or fabric to cover the rows that haven't sprouted yet.

Expose the seedlings to strong light after germination. Move the tray to a south-facing window (north if you're in the southern hemisphere) where it can receive ample light. If the light and temperature conditions at the windowsill are significantly different from the previous spot, gradually increase the light intensity. Sudden changes may harm the seedlings.

• If it's quite cold outside, consider placing a heat mat between the tray and the window to prevent cold air from slowing the seedling growth.
• For regions at high latitudes that receive little sunlight, hang grow lights about 15 cm above the seedlings and keep them on for 14-16 hours daily. Move the light higher as the seedlings grow to avoid burning them.

Rotate the plants daily. Plants often grow towards sunlight. If light only comes through the window, seedlings will lean towards it, causing weak and elongated growth. Rotate the tray by a quarter each day to ensure even growth.

Maintain a stable temperature. Unless specified otherwise on the seed packet, keep the daytime temperature between 18–24ºC and not lower than 13ºC at night. Extreme temperatures can stunt the growth, leading to weak and spindly stems.

Water regularly. Keep the soil moist, but not waterlogged, as excessive moisture can rot the fragile roots or suffocate them (not allowing oxygen absorption). Using a water tray under the plant pot is ideal, as it allows water to be absorbed from below, avoiding the risks of top watering.

• Seeds will die quickly if they dry out during the germination phase. Check the moisture at least once a day.

Fertilize once the first true leaves appear. The initial pair of leaves is called cotyledons, and the second pair are the first "true leaves" which indicate the plant is ready for real growth. Dilute balanced fertilizer to one-quarter of the recommended strength and pour into a wide tray, allowing the soil to absorb it from the bottom. Apply weekly or as directed on the packet.

• If using pre-fertilized soil, additional fertilizer isn't needed. Too much fertilizer can cause 'burning' or other issues.
• You can increase the fertilizer concentration to half once the seedlings are transferred to larger pots, and use full strength once they are fully grown.

Transplant seedlings into separate pots. If you have multiple seedlings in one tray, they may need to be moved to larger pots to avoid overcrowding. However, not all seeds require transplanting; this depends on the type of plant. Wait until the seedlings are strong enough to handle being moved. Typically, gardeners only transplant the healthiest seedlings. You can discard weaker ones or use them as compost. Here's how to do it:

• Wash the new pots with soapy water and rinse thoroughly.
• Fill the new pot with damp soil at room temperature and dig a hole that fits the seedling's root system.
• Use a popsicle stick or a thin object to loosen the soil around the seedling's roots.
• Gently grab the top leaves and lift the seedling. Do not hold the stem.
• Place the seedling in the hole and, if necessary, use a pencil to spread the roots slightly. Don’t worry if it doesn’t look perfect.
• Add damp soil around the roots until the seedling is at the same depth as before. Gently press the soil down.
• Avoid sudden changes in temperature and light for at least the first few days while the seedling recovers.

Harden off the seedlings. This process involves gradually acclimating your seedlings to fluctuating temperatures and outdoor weather conditions so they won’t go into shock when moved outside. Start this process ahead of the outdoor transplanting day:

• Lower the indoor temperature slightly.
• Water less frequently, but avoid letting the plants dry out.
• Bring the seedlings outside for one or two hours daily, placing them in shaded, sheltered areas. Avoid temperatures below 7ºC.
• Increase the outdoor exposure by about an hour each day, gradually introducing them to sunlight. (The level of sunlight exposure depends on the plant type and where it will be moved.)

Move the seedlings outdoors. Once the weather is warm and the seedlings can handle a full day outside, you can either transplant them into their permanent pots or into the ground. Follow the specific care instructions for each plant as their temperature and light needs vary. The following are general tips:

• If possible, transplant in the morning when there is no direct sun and little wind.
• Moisten the soil both in the pots and the new planting holes.
• Carefully transfer the root ball into the new hole, spreading the roots as much as possible without damaging them.
• Fill in with soil to ensure the plant is buried at the same depth as before.
• Water generously to ensure the soil is in good contact with the plant’s roots.

Maintain the plants. Moving plants is quite stressful for them, and it may take a few weeks for them to establish roots in their new location. After the first watering, make sure to keep the plant adequately moist but not waterlogged. Protect the plant from heavy rain and strong winds until it can handle these conditions on its own and grow healthy.

Prevent fungal infections in seedlings. Newly sprouted seedlings are very prone to fungal diseases, to the extent that this phenomenon is often referred to as "damping off." Try reseeding and follow these preventive measures to stop fungal spores from landing and growing:

• Sterilize the soil and clean all trays, pots, and gardening tools with a mixture of one part household bleach and one part water.
• Sprinkle vermiculite or perlite on the surface of the pots after planting.
• Avoid wet and cool conditions. If you squeeze a handful of soil and see water seeping out, it’s too wet.
• For best results, treat the soil with antifungal agents and follow the instructions on the packaging.

Understand why seeds might not germinate. Many types of seeds, including citrus and apple, require special treatment to encourage germination. To get the best results, follow the instructions specific to each plant species. Most of these plants need one or two of the following treatments:

• Scarification: Hard-shelled seeds may need to have their shells removed or thinned. You can try filing them with a nail file or scoring them with a knife. Alternatively, you can boil some hard seeds to soften the shells.
• Stratification (the process of moist-cold treatment): In nature, many seeds lie on the ground through winter and germinate in the spring. A few weeks in a cold, moist environment, mimicking this condition, will tell the seed it’s time to germinate. Try placing seeds between two damp paper towels, putting them in a plastic bag, and storing them in the fridge.