Plant Seeds: Types, Germination & Growing

What Are Seeds?

A seed is an embryonic plant enclosed in a protective outer covering, along with a food supply. Seeds are the primary method of reproduction for most flowering plants (angiosperms) and gymnosperms. They range from dust-like orchid seeds weighing fractions of a milligram to coconut seeds weighing several kilograms.

Every seed contains three key components: the embryo (the baby plant), the endosperm (stored nutrients to fuel initial growth), and the seed coat (a protective outer layer). Understanding these components helps explain why different seeds have different germination requirements.

Seed Types

Seeds are broadly classified by the plants they produce. Monocot seeds like grasses, palms, and orchids have a single seed leaf (cotyledon). Dicot seeds — which include most houseplants, vegetables, and flowering plants — have two seed leaves. This distinction affects how the seedling emerges and what early care it needs.

Seeds also vary by their dormancy requirements. Some germinate immediately when conditions are right. Others need cold stratification (a period of cold to simulate winter), scarification (physical abrasion of the seed coat), or specific light conditions before they will sprout.

How Germination Works

Germination begins when a seed absorbs water (imbibition), causing it to swell and break through its seed coat. The radicle (embryonic root) emerges first, anchoring the seedling and beginning to absorb nutrients. The shoot then pushes upward toward light.

Three factors control germination: water, temperature, and oxygen. Most seeds germinate best between 65–75°F (18–24°C) in consistently moist but not waterlogged soil. Some seeds also require light to germinate (lettuce, petunias), while others need darkness (calendula, phlox).

Growing Plants from Seed

Starting plants from seed is the most economical way to grow a garden or expand a houseplant collection. The basic process: fill containers with sterile seed-starting mix, sow seeds at the depth recommended on the packet (a general rule is 2–3 times the seed diameter), keep the soil consistently moist, and provide warmth and light.

Common mistakes include planting seeds too deep, letting the soil dry out during germination, overwatering (which causes damping off — a fungal disease that kills seedlings), and insufficient light after sprouting. Seedlings need 12–16 hours of bright light daily once they emerge.

Seed Viability & Storage

Seeds don't last forever. Most vegetable and flower seeds remain viable for 2–5 years if stored properly. Onion and parsley seeds lose viability after just one year, while tomato and cucumber seeds can last 5+ years. The key to long seed storage: keep them cool, dry, and dark. An airtight container in the refrigerator is ideal.

To test if old seeds are still viable, place 10 seeds on a damp paper towel, fold it into a bag, and keep it warm for 7–10 days. Count how many sprout — if 7 out of 10 germinate, the batch is 70% viable and still usable (just sow more densely to compensate).

Common Seed Problems

When seeds fail to germinate, the most common causes are old or improperly stored seed, incorrect temperature, planting too deep, soil that is too wet or too dry, or a dormancy requirement that wasn't met. If seedlings emerge but then collapse at the soil line, the likely culprit is damping off — improve air circulation and reduce watering.

Once seedlings are established, they can develop the same problems as mature plants: yellow leaves from nutrient deficiency, leggy growth from insufficient light, or pest issues. Our diagnosis tool and plant guides can help with these later-stage problems.