Plants That Have Seeds With Hard Outer Layers

Seeds are composed of three main parts: the seed coat, the endosperm and the embryo. The function of the seed coat, or outer layer, is to protect the other parts of the seed during dormancy. Because some seeds need just the right conditions to germinate, their outer coats may be a little tougher than others. In order to break the seed's dormancy and encourage it to germinate, the gardener performs a process known as "scarification," or breaking through the hard, outer seed coat so that water can penetrate. This can be accomplished in a number of ways, most commonly with either a hot water soak, or mechanically, with the use of a razor blade, sandpaper or baby nail clippers.

Baptisia australis

Commonly known as blue false indigo, this flowering perennial makes a striking statement in the garden. With a bushy, rounded growth, it blooms with tall spikes of flowers in shades of deep blue and purple. It is drought and heat-tolerant and is hardy to USDA zones 3 to 10. Baptisia australis seeds have a very hard coat and should be either mechanically scarified, or placed in a bowl of hot water (180 degrees F) and allowed to soak overnight, prior to planting.

Callirhoe bushii

Bush's poppy mallow, native to the United States, is a wildflower that grows 2 to 3 feet tall with bright red flowers. This plant grows best in full sun and is hardy to USDA zones 3 to 9. The small, bean-shaped seed of this mallow is covered by a tough, hard seed jacket, which can be scarified by rubbing the seed gently between two pieces of sandpaper.


The seeds of the canna plant have an extremely hard seed coat that water cannot penetrate. In order to germinate the seeds, they will need to be scarified mechanically. Using a razor blade or small nail clippers, remove just a tiny piece of the outer layer of the seed. You will know the seed coat has been penetrated when you can see the white of the embryo. Once the seed is scarified the plant is easy to grow and will add a dramatic, tropical flair to your garden. Canna is hardy to USDA zones 4b to 11.

Keywords: seeds with hard outer layers, seeds that need to be scarified, seed germination

About this Author

Victoria Hunter, a former broadcaster and real estate agent, has provided audio and written services to both small businesses and large corporations. Hunter is a freelance writer specializing in the real estate industry. She devotes her spare time to her other passions: gardening and cooking. Hunter holds a Bachelor of Arts in English/creative writing.