The first year after a seed sprouts may bring drought, predation, flood, uprooting, fire, lawnmowers, herbicides, and the gloved hand of humans. With each passing year, it is a requirement that some seedlings fail. Each species has its required space. In the Mojave Desert, creosote bushes secrete a substance that inhibits any other creosote bush from growing within a precise perimeter. This results in both sufficient water for each bush to mature and make seeds and it also produces an eerie regularity to the landscape.
In contrast, “weed” trees like poplars grow neck in neck. It may take twenty years for the strongest trees to muscle out the weaklings. In the meantime, fire, browsing and other hazards will make the abundance of seedlings seem wise. A fifty-year-old poplar is rare.
Each plant’s life is determined by an interwoven set of circumstances. There is no, “in general”, when it comes to seed to seedling and seedling to mature plant ratio. All plants are genetically programmed to produce offspring. That one plant needs three weeks to make seed while another needs twenty years is often reflected in their structural character. We can get to know what to expect from a given species if we know it as an individual. Take an oak for instance. Place a red oak from Maine next to a canyon oak from California and the difference will be startling. Look at a red oak atop a ledge in Crawford Notch and one in the deep glacial till of coastal Maine and except for bud and leaf the contrast will be great. If you live near an oak, or any other large old tree, you will come to know it as more than its species name. If you are fortunate to watch a tree grow old, it will grow into you. In this way, there will be no other tree like it. This is one of the opportunities of the gardener.
We say that someone who lives where their family has lived for many generations has deep roots; someone who wanders has shallow roots. The origin of these metaphors is in the plants around us. Plant a deep-rooted tree such as an oak or maple, and you make a commitment to the future, an immovable object, a sentinel. When I plant a deep-rooted tree, I see the future giant in the sapling. Planting thyme, sedums, dianthus is done lightly, experimentally. Hens and chicks can be moved almost daily; they are the doodles of the cultivated plant world.