Chip O’Leary is the Deputy Director of Resource Management for the Forest Preserves of Cook County.
Why is seed so important in restoration?
Seeds are of course the next generation of plants. For natural areas that are degraded, the first indication is a reduction in native plant diversity and cover. Some plants can shrink back and hold out until conditions improve. For example, wild lupine can live 30 years or more. However for most plants, this is not an especially long time. Annuals and biennials have particularly short life spans, but a typical non-woody plant lives only 5-7 years. Because of this, the recovery of natural populations of plants often relies on the availability of seed to re-establish.
What do you mean by “Native Seed Bank”? How do you know if a newly restored site has a sufficient native seed bank?
Although LaMarck was wrong and we can’t expect spontaneous generation of native plants, plants have many strategies to overcome bad times and persist. The most effective strategy is a very high production of seeds, many that remain intact in the soil for extended periods of time. Locally, we see plants in wet soils persist longer than those in drier soils. When good growing conditions are restored to a natural area, some native plants simply appear. These are the “stored” seeds in the soil that finally have an opportunity to germinate and grow. These stored seeds are referred to as a seed bank. Predicting the presence of a seed bank is a tricky business but it can be a very inexpensive and beneficial way to restore natural populations. We know there is a good chance for a healthy seed bank when restoration happens within a decade of degradation. After that, it becomes harder to predict. There have been amazing successes and failures gambling on a seed bank for periods longer than 20 years. One way to hedge bets is to restore around small intact pockets – that way if the seed bank isn’t great, there is the opportunity for expansion from the intact areas. This is the classic technique used by stewards over the years that has proven effective. For areas with little or no seed bank, a plan B for seed material is essential, which may include predictive seed collection.
How does a plant normally disperse their seeds?
Like anything in the natural world, seeds are subject to predation and circumstance. Most plants produce a large crop of seeds each year to account for those eaten by birds, mammals, and insects as well as those seeds that fall in bad growing locations. As an alternative strategy, plants employ a wide range of dispersal mechanisms. Some encase their seeds in a fruity pulp so that seeds are eaten by more mobile animals and are then deposited (after digestion) in a new location. Some wetland plant seeds float – they are carried away by current or wave action to new locations. Others hitch a ride on fur (or clothing), such as the ever-annoying tick-seeds and nettles. Some are light and have a fluffy case that encourages floating through the air – think of the cottonwood seeds that have been netted out of the air from the top of Willis tower.
Do all plants produce seeds in the same way and at the same time?
Plants flower and then go to seed within timeframes unique to each species. The advantages to each are too long to list. For restorationists, locating, picking, drying, and planting seeds can be a challenge requiring patience, a sharp eye, and sinuses made of steel. Some species make it nice and easy with seeds clustered in bunches at waist height, showing their ripeness with an easy to detect color, and only allowing easy removal when ripe. Others can be maddeningly difficult to collect – those that ripen differentially or expel seeds shortly after ripening can be especially challenging. Who hasn’t fallen for the porcupine grass’ easy to find and pick seeds in the afternoon, only to discover a Gordian knot the next morning? Slowly and through trial, error, and ingenuity, native plant seed collectors have found ways around each trick, each challenge, and each pitfall. Who can’t appreciate the elegant use of a match to “de-fluff” milkweed seeds?
If a site needs more seed, where do you get more?
For preserves with solid remnant areas, finding seed can be somewhat easy. A location may have a solid seed bank, in which case removing invasives and applying fire may be sufficient. A different location may not have much of a seed bank in places, but a solid remnant area adjacent to it from which to selectively collect and drop seed; a sort of “fill in the blanks” strategy. After that, for locations without the above options, it takes some careful thought and consideration on next steps. A good document that outlines considerations is the Forest Preserves’ Seed Source Policy and Guidelines. This document covers questions to such as how to match species to natural communities, distance from collection site, genetic issues, historic records, documentation, etc.
In more depauperate locations, seed can be obtained from native seed growers. This route can be very effective but must be used with care. The source of seeds can be a challenge to determine. Before taking this step, working with a Forest Preserves ecologist is essential.
Why is it important that a landowner have a seed policy?
The Forest Preserves’ Seed Source Policy and Guidelines (PDF) is an attempt to bring the current science to bear on how to best select seed sources and determine where seed material can be moved to so the resulting restoration is most effective.
What can volunteers do to help?
Many Forest Preserves volunteer sites use seed collection as a strategy for restoration. Using the Forest Preserves’ Seed Policy and Guidelines will help us all stay on the same page and remind us of what we are all trying to achieve. The care taken to collect responsibly will pay off for the next generations of both plants and restorationists. Volunteers interested can tap into locations where this activity is already happening as a way to learn and share knowledge.