Ecology lessons from the vegetable garden?

The strawberry patch, taken over by weeds

Lesson: No matter how many weeds you pull from the vegetable garden, you never exhaust the supply of weeds.

  • As long as there is bare soil (an empty niche as a result of disturbance), weeds will recruit. There are always more seeds - probably hundreds per cubic inch.
  • To fill a niche so weeds don't recruit, a robust desired plant needs to be occupying that niche.

A lot of my work is in invasive plant removal-- as a component of ecological restoration. What lessons are my garden teaching me that might apply to my work? Perhaps, that the supply of invasive plant seeds will never go away. That the only way to really "remove" invasives from the landscape is to prevent their recruitment, by:

  • Having the niche already filled by robust (i.e. not decimated by deer) native plants
  • Having the seedbank saturated with native seeds so that recruits after disturbance are at least as likely to be native as exotic. The corollary to this is that the seedlings need to survive, so deer browse must not take place. Also, I've noticed that many native shrubs and herbs are so browsed that they are not producing seed.

Native herbs cover the ground along Maine coast

I just got back from Maine, and the plants there are amazing - robust, densely packed, and producing tons of seeds. So many berries everywhere - we gorged on huckleberries and blueberries and nibbled an occasional bunchberry as well.

I kept asking myself on the car ride back to NJ - is it impossible to get NJ back to being as nice as Maine? Maybe - fragmentation and habitat destruction is much further along here, and all that unfragmented (though heavily harvested!) forest in Maine supports much greater densities of wildlife than here.

But what about our remaining wild areas, of which there are many? Is it impossible that they be as robust as Maine's wilderness? I don't think so... but just pulling weeds won't make it happen. We need to stop creating so many empty niches (bulldozers, thoughtless forestry, critically overpopulated deer). Then, we need to help put some of the missing pieces back. No virginia snakeroot left in Princeton township? Propagate and plant it in suitable habitats.

Although "just pulling weeds" doesn't make the landscape spring back to robust health, here's another lesson from the garden...

Lesson: If you don't pull the weeds, they'll overwhelm your vegetables.

I know that domesticated annual vegetables are not the toughest plants on the block. By contrast, I think our natives could easily overtake many of our invasives, given the chance (again, the deer issue). Nevertheless, I think that an established plant community is very hard to transform without radical disturbance. We see this time and again in the woods when we find slivers of remnant, mature forest. They may be diminshed, but they are frequently not invaded - until a major disturbance comes through (tree mortality, forestry etc.) that is.

Unfortunately, the same is true for non-native plant communities. An "invaded" forest with a shrub layer of oriental photinia and a ground cover of garlic mustard and japanese honeysuckle is likely to stay that way... unless there is a radical disturbance, like a crew of land stewards with chainsaws and herbicide.

The more that invasive plant infestations are allowed to spread, the more chainsaws and herbicide we'll need if we ever want to restore them to native plant communities - and the more patience too, because it ain't gonna be fast or easy, and the soil chemistry and fauna is going to be inhospitable to natives.

Now, I wrote earlier that there are always more weed seeds, and I believe this to be true in central NJ. I think our seedbank is saturated. In Maine, there are many weeds seeds too, but fortunately most of the "exotics" up there are only early successional weeds that get outcompeted as the robust northern forest reclaims disturbed land.

Despite the cut stump, invasives can't recruit in this Maine landscape!

I think our wild area seedbanks are saturated with invasive plant seed, but I don't think every place is yet saturated with every weed. Here's a garden analogy: My mom's garden is absolutely saturated with galinsoga, and every time she goes away for a week, she returns to a carpet of it. Here, we just have a few and I try to grab them as soon as I notice them. Up here the weed that would take over if we abandoned our garden is evening primrose. Not bad, huh?

I think that the same can be said about our invasive seedbank. I've seen "remote" spots in the Sourlands sprout wineberry, barberry, ailanthus just after logging. But, these spots aren't yet sprouting photinia or siebold's viburnum, the way an analogous spot in Princeton would. So, I think there is value to the "Early Detection/Rapid Response" strategy of stewardship. We don't need our seedbank to contain even more competitors with natives, each with slightly varied tolerances. The more of these we get, the fewer niches we'll have where natives are superior competitors, and the more likely we are too see local extirpations and possibly regional extinctions in the future - even if we solve the deer overpopulation crisis and cease disturbing or destroying so much wild habitat.

The native perennial Allium cernuum in the vegetable garden