Every gardener will devote a lot of time to weeding. We always try to pull most weeds at an early stage, before they take over. We also find many unwanted or unplanned "good" plants, that we may either treat like a weed, or save. These are often referred to as "volunteers".
Volunteers could be self-seeded offspring of last year's plants, seeds from compost, or seeds scattered by birds and squirrels. Some plants, like raspberries or mint, can send runners underground, producing more volunteers. One important thing for new gardeners to understand, is that they can't keep all volunteer seedlings, as there's really no room in the garden. Some can be given away but many will end up in the compost.
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| Tomato seedlings near a pistachio shell |
These tomato seedlings could be from the compost or from dropped fruit. Most gardens do indeed have some dropped fruit, even if we aim for zero waste...just because they ripen so quickly in the late Summer. Birds and squirrels will also grab some fruit before picked by humans. But, from the shear volume of volunteer tomatoes that appear by mid-May, my guess is that the majority are from the compost bin. If we don't remove most of our tomato seedlings, there would be nothing else growing in the garden.
Volunteer tomatoes are the survivors, and usually grow more vigorous and bear more fruit than the more sought-after heirloom varieties. These seedlings will not emerge until late April or early May, but they will eventually catch up and surpass the indoor-started tomato seedlings. The fruit-type is a wild-card. In the past, most of ours have been cherry tomatoes, but last season we had a lot of larger-fruit varieties. My guess is that the open pollenated, fallen fruit from our own garden, will produce smaller, mongrel types, whereas the larger fruits that were grown in farms, and left in the compost bin, may produce true offspring. I also think that some of the heirlooms from the compost bin may grow at a similar rate as the mongrel varieties, just because the survivors have been self-selected form the hundreds of seeds; but, I'm not positive about this theory. Just think, do we plant 300 seedlings under the grow lights to chose one? Definitely not. As for hybrids, I'm not sure what their offspring will look like, and maybe the seeds are not even viable.
My advice is to keep a few and see how they do. If you didn't start seeds indoors, try only growing volunteers and skip buying plants. Also, give many away. In past Mays and Junes, I have given hundreds of volunteer tomato seedlings from our school gardens, to the kids, and then I have gotten lots of positive feedback the following Falls. People are generally not disappointed, as large yields are often more appreciated than fancy heirloom names.
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| Squash seedlings |
Volunteer squash seedling are also very prolific, and these too can take up a lot of space if not thinned out. Similar to the tomatoes, there's some mystery element to the fruit type. We do know for sure that all squash will be the fall/winter squash varieties, all vines.
Nearly all summer squash (i.e., zucchini, patty-pan, yellow squash) are varieties of the Cucurbita pepo species, all harvested in the unripe state, thus before the seeds are fully formed. Composted summer squash will not have viable seeds.
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| Squash seedling |
There are three common species of fall/winter squash, each with many varieties. Most of these are also the Cucurbita pepo species, so can cross pollinate with summer squash. But, since most squash in the compost bins are store bought and grown on larger farms, we assume and hope that most are not cross pollinated, but can't be too sure. The most frequent volunteer squash I have seen is the butternut squash, and the squash type can usually be identified by the shape on the female flower bud. Since squash plants take up a lot of space, and a weird cross pollinated variety may not be too palatable, it's worth keeping one or two, but not dedicate the entire squash production to volunteers. Plus, unlike tomatoes, seedlings do not have to be started too far in advance. Rather then let mystery plants survive, you can just direct sow specific varieties that you want, or start indoors a couple weeks earlier.
One more thing about squash seedlings... They may actually be another family member, like a melon. These will be identifiable from their first true leaves, which will be similar but with rounder edges. I'll post examples when some of mine grow.
Sunflowers will drop seeds that will sprout in their proximity the following April. Birds, squirrels and other animals will also scatter seeds. Or, they can be in the compost, as people compost their garden waste.
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| Sun flower |
Similar to other volunteer plants, these will be easier to grow and more vigorous. The flowers are usually a lot smaller than the type we plant, but still very nice. I would keep a few and pot and give away others. Each spring, I start fancier varieties indoors, and if the transplants do not make it, I would let the volunteers grow. Usually we have some of each.
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| More sun flowers |
My predecessor created this rooftop garden a few summer's ago, but last year he moved on to a larger restaurant "farm" in Manhattan, leaving this roof fallow during the Summer of 2012. I inherited some good soil, but mostly filled with deep-rooted chickweed, grass, and also a few little tree saplings.
I'm using shallow food trays with train-holes. These will mostly grow shallow-rooted salad greens, mint, and some other vegetables that I find suitable. The initial planting was on April 11, and there have been a few other staggered plantings of lettuce, arugula, spinach, endive, chard and beets (for greens). Germination was slow due to low temperatures, but this has also been a blessing in disguise because of the lack-of-rain. We should have an irrigation system set up sometime in May, but until then I will have to rely on rain and infrequent hose waterings.
The sidewalk planters were built in late March. Now they're thinly planted with simple things like Pansies and English Daisies, just so they have something while pea, fava bean, chard and nasturtium seeds are germinating. The end result will have sorghum, okra, hibiscus, peppers, chard, and cascading nasturtiums and sweet potatoes. It will be simpler than my vegetable gardens, but have enough complexity to spark interest from passersby, and set the tone of fresh produce for diners. 
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