Grass in Driveway, Patio and Sidewalk Cracks
by Ken Lain, the mountain gardener
There are three chores that gardeners must complete in March.
A reader wrote, “It's winter, and there peeking through a bit of snow on my drive is spring- green grass! Why does grass grow better in the driveway than in my lawn?”
Come summer folks will be puzzling over grass growing in asphalt driveways at 100+ degrees! That “grass in the cracks” is teaching us lessons in microclimates.
Driveway and sidewalk cracks retain a surprising amount of soil and organic matter, creating the perfect beds for grass and weed seeds. Moisture that seeps into these cracks remains a lot longer than in other parts of the landscape. A driveway's surface can contain moisture the same way mulch does.
Some grasses and weeds thrive in heat. A good example is crabgrass; it's a warm season grass that flourishes in driveway and patio cracks. In cold weather, a dark-colored asphalt driveway absorbs sunlight, keeping the soil underneath it warmer than the surrounding landscape.
As for the salts in ice melt products, some grasses and weeds can tolerate them! Fescue is a cool-season grass that is salt-tolerant, so has a good chance of surviving in a winter driveway. Then there are the cold-happy weeds, like chickweed, that seem to scoff at temperatures that would have caused other plants to have disappeared.
To discourage grass in driveway, patio, and sidewalk cracks, here are some home remedies to drive off broadleaf weeds and grasses:
Boiling water. Pour boiling left-over cooking water on weeds rather than down the drain. Don't worry if there's salt in the water; salt helps kill many weeds. Avoid using water with oil or meat residue leftover from cooking. After a few douses of boiling water most broadleaf weeds and grasses give up.
Kitchen vinegar concoction. A mixture of 1 cup salt dissolved in one gallon of white vinegar will kill most weeds and grasses. To make it even more caustic, add 1 cup of lemon juice and 2-tablespoons of dish soap.
Horticultural vinegar. This kind of vinegar is 20% acetic acid that's hard to find in local stores, but is easily found online. Mix it with orange oil and a bit of phosphate-free dishwashing soap. Acetic acid burns the plant's top growth, depriving it of the ability to photosynthesize. Don't forget protection for the applicant's hands and eyes! Weeds may come back, primarily those perennial weeds that have strong roots. As there may be lots of weed seeds waiting in the cracks, be prepared to apply this mixture more than once. Use the same solution to kill moss in sidewalk and patio cracks, too.
CAUTION! Limit salt mixtures to hardscape areas. Do NOT allow them to run onto lawns and flower gardens.
Watters' once-and-done special mixture of weed death. Weeds really like to grow under our greenhouses, between the pavers, and under the tree racks because those areas are perfect growing environments. But we have perfected the solution to keep pesky weeds under control! This stuff also works on rock lawns where you don't want anything to grow . . . ever. 
In a pressure sprayer blend Hi-Yield 'Killzall', but replace one gallon of water with Bonide 'Vegetation Killer'. Spray the mixture directly onto weeds and watch them melt away, with nothing growing back for up to a year! This trick really cuts down on back-breaking weeding. Be careful not to get close to desirable plants, and don't spray under the canopies of trees and shrubs.
Garden Announcement - The colors of spring are bursting for Watters 56th Spring Open House. Come and talk 
directly with our farmers as they show off the newest flowers and brightest evergreens. Friday, March 16, we will have free shamrocks with purchases of evergreen trees. Saturday and Sunday, March 17 & 18, visitors can enjoy impromptu gardening classes, sidewalk art, corn hole contests, and drawings.
Please consider this your personal invitation to the garden fun at Watters Garden Center's 56th Spring Open House Friday, Saturday and Sunday, March 16-18.
Open this link to see all of Watters garden classes this spring.
Until next issue, I'll be here at the garden center helping locals win their wars against weeds!
- Fertilize everything in the garden this month with 7-4-4 All Purpose Plant Food. At the same time I apply an equal amount of 'Soil Sulfur' to reduce soil pH of all my gardens, raised beds, and native trees.
- Add fresh potting soil to your raised beds and containers. Soil gets used up by plants and needs to be replaced or refreshened each year. Add a 2-3-inch layer to raised beds, and replace the top 8 inches of the soil in containers before replanting them.
- Important Notice– Pinyon Pine scale and bark beetle are bad this spring. Treat the evergreens in your yard with Watters 'Plant Protector'. Simply apply this solution directly around the bases of trees. This uncomplicated task eliminates the expense of a costly arborist bill. Apply it during the next few weeks of March.
A reader wrote, “It's winter, and there peeking through a bit of snow on my drive is spring- green grass! Why does grass grow better in the driveway than in my lawn?”
Come summer folks will be puzzling over grass growing in asphalt driveways at 100+ degrees! That “grass in the cracks” is teaching us lessons in microclimates.
Driveway and sidewalk cracks retain a surprising amount of soil and organic matter, creating the perfect beds for grass and weed seeds. Moisture that seeps into these cracks remains a lot longer than in other parts of the landscape. A driveway's surface can contain moisture the same way mulch does.
Some grasses and weeds thrive in heat. A good example is crabgrass; it's a warm season grass that flourishes in driveway and patio cracks. In cold weather, a dark-colored asphalt driveway absorbs sunlight, keeping the soil underneath it warmer than the surrounding landscape.
As for the salts in ice melt products, some grasses and weeds can tolerate them! Fescue is a cool-season grass that is salt-tolerant, so has a good chance of surviving in a winter driveway. Then there are the cold-happy weeds, like chickweed, that seem to scoff at temperatures that would have caused other plants to have disappeared.
To discourage grass in driveway, patio, and sidewalk cracks, here are some home remedies to drive off broadleaf weeds and grasses:
Boiling water. Pour boiling left-over cooking water on weeds rather than down the drain. Don't worry if there's salt in the water; salt helps kill many weeds. Avoid using water with oil or meat residue leftover from cooking. After a few douses of boiling water most broadleaf weeds and grasses give up.
Kitchen vinegar concoction. A mixture of 1 cup salt dissolved in one gallon of white vinegar will kill most weeds and grasses. To make it even more caustic, add 1 cup of lemon juice and 2-tablespoons of dish soap.
Horticultural vinegar. This kind of vinegar is 20% acetic acid that's hard to find in local stores, but is easily found online. Mix it with orange oil and a bit of phosphate-free dishwashing soap. Acetic acid burns the plant's top growth, depriving it of the ability to photosynthesize. Don't forget protection for the applicant's hands and eyes! Weeds may come back, primarily those perennial weeds that have strong roots. As there may be lots of weed seeds waiting in the cracks, be prepared to apply this mixture more than once. Use the same solution to kill moss in sidewalk and patio cracks, too.
CAUTION! Limit salt mixtures to hardscape areas. Do NOT allow them to run onto lawns and flower gardens.
Watters' once-and-done special mixture of weed death. Weeds really like to grow under our greenhouses, between the pavers, and under the tree racks because those areas are perfect growing environments. But we have perfected the solution to keep pesky weeds under control! This stuff also works on rock lawns where you don't want anything to grow . . . ever.
In a pressure sprayer blend Hi-Yield 'Killzall', but replace one gallon of water with Bonide 'Vegetation Killer'. Spray the mixture directly onto weeds and watch them melt away, with nothing growing back for up to a year! This trick really cuts down on back-breaking weeding. Be careful not to get close to desirable plants, and don't spray under the canopies of trees and shrubs.
Garden Announcement - The colors of spring are bursting for Watters 56th Spring Open House. Come and talk directly with our farmers as they show off the newest flowers and brightest evergreens. Friday, March 16, we will have free shamrocks with purchases of evergreen trees. Saturday and Sunday, March 17 & 18, visitors can enjoy impromptu gardening classes, sidewalk art, corn hole contests, and drawings.
Please consider this your personal invitation to the garden fun at Watters Garden Center's 56th Spring Open House Friday, Saturday and Sunday, March 16-18.
Open this link to see all of Watters garden classes this spring.
Until next issue, I'll be here at the garden center helping locals win their wars against weeds!