WASHINGTON – Garden Editor Mike McGrath has tips for protecting plants from a late spring frost, growing big tomatoes and keeping lawns green.
Cold weather warning
Some areas may get frost Monday and Tuesday morning.
The current forecast shows nighttime temperatures dropping down to at least 40 degrees in some outlying areas on Sunday and Monday night. Listeners in chilly pockets may well see temperatures in the 30s early Monday and especially Tuesday morning.
To make things worse, skies are expected to be clear over much of the area, which makes the chance of frost even more likely. Luckily, we have lots of warning, so if you have warm weather crops like tomatoes and peppers in the ground, keep checking your local forecast — the one for your specific neck of the woods, not just D.C., especially if you live well outside of the District.
If it looks like temperatures will drop to or below 40 degrees, be ready to cover each plant with its own individual cardboard box by 7 p.m. the evening before the possible frost. Remove the boxes first thing in the morning. Do not let the plants sit under the boxes all day.
Spun polyester row covers or sheer curtains can also be used, but do not drape them right on top of the plants. Create some kind of structure and lay the protective fabric over the structure to trap heat around the plants. True row covers like the “Reemay” brand can stay on during the day, and are an essential and inexpensive gardening tool.
Do not cover your plants with plastic, tarps or other heavy, non-breathable material. Better to take your chances with cold weather.
If your plants aren’t in the ground yet, just bring them inside around 6 p.m. and put them back outside after 7 a.m. until nights warm up.
When planting tomatoes, keep the compost on the surface
Jarrett in Fredericksburg has a question about the use of compost when planting tomatoes. He writes: “In the past, I have dumped a shovelful of compost in the hole prior to planting. Is this a good idea? Or should I spread the compost around the plant?”
You absolutely want the compost to be applied as mulch on the surface of the soil and not in the hole, Jarrett. A 1-inch to 2-inch-deep layer of compost mulch, beginning an inch from the stem and extending out a solid two feet from the tomato plant, will give the plants a nice gentle feeding every time it rains and provide a physical barrier against disease, since the living organisms in compost will eat disease spores.
Whatever you do, don’t mulch with wood or bark. Wood mulch breeds plant disease.
Proper tomato planting tips
It’s tomato planting time. At least, it will be, as soon as nighttime temperatures stay reliably in the 50s in your area.
Pick an area that gets morning sun where tomatoes have not been grown in the past few years.
Dig a deep hole, pull off the bottom leaves of your transplants and bury three-quarters of the stem underground, so that the plant will develop extra roots all along the buried stem. Don’t do this with other plants, just tomato plants.
Before you fill in that hole, add the dried crushed shells of a dozen eggs to provide the calcium that will prevent the heartbreak of blossom end rot later in the season. No eggshells? Use a dozen Tums, calcium carbonate supplements or an organic plant food that specifies it is for use on tomatoes.
Fill the rest of the hole with regular garden soil.
Apply a 1-inch to 2-inch deep and 2-foot-wide mulch of compost to the surface of the soil underneath the plants to prevent disease.
Provide strong support so the vines do not sprawl.
Support your local tomatoes
Getting ready to plant your tomatoes? It’s important to recognize the difference between two basic types. “Determinate” tomatoes are bred to produce their fruits early in the season. The vines stay relatively short, topping out between 4 feet and 6 feet in height. Often identified by adjectives like patio, bush or compact, these are the best tomatoes for containers and small-space gardens, and can get by with the normal tomato cages you see in hardware stores and garden centers.
“Indeterminate” tomatoes typically produce much larger fruits later in the season on monster vines that can easily reach 10 feet to 12 feet in length. All of the legendary great-tasting heirlooms fall into this category, and all indeterminates require a sturdy cage made of welded wire fencing, such as animal fencing or concrete reinforcing wire, to keep the fruits safely contained.
Cut 6 feet of fencing material, curl it into a tube about two feet in diameter and center it over the small transplant, which won’t be little for long. Then get a sturdy garden stake or length of rebar, drive it through the sides of the cage and hammer it into the ground until the cage is stable.
Do not attach the plant to the stake. Allow the vine to slowly curl up the inside of the cage and your huge tomato plant will stay nicely inside — as will all your huge tomatoes.
Do not collect your clippings
Betsy in Falls Church writes: “We were wondering if we should put our grass clippings into our compost pile?”
The answer is no, Betsy, for at least three reasons.
The first is that removing the clippings starves your lawn of necessary nutrients. Returning the pulverized clippings to the turf, ideally with a mulching mower, provides a gentle, natural feeding every time you mow.
The second is that grass clippings are a “wet green” nitrogen-rich material, and most compost piles already have too much of that component this time of year. If anything, they need more dry, brown, shredded leaves, not greens.
The third reason is that clippings from lawns that have been treated with chemical herbicides are deadly to other plants, even after being composted.
But no matter how you care for the turf, the best place for your clippings is right back where they came from.