Time is an elastic dimension in the vegetable garden. Once the garden is up and thriving,the pace can become dizzying: the sudden swelling of a zucchini, the swift climb of a bean vine up a trellis, the bristling expansion of broccoli heads.
At this time of year, however, the gait is more akin to a snail’s. Each day, the gardener pads outside and peers intently at the dark earth, willing the emergence of a tiny seedling. The wise gardener understands the miracle of new life from tiny, dried colorless flecks of seed and can afford to be patient.
Seed germination varies widely from plant to plant, garden to garden, month to month. But the common factor is the preferred balance of water, warmth and air.
Water starts the process, stimulating cells to begin growing. Soil-temperature requirements differ from one variety to another. Some seeds germinate when soil temperatures are just 40 degrees; others stubbornly wait for warmth of 70 degrees. Oxygen is as important to seed germination as it is to root development. Aerated soil is one way of ensuring an adequate oxygen supply, but the other is in not burying seeds too deeply when they are planted. Very small seeds need a mere dusting of soil or fine compost or just a light sprinkling of mulch as cover. Bigger seeds, such as peas and beans, germinate best when topped with an inch of soil.
Pre-soaking seeds is one of the most common ways to prepare them for planting. Soaked in water for a few hours or overnight, seeds will lose their dried, sometimes-shriveled appearance and swell up. If left indoors where it’s warm, these seeds will sprout within 48 hours. Sprouting won’t occur quite as fast when they are sown outside, but the soaking does speed up germination compared with seeds that have not been soaked.
Peas, beans and corn are all good candidates for pre-soaking - at the appropriate planting time. Corn kernels forced into life now would soon perish outdoors. At the right moment, place seeds in a jar or heavy plastic bag, add tepid water and soak for several hours. Drain and rinse the seeds and let them sit overnight before planting.
Beans and peas should be mixed with nitrogen-fixing powder, an organic compound available at garden centers. The powder stimulates legume growth as well as the production of nitrogen in the soil. Drain well after soaking. Never allow pre-soaked seeds to dry out before planting or they will die.
Another method of pre-soaking is to sprout seeds on a paper towel before planting. This works especially well with members of the squash family - cucumbers, summer squash, pumpkins, melons, watermelons and winter squash. The procedure is foolproof: Take a paper towel, soak it and squeeze out excess water, spread seeds on the towel and cover it with plastic wrap. Place it on the top of a gentle heat source, such as the refrigerator. Within 48 hours, seeds will germinate and you can place them gingerly into warm soil (these summer crops like ground temperatures above 60 degrees).
Pre-sprouting seeds is especially effective for seeds that are left over from previous years, to establish which ones are still viable before reserving valuable garden space for them. Again, wait until the appropriate time. Some gardens warm up quicker than others - welldrained black earth will be much warmer than soggy clay, for example - but generally, soil temperatures climb to 40 degrees by the end of March; 50 degrees by mid-April; 60 degrees by early May; 70 degrees by early June, and 80 degrees in high summer.
Hence, if you want to start summer crops early, you will need indoor growing space (with sufficient natural or artificial light) to hold them until they can go outside in about six weeks.
And while some like it hot, others don’t: Spinach is notorious for poor germination. Seeds go dormant when soil temperatures are too high. This is one reason spinach is such a good early-spring crop: Sown now, it will emerge as soon as soil is a constant 40 degrees. If spinach is to be grown as a fall crop, it should be sown no earlier than September. Another reason for slow germination in spinach is the hard outer shell coating the seeds. An overnight soaking in water spiked with vinegar (one tablespoon per quart) will spur things on.
Beet seeds too will benefit from a good soaking in water. This will dissolve the outer shell and release the tiny seeds, which are clumped into one cork-like kernel.
Here is a checklist of some varieties and proper treatment at planting time:
Beans: Germinate at 60 degrees. Benefit from pre-soaking. Treat with inoculant when planting.
Beets: Germinate at 40 degrees. Soak overnight in water and then sow in a mixture of sand or sawdust to avoid clumping of seedlings.
Broccoli: Plant as seedling in late April; avoid sowing directly into garden.
Cabbage: Treat as you would broccoli.
Carrots: Germinate best at 50 degrees. Cover seeds sparingly when sowing and mix with radishes, which will help break up soil around slowgerminating carrots, thus making it easier for them to sprout.
Corn: Soak four to six hours before planting. Regular hybrids will germinate at 50 degrees. New supersweet varieties, which sprout at 70 degrees, germinate poorly in cool soil and should be planted shallowly.
Cucumber: Germinates at 60 degrees or above. For high germination rate, sprout seeds indoors on paper towels before planting in the ground.
Peas: Germinate at 40 degrees. Soak in water and treat with inoculant before sowing. Sow dwarf varieties on either side of climbing types to give extra support. Sow peas thickly and do not thin.
Radishes: Germinate at 40 degrees.
Spinach: Germinates at 40 degrees. Soak overnight in acidified water for best germination. Avoid sowing when soil temperatures are above 75 degrees.
Squash: Germinates at 60 degrees or above. All types of squash are best sown from seed, but benefit from being pre-sprouted on paper towels before being put into the garden.