You are not going to like my answer. Just wanted you to know that in advance.
If I were planting seeds tomorrow and only had a garden hose, I would keep the soil moist until the seedlings are established. I know, the same old advice. Problem is, it's good and sufficient advice. Let me explain why.
We have, in much of our lives, grown accustomed to a certain precise relationship between inputs and outcomes. We open up a cardboard box, place the contents in the microwave for the specified period of time, and a perfectly cooked meal arrives. We open up another cardboard box, push Tab A into Slot B, and we have a perfectly balanced and functional piece of furniture. We open up another box, this one plastic, type in a specific combination of letters and symbols, and a perfectly functional Web site appears before our eyes.
It's all rather comfortably predictable and precise.
But the created world – the true created world, not our version of it – doesn't work that way. Deo gratias.
The true world is full of mysteries and relationships. The true world – and that is the realm within which gardening lies – offers us an invitation, and it is an invitation to participation. We are free to accept or reject that invitation, but if we reject it, we reject its fruits (and vegetables), and if we accept it, we accept the continuing call to participation which it entails.
What does this mean for your vegetable seedlings? Because we live in the desert, inadequate watering is, as you noted, frequently the proximal cause for mediocre results in the vegetable garden. But the ultimate cause is very often our belief that we can calculate our inputs, leave them to run, and expect good results.
There have been many times when I have walked into a client's garden and had a version of the following conversation:
- Gardener: Why do my plants look so bad?
- Me: The soil is completely dry and they need water.
- Gardener: But they're scheduled to be watered two days from now.
- Me: They need water today or they will die.
- Gardener: But they're scheduled to be watered two days from now.
- Me: They'll be dead by then.
- Gardener: But I always water them on Saturday.
The watering needs in your garden are determined not by the clock or the calendar, but by the complex relationship between sun, soil, humidity, weather and the type of plant you select. Your garden is unique to you; no other is precisely like it. It simply isn't possible for me to give you an exact schedule with precise amounts.
That means you're going to have to water your seeds when you plant them and then every morning and evening go out there and see how things are going. Get down and stick a finger in the soil to make certain it's moist, and water if it's getting dry. Water gently, so you don't wash the soil away. Spread a layer of mulch around the seedlings once they sprout, to help conserve moisture in the soil.
As they grow, water more deeply, to a depth of six inches or more, and then you can begin watering less frequently. How will you know when to water less frequently?
You'll have to learn by watching and participating.
If the days are hot and dry, you may water every day. If cool and rainy, maybe not for a week. You're going to learn to watch your plants: If they start to wilt after four days with no water, then perhaps you need to water on the third day instead.
All plants need deep, but infrequent water. Learning what that means in practice takes, well . . . practice. I told you you weren't going to like my answer.
If you have more questions as your garden grows, let me know.
I hope this helps,
Tyler