Spring Seeding Guide - Watering
Perhaps the steepest and fastest learning curve in raising plants from seed relates to watering practices – especially so in early spring when one heavy-handed or ill-timed watering can create knock-on effects that kill many plants. Wherever possible, have an experienced hand demonstrate their watering style to you. Have them critique your efforts.
Some experts water their plants from underneath, by placing flats in water-filled trays or troughs. If you have the resources and patience for this approach, great. Most go with top-watering with a wand.
Use a watering wand with a light spray. Most watering wands put out too heavy a shower – they are better suited to watering perennials in gallon pots. The Gardena watering wand is a favorite among experienced hands hereabouts. Keep your watering wand off the ground as soil-borne nasties can be picked up and spread. Also, they do have a tendency to get stepped upon if at foot level.
Some simple hints. The weather conditions of spring – with its warm days and cold nights and lots in the way of daily fluctuations – demand a flexible approach to watering. Nurserypeople watch the skies as well as the plants.
A simple rule is: don’t have the plants damp going into an evening. Often this means watering no later than late morning or early afternoon. It is not difficult to over-water and hence waterlog plants. Once soils are waterlogged, ushering them back into balance can prove more troublesome than you might reckon. Be modest with your watering. But if, during a hot day in Feb/Mar, you anticipate a good four hour stretch of sunshine heat, you can be more generous, ‘topping up’ your flats with the confidence that evaporation will compensate for the additional dousing.
Sometimes, the soil layer in your flats may become top-heavy with water, and dryer toward its base. Lift the flats and spray them slightly from underneath. Bottom drying-out is an especially common development with trays on heat mats. Whatever the time of year, lifting the edge of a flat a couple of inches off the bench will alert you to how much water is held in the soil (a watered flat is a great deal heavier than a dry one). Sticking your fingertip in the soil is a good test, too.
Nurserypeople who watch their greenhouses like hawks will tend to let the surface of the soil in their flats dry down before stepping in immediately and watering – this tactic appears, among other benefits, to reduce the likelihood of surface algae/mold forming on active soil mixes. When algae/mold does form, it seems not to hurt the plants directly, but does form a surface barrier preventing the free flow of air and moisture into and out of the soil. Simply ‘rough up’ the soil surface with your fingertip and adjust your watering style.
It is better to make
several gentle watering passes over starts than attempt a one-pass soaking.
Experience will give you a sense of how to read soil in your flats, and
the confidence, over time, to develop an original watering regimen that
suits your situation and style of watering plants. Each gardener does
it best her or his way.
By Nick Routledge for the Observer Allotment Blog