There are several methods growers use to water newly planted starts while the traditional overhead watering works great for some plant starts, some tender seedlings can get damaged during waterings. Many growers use a bottom tray to water from below. If you are new to this watering method, read below for tips to avoid common mistakes growers make when bottom-watering.
OVERFILLING THE BOTTOM TRAY
When using the bottom-watering method with seedlings and microgreens, growers often fill the bottom trays too full. This mistake becomes an issue because often, stagnant water is left in the tray throughout overnights when water-borne bacteria thrive. Trapped moisture makes a perfect incubator for anaerobic bacteria. Ever wonder why hydroponic growers use so many air pumps? We recommend starting slow with filling the bottom trays. We recommend filling with enough water to cover the entire bottom of the tray with about a 1/2 inch, ideally in the morning when lights are in use. Return and check trays mid-afternoon until your plant's water needs are dialed in. If you completely over-did it, remove the top tray and drain out the excess.
JUDGING MOISTURE LEVELS BY WEIGHT
Once you have this trick down, we promise it is an easier way. When new growers are trying to learn this method, I recommend that they properly saturate whatever they are growing and pay close attention to how it feels. Once you have done this a few times, you will never go back to relying on "eyeballing" the moisture level or inserting a finger to test it. This is important as it is a more reliable gauge than previously noted methods. In conjunction with bottom-watering, this method will ensure that your plants get all of the moisture they need.
OTHER BENEFITS OF BOTTOM-WATERING
The beginning stages of germination require heavy watering, but once you see newly sprouted growth, it's time to ditch the topwater. Why? Because it can cause damage to the seedlings, and having any wet foliage can put your starts at risk for fungal issues. It is imperative to water from below if using nutrient solutions as you do not want those to touch delicate growth. Overall you will be delighted with the results you will yield when bottom-watering.
Soil blocking is a method of propagating seedlings that involves filling a metal blocking tool with soil and squeezing to form a compressed cube. Seeds are planted directly into the formed block. Soil blocks come in various sizes and are advantageous for air pruning roots.