What Does Water Do?
Water provides structural support, cools your plant down, and moves minerals to all the right places.
Plant cells are like water balloons. When they are filled, they become stiff and your plant stands upright. When there is a lack of water, the cells deflate and the plant looks wilted — a clear sign your plant needs more water. Plants produce cellulose that help keep its shape, but it’s water pressure (water flowing through your plant) that helps plants gain and retain their shape better than cellulose alone.
When you water your plant, an invisible process called transpiration takes place where the sun evaporates water from the leaves through stomatal pores, causing water loss in the leaf. That’s great, because water will go where it’s needed most. Ideally, the water is pulled up from the roots, but if roots are dry, water is taken from the leaves themselves, which can result in a deflated plant — an indication your plant is thirsty.
Keep in mind your soil is like a sponge. Most houseplants like a porous soil, allowing room for water and air pockets. If your soil is moist to begin with, hold off on watering for now. If you notice water pours out through the drainage holes immediately, your soil is actually bone dry and the soil is repelling water, rather than soaking it in. Avoid pouring water onto bone dry soil. Water will only move through and around the edges of your planter and will not be absorbed by the roots. Your plant should absorb water slowly through its roots so, before you water again, you’ll want to check how dry the soil is. Use your fingers and feel if the soil is wet at least 2 inches below the surface. If so, you can add water. If your soil is wet at the surface, you can hold off.
How Much is Too Much?
Much like different plants need varying amounts of light, different plants need varying amounts of water. Think of your plants’ natural environment: is it rainy and tropical or hot and dry? These simple questions will help you gauge how much water your plant needs.
Desert-natives like cacti and succulents like to stay dry and will benefit from less water. When you water your cacti, succulents and euphorbs, feel free to give them a soak, but make sure they dry out completely — wait a few weeks (even months) before watering again. Humidity-loving ferns need a good watering once or twice a week.
Plant size will also determine how much water your plant needs. In smaller pots with less soil, the soil will dry out faster than in larger pots with lots of soil. If you have two of the same plant and one is larger than other, one will need water more often than the other.
Tip: For large plants, pour water and let it soak in. Repeat until soil is saturated. Let it dry until watering again. For smaller plants do a semi-soak by placing the potted plant in a tray and pouring water over the soil until the tray has about ¼ of an inch of water. Let the plant sit for 8 hours, then drain the water.
We’re inclined to ‘stay hydrated’ but plants can drown if they are flooded with too much water. If soil is left too wet for too long, it can cause root rot. That’s what we call overwatering. On the other hand, if your plant’s soil is consistently too dry you’re likely underwatering. Letting your soil dry out before watering is key for plants to receive the the perfect balance of water and oxygen.
Tip: It’s okay to be flexible in your plant care habits. Monitor how water affects your plant. The rule of thumb is: most common houseplants prefer frequent waterings, but there will be special exceptions.