Questions: What time of day should I water my raised bed garden? Why is water pooling on the soil surface? When is the right time to pull garlic?
Answers: Whether you’re gardening in raised beds or directly in the ground, deciding what time of day to water is worth some discussion. If you were to Google that question, you’ll find that watering in the morning is regarded as the best practice by many gardening sites. This is a great example of how Googled answers might steer readers in the wrong direction. The main reason for watering in the morning in other areas of the country is that they are dealing with a higher prevalence of fungal pathogens common in super-moist conditions that are worsened by nighttime soaks. Watering in the evening or at night is recommended by many local gardeners both because we have relatively fewer fungal issues in our New Mexico soils and because so much water evaporates from the soil surface during the day with our intense sun exposure and dry air. More important than watering at a specific time of day is allowing soils to dry slightly between waterings and taking care to apply water as efficiently as possible.
Pooling water on the soil surface could be a sign that there’s a salinity problem and a crust has formed that impedes water movement into the root zone. Sometimes, but not always, this salt crust is white and chalky. Salty crust sounds delicious on a pizza, but it is bad news for roots. For a full description on why this is a problem, check out the NMSU Extension Circular 656, “An Introduction to Soil Salinity and Sodium Issues in New Mexico”. The NMSU Learning Games Lab on the main campus in Las Cruces produces educational, research-based games and media, including cute videos. Their short cartoon video “Unavailability of Water in Saline Soils,” created in collaboration with content experts Dr. Robert Flynn and Dr. April Ulery (who also authored Circular 656), describes how salt can interfere with water uptake by plant roots. It’s available on YouTube here. The Learning Games Lab studio production team is developing new materials on water and how it is absorbed in the soil, so stay tuned!
If you forget to water your garden plants—something I never, ever forget to do—water as soon as you can, even if it’s the middle of the day. Of course, if you live in a community with watering restrictions, be sure to abide by those rules. While it makes more sense from a conservation perspective to apply water to the soil directly than to water the foliage, you don’t need to worry about wet leaves getting scorched by the afternoon sun. That’s a myth that has long been debunked by researchers studying all sorts of plants. Leaves can be damaged by the sun, especially if they were growing in the shade and all of a sudden, like after pruning, are receiving full sun, but droplets of water on the leaf surface won’t pose a problem. Watering foliage can increase the chances of getting powdery mildew, a fungus that is common in New Mexico and worldwide, especially on rose bushes. For more information on powdery mildew, including links to resources written specifically about powdery mildew on chiles and grapes in New Mexico, find my column “Blame It On the Rain” by searching the NMSU Desert Blooms blog here.
Now on to the garlic question. For long-term storage, the right time to harvest garlic is when the tops begin to brown and die down. More specifically, when the older leaves have died, but the younger leaves are still partially green. Workshop attendee and long-time Extension Master Gardener volunteer Bill Shen explained why it’s a good time to pull your garlic when you see some brown and some green leaves: that’s when it’s mature enough to dry and store well as whole bulbs. If you wait too long, the bulbs fall apart in storage and cloves may not last as long as they would when they are tightly assembled. On the other hand, if you pick too early, drying and storing becomes risky and your garlic is more likely to mold. For cooking fresh, Shen says, by all means, harvest it green and enjoy fresh garlic! It’s the long-term storage concerns that dictate the perfect harvest window. If you were to follow a young leaf carefully down into the mother bulb, you’d see that those leaves form the papery sheaths that wrap and protect individual cloves. NMSU Extension Guide H-234, “Garlic Production in New Mexico.” (Fun fact: in Spanish, garlic cloves are called “dientes de ajo” or garlic teeth).
Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at firstname.lastname@example.org.
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For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.