Globes, Bulbs, and Spikes: Self-Watering Garden Gadgets, Ranked

It’s that time of year again: I’m heading off to Italy for a month and scheming about ways to keep my plants alive while I’m gone. 

Last year I semi-succeeded with a combination of DIY self-watering methods and the help of my neighbor, Vera. This year, Vera’s having some health issues, and I wanted a system that would effectively water all my plants better and longer. I’ve been testing four types of self-watering gadgets over the past few months and am here to report on my findings for all my world-traveling container gardeners! As always, this is not sponcon, just friendly knowledge sharing.

Like many people, I don’t have access to a water source on the balcony, so these all use the same basic technology: a small reservoir that slowly releases water into the soil. I’m using a combination of the four to keep my pots of various sizes watered for a maximum of two weeks. At that point, my very kind sister will drop by to give all the plants a good drink and refill the reservoirs. I wanted to minimize her trips across the Bay, and this way she should only have to come twice during our month away.

That said, I haven’t found any of the options below to be sufficient for really thirsty plants, like my sunflowers or runner beans. For them, nothing beats a thorough soak, and these irrigators provide just enough water to keep them alive but not thriving. But they have worked well for more drought-tolerant plants like salvia, cosmos, California natives, Mediterranean herbs, and even my potted fig, olive, lemon, and bay trees.

Nature doesn’t take vacations, and probably neither should gardeners. But no one wants to hear that, including me! So, without further ado . . .

Best Overall: Terracotta Spike with Glass Bottle

This option wins because it’s effective, inexpensive, and easy to set up with widely available terracotta spikes and any old glass bottle.

The first three methods on this list all harness the porous magic of terracotta to slowly release moisture into the soil. Terracotta spikes can be found in packs online or at your local garden center for a relatively low cost. Then, just take any bottle from the recycling bin, fill it with water, and pop it upside down into the spike (hooray for reuse!). I use wine bottles for large pots and beer bottles for smaller ones. They seem to last one to two weeks depending on the weather, the plant, and the level of sun exposure.

A few tips:

• Use dark-tinted or green glass bottles as they’ll filter the sunlight; curved, clear glass can refract the sun’s rays, creating disconcerting hot spots and burning plants (yikes!).
• Ideally, think ahead and insert the spike when you plant up your container. Once plants have become established, it can be hard to insert the spike all the way in, plus it disturbs the roots. If you can’t get the spike all the way in, it will still work. Just more surface area buried = more moisture released.

Runner Up: Fancy Glass Globes

These Etsy finds cost a lot more than terracotta spikes and use the exact same technology, but they look pretty, are easier to refill, and hold a larger quantity of water.

Compared to the Best Overall option which costs practically nothing, these cost a pretty penny for essentially the same thing: a glass reservoir atop a terracotta spike. I’m still glad I splurged on three of them because their ample capacity makes them great for my XL containers (the ones I got hold 1600 mL, or just over two wine bottles). Plus, their cute little stoppers can be removed to allow for easy refilling, which I’m sure my sister will appreciate.

Because these hold so much water, they last a long time. They look better than anything else I’ve seen and are available in several beautiful hues. I opted for clear, which was dumb, because again — scary sun refraction. I’ve had to cover these with dishtowels on warm afternoons, and will definitely be leaving them covered when I go. A longer-term solution might be to try out some glass paint, which sounds like a fun craft project for a rainy day.

Good Enough: Small Plastic Globes

Great for shallower pots, these take up less space and still hold a fair amount of water, but they’re cheaply made.

I ordered these from a weird website, Light in the Box, because I wasn’t seeing anything else quite like them anywhere. They’re the perfect size for my long rectangular planters, which need a reservoir on each end to be evenly watered, and for my smaller pots containing thirsty plants like mint and strawberries. 

The terracotta spikes are nice and shallow, and the globes hold a decent amount of water and are easy to refill from the hole at the top. But they’re flimsy and plastic, and pose the same refraction problem as the globes above. 

Worst: Plastic Bulbs

These inexpensive bulbs can be bought in bulk for those with many small pots, but they only work with a DIY modification.

At first, I found these completely useless; I would fill them up, stick them in the soil, and watch them drain out within minutes, even after thoroughly watering the pots as instructed. But I didn’t want them to go to waste. 

Eventually, I tried stopping up the tips with little wads of cotton, and there you go: problem solved. The cotton absorbs the water and then releases it slowly, drip by drip. These now serve to keep my petite pots of herbs watered, which I was quite worried about because smaller pots dry out fastest.

However, these will also be the most annoying for my sister to refill because she’ll have to fiddle with the cotton balls, earning a firm spot in last place.

A Few Last Tips before Departure

Beyond adorning each and every pot with its own mini reservoir, there are other steps you can take to slow water evaporation:

• Mulch pots with straw or gravel to hold in moisture below the surface 
• Cluster pots together to create cooler micro-climates 
• Consider moving full-sun planters into partly sunny spots in case there’s a heat wave while you’re gone

Lastly and most importantly: let go. You might lose a few things. Others might thrive under a little neglect. Having an imperfect garden is a price I’m willing to pay to spend quality time with my husband and his family across the globe. If you’re in a similar boat, I wish you safe travels, a wonderful trip, and a mostly alive garden upon your return.

Coda

I’m back from my trip and happy to report that after four weeks away, all my plants survived! Shout out to my sister, who came twice over the course of the month in two-week intervals to give the pots a good soak and refill the reservoirs. I can now confidently say that the self-watering gadgets above can work for up to two weeks! It’s worth noting that I benefited from the Bay Area’s cool, mild summers and having mostly drought-tolerant pants. For thirstier plants or in a hotter, dryer place, I’m guessing more frequent visits from a plant-sitter would be necessary.