Tablet Feeder, Rainbow Model 300, 1 or 3 Tabs

The Verdict

If you fertilize trees and shrubs more than once a season, you’ve probably had this thought while kneeling in the dirt with a hand trowel: there has to be a better way. The Rainbow Model 300 tablet feeder is that better way—provided you’re already using fertilizer tablets. It’s a niche tool, but for its intended job, it’s about as simple and durable as it gets.

What you actually get

The box contains the feeder unit, a brass hose adapter, and a small instruction sheet. That’s it. No fertilizer tabs, no carrying case, no extra gaskets. The feeder itself is a short, pistol-grip-style wand with a brass head and a clear plastic chamber where the tablet sits. It attaches to any standard garden hose. The design is refreshingly low-tech—you drop a tab in, snap the chamber closed, and water pressure dissolves it as it flows past.

The key spec here is dual compatibility: it handles both 1-inch tabs (for smaller ornamentals and young trees) and 3-inch tabs (for established shade trees and large shrubs). That’s a wider range than most single-purpose feeders on the market, and it’s the main reason the Model 300 has stuck around for decades in this category.

How it performs where it matters

The brass construction is the headline. This is not a thin-walled plastic throwaway. Owners consistently mention getting 5-10 years of service. One reviewer noted, “I’ve had mine for six seasons and it still works like day one. The brass is worth every penny.” Another said, “Left it outside all winter by accident. Hooked it up in spring and it worked fine.” That kind of resilience is rare in hose-end garden tools.

Functionally, it’s straightforward: the water flow dissolves the tablet at a fairly consistent rate, and you can throttle the flow to adjust how quickly the fertilizer disperses. Most users report a full 3-inch tab dissolves in about 10-15 minutes at moderate pressure. The clear chamber lets you see when the tablet is gone, which is more useful than it sounds—you’re not guessing whether you’ve applied enough.

What buyers consistently praise

Beyond durability, the recurring themes in positive reviews are simplicity and speed. “I fertilized 12 mature trees in under 30 minutes, no digging, no mess,” is a typical comment. Another common note: “This works exactly as advertised. If you use fertilizer tabs, stop using a trowel and buy this.” Ease of cleaning also gets mentioned—a quick rinse through the chamber clears residual buildup.

Where it falls short

Let’s be honest about the downsides. The plastic prongs inside the chamber that hold the tab in place can snap if you’re rough with them—especially if a tab has absorbed moisture and swelled slightly. It’s not a common failure, but it’s the weak point in an otherwise metal construction. Replacement parts are hard to find, so treat the prongs with care.

There’s also no shutoff valve on the unit itself. You have to walk back to the faucet or use a hose-end shutoff to stop the flow mid-application. Minor annoyance, but real.

And the price—typically $30-40—feels steep for what’s essentially a brass tube with a clip. You’re paying for durability, not complexity. If you only fertilize a couple of plants once a year, this is overkill. If you have a real orchard or a lot of established landscaping, it pays for itself in avoided back strain.

Who should buy this

• Hobby orchardists with 5+ fruit or nut trees. This is your tool.
• Landscaping enthusiasts who use fertilizer tabs religiously and want a faster application method.
• Anyone who’s tired of digging 6-inch holes around the drip line of trees every spring.

Skip it if you use granular fertilizer (it won’t work), if you have a tiny yard with one or two shrubs, or if you’re looking for a multi-purpose hose-end sprayer—this does one job and one job only.

FAQ

Q: Can I use this with liquid fertilizer instead of tablets? A: No. The chamber is designed to hold solid tabs and let water dissolve them. Liquid fertilizer would just flow straight through. Use a separate sprayer for liquids.

Q: How long does a 3-inch tab take to dissolve? A: At normal household water pressure, roughly 10-15 minutes. Slower flow = slower dissolve, which is actually better for deep root feeding.

Q: Will this work with any brand of fertilizer tablet? A: Yes, as long as the diameter matches (1-inch or 3-inch). The Rainbow tabs are the most common, but generics fit fine.

The Verdict

Rating: 4.2/5 — A well-built, specialized tool that excels at its single job. The brass body will outlast your hose, and the dual-size compatibility makes it genuinely versatile for tree care. Deduct half a star for the fragile prongs and another for the missing shutoff valve.

Buy it if: You use fertilizer tablets regularly and want a faster, cleaner application method. Skip it if: You’re a casual gardener who can count your trees on one hand.

For the right buyer, the Rainbow Model 300 is a buy-once, keep-forever tool that makes a tedious chore genuinely easier.

Where to Buy

👉 Check Price on Amazon →

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Last updated: 2026-08-06. Ratings and prices current as of review date. Verify on Amazon before purchasing.