Introduction: Seedling Planting Aid for Hydroponic Pea Gravel Bed

About: Civil engineer, saved by a misaddressed scholarship offer from becoming a CA

I love my hydroponic 'farmlet' but transplanting seedlings into the pea gravel beds always gave me the willies.

Somehow you have to make a hole in the gravel at the right depth, get the seedling's roots into the hole and fill the hole around the seedling. Sounds simple?


The thing about wet pea gravel is that what it loves doing best is falling back into the hole you've just scraped out immediately that you take your fingers (or trowel, or whatever...) out of the hole to pick up the seedling. So you have to stop, put down the seedling and re-dig the hole.

Then you take your fingers out the hole to pick up the seedling and the hole collapses again...

Fourth time round you say something rude and just jam the seedling in with a bit of stick. Doesn't do the seedling much good and you depart the scene somewhat disillusioned with this whole stupid hydroponic idea anyway!

Time to get inventive...

Step 1: Before I Start...

This is one of those Instructables where you only think of making the instructable after you've made the product.

That's why the parts look a bit grubby... sorry about that but luckily I was able to scratch the cut off bits out of the garbage and sort of reassemble them...

Step 2: What You Need...

1. Large plastic funnel with neck about 30mm diameter

2. ± 200mm of 6mm threaded bar, prefer stainless but galvanised is OK. Plain steel will work as well if you don't mind the rust...

3. 5 x 6mm nuts. Ditto comment about material

4. 1 x 6mm cap (domed) nut

5. 1 x 6mm x 20mm fender washer

6. 1 x 6mm x 30mm fender washer

7. ± 30ml (cc) slow setting epoxy glue

8. Hacksaw

9. 2 x 10mm spanners

10. Spatula to mix the epoxy with (I keep a bundle of tongue depressors for just this)

11. Disposable latex gloves (this gets messy!)

12. Acetone and paper towels for cleaning up

13. Vaseline, Spray & Cook or the like as releasing agent

Step 3: The Making...

The device consists of two parts.

1. Chopped off funnel

2. Push stick

Don't chop the funnel yet.

First assemble the push stick parts as shown in photo 1

Tighten the nuts holding the bigger washer good and tight. You don't want it wandering around when glueing up...

Take off the small washer and do a pre-assembly as in photo 2 to check it all fits.

If you're happy, take off both small end nuts and the small washer and pull the stick with the big washer still in place out of the funnel.

Put on the disposable gloves. You will be sorry if you don't...

Spray the inside of the funnel with Spray & Cook or smear it lightly with something oily.

Mix up the epoxy and shove it down the funnel spout. Fill the spout all the way and beyond up into the funnel. You need enough to be able to embed the big washer in epoxy. (you might need to mix more - which is why you need slow setting epoxy). Try to avoid getting bubbles in it but don't get neurotic.. Use your fingers, that's why you put gloves on, remember? Unfortunately I don't have pictures of this part... I was on my own and getting to a camera with epoxy coated fingers was not an option.

From the funnel end, push the 'small' end of the push stick assembly through the epoxy and put on the first of the two 'small end' nuts. Tighten it up until it disappears all the way into the small end of the funnel spout (you can do this by winding up the nut at the big end). This should line everything up nicely.

Put on the small washer and second nut. Tighten them firmly, thus pulling the big washer nicely into the centre of the funnel.

Wipe off the excess epoxy with paper towels and acetone.

Leave to set overnight.

Next morning, decide where you want to chop off the funnel spout and, using the hacksaw (I actually used a small angle grinder) cut it off. The length will be for each one to decide but what is important is that the inside diameter of the spout at the chop line mustn't be much less than 15mm. You will see why later...

Pull the push stick out of the funnel. It should come out easily enough but you might have to tap it loose with a small hammer.

Screw the last nut and the dome nut onto the free end of the push stick. Lock them up tight, tidy up any rough epoxy edges and you're done.

Now to use it...

Step 4: Using It...

(The hydroponic method I'm using here is an ebb and flow system using a constantly running pump and automatic bell siphons. For those who are not familiar with the terminology, please have a look at one of the available hydroponic instructables)

To get the right depth of planting you need to adjust the water level in the bed to the maximum height it will reach during normal operation and keep it there during transplanting. You will see why shortly...

And now to it...!

Choose where you want to place the seedling.

Position the funnel and using the push stick, wiggle it down into the gravel until it is deep enough (photo 1)

Holding the funnel in place with one hand, pull out the push stick. If you've got it right you should see a nice clean hole with the water level just above the neck of the funnel (photo 2)

Drop the roots of the seedling down the spout, using the dome nut end of the push stick to help if needed (photo 3 & 4)

Gently lift the funnel upwards with one hand while holding the seedling down with the other (photo 5). Use the dome end of the push stick if needed to hold the seedling down while you pull the funnel up past the leaves.

Using your fingers, tuck the gravel firmly around the stem of the seedling.

You're done!

Next seedling please O:-)

Step 5: Some Obvious Caveats...

1. The success of this obviously depends on the seedling being transplanted and its state of growth. The leaves must be able to fold without damaging them as you pull them through the funnel... That's also why the diameter at the 'chop' line needs to not be too small...

2. You obviously have to wash the roots clean of whatever you had grown the seedling in or you won't get the roots down the spout.