36 Pack Refill Sponges for the 18-cell Planting Block

18-cell Pack of 36
Item #09323-PK-36


Time for Another Crop in the 18-Cell Bio Dome

This rooting medium is intended for use with Park's Bio Dome with 18 Cells seed-starting system.

Your Bio Planting Block will last a lifetime with these handy, economical Bio Sponges. When you're ready to begin a new crop in the Planting Block, first be sure that the block has been thoroughly disinfected (warm water with a splash of bleach is fine). Then soak 18 of the Bio Sponges in warm water for a few minutes. They expand, revealing the pre-drilled planting hole at one end. Simply slip one seed into the hole of each Bio Sponge, place the Sponge seed-side-up in the cell of the Planting Block, and you're on your way to another bumper crop of healthy, strong, super-quick seedlings.

Bio Sponges are comprised of a combination of coconut coir, peat moss, and bio char and are now enriched with oilseed extract, giving your seedlings an extra boost of nutrition. You'll love the results!

These giant sponges are replacements for Park's Original Bio Dome with 18 Whopper Cells, the largest of the Bio Dome family of seed starting systems. The Whopper Dome is great for larger seeds and rooted cuttings. It is also ideal for seedlings that need to be grown to a larger size in the Dome before being transplanted to their permanent location.

In this refill pack you get 36 sponges, enough to fill the Whopper Dome twice.


Skip Product Specs
Item Form Pack of 36
Color Pack of 36
Size 18-cell
Restrictions *Due to state restrictions we cannot ship to the following:
Canada, Guam, Puerto Rico, Virgin Islands

Product Review Summary

Based on 6 reviews
The average rating for this product is 5 out of 5 stars
Overall Rating: 5.0/5.0

Customer Reviews

April 16, 2020

These are the best for starting seeds inside!!

This shopper rated the product 5 out of 5 stars

I have been starting seeds inside for 50 years. For the past three I have been using the cell blocks, sometimes with the cover on and sometimes with the cover off. I have been using all three sizes of the cell blocks. These are excellent, no mess, easy clean up. I bleach the styrofoam cells containers and use them over and over. I highly recommend them!!

Brian Phillips from IL
March 04, 2020

Great for starting green beans indoors

This shopper rated the product 5 out of 5 stars

For 6+ years I have used these for successfully starting my bush French Beans indoors to speed up the season and harvest. I can control the temps and germination more easily and plant 5 inch bean plants outdoors instead of seeds! All of my bean transplants have always survived the process. I did have to replace the foam blocks after 5 years. They would have probably made it another year or two, but they were getting a little broken up from heavy Spring use. I have already brought them out and gotten them ready to go for beans!

Vermont Gardener from VT
February 10, 2020

Kinda pricy, but foolproof method for seed starting

This shopper rated the product 5 out of 5 stars

Have used bio dome sponge inserts for tomato and pepper seed germination for several years with perfect success. Place bio dome in window of our sunroom in January; daytime sponge temps with the dome vents closed are in the 80's to 90's. When seedlings are an inch or so high, open vents. When seedlings reach the dome, I transplant to 4" pots. Great system. Plants go in the ground in March (San Diego, CA).

John D from CA
January 06, 2020

These large sponges work well for tomatoes and other large plants.

This shopper rated the product 5 out of 5 stars

I have purchased and used the 18 count bio-cells for quite a few years now. They are perfect for starting tomatoes and like plants which grow inside to a pretty good and strong size - ready to transplant direct to the garden.

Anne Rodgers from OK
May 04, 2013

Park's Original Bio Dome with 18 Whopper Cells

This shopper rated the product 4 out of 5 stars

The Biodome works really well. I use it with the 18-cell block for any seeds that grow big fast, or which I may want to delay transplanting (for example waiting for the weather to warm up). The description of the product above is accurate except for one thing -- the polystyrene block is actually rather fragile, because the edges are too thin. Since the 18-cell block is smaller than the Jumbo and Original blocks, it could be made MUCH more sturdy and still fit well into the Biodome. Its too bad the manufacturer/designer was so greedy early on, since redesigning and retooling would cost MUCH more than the insignificant difference in cost of more styrofoam. I think Park's should pressure them to do it anyway -- it is the difference between shoddy and excellent. I would have given it five stars except for this

Bill Gresham from WA

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