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18-cell Whopper Planting Block

18-cell Whopper Planting Block

Fits all single-size Bio Domes, from the original 60-cell to the 4-cell version!

Whopper 18-cell
Item # 09322
Instock - allow 3-5 business days for processing prior to shipment.
Buy 2+ at $17.95 ea
Ready to try the 18-cell planting block -- or has your first one already worn out from plenty of hard use?! Here is one 18-cell Bio Planting Block filled with 18 Bio Sponges. (They may also be used with your own trays and covers.)

The 18-cell Bio Planting Block is a long-lasting polystyrene block with 18 cells for planting (1 seed per cell). The cells are larger than average, making them ideal for rooting cuttings of your favorite plants, starting large seeds, and growing young plants a bit larger and stronger before transplanting them.

Bio Sponges are made of a remarkable, sponge-like rooting medium that supports fragile roots so completely that seedlings experience no transplant shock.

This planting tray is 13 1/3 inches long, 3 inches high, and 6 1/3 inches wide, with 3 rows each containing 6 holes. The bio-sponges in each hole are 3 inches high and 1 3/4 inches in diameter at the top, tapering to 7/8-inch at the base (where they contact the water at the base of the dome).

Park's Bio Dome Seed Starter system gets your seedlings off to the best possible start. To find out more please see the Park's Original Bio Dome with 18 Whopper Cells.

Review Summary
(Based on 3 Reviews)

Overall Rating: 5.0 / 5.0


Bruce from AZ wrote on November 18, 2019

I love this germination kit its quick easy and works great.

very happy with results
Giovanna from NY wrote on May 05, 2019

I have used these domes for 2 seasons now and I couldn't be happier with them They are very easy to use under grow lights.The 18 cell dome is my favorite for tomatoes, eggplant as well as zinnias. I have seen many seeds sprout within 72 hours! Germination rate for me is about about 90% with most seeds- with some even higher. Once the plants get too tall for the dome - which can be very quick- they continue to do well without it. Once they get too large for the cell, I transplant them into pots if needed before going in the garden. I have had Zinnias and tomatoes flower under my grow lights 7 to 8 weeks after the seeds were sown in my domes. The base and styrofoam are easy to clean. After two years and many uses, my biodomes look almost new. They have paid for themselves many times over as I have grown hundreds of plants in them.

Best Seed Growing System
Franco M from IL wrote on November 10, 2014

I have been using the 18 Pack for over 3 years now, I think it is the very best available. If you leave about a finger of water mixed with Park's fertilizer in a weak form in the container the plants will grow without daily attention and they grow very healthy I grow all my seeds in 4 of these containers, I can grow any type of deed in them. Franco M

What are the differences between the various Bio Domes: 60-cell, 40-cell, and 18-cell?
Bio domeThe original 60-cell Bio Dome has a 60-cell planting block with 60 Bio Sponges and will produce 60 plants at one time. The 1" wide by 2 ¼" deep cells are larger than average, and a spacious 1 3/8" apart. The bio-sponges are the same size as the cells; 1" wide by 2 1/4" deep. You can grow and keep plants in the 60-cell bio-dome for 6-8 weeks before transplanting. Many varieties will just need 6 weeks until transplanting. Tomatoes and peppers would appreciate the full 8 weeks before transplanting. So, the original 60-cell bio-dome would be great for starting all of your favorite vegetable and flower seeds, with a larger number of plants produced at one time.

The 40-cell Bio Dome has a 40-cell jumbo planting block with 40 Bio Sponges and will produce 40 plants at one time. The cells are wider and deeper than the original 60-cell planting block and provide good spacing to maximize air flow. The cells are 1 1/4" wide by 2 1/2" deep. The Bio Sponges are also 1 1/4" wide by 2 1/2" deep. You can grow and keep plants in the 40-cell bio-dome for at least 6-8 weeks and some for up to 9-10 weeks, because of the wider spacing and cell/sponge size. It too would be excellent for starting all your favorite vegetable and flower seeds, with the added benefit of giving more room and time for larger plant development.

The 18-cell Bio Dome has an 18-cell whopper planting block with 18 Bio Sponges and will produce 18 plants at one time. It has the largest cells of any of the Bio Domes we offer and is great for growing extra-stocky transplants and even for rooting cuttings. The cells are 3" tall by 1 3/4" wide. The Bio Sponges are also 3" tall by 1 3/4" wide. You can grow and keep plants in the 18-cell Bio Dome for at least 8-10 weeks and some for up to 12 weeks, giving the maximum amount of growing time and spacing between plants as compared to the 60-cell and 40-cell Bio Domes. If you are looking to grow your favorite vegetable and flower seeds into large, stocky transplants for setting out in spring, then the 18-cell Bio Dome is the one you want to buy. It would be excellent for growing Tomatoes and Peppers.

How much water should be put in the Bio Dome and how often?
SeedlingsThe beauty of the Bio Dome is that you cannot overwater! You just keep water in the tray and float the block. The larger the seedlings get, the more water they will use and you will need to add water more frequently as they grow. Initially, during germination, you may not have to water as frequently, because minimal water is being used and Bio Sponges will stay moist longer, so you may only have to water once every 1-2 weeks. Later, as plants grow and water use is greater, depending on the room temperature and the amount of light received, you may have to water more often -- possibly 1-2 times a week -- or as often as required to keep the sponges moist.
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