Skip to content
Microgreens Guru
Español

Using your own seeds in a LetPot: sponges, seed count and light

Cal HewittPublished Checked

  • growing
  • letpot
  • pod gardens
  • seeds
Small white ceramic dish of loose basil and lettuce seeds on a kitchen counter beside dry brown grow sponges, empty plastic pod baskets and clear domes, a countertop garden behind

Put 2 to 3 seeds in each soaked sponge. That is the number in the LPH-Lite manual, which also tells you to soak the sponges in water for 6 to 12 hours first, and it is the same number in LetPot's customer FAQ. Then cover the pod with its dome and set the light about 4 inches from the seed, according to the FAQ, and remove the dome when two to three leaves appear.

Plant to the depth on your seed packet where that is practical, or ask LetPot for your model's figure. Below: the planting order with a tray in front of you and a packet on the counter, then the failures LetPot owners have reported.

This page is monetized. Microgreens Guru may earn a commission if you buy from a link to a retailer such as LetPot. Prices below were shown on LetPot's own pages on November 7, 2026, and can change.

What to buy and what your model comes with

Check the box before you buy anything. According to the LetPot manuals listed on LetPot's user-manual page, the LPH-SE comes with 12 sponges, 12 basket kits, 12 germination covers and 12 light-blocking stickers. The LPH-Air comes with 10 sponges, baskets and covers, and the LPH-Max with 21 of each. The LPH-Lite manual (on Manuals.plus) lists 12 planting pods with sponges, baskets, pod covers, A and B nutrients, tweezers and grow domes.

One reviewer at Gardening Know How wrote that the LPH-Max did not include seeds, so the packet on your counter is your own to buy.

When your first batch of sponges is used up, LetPot sells refills for the LPH-Max, LPH-SE, LPH-Lite and LPH-Air. These are the prices shown on LetPot's accessories page:

  • AC200 Round Grow Sponge Refill Kit, 200 sponges, $24.99.
  • AC172 Round Seed Pod Refill Kit, 60 sponges, 60 germination covers, 25 basket kits, 60 shading stickers and two A/B plant-food bottles, $26.89.

The LPH-Mini uses a different shape. LetPot's AC77 Square Seed Pod Refill Kit is listed from $18.86. Match the refill to your exact model and pod shape before you order, because a round sponge is not a safe guess for a square pod. A retailer listing for square LetPot-compatible sponges warns that round AeroGarden sponges do not fit LetPot's square or box-shaped systems.

LetPot says the sponges and baskets in the 172-piece kit are compatible with AeroGarden, iDOO and Click & Grow systems, per its refill kit page. That is the manufacturer's statement. If you are mixing brands, test the fit with one sponge before buying a large pack.

If you want a separate seed-starting tray rather than the main unit, LetPot also sells the SS-Pro Smart Seed Starter Kit with a 40-cell tray, a 24W light, a heated base and a humidity dome, shown at $119.99 on its product page. Its 80-piece sponge pack is $21.99. That kit is a different machine from the pod units above.

Soak the sponge first

The LPH-Lite manual says: "Soak the provided sponges in water for 6-12 hours before planting." Start the soak the evening before, or in the morning for an evening planting. The manual is reproduced on Manuals.plus.

Six round brown peat grow sponges soaking in a shallow clear glass bowl of water on a kitchen counter with a few small bubbles rising from them

Seat each soaked sponge in its basket. If your model uses stickers, the SE manual says to cover the sponges and basket tops with the seed pod stickers during the planting and seedling stages, and to put blackout covers on any pods you are not using so light does not reach the water. Mold turns up often in owner reports, covered below.

How many seeds go in each pod

The LPH-Lite manual says to place 2 to 3 seeds into each soaked sponge. The FAQ says to plant 2 to 3 seeds in each pod. The SE and Air manuals say the same, and the Max manual repeats the 2 to 3 seed instruction with domes and the light low at germination.

Macro view looking down into the center hole of a damp brown grow sponge in a plastic pod basket, with three tiny dark basil seeds resting in the hole

The sequence for each pod looks like this:

  1. Place 2 to 3 seeds into the soaked sponge. Follow the planting guidance on your seed packet where that is practical, or ask LetPot for a model-specific figure.
  2. Cover the pod with the light-blocking sticker and remove the central circle, per the FAQ.
  3. Put the transparent germination dome over it. The manual says this creates a warm, humid place for germination.
  4. Remove the dome when two to three leaves appear.

More seeds per pod is not the point. Mary's Test Kitchen reviewed an LPH-SE and said that 12 mature plants felt crowded and competed for light. That is one reviewer's experience, not a rule.

Where the light sits during germination

LetPot's FAQ puts the light about 4 inches from the seeds and calls for 6 to 8 hours of light during germination. The SE and Air manuals give the same idea as the lower position, about 4 to 5 inches from the plants. The Air manual adds that its Low brightness setting is suggested for seedlings and germination.

Countertop hydroponic garden with its lamp lowered close to the deck, every pod covered by a small clear dome with faint condensation and tiny green sprouts just visible

LetPot models differ in how their lights work. The SE runs 16 hours on and 8 hours off by default, and the Air manual says light on-time is generally set between 12 and 16 hours. The FAQ's 6 to 8 hour figure belongs to germination, not to the whole life of the plant. Open your own model's manual from the LetPot user-manual page and use its light position and schedule if they differ from the FAQ.

Larger seed: the paper towel method

For larger seed such as spinach, beet and cilantro, the FAQ describes a different route. Germinate the seed first on a moist paper towel inside a transparent bag, then move the sprouted seed to the sponge with tweezers or your fingers.

Folded damp white paper towel opened on a plain white plate, with a dozen plump pea seeds on it each showing a short white root, on a kitchen counter

Treat this as an option, not the default. The direct-in-sponge method is what the manuals describe, and the paper towel method is for the big seed.

One caution comes from an owner who used a zip-top bag. On Reddit, an LPH-Lite owner said their pre-germinated seeds turned yellow or mushy after going into LetPot sponges. That is one report, not a test of the method. If you try it, follow the FAQ: a moist paper towel in a transparent bag, then move the sprouted seed to the sponge.

Fresh seed and germination temperature

Two reviewers reported poor sprouting from old seed. Mary's Test Kitchen said that seeds 15 to 20 years old performed poorly, with only one rosemary seed sprouting, and that fresh replacement seeds sprouted much better. The Gardening Know How LPH-Max reviewer used old, expired seeds for several crops and reported that most failed to sprout. Both are single reviewers, not trials, but the advice is cheap to follow: buy a fresh packet.

Seed companies and extension services publish germination ranges by crop. These are not LetPot-specific, so use them as a guide to the room, not as a promise for a pod:

  • Basil: about 70°F and 5 to 10 days, per Johnny's Selected Seeds.
  • Cilantro: 65 to 70°F and 7 to 10 days, per Johnny's cilantro guidance. Johnny's adds that cilantro seed may hold two embryos and that natural germination rates can fall below 50%.
  • Parsley: about 70°F and 21 days, per the same Johnny's herb table.
  • Lettuce: germinates best at 60 to 68°F, and Johnny's says it may go into thermal dormancy above 75°F, which means it slows or stops sprouting when it is too warm.

Johnny's lists parsley at about 21 days to germinate, so check the packet's timing before you pull a pod that looks empty at day 10.

What owners have reported going wrong

Every item here is one person's experience. None is a controlled result.

Mold in the pods. Mold turns up often in owner reports. A Gardening Know How review of the SS-Pro reported algae and white fuzzy mold after several weeks, and some seedlings died from damping off, a seedling disease tied to fungus or water management. Reddit owners posted similar reports in November 2024, January 2026 and September 2026. In April 2026, an owner planted 2 to 3 seeds per pod and reported that four pods grew mold and never sprouted.

Owners often link mold and rot to saturated sponges, high water levels, little airflow, old seed or seed sitting in stagnant moisture. Those are their observations, not proven causes. LetPot's own SE manual says to drain and rinse the tank, discard sponges or plants touched by mold or algae, and clean the baskets and covers.

Mushy or yellow seedlings. The zip-top bag story above is one. A Trustpilot reviewer wrote in January 2025 that some bean seeds rotted.

Crops that did well and badly. In the April 2026 Reddit report, basil, dill and cilantro did well, while sage, parsley and chives barely grew. Mary's Test Kitchen reported mint, holy basil, cilantro, Thai basil and oregano growing across three rounds, with rosemary hard to get going. Results on cilantro vary by owner: one November 2024 Trustpilot reviewer reported repeated cilantro failures while basil and spinach grew.

Third-party sponges. The LPH-Lite owner above compared LetPot sponges with third-party sponges in an AeroGarden. The LetPot seedlings rotted; the AeroGarden seedlings grew. After switching the third-party sponges into the LetPot, the owner reported that every new seedling thrived. This is one owner's comparison, not a compatibility test and not a recommendation to swap sponges. If you try an outside sponge, try it in one pod first and compare it against a LetPot sponge in the next.

Run a small first round

So, run your first round as a small test and keep a record. For each pod, write down the crop, the seed count, how old the seed is, the water level, whether the dome is on, and what sprouted and when. After one round, you will know which of your crops and which pods work in your machine, which is more useful than any average from other people's trays.

FAQ

Can I use any seed in a LetPot? The manuals say 2 to 3 seeds per sponge, and LetPot's FAQ suggests pre-germinating larger seed such as spinach, beet and cilantro on a moist paper towel. Owner results differ by crop, with basil, dill and cilantro reported doing well in one account and sage, parsley and chives barely growing in the same account.

How long do I leave the dome on? LetPot's FAQ and the Air manual say to remove the dome when two to three leaves appear. Until then the dome holds warmth and humidity around the seed.

How much plant food do I add? The SE manual says to dissolve each nutrient in 100 ml of pure water first, then lists 5 ml of A and 5 ml of B per liter of water, so 25 ml of each for a 5 L tank, with the first fill not over 5.5 L. The Air manual calls for 20 ml of each in 4 L, with the first fill not over 4 L. Check your model's manual for its own figures.

Do I need LetPot's own refills? LetPot sells round sponge refills for the Max, SE, Lite and Air, and a square kit for the Mini. Match the shape to your model; LetPot says some of its sponges fit other brands, and that claim comes from the manufacturer.

If you also grow in an AeroGarden, the own-seed guide for AeroGarden covers the same job for that machine. For this one, start small, count what sprouts in each pod and plant the next round from that count.

Sources

Prices, stock and specifications are as the linked pages showed them on 2026-11-07.

Keep reading