Size Guide

By Dan & Ashley Dubiel, Swift Blocker · Updated July 23, 2026

Match the block size to what you're growing. Bigger blocks need less-frequent watering and suit larger seeds and robust transplants; smaller blocks pack more plants per tray and dry out faster — most cut flowers thrive in 0.9″ micro blocks. Choose a bigger block if you can't water often.

Still not sure? Take the 60-second size quiz — answer a few questions about what you grow and get a specific recommendation.

Block size at a glance

Bigger blocks hold moisture longer and carry a seedling further before it needs potting up; smaller blocks pack more plants per tray and dry out faster. Rough transplant ceilings by block size:

Block size Rough transplant ceiling Best for
0.9″ ~3 weeks Micro blocks; most cut flowers and small seeds
1.125″ ~3–4 weeks Everyday veggies and flowers
1.5″ ~4–6 weeks Larger seeds and longer holds
2″–2.25″ ~6 weeks Robust transplants; least-frequent watering

Take the 60-second size quiz for a recommendation matched to what you grow.

Which block size?

Match by block size, not just model, so you start seeds at the right density. Smaller blocks pack more per tray but dry out faster.

Block size Swift Blocker models Best for
0.9" (micro) Nano 25 · Mini 75 · Commercial 200 Tiny seeds & most cut flowers; highest density (dries fastest)
1.125" Nano 16 Forgiving all-rounder
1.5" (workhorse) Nano 9 · Mini 27 · Commercial 72/128 Most veg, herbs & flowers; nightshade starts
2"–2.25" (large) Nano 4 · Commercial 50 Large seeds — sweet peas, sunflowers, squash
Potting up / cuttings The Dahlia Blocker (1"–2") Dahlia cuttings, melons, pumpkins, bumping up

Choose bigger if you can't water often.