Growing catnip from seed rewards you with fragrant leaves for tea and cat toys within a few months. The single thing that matters most is patience at the start, since catnip seed germinates slowly and unevenly. Sow it correctly once, and an established plant often self-seeds for years afterward. Nepeta cataria tolerates poor soil and short dry spells once it is settled in. That makes it a forgiving first herb to try.
What you need
- Catnip seed (Nepeta cataria)
- A seed tray or small pots with good drainage
- Fresh, peat-free seed-starting compost
- A clear lid or a loose plastic bag, to hold in humidity while the seed germinates
- A watering can fitted with a fine rose
- A bright windowsill, or a sheltered spot outdoors once seedlings are ready
- Wire mesh, a cloche, or an upturned basket to protect young plants from cats
When to sow
Sow catnip seed once the soil has warmed and the risk of frost has passed in your area. Indoors, you can start it any time. A windowsill supplies steady warmth regardless of the season outside. Germination is slow and uneven, so treat several weeks of waiting as normal rather than a sign of failure. In cooler climates, start seed indoors six to eight weeks before your last expected frost. Move the plants outside once night temperatures stay reliably above 45°F (7°C). In warmer climates, sow directly outdoors once the last frost date for your area has passed. The ground is already warm enough by then. Whichever route you choose, avoid sowing catnip while frost still threatens. Young seedlings have almost no tolerance for it.
Step 1: Sow the seed
Fill a tray or small pots with fresh, damp seed-starting compost. Firm it gently, but do not pack it hard. Scatter catnip seed thinly across the surface, since it needs light to germinate well. Press the seed down lightly with your fingers or a flat board, rather than burying it. You can cover the seed if you prefer. Add only a light dusting of compost, no more than 1/8 inch (3 mm). Water gently with a fine rose, so you do not wash the seed to one side. Cover the tray with a clear lid or a loose plastic bag, to hold in humidity while the seed germinates.
Step 2: Provide the right germination conditions
Keep the tray somewhere warm, ideally around 70°F (21°C). Cooler conditions slow germination considerably. Bright, indirect light suits catnip better than deep shade or strong direct sun on a hot windowsill. Check the compost daily. Mist it if the surface starts to dry out, since catnip seed will not germinate in dry compost. Expect the first seedlings within one to three weeks, though a few stragglers can take longer still. A heat mat speeds things along in a cool room, though it is not essential. Remove the lid once most seeds have sprouted, so the seedlings do not rot in trapped moisture. From here, give catnip the same care as any other seedling. It needs steady warmth and bright light, plus compost that stays evenly moist but never waterlogged.
Step 3: Thin the seedlings
Once seedlings show their first true leaves, thin them so each one has room to grow. Remove the weakest seedlings in each cluster. Snip them at the base instead of pulling them. Pulling disturbs the roots of those left behind. Aim to leave one seedling every 2 inches (5 cm) if you are growing on in a shared tray. Thinning can feel wasteful. Crowded seedlings stay thin and stretched, and they rarely transplant well later. If you sowed into individual small pots instead, simply thin each pot down to its single strongest seedling. Add the removed seedlings to the compost heap rather than trying to replant them. Disturbed catnip roots seldom recover well at this stage.
Step 4: Transplant the seedlings
Pot on each seedling once it has two or three sets of true leaves. Choose a pot 3 to 4 inches (8 to 10 cm) across. Fill it with fresh, general-purpose compost. Set the seedling at the same depth it was growing before. Water well after potting. Keep newly potted seedlings out of strong, direct sun for a few days while the roots settle in. Before planting outside, harden off the seedlings. This means getting them used to outdoor conditions gradually. Do this by moving pots outdoors for a few hours a day, increasing the time over a week or two. Once seedlings are hardened off and all frost risk has passed, plant them outside. Space plants about 18 inches (45 cm) apart, since mature catnip spreads wide.
Step 5: Protect young plants from cats
Cats are drawn to catnip's scent long before a plant is established enough to survive their attention. Cover new transplants with a wire cloche or an upturned basket, pinned firmly in place. Do this for the first few weeks after planting out. Leave gaps for light and rain to reach the plant. Make sure the gaps are too small for a cat to squeeze through or roll on the leaves. Established catnip tolerates rolling and nibbling far better than young plants do. Its roots run deeper and its stems grow tougher by then. As a rough guide, six to eight weeks of unrestricted outdoor growth is usually enough. Keep protection in place longer if a particularly determined cat visits your garden. Remove the barrier gradually rather than all at once. This avoids exposing the plant suddenly.
Step 6: Harvest the leaves
Start picking leaves once the plant is at least 8 inches (20 cm) tall and growing strongly. Snip individual leaves or whole stems with clean scissors. Cut just above a pair of leaves, which encourages bushier regrowth. Harvest in the morning once any dew has dried. Leaf oils are strongest at this time of day. You can use leaves fresh. Or dry them somewhere warm and airy, away from direct sun. Dried leaves are ready once they crumble easily between your fingers. Store dried, crumbled leaves in a sealed container. Keep the container away from light and heat. They keep well for cat toys or for tea. Regular light picking encourages a bushier plant, so do not be afraid to harvest often once catnip is established.
Common problems
Seedlings collapse at the base and topple over
This is usually damping off, a fungal problem caused by compost that stays too wet with poor airflow. Water from below where you can, letting the surface dry slightly between waterings. Avoid overcrowding seedlings, and increase airflow once the tray's lid comes off. Remove badly affected seedlings promptly. The fungus spreads quickly to healthy neighbors nearby.
Seed never germinates
Old seed loses viability quickly, so check the seed's age before troubleshooting further. Catnip seed is often slow even when fresh, so give it more time than you expect. Confirm the compost has stayed consistently moist and warm throughout. Drying out even once can end germination for good. If nothing appears after four weeks in good conditions, resow with fresh seed.
Leaves turn yellow and growth stalls
This usually points to compost that stays too wet for too long. Waterlogged compost starves the roots of oxygen. Improve drainage, and let the surface dry slightly between waterings. Avoid letting pots sit in a saucer of standing water.
A cat has flattened or eaten the plant
Established catnip usually recovers from an occasional visit. New growth appears from the base within a couple of weeks in most cases. Reinforce or replace the protective barrier straight away. Cut back badly damaged stems, which encourages fresh shoots to form.
Plants become tall, sparse and woody
Catnip can turn leggy after its first flush of growth, especially if you skip regular picking. Cut the whole plant back by about half once flowering finishes. This encourages a fresh, bushy flush of new leaves. Regular light harvesting afterward helps keep the habit compact.
What to do next
Once catnip is established and cropping well, let a few flower spikes open for the bees. Catnip flowers are a reliable draw for pollinators through summer. Save seed from the driest flower heads if you want to sow again. Established plants often self-seed on their own, so watch nearby soil for volunteer seedlings the following season.