Seedling care: transplanting, thinning, and preventing disease
Step-by-step instructions and helpful tips
When the seedlings have developed their second set of true leaves, it’s time to transplant or thin them. If you don’t need many plants, you can thin them in place: just pinch or snip off the excess seedlings, leaving the remaining ones spaced about 2 inches apart. Seedlings in individual pots or cells should be thinned to one plant per pot or cell. If you want to save most of the plants that have germinated, you’ll need to transplant them to larger containers for growth to planting-out size. It’s best to use individual pots or cell-packs for this purpose so that seedlings won’t suffer much root disturbance when planted out in the garden.
To transplant seedlings, fill each new container with a moist planting mix. Loosen the soil around the seedlings (a kitchen fork or spoon is handy for this); then carefully lift them out, one at a time. Or lift a clump of seedlings and gently separate individual plants by carefully teasing apart the tangled mass of roots. Handle seedlings by their leaves to avoid damaging the tender stems. Poke a hole in the new container’s planting mix, place the seedling in the hole, and firm soil around it. Water the transplant right away. Keep the containers out of direct sunlight for a few days to let the transplants recover from the move.
About 10 days before the seedlings are ready to plant outside, harden them off so they can withstand bright sun and cooler temperatures. Stop fertilizing them, and set them outdoors for several hours each day in a wind-sheltered spot that receives filtered light. A cold frame is useful for hardening off seedlings. Over the next week or so, gradually increase exposure until the plants are in full sun all day (shade lovers are an exception; they shouldn’t be exposed to day-long sun). Then set them out in the garden as illustrated in Planting annual and perennial seedlings.
If your seedlings suddenly collapse and die, one of the fungal diseases called “damping off” or “seed and seedling rot” may be to blame. In one type of damping off, the seedling’s stem collapses at or near the soil surface; in another type, the seedling rots before it emerges from the soil, or the seed decays before it even sprouts.
To prevent these problems, use pasteurized potting mix and new or thoroughly washed and disinfected containers. Try using seeds treated with a fungicide. Take care not to overwater seedlings; be sure to provide good air circulation and ventilation, so tops of seedlings stay dry and standing moisture is kept to a minimum. Thinning seedlings to eliminate crowding is also helpful.
Our Favorite Gardening Tools from the Sunset Store
The Sunset Store is full of tools, puzzles, knickknacks, and more to remind you of all the reasons you love the west. The gardening tools below were handcrafted with the home gardener in mind; check them out and don’t forget to tag us in your garden pics @SunsetMag on all social platforms.
Sunset Gardening Apron
We’ve teamed up with the good people at White Bark Workwear in Los Angeles, California, to produce our first official Sunset garden apron—a sustainable and practical tool for gardeners everywhere. The spacious utility pockets are gusseted to expand and provide extra room for tools, twine, garden clippings, and anything else you might need to keep near.
Fisher Blacksmithing Hand Trowel
The subtle patina and refined hardwood handle give this trowel modern flair. The blade is made from high carbon steel and the handle from American Black Walnut. Simple and sturdy, this tool is reminiscent of what you might find in your grandparents garden or farm shed. The wide blade holds a lot of soil and the pointed shape allows you to get through more stubborn substances as well.
Fisher Blacksmithing Garden Cultivator
This elegant rake is great for breaking up dirt and attacking weeds! The tines of the rakes are ideal for working with grasses and other weeds that have shallow, rhizomes, or runner-type growth. The carefully bent side tines flare slightly below the ferrule creating a beautiful, fleur de lis image. The solid steel rivets are set horizontally to the direction of pressure providing additional stability for the rake.
Vintage Sunset Camellias Cover Personalized Garden Flag
Plant your flag! Our weather-resistant garden flags come custom-printed with your family’s name. Show off your pride in the West— and, ahem, your good taste— with your favorite vintage Sunset covers.
Read the 2021 Wellness Issue
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