How to Care for & Overwinter Geraniums in Carts

Repot your chosen geraniums into new pots with fresh, sterile soil. This step is optional, but ensures you won't be bringing any outdoor insects into your house. If you wish to bring the entire planter indoors, check it very carefully for pests before bringing it inside and monitor it frequently through the winter.

Prune back your geraniums to about half of their current size. Strip away any dead leaves, stems or blossoms.

Find a place where your geraniums will receive full sunlight. They need 12 to 16 hours of light each day, and if your climate doesn't provide it they'll need artificial light from a full-spectrum fluorescent in order to thrive. If you've brought the entire cart inside with you, you'll likely need to have a solarium, greenhouse or sun porch to accommodate it. Individual pots can go on a windowsill or shelves near a window.

Water the geraniums just often enough to keep them from drooping and wilting, approximately once a week. Water the soil itself rather than sprinkling over the plants, which can promote diseases and fungal growth. Geraniums tolerate drought better than dampness, so err on the side of underwatering.

Check the geraniums every week, and strip away any dead blossoms or leaves. If they show signs of becoming long and spindly, that indicates they're not receiving enough light. Cut back the thin stems and rearrange the pots or add lighting to promote a sturdier growth habit.

Replant or return your cart to the outdoors once any danger of frost has passed. Harden the plants by leaving them out for a longer period each day, beginning a week before you leave them out for the summer.