Too many caterpillars on a small plant can destroy it before it gets a chance to grow big! You might need to remove some of the eggs until the plants are big and strong. Sow more seeds every few weeks so that you’ll have plenty of food for the hungry caterpillars through until autumn. Monarch butterflies aren’t the only creatures that like to feed on swan plants. Protect your seedlings from slugs and snails, which come out at night. Also look out for tiny yellow aphids and squash them with your fingers.